Medication Update

Calcium Channel Blockers

Mode of Action

Inhibition of the influx of calcium through slow channels in the vascular smooth muscles and myocardial tissue during depolarization. This results in systemic and coronary artery vasodilation, decreased myocardial contractility, and sinoatrial (SA) and atrioventricular (AV) nodal depression.

Contraindications

Hypersensitivity to the particular calcium channel blocker agent. Second or third degree heart block, Wolfe-Parkinson-White syndrome, or sick sinus syndrome. Symptomatic hypotension. Congestive heart failure or coronary artery disease.

Adverse Effects

Cardiovascular effects include AV heart block and peripheral edema. Central nervous system effects include headache and dizziness. Gingival hyperplasia has been reported with some agents. GI disturbances include constipation.

Drug-Drug Interactions

Beta blockers, digoxin, and amiodarone may have additive cardiovascular effects when used in combination with calcium channel blockers. Some agents may inhibit the clearance of digoxin, resulting in increased risk of digoxin toxicity. Cimetidine in combination with nifedipine or diltiazem may result in increased cardiovascular toxicity. Carbemazeine, phenytoin, and tacrolimus metabolism may be inhibited by concomitant use with diltiazem. Cyclosporine metabolism may be inhibited by certain calcium channel blockers, resulting in an increased risk of cyclosporine toxicity. Azole antifungal agents may increase the potential for cardiovascular toxicity of dihydropyridine calcium channel blockers due to inhibition of metabolism. Hypotension may occur when calcium channel blockers are used in conjunction with fentanyl anesthesia. Theophylline metabolism is inhibited by diltiazem and alterations in theophylline serum concentrations (increase or decrease) can occur with nifedipine use.

Calcuim channel blockers interact with numerous agents, and these interactions vary depending upon the agent selected.

Drug-Food Interactions

Diltiazem should be taken before meals. Grapefruit juice should be avoided with felpodpine use.

Available Agents

diltiazem: Cardizem, Cardizem CD, Cardizem SR, Dilacor XR, Tiazac.

verapamil: Calan.

amlodipine: Norvasc.

felodipine: Plendil.

isradipine: DynaCirc.

nicardipine: Cardene, Cardene SR.

nifedipine: Adalat, Adalat CC, Procardia, Procardia XL.

Recommended Dose

Depends upon the agent chosen.

Dosage Forms Available

Available in many different dosage forms and strengths.

Manufacturer

Various.

References

1. DRUGDEX System. Hutchison TA, Shahan DR (ed). MICROMEDEX Inc., Greenwood Village, Colo (Edition expires 2001)

2. Martindale: The Complete Drug Reference. Sweetman S (ed). London, Pharmaceutical Press. Electronic version.

South Med J. 2001;94(11) © 2001  Lippincott Williams & Wilkins

Cite this: Medication Update - Medscape - Nov 01, 2001.