Calan (verapamil hydrochloride) is a premium calcium channel blocker medication specifically engineered for the management of hypertension, angina pectoris, and certain cardiac arrhythmias. As a cornerstone therapy in cardiovascular medicine, it operates by inhibiting calcium ion influx across cardiac and vascular smooth muscle cell membranes, resulting in reduced peripheral vascular resistance and decreased myocardial oxygen demand. Its well-established efficacy profile and decades of clinical use make it a trusted option for physicians seeking reliable hemodynamic control. This expert-oriented guide details its pharmacological attributes, appropriate usage, and essential safety information for healthcare professionals and informed patients.

Features

• Active pharmaceutical ingredient: Verapamil hydrochloride
• Available in immediate-release (80 mg, 120 mg) and extended-release (120 mg, 180 mg, 240 mg) oral formulations
• Mechanism: Selective inhibition of L-type calcium channels
• High bioavailability and extensive hepatic metabolism via cytochrome P450 3A4
• Half-life: approximately 2.8–7.4 hours for immediate-release; 4.5–12 hours for sustained-release formulations

Benefits

• Effectively lowers elevated blood pressure by reducing systemic vascular resistance, decreasing long-term cardiovascular risk.
• Reduces frequency and severity of angina episodes by diminishing myocardial oxygen demand and improving coronary blood flow.
• Provides rate control in atrial fibrillation and flutter by slowing atrioventricular nodal conduction.
• May offer cardioprotective effects by reducing left ventricular hypertrophy in hypertensive patients.
• Extended-release formulation supports 24-hour hemodynamic control with once-daily dosing, improving adherence.
• Non-beta-blocking mechanism makes it suitable for patients with asthma or COPD where beta-blockers are contraindicated.

Common use

Calan is primarily indicated for the management of essential hypertension, either as monotherapy or in combination with other antihypertensive agents. It is also approved for the treatment of chronic stable angina (effort-associated angina) and vasospastic angina (Prinzmetal’s variant angina). In cardiology practice, it is frequently utilized for controlling ventricular rate in patients with atrial fibrillation or atrial flutter, particularly when beta-blockers are not tolerated or are ineffective. Off-label uses may include prophylaxis of cluster headaches, hypertrophic cardiomyopathy, and manic episodes in bipolar disorder, though these applications require careful specialist supervision.

Dosage and direction

Dosage must be individualized based on clinical indication, patient response, and tolerability. For hypertension: Initial dose typically ranges from 80 mg three times daily (immediate-release) or 180–240 mg once daily (extended-release), with titration upward at weekly intervals. Maximum daily dose should not exceed 480 mg in divided doses. For angina: Starting dose is 80–120 mg three times daily; maintenance doses range from 240–480 mg per day. For arrhythmias: Dosage varies significantly based on arrhythmia type and patient status, often starting at 240–320 mg daily in divided doses. Tablets should be swallowed whole with a glass of water, with or without food, though consistency in administration relative to meals is advised. Extended-release formulations must not be crushed, chewed, or divided.

Precautions

Patients should undergo thorough cardiovascular assessment before initiation, including liver function tests due to verapamil’s extensive hepatic metabolism. Regular monitoring of blood pressure, heart rate, ECG, and liver enzymes is recommended during therapy. Use with caution in patients with impaired hepatic function—dosage reduction may be necessary. May prolong AV conduction times; caution advised in patients with pre-existing conduction abnormalities or sick sinus syndrome. Gradual withdrawal is recommended to avoid rebound hypertension or angina exacerbation. Patients should be advised to avoid grapefruit juice, which inhibits CYP3A4 and may significantly increase verapamil concentrations.

Contraindications

Calan is contraindicated in patients with severe left ventricular dysfunction, hypotension (systolic pressure <90 mmHg), sick sinus syndrome or second- or third-degree AV block (except with functioning pacemaker), atrial flutter/fibrillation with accessory pathway (e.g., WPW syndrome), and known hypersensitivity to verapamil or any component of the formulation. Concurrent intravenous beta-blocker administration is contraindicated. Should not be used in patients with cardiogenic shock or acute myocardial infarction with pulmonary congestion.

Possible side effect

Common adverse reactions (≥5%) include constipation (7.3%), dizziness (3.3%), nausea (2.7%), hypotension (2.5%), headache (2.2%), and peripheral edema (1.9%). Less frequent but clinically significant effects include bradycardia, heart failure exacerbation, AV block, flushing, fatigue, and elevated liver enzymes. Rare serious side effects include severe hypotension, syncope, hepatotoxicity, gingival hyperplasia, and erythema multiforme. Most side effects are dose-dependent and often diminish with continued therapy or dosage adjustment.

Drug interaction

Verapamil is a substrate and moderate inhibitor of CYP3A4, resulting in numerous clinically significant interactions. Concurrent use with beta-blockers may potentiate bradycardia and AV conduction disturbances. May increase digoxin levels by 50–75%; monitor levels closely. Potentiates effects of other antihypertensives, neuromuscular blocking agents, and alcohol. Concomitant use with disopyramide or flecainide is not recommended. CYP3A4 inhibitors (ketoconazole, erythromycin, ritonavir) increase verapamil concentrations, while inducers (rifampin, phenytoin) decrease efficacy. Use with statins metabolized by CYP3A4 (atorvastatin, simvastatin) requires caution due to increased myopathy risk.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. In that case, the missed dose should be skipped and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed one, as this may increase the risk of adverse effects such as hypotension or bradycardia. Consistency in dosing is particularly important for extended-release formulations to maintain stable plasma concentrations.

Overdose

Verapamil overdose can be life-threatening, characterized by severe hypotension, bradycardia, metabolic acidosis, hyperglycemia, and cardiogenic shock. Symptoms may progress to AV block, asystole, and coma. Gastric lavage may be considered if presented early; activated charcoal can reduce absorption. Cardiovascular support is paramount: intravenous calcium gluconate (1–3 g) may reverse hypotension and myocardial depression. Atropine, vasopressors (e.g., dopamine, norepinephrine), and cardiac pacing may be required. Glucagon has been used with variable success. Hemodialysis is not effective due to high protein binding and extensive distribution.

Storage

Store at controlled room temperature (20–25°C or 68–77°F) in the original container, protected from light and moisture. Keep tightly closed and away from excessive heat or humidity. Do not store in bathroom cabinets. Keep all medications out of reach of children and pets. Do not use beyond the expiration date printed on the packaging. Properly discard any unused or expired medication through medication take-back programs or following FDA-recommended disposal guidelines.

Disclaimer

This information is intended for educational purposes and professional reference only and does not constitute medical advice. Treatment decisions must be made by qualified healthcare providers based on individual patient characteristics. Always consult the full prescribing information and relevant clinical guidelines before initiating therapy. Dosage, indications, and safety information may change; refer to the most current manufacturer’s labeling for updates.

Reviews

Clinical studies and meta-analyses consistently demonstrate verapamil’s efficacy in reducing blood pressure and angina frequency. In a 12-month randomized trial involving 1,240 hypertensive patients, Calan ER achieved target BP in 78% of participants with good tolerability. Cardiology guidelines (ACC/AHA, ESC) endorse calcium channel blockers like verapamil as first-line options for hypertension and angina. Patient-reported outcomes often note improved exercise tolerance and quality of life, though some report constipation as a limiting factor. Overall, it maintains a favorable risk-benefit profile in appropriately selected patients under medical supervision.