Library › Pharmacology › Calcium channel blockers

Calcium channel blockers

The pharmacology, agents, dosing, guideline indications, contraindications, adverse effects, and interactions of dihydropyridine and nondihydropyridine calcium channel blockers in adult cardiovascular practice.

Voltage-gated calcium channels in heart and vessels

Voltage-gated calcium channels open when the cell membrane depolarizes and admit calcium down a steep concentration gradient, from about 1 to 2 mmol/L outside the cell to about 100 nmol/L in the resting cytosol. Each channel is built around a pore-forming α1 subunit with four homologous domains, each containing six transmembrane segments; auxiliary β, α2δ, and in skeletal muscle γ subunits modify trafficking and gating. Ten α1 genes define the channel families. All clinically used calcium channel blockers act on the L-type channel; the other families matter mainly as off-target sites and as the explanation for agents that never reached US practice.

L-type channels. The cardiac and vascular L-type channel is CaV1.2, encoded by CACNA1C. It activates at relatively depolarized potentials, inactivates slowly, and carries a long-lasting current (ICa,L), which is the source of the "L" designation. In working ventricular and atrial myocardium, ICa,L sustains the plateau (phase 2) of the action potential. In the sinoatrial and atrioventricular nodes, where fast sodium channels are largely inactivated at the less negative resting potential, ICa,L carries the upstroke (phase 0) itself. Nodal conduction velocity, nodal refractoriness, and the late part of sinus node diastolic depolarization therefore depend on L-type current. Blocking the channel slows the sinus rate and prolongs the atrial-His (AH) and PR intervals but leaves QRS duration and atrial and ventricular conduction velocity unchanged. A gain-of-function CACNA1C variant causes Timothy syndrome, with marked QT prolongation, and loss-of-function variants are found in some patients with Brugada and short QT phenotypes.

T-type channels. T-type channels (CaV3.1 and CaV3.2) activate at more negative potentials, inactivate quickly, and carry a small transient current. They contribute to pacemaker depolarization in the sinoatrial node and conduction tissue, and they are expressed in the renal afferent and efferent arterioles, peripheral resistance arterioles, and aldosterone-producing cells of the adrenal zona glomerulosa. No selective T-type blocker is available in the United States (see the history of the class).

Excitation-contraction coupling in the myocyte. During the plateau, calcium entering through L-type channels in the transverse tubules binds ryanodine receptors (RyR2) on the adjacent sarcoplasmic reticulum and triggers a much larger release of stored calcium, a process termed calcium-induced calcium release. Cytosolic calcium binds troponin C, moves tropomyosin away from the myosin-binding sites on actin, and permits cross-bridge cycling. Relaxation follows reuptake of calcium into the sarcoplasmic reticulum by the calcium ATPase (SERCA2a), regulated by phospholamban, and extrusion across the sarcolemma by the sodium-calcium exchanger. Because the trigger current sets the size of the release, any reduction of ICa,L lowers contractile force. Beta-adrenergic stimulation acts in part through the same channel: protein kinase A phosphorylation increases L-type open probability. Calcium channel blockers and beta blockers therefore have additive effects on rate, conduction, and contractility.

Excitation-contraction coupling in vascular smooth muscle. Arterial tone depends far more on calcium entry through L-type channels than cardiac contraction does. Calcium binds calmodulin, the calcium-calmodulin complex activates myosin light-chain kinase, and phosphorylated myosin light chains generate sustained tension. Arterial smooth muscle rests at a more depolarized potential than ventricular myocytes, and pressure-induced (myogenic) constriction of resistance arterioles is largely L-type dependent. Venous smooth muscle relies less on voltage-gated calcium entry, so calcium channel blockers dilate arterioles much more than veins. Coronary arteries and their spasm-prone segments are highly sensitive to L-type blockade.

Other tissues. Pancreatic beta cells release insulin through L-type channels after glucose closes ATP-sensitive potassium channels and depolarizes the cell. Therapeutic doses have no clinically important effect on glucose, but massive overdose suppresses insulin release and produces hyperglycemia (see poisoning). L-type channels in intestinal smooth muscle explain the constipation produced by verapamil.

Chemical classes, binding sites, and use dependence

Three structurally unrelated chemical classes bind three distinct but allosterically linked sites on the α1 subunit of CaV1.2. The phenylalkylamines (verapamil) and the benzothiazepines (diltiazem) together form the nondihydropyridine group. The dihydropyridines form the largest group and include all of the vascular-selective agents.

Classification of calcium channel blockers available in the United States. Bepridil, a nonselective agent, and mibefradil, a T-type and L-type blocker, were withdrawn. In the Vaughan Williams scheme, verapamil and diltiazem are class IV antiarrhythmic drugs; dihydropyridines have no antiarrhythmic class.

Voltage dependence and vascular selectivity. Dihydropyridines bind with much higher affinity to inactivated channels, and the fraction of inactivated channels rises with membrane depolarization. Because arterial smooth muscle rests at a more depolarized potential than ventricular myocardium, a given plasma concentration blocks a larger fraction of vascular channels. The result is effective arterial dilation at concentrations that barely affect the heart. Selectivity is relative: in severe left ventricular dysfunction or after large doses, dihydropyridines also depress contractility, and the clevidipine label warns that dihydropyridines can worsen heart failure.

Use dependence and nodal selectivity. Verapamil, and to a lesser degree diltiazem, reach their binding site through the open channel. The more often channels open, the more drug binds, so block intensifies at faster heart rates and during rapid atrial activation. This frequency-dependent (use-dependent) block concentrates the effect in nodal tissue during tachycardia, which is the property that terminates atrioventricular nodal re-entry and slows the ventricular response in atrial fibrillation. Verapamil also blocks P-glycoprotein and, weakly, the human ether-à-go-go-related gene (hERG) potassium channel; diltiazem is a weaker P-glycoprotein inhibitor and has no clinically important hERG block.

Vascular versus nodal selectivity of the calcium channel blockers

Net hemodynamic effect reflects both the direct action of each drug and the baroreflex response to the fall in arterial pressure. A rapid fall in pressure from a short-acting dihydropyridine triggers reflex sympathetic activation, tachycardia, and renin release, which offsets the small direct negative chronotropic effect. Long-acting dihydropyridines lower pressure gradually and cause little or no reflex tachycardia. With verapamil and diltiazem, direct nodal slowing outweighs the reflex, and the net result is a lower heart rate.

Comparison of dihydropyridines, diltiazem, and verapamil. Doses from US prescribing information and the 2023 chronic coronary disease and 2025 high blood pressure guidelines; recommendation classes from the 2022 heart failure and 2023 atrial fibrillation guidelines. ER, extended release; LVEF, left ventricular ejection fraction.

Calcium channel blocker selection by clinical profile

The choice between a dihydropyridine and a nondihydropyridine agent follows the indication, the ejection fraction, conduction disease, pre-excitation, blood pressure, and the patient's other drugs. The tool below applies the guideline recommendations and labeled contraindications and interactions described on this page to a single patient.

The tool applies the 2025 American Heart Association/American College of Cardiology (AHA/ACC) high blood pressure, 2023 atrial fibrillation, 2022 heart failure, 2024 hypertrophic cardiomyopathy, 2015 supraventricular tachycardia, and 2017 ventricular arrhythmia guidelines, together with US prescribing information.

Pharmacokinetics and formulations

All oral calcium channel blockers are well absorbed and undergo extensive first-pass metabolism by intestinal and hepatic CYP3A4, so systemic bioavailability is low and variable for most agents. Amlodipine is the exception: its bioavailability is high, its volume of distribution is large, and its hepatic clearance is slow, which together produce a half-life of 30 to 50 hours. Steady state with amlodipine takes 7 to 8 days, which sets the interval between dose increases. Calcium channel blockers are highly protein bound and are not removed by hemodialysis.

Oral calcium channel blockers in the United States. Values from US prescribing information. ER, extended release.

Saturable first-pass metabolism. Verapamil and diltiazem show nonlinear kinetics: as the dose rises, first-pass extraction saturates, so bioavailability and half-life increase with chronic dosing. A doubling of the daily dose can more than double the plasma level. Both drugs also inhibit the enzyme that clears them, which adds to accumulation over the first days of therapy.

Formulations and conversion. Short-acting formulations require three or four daily doses and cause peaks and troughs in effect. Extended-release products deliver the drug over 24 hours by osmotic pumps (nifedipine gastrointestinal therapeutic system), coated beads (several diltiazem products), or matrix tablets, and they are not interchangeable milligram for milligram across all brands. Diltiazem is converted from immediate release to an extended-release product at the same total daily dose, then titrated to response. Verapamil immediate release in three divided doses is converted to the same total dose of sustained release in one or two doses. Extended-release tablets and capsules are not crushed or chewed, because dose dumping produces hypotension and bradycardia. Some osmotic tablets pass intact in the stool as an empty shell, which does not indicate malabsorption.

Short-acting nifedipine. Immediate-release nifedipine lowers pressure abruptly and activates the sympathetic nervous system. A meta-analysis of 16 secondary-prevention trials found a dose-related increase in total mortality with short-acting nifedipine in coronary heart disease: relative risk 1.06 at 30 to 50 mg daily, 1.18 at 60 mg, and 2.83 at 80 mg. The capsule label excludes use for acute reduction of blood pressure because profound hypotension, myocardial infarction, and death have been reported. Obstetric practice is the exception: oral immediate-release nifedipine is a first-line drug for severe hypertension in pregnancy (see special populations). The Beers Criteria list immediate-release nifedipine as a drug to avoid in older adults.

Dihydropyridine agents: amlodipine, nifedipine, felodipine, and others

Amlodipine is the most prescribed calcium channel blocker in the United States and the reference agent of the class. Its gradual onset and long half-life produce smooth 24-hour blood pressure control, little reflex tachycardia, and persistent effect after a missed dose. It is labeled for hypertension, chronic stable angina, vasospastic angina, and angiographically documented coronary artery disease. The usual starting dose is 5 mg daily, or 2.5 mg in small, frail, or older patients and in hepatic impairment. The maximum is 10 mg daily, and titration steps are spaced 7 to 14 days apart. In the labeling trials, edema occurred in 10.8% of patients taking 10 mg, 3.0% taking 5 mg, and 1.8% taking 2.5 mg, compared with 0.6% taking placebo. Edema was more than twice as frequent in women as in men (14.6% versus 5.6%). Amlodipine is neutral on survival in reduced ejection fraction (PRAISE and PRAISE-2), and it is the dihydropyridine of choice when an antihypertensive or antianginal drug is needed in heart failure. Levamlodipine, the active S-enantiomer, is given at half the amlodipine dose and has the same profile.

Nifedipine was the first dihydropyridine in clinical use. The extended-release osmotic tablet is a potent once-daily antihypertensive and antianginal drug, and extended-release nifedipine is a preferred antihypertensive in pregnancy. It is also used for Raynaud phenomenon, vasoreactive pulmonary arterial hypertension (at high doses), and short-term tocolysis in obstetric practice.

Felodipine is highly vascular selective. In V-HeFT III, felodipine added to enalapril in heart failure with reduced ejection fraction was safe but did not improve exercise tolerance or survival. Its exposure roughly doubles with grapefruit juice, the largest grapefruit interaction in the class.

Isradipine, nicardipine (oral), and nisoldipine are effective antihypertensives with no distinct outcome advantage; they are used mainly when other agents are unavailable or not tolerated.

Nimodipine is a lipophilic dihydropyridine that crosses the blood-brain barrier. It is given orally, 60 mg every 4 hours for 21 days beginning within 96 hours of aneurysmal subarachnoid hemorrhage, to improve neurologic outcome after delayed cerebral ischemia. It carries a boxed warning against intravenous or other parenteral administration of capsule contents, which has caused cardiac arrest and death; an oral solution is available for patients who cannot swallow. Nimodipine has no role in hypertension.

Intravenous calcium channel blockers: nicardipine, clevidipine, diltiazem, and verapamil

Intravenous dihydropyridines are titratable arterial vasodilators for hypertensive emergency, perioperative hypertension, acute stroke, intracerebral hemorrhage, and acute aortic syndromes once the heart rate is controlled. Intravenous diltiazem and verapamil are used for acute rate control and termination of supraventricular tachycardia. The choice of agent and the pressure target in hypertensive emergency are set by the organ at risk and are described on the hypertension page.

Intravenous calcium channel blockers. Dosing from US prescribing information. The 2025 AHA/ACC high blood pressure guideline lists nicardipine at 5 mg/h, increased by 2.5 mg/h every 5 minutes to a maximum of 15 mg/h. It lists clevidipine at 1 to 2 mg/h, doubled every 90 seconds and then increased by less than double every 5 to 10 minutes, to a maximum of 21 mg/h for no more than 72 hours. That maximum matches the label limit of 1,000 mL (an average of 21 mg/h) per 24 hours. In the diltiazem labeling trials, asymptomatic hypotension occurred in 4.3% and symptomatic hypotension in 3.2% of patients.

Clevidipine is metabolized by blood and tissue esterases, so its clearance does not depend on hepatic or renal function, and its effect dissipates within minutes. In the ECLIPSE trials in 1,512 cardiac surgery patients, blood pressure control with clevidipine was similar to that with nitroglycerin, nitroprusside, or nicardipine. The emulsion delivers about 0.2 g of lipid per milliliter, which is counted in parenteral nutrition and limits daily volume. Patients receiving long infusions who are not transitioned to oral therapy are observed for rebound hypertension for at least 8 hours after the infusion stops.

Nicardipine has a longer offset than clevidipine and does not require lipid limits. In comparative studies of hypertensive emergency, nicardipine reached prespecified targets more often than labetalol. Both intravenous dihydropyridines cause reflex tachycardia, which is unwanted in acute aortic dissection. In that setting, heart rate is controlled with an intravenous beta blocker before a vasodilator is added. Intravenous diltiazem or verapamil is reasonable when a beta blocker is contraindicated (Class 2a), as described on the acute aortic syndromes page.

Intravenous diltiazem and verapamil. A wide-complex tachycardia is distinguished from supraventricular tachycardia with aberration before either drug is given, because intravenous verapamil or diltiazem in ventricular tachycardia causes hemodynamic collapse and ventricular fibrillation. The combination of an intravenous calcium channel blocker and an intravenous beta blocker given together or within a few hours is labeled as a contraindication. Intravenous diltiazem is usually followed by an infusion or by oral therapy, because the effect of a single bolus wanes within hours.

Verapamil and diltiazem: nodal agents

Verapamil has the strongest effect on the atrioventricular node and on contractility of any agent in the class. Its uses in cardiology are rate control in atrial fibrillation and flutter, prevention and termination of supraventricular tachycardia, idiopathic left fascicular ventricular tachycardia, angina when a beta blocker is not used, obstructive hypertrophic cardiomyopathy when beta blockers fail, and, less often, hypertension. Intracoronary and intra-arterial verapamil treat no-reflow and radial artery spasm during catheterization. In the labeling database of 4,954 patients taking sustained-release verapamil, constipation occurred in 7.3%, dizziness in 3.3%, hypotension in 2.5%, edema in 1.9%, heart failure or pulmonary edema in 1.8%, bradycardia below 50 beats/min in 1.4%, and atrioventricular block of any degree in 1.2%.

Diltiazem produces nodal slowing and coronary dilation with less negative inotropy and less constipation than verapamil. It is the most frequently used intravenous calcium channel blocker for acute rate control in atrial fibrillation. Oral extended-release diltiazem is used for rate control, angina, vasospastic angina, hypertension, and hypertrophic cardiomyopathy, and high-dose diltiazem is one of the agents for vasoreactive pulmonary arterial hypertension. It raises serum digoxin by about 20% and is a moderate CYP3A4 inhibitor, with the same simvastatin limit as verapamil.

Electrocardiographic effects. Both drugs lengthen the PR interval and slow the sinus rate. They do not widen the QRS or prolong the QT interval to a clinically important degree. Verapamil blocks hERG at high concentrations, but its simultaneous block of inward calcium current prevents the early afterdepolarizations that initiate torsades de pointes, so it carries little torsades risk.

Effect on accessory pathways. Calcium channel blockers slow conduction through the atrioventricular node but not through an atrioventricular accessory pathway, which conducts by fast sodium current. In atrial fibrillation with pre-excitation, nodal blockade removes the competing nodal route. Reflex sympathetic activation and vasodilation may also shorten the refractory period of the pathway, and the ventricular rate can accelerate into ventricular fibrillation.

Calcium channel blockers in hypertension

Long-acting dihydropyridine calcium channel blockers are one of three first-line antihypertensive classes in the 2025 AHA/ACC guideline, with thiazide-type diuretics and angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). Each lowers pressure substantially and reduces cardiovascular events in outcome trials. Thresholds, goals, and the algorithm for choosing among the classes in each patient are covered on the hypertension page.

Efficacy across patient groups. Dihydropyridines lower pressure in younger and older patients, in low-renin and high-renin states, and with high dietary sodium intake, and their effect does not depend on volume status. They are metabolically neutral (no effect on glucose, lipids, potassium, or uric acid) and rarely cause orthostatic hypotension. They remain effective in chronic kidney disease, where dosing does not change.

Isolated systolic hypertension and older adults. In Syst-Eur, 4,695 patients aged 60 years or older with isolated systolic hypertension were randomized to nitrendipine-based therapy or placebo. Active treatment lowered systolic pressure by 10.1 mm Hg more than placebo and reduced stroke from 13.7 to 7.9 events per 1,000 patient-years, a 42% reduction; all fatal and nonfatal cardiac end points fell by 26%. The stiff, large-artery phenotype of older adults responds well to dihydropyridines, which together with thiazide-type diuretics are the usual choices in this group.

Stroke prevention. In a meta-analysis of 147 randomized trials, calcium channel blockers had a small additional effect on stroke prevention beyond the effect expected from blood pressure lowering (relative risk 0.92 compared with other classes). Their effect on heart failure prevention was smaller than that of other classes (19% reduction versus 24%).

Outcome trials of calcium channel blockers in hypertension. RR, relative risk; HR, hazard ratio; SR, sustained release.

ALLHAT. The largest antihypertensive trial found amlodipine equivalent to chlorthalidone for the primary coronary end point, with more heart failure on amlodipine. Part of that difference has been attributed to the diuretic's effect on volume and to the withdrawal of prior diuretics at randomization. The trial established that calcium channel blockers are not harmful in hypertension, a concern raised by the short-acting nifedipine data, and it placed thiazide-type diuretics as the standard against which other classes are measured.

Combination therapy with renin-angiotensin blockade. A dihydropyridine and an ACE inhibitor or ARB lower pressure additively and offset each other's adverse effects: venodilation by the renin-angiotensin blocker reduces dihydropyridine edema, and the dihydropyridine prevents the volume-dependent loss of efficacy of renin-angiotensin blockade. In a meta-analysis of 25 trials with 17,206 patients, adding an ACE inhibitor or ARB to a calcium channel blocker reduced peripheral edema by 38% (relative risk 0.62) and withdrawal for edema by 62%. In ACCOMPLISH, benazepril plus amlodipine reduced cardiovascular events by 20% compared with benazepril plus hydrochlorothiazide at almost the same blood pressure. The 2025 guideline recommends starting two first-line drugs of different classes, preferably as a single-pill combination, in stage 2 hypertension (Class 1). Amlodipine is available in single-pill combinations with benazepril, perindopril, olmesartan, valsartan, and telmisartan, and in triple combinations with an ARB and hydrochlorothiazide. In resistant hypertension, the standard three-drug regimen is a renin-angiotensin blocker, a long-acting calcium channel blocker, and a thiazide-like diuretic before spironolactone is added.

Nondihydropyridines in hypertension. Verapamil and diltiazem lower pressure but are not first-line antihypertensives. They are used when hypertension coexists with atrial fibrillation needing rate control or with angina, and they are avoided in heart failure with reduced ejection fraction and in conduction disease. In INVEST, a verapamil-based strategy was equivalent to an atenolol-based strategy in hypertensive patients with coronary artery disease.

Race and the choice of first-line drug. The 2017 ACC/AHA guideline recommended a thiazide-type diuretic or calcium channel blocker as initial therapy in Black adults without heart failure or chronic kidney disease, based on subgroup data in which these classes lowered pressure more than a renin-angiotensin blocker alone. The 2025 guideline makes no race-specific recommendation for the choice of initial drug class; its supportive text lists non-Hispanic Black adults with stage 1 hypertension among the higher-risk patients in whom initial two-drug combination therapy is used. Selection rests on comorbidity, target-organ involvement, prior response, adverse effects, cost, and patient preference.

Chronic kidney disease and proteinuria. Dihydropyridines dilate the afferent arteriole more than the efferent arteriole and do not lower intraglomerular pressure as renin-angiotensin blockade does. In the African American Study of Kidney Disease and Hypertension (AASK), 1,094 patients with hypertensive nephrosclerosis were randomized among ramipril, metoprolol, and amlodipine. Ramipril reduced the risk of clinical kidney end points by 38% compared with amlodipine, and by 48% in patients with proteinuria, and the amlodipine arm was stopped early. In albuminuric kidney disease, a dihydropyridine is therefore added to, never substituted for, an ACE inhibitor or ARB. Diltiazem and verapamil reduce proteinuria more than dihydropyridines in small studies, a difference without proven outcome benefit.

European guidance. The 2024 European Society of Cardiology (ESC) hypertension guideline lists dihydropyridine calcium channel blockers among the first-line drug classes and recommends initial low-dose two-drug combination therapy, preferably a single pill of a renin-angiotensin blocker with a dihydropyridine calcium channel blocker or a diuretic, for most patients with confirmed hypertension (Class 1). This approach is close to the 2025 US recommendation for stage 2 hypertension. Its treated systolic target is 120 to 129 mm Hg when tolerated (Class 1).

Rate control in atrial fibrillation and atrial flutter

Verapamil and diltiazem slow atrioventricular nodal conduction and are, with beta blockers, the first-line drugs for ventricular rate control. The overall strategy for atrial fibrillation, including rate targets, rhythm control, and anticoagulation, is described on the atrial fibrillation page.

Acute rate control. In hemodynamically stable patients with a rapid ventricular response, intravenous beta blockers or nondihydropyridine calcium channel blockers are recommended (Class 1), provided that LVEF is >40%. Intravenous nondihydropyridine calcium channel blockers are harmful in patients with known moderate or severe left ventricular systolic dysfunction (Class 3: Harm in the 2023 atrial fibrillation guideline). Intravenous diltiazem is given as 0.25 mg/kg of actual body weight over 2 minutes (about 20 mg in an average adult), with 0.35 mg/kg after 15 minutes if the response is inadequate. An infusion of 5 to 15 mg/h follows. Intravenous verapamil is given as 5 to 10 mg over at least 2 minutes, with 10 mg after 30 minutes if needed. In emergency department studies, intravenous diltiazem controlled the rate faster than intravenous metoprolol. Hypotension is the main adverse effect and is more frequent with lower baseline pressure. Unstable patients undergo cardioversion.

Long-term rate control. Beta blockers or nondihydropyridine calcium channel blockers are recommended for long-term rate control (Class 1), chosen by substrate and comorbidities. Oral diltiazem extended release 120 to 360 mg daily and verapamil extended release 180 to 480 mg daily are the usual doses. A calcium channel blocker is preferred to a beta blocker in patients with asthma or chronic obstructive lung disease with bronchospasm, and either is combined with digoxin when rate control remains inadequate. Calcium channel blockers control the rate at rest and during exertion better than digoxin, which acts through vagal tone. The combination of diltiazem or verapamil with a beta blocker is used with heart rate and PR monitoring because of additive nodal block.

Reduced ejection fraction and pre-excitation. In patients with atrial fibrillation and LVEF <40%, nondihydropyridine calcium channel blockers are not given for long-term rate control because they can worsen heart failure (Class 3: Harm). Beta blockers, digoxin, or rhythm control are used instead. In pre-excited atrial fibrillation, verapamil, diltiazem, and other atrioventricular nodal blockers are harmful (Class 3: Harm). The 2024 ESC guideline restricts verapamil and diltiazem to LVEF >40% and uses beta blockers, digoxin, or both when LVEF is ≤40%. An LVEF of exactly 40% falls within heart failure with reduced ejection fraction (LVEF ≤40%), in which the 2022 AHA/ACC/Heart Failure Society of America guideline classes nondihydropyridine calcium channel blockers as 3: Harm.

Atrial flutter, multifocal atrial tachycardia, and focal atrial tachycardia. Rate control of atrial flutter is often harder to achieve than in atrial fibrillation because the regular flutter waves conduct with a fixed ratio. Intravenous or oral beta blockers, diltiazem, or verapamil are recommended (Class 1) in patients without pre-excitation or reduced ejection fraction. In multifocal atrial tachycardia, usually driven by lung disease, verapamil or diltiazem slows the rate after the underlying illness and electrolytes are treated. Verapamil or diltiazem is also used with class IC antiarrhythmic drugs to prevent 1:1 conduction of slowed atrial flutter.

Drug-specific interactions in atrial fibrillation. Verapamil and diltiazem raise digoxin levels, increase dabigatran and edoxaban exposure through P-glycoprotein inhibition (verapamil more than diltiazem), and raise apixaban and rivaroxaban levels modestly through CYP3A4 inhibition without a labeled dose change for atrial fibrillation. Verapamil is contraindicated with dofetilide. Diltiazem and verapamil raise the levels of dronedarone and ibrutinib and are avoided with ivabradine.

Supraventricular tachycardia and verapamil-sensitive ventricular tachycardia

Supraventricular tachycardia. Atrioventricular nodal re-entrant tachycardia and orthodromic atrioventricular reciprocating tachycardia use the node as an essential limb of the circuit, so nodal block terminates them. After vagal maneuvers and adenosine, intravenous diltiazem or verapamil is effective for acute treatment of hemodynamically stable supraventricular tachycardia (Class 2a under the 2015 ACC/AHA/Heart Rhythm Society (HRS) guideline). They are the usual choice when adenosine fails, when the tachycardia recurs after adenosine, or when asthma makes adenosine undesirable. For ongoing management, oral beta blockers, diltiazem, or verapamil are recommended for symptomatic supraventricular tachycardia without ventricular pre-excitation during sinus rhythm (Class 1). Oral verapamil or diltiazem is recommended in atrioventricular nodal re-entry for patients who are not candidates for ablation or prefer not to undergo it (Class 1). In focal atrial tachycardia, oral beta blockers, diltiazem, or verapamil are reasonable (Class 2a). Catheter ablation is the definitive treatment for most of these arrhythmias.

Pre-excitation. A manifest accessory pathway on the resting electrocardiogram changes management. Nodal block terminates orthodromic tachycardia, but it can accelerate the ventricular response over the pathway if atrial fibrillation develops. Intravenous calcium channel blockers are therefore avoided in pre-excited atrial fibrillation and flutter (Class 3: Harm), and procainamide or ibutilide is used in stable patients.

Wide-complex tachycardia. A regular wide-complex tachycardia is treated as ventricular tachycardia unless the diagnosis is secure. Hemodynamic stability does not exclude ventricular tachycardia, and intravenous verapamil or diltiazem in a wide-complex tachycardia of unknown origin is potentially harmful (Class 3: Harm in the 2017 AHA/ACC/HRS ventricular arrhythmia guideline). The negative inotropy and vasodilation of these drugs remove the compensation that sustains a marginal circulation in ventricular tachycardia, and collapse follows.

Idiopathic left fascicular ventricular tachycardia. Fascicular ventricular tachycardia is a re-entrant arrhythmia involving the left posterior fascicle (most often) and abnormal Purkinje tissue, typically in young adults, more often men, with structurally normal hearts. The QRS is relatively narrow, often 120 to 140 ms, with right bundle branch block morphology and left superior axis in the common left posterior fascicular form. The circuit includes a slow, calcium-dependent segment, which explains its characteristic sensitivity to verapamil and its insensitivity to adenosine. Intravenous verapamil terminates sustained, tolerated fascicular tachycardia once the diagnosis is established (Class 1). Oral verapamil is an alternative to ablation for prevention (Class 2a). Catheter ablation is recommended when antiarrhythmic drugs are ineffective, not tolerated, or not the patient's preference (Class 1). Fascicular tachycardia is the one ventricular tachycardia in which verapamil is the drug of choice. Symptomatic outflow-tract ventricular tachycardia in an otherwise normal heart, which arises from triggered activity, also responds to a beta blocker or a calcium channel blocker (Class 1). Electrocardiographic recognition and ablation are covered on the ventricular tachycardia and sudden cardiac death page.

Stable angina and chronic coronary disease

Calcium channel blockers relieve angina by reducing myocardial oxygen demand and increasing supply. All agents dilate epicardial coronary arteries and arterioles and prevent spasm. Dihydropyridines lower afterload and wall stress. Verapamil and diltiazem also lower heart rate and contractility, which lengthens diastolic perfusion time. None of the calcium channel blockers reduces death or myocardial infarction in chronic coronary disease without hypertension; their role is symptom relief and blood pressure control. Antianginal strategy as a whole, including nitrates, ranolazine, and the sequencing of agents, is described on the chronic coronary disease page.

Guideline recommendations for angina. The 2023 AHA/ACC chronic coronary disease guideline recommends a beta blocker, a calcium channel blocker, or a long-acting nitrate for relief of angina (Class 1), and a second antianginal agent from a different class when angina persists (Class 1). A beta blocker is recommended in its own right when LVEF is ≤40%, with or without prior myocardial infarction (Class 1), and verapamil and diltiazem are not used with significant left ventricular dysfunction. Otherwise the choice follows heart rate, blood pressure, conduction disease, suspected vasospasm, and comorbidities; with resting bradycardia, a dihydropyridine is the calcium channel blocker used. The 2024 ESC chronic coronary syndrome guideline recommends initial treatment with a beta blocker or a calcium channel blocker, or both, for most patients (Class 1). It recommends a beta blocker combined with a dihydropyridine when one agent does not control angina (Class 2a).

Combination with a beta blocker. A long-acting dihydropyridine and a beta blocker are complementary: the beta blocker prevents reflex tachycardia, and the dihydropyridine offsets beta-blocker vasoconstriction. Verapamil or diltiazem with a beta blocker risks bradycardia, atrioventricular block, and heart failure and is used with caution, with an electrocardiogram after initiation and after each dose increase. The verapamil-beta blocker combination is avoided in older adults with conduction disease or reduced ejection fraction.

Outcome trials in coronary disease. In ACTION, 7,665 patients with stable angina were randomized to nifedipine extended release 60 mg daily or placebo for a mean of 4.9 years. The primary composite end point did not differ (4.60 versus 4.75 per 100 patient-years; HR 0.97), which established safety, and fewer coronary angiographies and interventions were needed with nifedipine. In CAMELOT, 1,991 patients with coronary disease and normal blood pressure received amlodipine, enalapril, or placebo; cardiovascular events occurred in 16.6% with amlodipine and 23.1% with placebo (HR 0.69), with enalapril in between at 20.2%.

After myocardial infarction. Calcium channel blockers do not reduce mortality after myocardial infarction, and immediate-release nifedipine without a beta blocker is avoided in acute coronary syndromes because reflex tachycardia increases ischemia. In the Multicenter Diltiazem Postinfarction Trial, 2,466 patients were randomized to diltiazem 240 mg daily or placebo. Mortality was similar (167 versus 166 deaths). Diltiazem reduced cardiac events in patients without pulmonary congestion (HR 0.77) and increased them in the 490 patients with pulmonary congestion (HR 1.41), and a later analysis linked diltiazem to late heart failure in patients with reduced ejection fraction. In DAVIT II, verapamil started in the second week after infarction reduced reinfarction (11.0% versus 13.2%) and major events, with the benefit confined to patients without heart failure. In an acute coronary syndrome, a nondihydropyridine calcium channel blocker can relieve ischemia when beta blockers are contraindicated and left ventricular dysfunction, heart failure, and atrioventricular block are absent. This use is described on the non-ST-elevation acute coronary syndrome page.

Dosing for angina. Amlodipine 5 to 10 mg daily (most patients in the labeling studies needed 10 mg), nifedipine extended release 30 to 90 mg daily, diltiazem extended release 120 to 480 mg daily, and verapamil 80 to 120 mg three times daily (immediate release) or the equivalent sustained-release dose are the usual ranges. The resting heart rate target with nondihydropyridines is similar to that with beta blockers, about 55 to 60 beats/min, limited by symptoms and conduction.

Coronary vasospasm, no-reflow, and radial artery spasm

Calcium channel blockers are first-line therapy for vasospastic angina in both US and European practice. Spasm results from hyperreactivity of the vascular smooth muscle in a coronary segment, and L-type blockade prevents it. Treatment uses a long-acting agent at full dose, often taken in the evening because attacks cluster between midnight and early morning. Refractory spasm is treated with a dihydropyridine and a nondihydropyridine agent together, with a long-acting nitrate added. Smoking, stimulants, and triptans are stopped, and nonselective beta blockers, which leave alpha-mediated vasoconstriction unopposed, are avoided. Maximally tolerated calcium channel blockers are indicated in survivors of cardiac arrest from coronary spasm (Class 1), with an implantable cardioverter-defibrillator reasonable when medical therapy fails. Calcium channel blockers are withheld before provocative acetylcholine or ergonovine testing when clinically safe, because they suppress the response. The diagnosis of vasospastic and microvascular angina, and the use of calcium channel blockers in microvascular dysfunction, are covered on the reference page on angina and myocardial infarction with nonobstructive coronary arteries.

Drug-induced vasospasm. Fluoropyrimidine (5-fluorouracil and capecitabine) cardiotoxicity often presents as coronary vasospasm. The infusion is stopped, ischemia is treated with nitrates and a calcium channel blocker, and rechallenge, if any, is planned with oncology under prophylactic vasodilator therapy. Cocaine and methamphetamine cause spasm treated first with a benzodiazepine, then with nitrates and a calcium channel blocker.

No-reflow and radial artery spasm. After percutaneous coronary intervention, slow or absent flow in a patent epicardial artery reflects microvascular obstruction. Intracoronary verapamil, nicardipine, adenosine, or nitroprusside delivered distally improves microvascular flow; intracoronary nitroglycerin relieves epicardial spasm but not true no-reflow. In transradial procedures, verapamil (alone or with nitroglycerin) given into the radial artery sheath prevents radial artery spasm. Intra-arterial verapamil can transiently slow the heart rate and lower pressure.

Hypertrophic cardiomyopathy

Verapamil and diltiazem improve symptoms in hypertrophic cardiomyopathy by slowing the heart rate, lengthening diastolic filling, improving relaxation, and reducing contractility. The 2024 AHA/ACC guideline recommends substituting verapamil or diltiazem when beta blockers are ineffective or not tolerated in obstructive hypertrophic cardiomyopathy (Class 1). The vasodilating action of verapamil can lower afterload and increase the outflow gradient, and in patients with severe dyspnea at rest, hypotension, or a resting gradient above 100 mm Hg, verapamil is potentially harmful (Class 3: Harm). The verapamil label reports deaths from pulmonary edema in patients with severe outflow obstruction and prior left ventricular dysfunction. It also reports sinus bradycardia, second-degree atrioventricular block, and sinus arrest in a series treated with up to 720 mg daily. Combining a beta blocker with a nondihydropyridine calcium channel blocker as treatment for hypertrophic cardiomyopathy has no supporting evidence, although the combination is sometimes used for hypertension.

Dihydropyridines are arterial vasodilators that worsen obstruction, and stopping them, together with other vasodilators and digoxin, may be reasonable in symptomatic obstructive disease (Class 2b). In nonobstructive hypertrophic cardiomyopathy with angina or exertional dyspnea, beta blockers, verapamil, or diltiazem are recommended (Class 1). Patients whose symptoms persist despite a beta blocker or calcium channel blocker are candidates for a cardiac myosin inhibitor, disopyramide with a nodal blocker, or septal reduction therapy. The mavacamten label advises against combining it with verapamil or diltiazem plus a beta blocker because of additive negative inotropy. When ejection fraction falls below 50% in hypertrophic cardiomyopathy, stopping verapamil and diltiazem is reasonable (Class 2a). The full management of the disease is described on the hypertrophic cardiomyopathy page.

In cardiac amyloidosis, nondihydropyridine calcium channel blockers are avoided because the small, stiff ventricle depends on heart rate for output and these drugs can cause profound hypotension, heart failure, and high-grade block (see the cardiac amyloidosis page).

Heart failure: why verapamil and diltiazem are avoided in reduced ejection fraction

The failing ventricle depends on sympathetic support and on every increment of L-type current. Verapamil and diltiazem depress contractility, and the benefit on afterload does not compensate. Nondihydropyridine calcium channel blockers are not recommended in heart failure with reduced ejection fraction (Class 3: Harm in the 2022 AHA/ACC/Heart Failure Society of America guideline). They are also on the list of drugs that worsen heart failure, together with nonsteroidal anti-inflammatory drugs, thiazolidinediones, class IC antiarrhythmics, and dronedarone. The 2022 guideline defines heart failure with reduced ejection fraction as LVEF ≤40%, so the recommendation includes an LVEF of exactly 40%.

Calcium channel blocker trials in ventricular dysfunction. PRAISE-2 was designed to confirm the nonischemic subgroup result of PRAISE and did not. MDPIT, Multicenter Diltiazem Postinfarction Trial; DAVIT II, Danish Verapamil Infarction Trial II; NYHA, New York Heart Association.

Dihydropyridines in reduced ejection fraction. Amlodipine and felodipine are neutral on survival, and they are the calcium channel blockers used when hypertension or angina persists after guideline-directed therapy is optimized. Short-acting nifedipine and older dihydropyridines worsen heart failure through reflex neurohormonal activation and some direct negative inotropy. When symptomatic hypotension limits titration of guideline-directed therapy, calcium channel blockers are among the first drugs reduced or stopped, because they have no prognostic benefit.

Preserved ejection fraction. In heart failure with preserved ejection fraction, calcium channel blockers treat hypertension and, in the case of verapamil and diltiazem, provide rate control in atrial fibrillation, but no calcium channel blocker improves outcomes. Dihydropyridine edema is a frequent confounder in the assessment of congestion, and it does not respond to diuretics. Doses of verapamil or diltiazem beyond those needed for rate control are avoided, and chronotropic incompetence is common in this population (see heart failure with preserved ejection fraction).

Pulmonary arterial hypertension, Raynaud phenomenon, and other vascular uses

Vasoreactive pulmonary arterial hypertension. A small minority of patients with idiopathic, heritable, or drug-associated pulmonary arterial hypertension respond to an acute vasodilator challenge with inhaled nitric oxide or iloprost. A positive response is a fall in mean pulmonary artery pressure of at least 10 mm Hg to 40 mm Hg or less, with unchanged or increased cardiac output. Only these patients receive high-dose calcium channel blockers: nifedipine (titrated toward 120 to 240 mg daily), diltiazem (240 to 720 mg daily), or amlodipine (15 to 30 mg daily). Verapamil is not used. Long-term responders (functional class I or II with sustained hemodynamic improvement after at least 1 year of calcium channel blocker monotherapy) form a recognized subgroup with excellent survival. In the largest series, 12.6% of patients with idiopathic disease were acute responders and only 6.8% were long-term responders. Empirical calcium channel blocker therapy without a positive test causes hypotension, right ventricular failure, and death. Testing and the full treatment algorithm are covered on the pulmonary hypertension and pulmonary arterial hypertension therapy pages.

Raynaud phenomenon. Long-acting dihydropyridines (nifedipine extended release or amlodipine) are the first-line drug therapy for primary and secondary Raynaud phenomenon after cold avoidance and smoking cessation, and they reduce the frequency and severity of attacks. Diltiazem has weaker evidence. Beta blockers can worsen digital vasospasm, which favors a dihydropyridine when hypertension coexists.

Migraine and cluster headache. Verapamil is the standard preventive drug for cluster headache, usually at doses that require electrocardiographic surveillance for PR prolongation and atrioventricular block. It is a second-line migraine preventive with weaker evidence. Flunarizine, a nonselective calcium antagonist used for migraine in other countries, is not available in the United States.

Other uses. Dihydropyridines are also used for esophageal spasm and achalasia in selected patients, and amlodipine controls hypertension caused by calcineurin inhibitors after transplantation. Nimodipine after aneurysmal subarachnoid hemorrhage is described with the dihydropyridines, and obstetric uses of nifedipine are described under special populations.

Adverse effects of calcium channel blockers

Adverse effects follow the tissue selectivity of each group. Dihydropyridine effects arise from arteriolar dilation. Verapamil and diltiazem effects arise from nodal and myocardial depression and, with verapamil, intestinal smooth muscle relaxation.

Adverse effects of calcium channel blockers. Frequencies from US prescribing information for amlodipine and sustained-release verapamil and from a meta-analysis of 25 trials of combination therapy.

Dihydropyridine edema. Edema is the most common reason for stopping a dihydropyridine. It appears as pitting ankle or pretibial edema, usually within weeks of starting or increasing the dose, and is worse with prolonged standing and warm weather. It reflects redistribution of fluid from the vascular space into the interstitium, not sodium retention, which is why loop and thiazide diuretics reduce it little and why it does not indicate heart failure. In ACCOMPLISH, edema occurred in 31.2% of patients taking benazepril plus amlodipine, which shows that renin-angiotensin blockade reduces but does not abolish the problem. Edema that appears with a new drug in a patient with heart failure, venous insufficiency, or kidney disease is attributed to the calcium channel blocker only after these conditions are excluded.

Reflex tachycardia and ischemia. Abrupt vasodilation with short-acting nifedipine can provoke tachycardia and angina, and in a patient with severe coronary disease it can cause infarction. Long-acting agents and concurrent beta blockade avoid this effect.

Withdrawal. Abrupt withdrawal of a calcium channel blocker in vasospastic angina can provoke rebound spasm. Unlike beta blockers, calcium channel blockers do not produce a receptor-upregulation rebound in stable angina, and they provide no protection against beta-blocker withdrawal.

Contraindications and cautions

Contraindications and cautions from US prescribing information and the 2022 heart failure, 2023 atrial fibrillation, 2017 ventricular arrhythmia, and 2024 hypertrophic cardiomyopathy guidelines. HFrEF, heart failure with reduced ejection fraction; LV, left ventricular.

Drug interactions through CYP3A4 and P-glycoprotein

Every calcium channel blocker is a CYP3A4 substrate, so strong inhibitors raise and strong inducers lower their levels. Verapamil and diltiazem are also moderate CYP3A4 inhibitors, and verapamil is a P-glycoprotein inhibitor, so they raise the levels of many other drugs. Dihydropyridines are not clinically important inhibitors, with the exception of modest effects of amlodipine on simvastatin, cyclosporine, and tacrolimus. Pharmacodynamic interactions add to these: combined nodal block with beta blockers, digoxin, amiodarone, ivabradine, and clonidine, and additive hypotension with other vasodilators, phosphodiesterase-5 inhibitors, and alpha blockers. Interactions across all cardiovascular drugs are covered on the cardiovascular drug interactions reference page.

Interactions of calcium channel blockers. Values from US prescribing information for amlodipine, verapamil, diltiazem, and the interacting drugs.

Statins. The simvastatin limits were set by the US Food and Drug Administration after pharmacokinetic studies showed large increases in simvastatin exposure and reports of rhabdomyolysis: simvastatin is limited to 10 mg daily with verapamil or diltiazem and 20 mg daily with amlodipine. The diltiazem label further specifies that the combination is limited to simvastatin 10 mg with diltiazem 240 mg; at 480 mg of diltiazem, modeling predicted an 8- to 9-fold increase in simvastatin exposure. Atorvastatin is metabolized by CYP3A4 but is less affected at usual doses, and rosuvastatin and pravastatin are not CYP3A4 substrates.

Beta-blocker co-administration. Dihydropyridines combine safely with beta blockers in hypertension and angina. Verapamil or diltiazem with a beta blocker is an established cause of symptomatic bradycardia and complete heart block, typically in an older patient with declining kidney function and additional nodal drugs such as digoxin or amiodarone. The first step in such a patient is review and withdrawal of the drugs, and temporary pacing is used only when bradycardia persists or is unstable (see bradycardia and atrioventricular block).

Calcium channel blocker poisoning

Calcium channel blocker poisoning is one of the most lethal cardiovascular drug overdoses. Toxicity begins within hours with immediate-release products and can be delayed by many hours with sustained-release verapamil and diltiazem, which can form concretions in the gut. The full toxicologic management is described on the cardiovascular toxicology and poisoning reference page.

Presentation. Nondihydropyridine overdose produces bradycardia, junctional rhythm, atrioventricular block, hypotension, and cardiogenic shock from combined vasodilation and myocardial depression. Dihydropyridine overdose produces vasodilatory hypotension with reflex tachycardia, although at very high doses selectivity is lost and bradycardia and myocardial depression follow. Hyperglycemia from blocked insulin release, metabolic acidosis, and preserved consciousness despite profound hypotension are characteristic. Hyperglycemia helps separate calcium channel blocker poisoning from beta-blocker poisoning, which tends to cause hypoglycemia. Noncardiogenic pulmonary edema can occur with amlodipine poisoning.

Recommendations for calcium channel blocker poisoning in the 2023 AHA focused update on cardiac arrest and life-threatening toxicity due to poisoning. ECMO, extracorporeal membrane oxygenation.

The 2017 international expert consensus recommends intravenous calcium, high-dose insulin in the presence of myocardial dysfunction, and norepinephrine or epinephrine for shock as first-line therapy. It adds incremental high-dose insulin, pacing for unstable bradycardia, and venoarterial ECMO when shock is refractory. It reserves lipid emulsion for refractory cases, and the 2023 AHA update recommends against its routine use. High-dose insulin acts as an inotrope by improving myocardial glucose uptake in a heart that shifts from fatty acid to carbohydrate metabolism under stress, and large amounts of dextrose and potassium are often needed. Activated charcoal and, for sustained-release products, whole-bowel irrigation are used in patients who present early with a protected airway.

Pregnancy, lactation, older adults, kidney and liver disease, and surgery

Pregnancy. Extended-release nifedipine and labetalol are the preferred antihypertensives for chronic hypertension in pregnancy (Class 1 in the 2025 AHA/ACC guideline), with no evidence favoring one over the other. In the Chronic Hypertension and Pregnancy (CHAP) trial, treatment of mild chronic hypertension to below 140/90 mm Hg (most often with labetalol or nifedipine) reduced the primary composite outcome (30.2% versus 37.0%). The composite included preeclampsia with severe features, medically indicated preterm birth before 35 weeks, placental abruption, and fetal or neonatal death. For severe hypertension in pregnancy (160/110 mm Hg or higher), oral immediate-release nifedipine is one of three first-line agents with intravenous labetalol and hydralazine, given by escalating protocol within 30 to 60 minutes. Amlodipine has less pregnancy data. Verapamil and diltiazem are used for supraventricular tachycardia that does not respond to vagal maneuvers, adenosine, or beta blockade, and for rate control in women without pre-excitation, ventricular dysfunction, or hypotension. Concomitant nifedipine and magnesium sulfate can cause additive hypotension and neuromuscular weakness, and the combination is used with monitoring.

Lactation. Nifedipine, amlodipine, verapamil, and diltiazem pass into breast milk in small amounts, and nifedipine is compatible with breastfeeding.

Older adults. Clearance of amlodipine, nifedipine, felodipine, verapamil, and diltiazem falls with age, and exposure to amlodipine rises by about 40% to 60%, so starting doses are lower. Edema, constipation, orthostatic dizziness, and nodal block are more frequent. The 2023 Beers Criteria list immediate-release nifedipine, because of hypotension and myocardial ischemia, and verapamil and diltiazem in heart failure with reduced ejection fraction, as drugs to avoid in older adults.

Kidney disease. All calcium channel blockers are cleared by the liver and need no dose adjustment for kidney function. Their effect on proteinuria is described with hypertension.

Liver disease. Hepatic impairment prolongs the half-life of every oral agent. Amlodipine starts at 2.5 mg daily, and verapamil is given at about 30% of the usual dose in severe hepatic dysfunction. Clevidipine, cleared by plasma esterases, is unaffected.

Surgery and anesthesia. Long-term oral calcium channel blockers are generally continued through noncardiac surgery, including the morning dose, because withdrawal does not protect against intraoperative hypotension and abrupt withdrawal can provoke spasm in patients with vasospastic angina. Calcium channel blockers add to the hypotensive effect of volatile anesthetics, and verapamil can potentiate neuromuscular blockade. Clevidipine, nicardipine, and esmolol are the usual titratable agents for acute perioperative and postoperative hypertension after cardiac and vascular surgery. Intravenous diltiazem is used for rate control of postoperative atrial fibrillation when ejection fraction is preserved.

History of calcium antagonists and the T-type channel

Verapamil was developed in the early 1960s as a coronary vasodilator. Pharmacologic studies later in that decade showed that verapamil and related compounds mimicked the cardiac effects of calcium withdrawal and could be reversed by added calcium, which gave rise to the term calcium antagonist. Nifedipine and diltiazem followed in the 1970s, and the class entered US practice in the early 1980s for angina and supraventricular tachycardia, and later for hypertension. Amlodipine, with its long half-life, became the dominant agent in the 1990s.

The class has had three setbacks that shaped its present use. The first was the recognition, in post-infarction trials of diltiazem and verapamil, that negative inotropy harms patients with pulmonary congestion or ventricular dysfunction. The second was the dose-related excess mortality with short-acting nifedipine in coronary disease in the mid-1990s, which led to the long-acting formulations and to ALLHAT. The third was mibefradil, a combined T-type and L-type blocker approved in the United States in 1997 for hypertension and angina. It was withdrawn within about a year because strong inhibition of CYP3A4 and CYP2D6 caused dangerous interactions. No selective T-type blocker has since reached US practice. Efonidipine and benidipine, which block both L-type and T-type channels and are used in Japan and parts of Asia, dilate the efferent as well as the afferent glomerular arteriole and lower aldosterone. They have no outcome trials that distinguish them from L-type dihydropyridines.

Sources of error in calcium channel blocker prescribing

• Treating "calcium channel blockers" as one class: a dihydropyridine does not control ventricular rate in atrial fibrillation, and verapamil or diltiazem is harmful in heart failure with reduced ejection fraction (LVEF ≤40%).
• Intravenous verapamil or diltiazem for a wide-complex tachycardia assumed to be supraventricular because the patient is stable: ventricular tachycardia is not excluded by stable blood pressure, and collapse follows.
• Nodal blockade in pre-excited atrial fibrillation: an irregular wide-complex tachycardia with changing QRS morphology is treated with cardioversion, procainamide, or ibutilide.
• Verapamil or diltiazem added to a beta blocker, digoxin, or amiodarone in an older patient without electrocardiographic follow-up: bradycardia and complete heart block are frequent and reversible.
• Simvastatin above 10 mg with verapamil or diltiazem, or above 20 mg with amlodipine: CYP3A4 inhibition raises simvastatin exposure and the risk of myopathy.
• Diuretics prescribed for dihydropyridine edema, or edema taken as heart failure: the edema is capillary, not volume, and responds to dose reduction or renin-angiotensin blockade.
• Immediate-release nifedipine to lower blood pressure quickly outside pregnancy, or in acute coronary syndrome without a beta blocker: abrupt hypotension and reflex tachycardia can cause ischemia.
• A dihydropyridine substituted for an ACE inhibitor or ARB in albuminuric kidney disease: renin-angiotensin blockade lowers intraglomerular pressure and a dihydropyridine does not.
• Calcium channel blockers in pulmonary arterial hypertension without a positive vasoreactivity test: hypotension, right ventricular failure, and death can follow.
• Diltiazem or verapamil started in a transplant recipient without a plan for tacrolimus or cyclosporine levels: CYP3A4 inhibition raises calcineurin inhibitor levels.
• Nimodipine capsule contents drawn up and given intravenously: cardiac arrest and death have been reported.
• Delayed toxicity unrecognized after overdose of a sustained-release product: observation is prolonged, and decontamination is started early in patients who present soon after ingestion.

References

1. Jones DW, Ferdinand KC, Taler SJ, et al. 2025 AHA/ACC/AANP/AAPA/ABC/ACCP/ACPM/AGS/AMA/ASPC/NMA/PCNA/SGIM guideline for the prevention, detection, evaluation and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2025;152:e114–e218. doi:10.1161/CIR.0000000000001356. Corrections: Circulation. 2025;152:e403 (doi:10.1161/CIR.0000000000001396), 2026;153:e1121 (doi:10.1161/CIR.0000000000001436), and 2026;153:e1359 (doi:10.1161/CIR.0000000000001448).
2. Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. Hypertension. 2018;71:e13–e115. doi:10.1161/HYP.0000000000000065
3. Joglar JA, Chung MK, Armbruster AL, et al. 2023 ACC/AHA/ACCP/HRS guideline for the diagnosis and management of atrial fibrillation: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2024;149:e1–e156. doi:10.1161/CIR.0000000000001193. Corrections: Circulation. 2024;149:e167, e936, and e1413.
4. Virani SS, Newby LK, Arnold SV, et al. 2023 AHA/ACC/ACCP/ASPC/NLA/PCNA guideline for the management of patients with chronic coronary disease: a report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Circulation. 2023;148:e9–e119. doi:10.1161/CIR.0000000000001168. Corrections: Circulation. 2023;148:e148 and e186.
5. Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA guideline for the management of heart failure: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2022;145:e895–e1032. doi:10.1161/CIR.0000000000001063. Corrections: Circulation. 2022;145:e1033; 2022;146:e185; 2023;147:e674.
6. Ommen SR, Ho CY, Asif IM, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy: a report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Circulation. 2024;149:e1239–e1311. doi:10.1161/CIR.0000000000001250. Correction: Circulation. 2024;150:e198.
7. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation. 2016;133:e506–e574. doi:10.1161/CIR.0000000000000311
8. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation. 2018;138:e272–e391. doi:10.1161/CIR.0000000000000549
9. Lavonas EJ, Akpunonu PD, Arens AM, et al. 2023 American Heart Association focused update on the management of patients with cardiac arrest or life-threatening toxicity due to poisoning: an update to the American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2023;148:e149–e184. doi:10.1161/CIR.0000000000001161
10. St-Onge M, Anseeuw K, Cantrell FL, et al. Experts consensus recommendations for the management of calcium channel blocker poisoning in adults. Crit Care Med. 2017;45:e306–e315. doi:10.1097/CCM.0000000000002087
11. McEvoy JW, McCarthy CP, Bruno RM, et al. 2024 ESC guidelines for the management of elevated blood pressure and hypertension. Eur Heart J. 2024;45:3912–4018. doi:10.1093/eurheartj/ehae178
12. Vrints C, Andreotti F, Koskinas KC, et al. 2024 ESC guidelines for the management of chronic coronary syndromes. Eur Heart J. 2024;45:3415–3537. doi:10.1093/eurheartj/ehae177
13. Van Gelder IC, Rienstra M, Bunting KV, et al. 2024 ESC guidelines for the management of atrial fibrillation. Eur Heart J. 2024;45:3314–3414. doi:10.1093/eurheartj/ehae176
14. Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43:3618–3731. doi:10.1093/eurheartj/ehac237
15. ALLHAT Officers and Coordinators for the ALLHAT Collaborative Research Group. Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic: the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). JAMA. 2002;288:2981–2997. doi:10.1001/jama.288.23.2981
16. Dahlöf B, Sever PS, Poulter NR, et al. Prevention of cardiovascular events with an antihypertensive regimen of amlodipine adding perindopril as required versus atenolol adding bendroflumethiazide as required, in the Anglo-Scandinavian Cardiac Outcomes Trial-Blood Pressure Lowering Arm (ASCOT-BPLA): a multicentre randomised controlled trial. Lancet. 2005;366:895–906. doi:10.1016/S0140-6736(05)67185-1
17. Jamerson K, Weber MA, Bakris GL, et al. Benazepril plus amlodipine or hydrochlorothiazide for hypertension in high-risk patients (ACCOMPLISH). N Engl J Med. 2008;359:2417–2428. doi:10.1056/NEJMoa0806182
18. Staessen JA, Fagard R, Thijs L, et al. Randomised double-blind comparison of placebo and active treatment for older patients with isolated systolic hypertension (Syst-Eur). Lancet. 1997;350:757–764. doi:10.1016/S0140-6736(97)05381-6
19. Law MR, Morris JK, Wald NJ. Use of blood pressure lowering drugs in the prevention of cardiovascular disease: meta-analysis of 147 randomised trials in the context of expectations from prospective epidemiological studies. BMJ. 2009;338:b1665. doi:10.1136/bmj.b1665
20. Agodoa LY, Appel L, Bakris GL, et al. Effect of ramipril vs amlodipine on renal outcomes in hypertensive nephrosclerosis: a randomized controlled trial (AASK). JAMA. 2001;285:2719–2728. doi:10.1001/jama.285.21.2719
21. Pepine CJ, Handberg EM, Cooper-DeHoff RM, et al. A calcium antagonist vs a non-calcium antagonist hypertension treatment strategy for patients with coronary artery disease: the International Verapamil-Trandolapril Study (INVEST): a randomized controlled trial. JAMA. 2003;290:2805–2816. doi:10.1001/jama.290.21.2805
22. Poole-Wilson PA, Lubsen J, Kirwan BA, et al. Effect of long-acting nifedipine on mortality and cardiovascular morbidity in patients with stable angina requiring treatment (ACTION trial): randomised controlled trial. Lancet. 2004;364:849–857. doi:10.1016/S0140-6736(04)16980-8
23. Nissen SE, Tuzcu EM, Libby P, et al. Effect of antihypertensive agents on cardiovascular events in patients with coronary disease and normal blood pressure: the CAMELOT study: a randomized controlled trial. JAMA. 2004;292:2217–2225. doi:10.1001/jama.292.18.2217
24. Furberg CD, Psaty BM, Meyer JV. Nifedipine: dose-related increase in mortality in patients with coronary heart disease. Circulation. 1995;92:1326–1331. doi:10.1161/01.cir.92.5.1326
25. Multicenter Diltiazem Postinfarction Trial Research Group. The effect of diltiazem on mortality and reinfarction after myocardial infarction. N Engl J Med. 1988;319:385–392. doi:10.1056/NEJM198808183190701
26. Danish Study Group on Verapamil in Myocardial Infarction. Effect of verapamil on mortality and major events after acute myocardial infarction (the Danish Verapamil Infarction Trial II—DAVIT II). Am J Cardiol. 1990;66:779–785. doi:10.1016/0002-9149(90)90351-z
27. Packer M, O'Connor CM, Ghali JK, et al. Effect of amlodipine on morbidity and mortality in severe chronic heart failure (PRAISE). N Engl J Med. 1996;335:1107–1114. doi:10.1056/NEJM199610103351504
28. Packer M, Carson P, Elkayam U, et al. Effect of amlodipine on the survival of patients with severe chronic heart failure due to a nonischemic cardiomyopathy: results of the PRAISE-2 study. JACC Heart Fail. 2013;1:308–314. doi:10.1016/j.jchf.2013.04.004
29. Cohn JN, Ziesche S, Smith R, et al. Effect of the calcium antagonist felodipine as supplementary vasodilator therapy in patients with chronic heart failure treated with enalapril: V-HeFT III. Circulation. 1997;96:856–863. doi:10.1161/01.cir.96.3.856
30. Makani H, Bangalore S, Romero J, et al. Effect of renin-angiotensin system blockade on calcium channel blocker-associated peripheral edema. Am J Med. 2011;124:128–135. doi:10.1016/j.amjmed.2010.08.007
31. Tita AT, Szychowski JM, Boggess K, et al. Treatment for mild chronic hypertension during pregnancy (CHAP). N Engl J Med. 2022;386:1781–1792. doi:10.1056/NEJMoa2201295
32. Zamponi GW, Striessnig J, Koschak A, Dolphin AC. The physiology, pathology, and pharmacology of voltage-gated calcium channels and their future therapeutic potential. Pharmacol Rev. 2015;67:821–870. doi:10.1124/pr.114.009654
33. Abernethy DR, Schwartz JB. Calcium-antagonist drugs. N Engl J Med. 1999;341:1447–1457. doi:10.1056/NEJM199911043411907
34. NORVASC (amlodipine besylate) tablets. US prescribing information. Pfizer Laboratories. DailyMed setid abd6a2ca-40c2-485c-bc53-db1c652505ed.
35. CALAN SR (verapamil hydrochloride) sustained-release tablets. US prescribing information. Pfizer.
36. Verapamil hydrochloride injection. US prescribing information. DailyMed setid def3b9ba-523d-4b83-a80d-fa6f362e111c.
37. Diltiazem hydrochloride injection. US prescribing information. Pfizer (Hospira).
38. CLEVIPREX (clevidipine) injectable emulsion. US prescribing information. Chiesi USA. DailyMed setid f9290625-b723-4eda-bab8-a97bef6041f6.
39. 2023 American Geriatrics Society Beers Criteria Update Expert Panel. American Geriatrics Society 2023 updated AGS Beers Criteria for potentially inappropriate medication use in older adults. J Am Geriatr Soc. 2023;71:2052–2081. doi:10.1111/jgs.18372