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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce myocardial oxygen demand and increase oxygen supply by blocking the influx of calcium into cardiac and vascular smooth muscle cells. This leads to vasodilation and, for non-dihydropyridines, decreased heart rate and contractility. They are categorized into dihydropyridines (e.g., amlodipine, nifedipine) and non-dihydropyridines (e.g., verapamil, diltiazem). ## Primary Indications * Hypertension * Angina pectoris (stable and vasospastic) * Certain supraventricular tachyarrhythmias (non-dihydropyridines) * Raynaud's phenomenon ## Adult Dosing Dosing is highly individualized and depends on the specific agent, indication, and patient response. Local protocols may also influence dosing. * **Amlodipine (Dihydropyridine):** * Hypertension: Start 5 mg orally once daily. Usual range 5-10 mg orally once daily. Maximum 10 mg orally once daily. * Angina: Start 5-10 mg orally once daily. Maximum 10 mg orally once daily. * **Nifedipine (Extended-Release - Dihydropyridine):** * Hypertension: Start 30-60 mg orally once daily. Usual range 30-120 mg orally once daily. * Angina: Start 30-60 mg orally once daily. Usual range 30-120 mg orally once daily. * **Verapamil (Non-dihydropyridine):** * Hypertension: Start 80 mg orally twice daily or 180 mg controlled-release orally once daily. Usual range 240-480 mg orally per day in divided doses. * Angina: Start 80 mg orally three times daily. Usual range 240-480 mg orally per day in divided doses. * Arrhythmias: IV doses are highly protocol-dependent (e.g., 2.5 mg IV bolus, repeat 5 mg IV bolus if needed, max 10 mg). Oral doses vary by indication. * **Diltiazem (Non-dihydropyridine):** * Hypertension: Start 30-60 mg orally two to three times daily or 180-240 mg extended-release orally once daily. Usual range 180-360 mg orally per day in divided doses for immediate-release, or 120-540 mg orally per day for extended-release. * Angina: Start 30-60 mg orally three times daily. Usual range 180-360 mg orally per day in divided doses. * Arrhythmias: IV doses are highly protocol-dependent (e.g., 0.25 mg/kg IV bolus, followed by infusion at 5-15 mg/kg/hr). Oral doses vary. ## Pediatric Dosing Pediatric dosing for CCBs is less established and often requires consultation with a pediatric specialist or adherence to specific institutional protocols. * **Amlodipine:** Hypertension: 0.05 mg/kg orally once daily, not to exceed 5 mg/day. * **Verapamil:** Supraventricular tachycardia: IV doses are protocol-dependent. * Dosing for other CCBs in pediatrics is not well-established and typically reserved for specific indications under expert guidance. ## Dose Adjustments * **Renal Impairment:** Generally, CCBs do not require significant dose adjustment for mild to moderate renal impairment, but caution is advised. Hemodialysis does not significantly clear most CCBs. * **Hepatic Impairment:** Non-dihydropyridines (verapamil, diltiazem) are extensively metabolized by the liver and may require significant dose reduction. Dihydropyridines also undergo hepatic metabolism and may require dose adjustment. Start with lower doses and titrate cautiously. ## Contraindications * Hypersensitivity to the drug or its components. * Severe hypotension. * Cardiogenic shock. * (Non-dihydropyridines) Sick sinus syndrome, second- or third-degree AV block without a pacemaker. * (Non-dihydropyridines) Congestive heart failure with reduced ejection fraction. * Acute myocardial infarction with pulmonary congestion. ## Adverse Effects Common adverse effects include: * **Dihydropyridines:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia. * **Non-dihydropyridines:** Bradycardia, AV block, constipation (especially verapamil), hypotension, dizziness, nausea. * Other: Gingival hyperplasia (long-term use), rash, liver enzyme elevations. ## Key Drug Interactions * **Beta-blockers:** Additive myocardial depression and AV conduction slowing. Avoid concurrent use of non-dihydropyridines and IV beta-blockers. * **CYP3A4 Inhibitors/Inducers:** Potentiate or reduce CCB levels. Examples: grapefruit juice (inhibitor, increases levels), rifampin (inducer, decreases levels). * **Digoxin:** Non-dihydropyridines can increase digoxin levels. * **Statins:** Increased risk of myopathy with simvastatin and lovastatin. * **Potassium-Lowing Agents:** Increased risk of hypokalemia and arrhythmias. ## Monitoring * Blood pressure and heart rate (regularly). * Electrocardiogram (ECG) for AV conduction and heart rate, especially with non-dihydropyridines. * Signs and symptoms of heart failure. * Electrolytes and renal/hepatic function tests periodically. * For verapamil, monitor for constipation. ## Clinical Pearls * Dihydropyridines are generally preferred for vasodilation in hypertension and angina without significant bradycardia or AV nodal dysfunction. * Non-dihydropyridines are useful when rate control in addition to blood pressure lowering is desired (e.g., atrial fibrillation with rapid ventricular response) or for vasospastic angina. * Short-acting nifedipine is generally avoided due to risk of reflex tachycardia and precipitating angina or MI. Use extended-release formulations. * Constipation is a common and dose-limiting side effect with verapamil. * Sudden discontinuation of CCBs may lead to rebound hypertension or angina. Taper gradually. *** **Disclaimer:** This information is intended for healthcare professionals. Always consult the current official prescribing information and relevant clinical guidelines before making any therapeutic decisions. Dosing and recommendations may vary based on specific patient factors and local protocols.