Verapamilo

Verapamilo, the Spanish and Italian name for verapamil, is a calcium channel blocker used in cardiovascular medicine. It belongs to the phenylalkylamine class and acts mainly on L-type calcium channels in cardiac tissue and vascular smooth muscle. By limiting calcium influx, it reduces heart rate, slows AV nodal conduction, decreases myocardial contractility, and lowers peripheral vascular resistance.

Mechanism of action and effects: Verapamilo produces negative inotropic, chronotropic, and dromotropic effects. In the heart, these actions slow conduction through the AV node and can terminate or prevent certain supraventricular tachycardias. In the vasculature, it causes vasodilation, which lowers blood pressure. The overall effect is reduced myocardial oxygen demand and improved blood flow in certain conditions.

Medical uses: It is used for chronic stable angina and vasospastic (Prinzmetal) angina, essential hypertension, and certain arrhythmias such as atrial fibrillation or flutter with rapid ventricular response. It may be chosen when beta blockers are contraindicated or not tolerated, and sometimes as part of combination therapy with other antihypertensives or antiarrhythmics, under careful monitoring.

Administration and pharmacokinetics: Verapamilo is available in immediate-release and extended-release oral formulations and as an intravenous preparation. Oral bioavailability is limited by first-pass metabolism and varies with formulation. It is extensively metabolized in the liver, mainly by CYP3A4, with multiple active and inactive metabolites. The elimination half-life is typically several hours, influenced by age, liver function, and drug interactions.

Adverse effects and interactions: Common side effects include constipation, dizziness, flushing, edema, and bradycardia. Hypotension and heart block can occur, especially with higher doses or in combination with other negative chronotropic agents such as beta blockers or digoxin. Interactions with CYP3A4 inhibitors or inducers can alter levels of verapamilo; caution is advised with other calcium channel blockers and certain antiarrhythmics.

Contraindications and cautions: Verapamilo is not recommended in severe bradycardia, advanced AV block without a functioning pacemaker, sick sinus syndrome, decompensated heart failure with reduced ejection fraction, or severe hypotension. Use during pregnancy or lactation requires careful risk-benefit assessment.