Isoptin Sr (Verapamil Hydrochloride)

• Verapamil is a calcium channel blocker used to treat several cardiovascular conditions.
• Hypertension: lowers systemic arterial pressure by inhibiting calcium influx in vascular smooth muscle, leading to vasodilation.
• Angina pectoris: reduces myocardial oxygen demand and improves coronary perfusion by decreasing heart rate, contractility, and arterial tone.
• Cardiac arrhythmias: stabilizes cardiac electrical conduction and controls ventricular rate in supraventricular tachycardia and atrial fibrillation by slowing AV nodal conduction.

• Verapamil selectively blocks L‑type calcium channels in cardiac myocytes and vascular smooth muscle. By reducing calcium entry, it decreases myocardial contractility, slows atrioventricular nodal conduction, and promotes vasodilation of arterial vessels, which together lower blood pressure and alleviate ischemic heart pain. The reduction in intracellular calcium also diminishes peripheral vascular resistance and modestly lowers heart rate, contributing to its antihypertensive and anti‑anginal actions.

Verapamil may be associated with a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Constipation: mild gastrointestinal discomfort and reduced bowel movements.
• Dizziness: transient light‑headedness, especially upon standing.
• Headache: mild to moderate tension‑type headache.
• Peripheral edema: swelling of the ankles or feet.
• Nausea: occasional feeling of sickness.
• Flushing: transient warmth and redness of skin.

Serious or Rare Side Effects

• Bradycardia: significant slowing of heart rate requiring medical attention.
• Hypotension: marked drop in blood pressure leading to fainting.
• Heart block: impairment of atrioventricular conduction that may necessitate a pacemaker.

• When prescribing Verapamil, several safety considerations should be observed.
• Dose adjustment: reduce dose in patients with hepatic impairment.
• Monitoring: regularly assess blood pressure and heart rate during therapy.
• Drug interactions: avoid concomitant use with strong CYP3A4 inhibitors without supervision.
• Cardiovascular disease: use cautiously in patients with severe left ventricular dysfunction.
• Pregnancy and lactation: safety not established; consider risk‑benefit before prescribing.
• Store at ambient temperature: keep below 25°C in original container, protect from moisture.

Verapamil interacts with several medicines; awareness of the interaction level is essential.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase verapamil plasma levels and risk of toxicity.
• Beta‑blockers (e.g., propranolol): can cause excessive bradycardia or AV block.
• Digoxin: increased risk of digoxin toxicity due to elevated serum concentrations.

Moderate Interactions (Monitor Closely)

• Carbamazepine: may reduce verapamil effectiveness.
• Rifampin: induces metabolism, lowering verapamil levels.
• Statins metabolized by CYP3A4 (e.g., simvastatin): may increase statin exposure, risk of myopathy.