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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce the influx of calcium ions into cardiac and vascular smooth muscle cells. This leads to vasodilation and/or decreased cardiac contractility, heart rate, and conduction velocity. ## Primary Indications * Hypertension * Angina pectoris (stable, vasospastic) * Certain supraventricular arrhythmias (e.g., atrial fibrillation, atrial flutter with rapid ventricular response) * Raynaud's phenomenon ## Adult Dosing Dosing varies significantly by specific agent and indication. Refer to specific drug monographs for detailed dosing. **Dihydropyridines (DHPs)** * **Amlodipine:** 5-10 mg orally once daily (max 10 mg/day). * **Nifedipine (extended-release):** 30-90 mg orally once daily (max 120 mg/day). * **Felodipine:** 5-10 mg orally once daily (max 10 mg/day in adults). **Non-Dihydropyridines (Non-DHPs)** * **Verapamil:** * Hypertension: 80-120 mg orally two to three times daily (max 480 mg/day). * Angina/Arrhythmias: 40-120 mg orally two to three times daily (max 480 mg/day). * **Diltiazem:** * Hypertension: 180-360 mg orally once daily (extended-release) or 30-60 mg orally three to four times daily (immediate-release). * Angina: 30-90 mg orally three to four times daily (immediate-release) or 120-360 mg orally once daily (extended-release). * Arrhythmias: 0.25 mg/kg IV bolus, followed by 5-10 mg/kg IV infusion over 15 minutes, may repeat bolus and infusion dose. ## Pediatric Dosing Limited data for pediatric use, and dosing often relies on expert consensus or specific protocols. * **Amlodipine:** Generally initiated at 0.1 mg/kg orally once daily (max 5 mg/day). * **Verapamil:** Dosing varies by age and indication, typically starting at lower doses and titrating slowly. Consult pediatric cardiology resources. * **Diltiazem:** Used for arrhythmias, often at 0.5-2 mg/kg IV over 15 minutes, followed by infusion of 0.1-0.2 mg/kg/hr. Oral doses vary. ## Dose Adjustments * **Hepatic Impairment:** Reduce dose by 25-50% for non-DHPs and amlodipine. Monitor closely. * **Renal Impairment:** Generally no dose adjustment needed for DHPs. Non-DHPs may require dose reduction in severe impairment. ## Contraindications * Hypersensitivity to the specific drug. * Severe hypotension. * Cardiogenic shock. * Second- or third-degree AV block (unless a functioning pacemaker is in place) for non-DHPs. * Sick sinus syndrome (unless a functioning pacemaker is in place) for non-DHPs. * Acute myocardial infarction with pulmonary congestion (for DHPs). * Congestive heart failure (caution with non-DHPs, particularly verapamil). ## Adverse Effects * **Common:** Peripheral edema (especially DHPs), headache, flushing, dizziness, fatigue, constipation (more common with verapamil). * **Cardiovascular:** Bradycardia, hypotension, AV block, exacerbation of heart failure. * **Other:** Gingival hyperplasia. ## Key Drug Interactions * **Beta-blockers:** Additive negative chronotropic and inotropic effects; increased risk of bradycardia and heart block. Avoid IV verapamil/diltiazem with IV beta-blockers. * **CYP3A4 Inhibitors/Inducers:** May alter CCB levels. Examples include grapefruit juice (inhibitor), azole antifungals, macrolide antibiotics, rifampin, and carbamazepine. * **Digoxin:** Non-DHPs can increase digoxin levels by reducing its renal clearance. * **Statins:** Some statins (simvastatin, atorvastatin) are CYP3A4 substrates and may have increased levels when co-administered with certain CCBs. ## Monitoring * Blood pressure and heart rate. * ECG for evidence of AV block or bradycardia. * Signs and symptoms of heart failure. * Renal and hepatic function. * Serum digoxin levels (if co-administered). ## Clinical Pearls * DHPs are generally more potent vasodilators and can cause reflex tachycardia. Non-DHPs have greater effects on cardiac conduction and contractility. * Start low and titrate slowly, especially in elderly patients or those with impaired cardiac function. * Constipation is a common side effect of verapamil and can often be managed with stool softeners. * Grapefruit juice should be avoided with most CCBs due to potential for significant drug interactions. *** *Disclaimer: This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and a qualified healthcare professional for any medical decisions or treatment.*