Isoptin Khk Retard (Verapamil Hydrochloride)

• Verapamil Hydrochloride acts on cardiovascular disorders that involve abnormal heart rhythm, elevated blood pressure, or myocardial oxygen demand.
• Hypertension: lowers systemic blood pressure by vasodilation and reduced cardiac contractility.
• Angina pectoris: relieves chest pain by decreasing myocardial oxygen consumption.
• Supraventricular tachyarrhythmias: controls heart rate by slowing atrioventricular nodal conduction.

• Verapamil selectively blocks L‑type calcium channels in cardiac and vascular smooth muscle cells, reducing intracellular calcium influx. This leads to decreased myocardial contractility, slowed AV‑node conduction, and vasodilation of coronary and peripheral vessels, thereby lowering blood pressure and heart rate while improving myocardial oxygen balance.

Verapamil may cause a range of adverse reactions, from mild to serious.

Common Side Effects

• Headache
• Dizziness
• Constipation
• Flushing
• Peripheral edema
• Nausea

Serious or Rare Side Effects

• Severe hypotension
• Bradycardia
• Heart block (second‑ or third‑degree)
• Hepatotoxicity
• Allergic reactions such as rash or angioedema
• Worsening heart failure

• Before initiating therapy, clinicians should evaluate patient‑specific risk factors and monitor for potential complications.
• Blood pressure monitoring: check for hypotension especially after dose changes.
• Cardiac function assessment: avoid in patients with severe heart failure.
• Conduction system evaluation: use caution in patients with existing AV‑node block.
• Drug interaction review: assess concomitant medications that affect CYP3A4 metabolism.
• Renal/hepatic impairment: consider dose adjustment in significant organ dysfunction.
• Store at ambient temperature: keep below 25°C in the original container, protected from moisture.

Verapamil interacts with several medicines; some combinations should be avoided while others require careful monitoring.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may raise verapamil plasma levels.
• Digoxin: increased risk of digoxin toxicity.
• Beta‑blockers: additive bradycardia and hypotension.
• Simvastatin: elevated statin concentrations, risk of myopathy.
• Amiodarone: heightened chance of AV‑node block.

Moderate Interactions (Monitor Closely)

• Diltiazem: additive cardiac depressant effects.
• Rifampin: may reduce verapamil concentrations.
• NSAIDs: potential impact on renal function.
• Diuretics: can potentiate hypotensive response.
• Calcium supplements or antacids: may diminish verapamil absorption.