Calcium%2520channel%2520blockers

# Calcium Channel Blockers ## Overview - Calcium channel blockers (CCBs) inhibit L-type calcium channels in cardiac and vascular smooth muscle. - **Dihydropyridines** (e.g., amlodipine, nifedipine) are more vasoselective; **non-dihydropyridines** (verapamil, diltiazem) have greater cardiac effects (negative inotropy, chronotropy, dromotropy). ## Primary Indications - Hypertension, stable angina, vasospastic (Prinzmetal) angina, atrial fibrillation/flutter (rate control), supraventricular tachycardia, Raynaud phenomenon. ## Adult Dosing - **Amlodipine**: 2.5–10 mg once daily; max 10 mg/day. - **Nifedipine extended-release**: 30–90 mg once daily; max 120 mg/day. Avoid immediate-release for hypertension. - **Verapamil immediate-release**: 80–120 mg three times daily; extended-release: 120–480 mg once daily. - **Diltiazem immediate-release**: 60–120 mg three to four times daily; extended-release: 120–540 mg once daily (various formulations). ## Pediatric Dosing - **Amlodipine**: 0.05–0.2 mg/kg once daily; max 5 mg (adolescents up to 10 mg). - **Nifedipine** (short-acting for hypertensive emergencies): 0.25–0.5 mg/kg/dose every 4–6 hours; max single dose 10 mg. - Verapamil/diltiazem: limited data; use only if clearly indicated and under specialist guidance. Dosing depends on local protocols. ## Dose Adjustments - **Hepatic impairment**: Reduce doses (particularly verapamil, diltiazem); start at lowest dose. - **Elderly**: Start at low end of dose range; titrate slowly. - **Renal impairment**: No routine adjustment, but monitor for hypotension/edema. ## Contraindications - Hypotension (systolic <90 mmHg), sick sinus syndrome (without pacemaker), second/third-degree AV block, severe left ventricular dysfunction (especially non-DHP), cardiogenic shock. - Non-DHP CCBs contraindicated in atrial fibrillation/flutter with accessory bypass tract (e.g., WPW). - Avoid immediate-release nifedipine for chronic hypertension. ## Adverse Effects - **Dihydropyridines**: Peripheral edema, headache, flushing, palpitations, dizziness. - **Non-dihydropyridines**: Bradycardia, AV block, constipation (verapamil common), heart failure exacerbation, gingival hyperplasia. ## Key Drug Interactions - **Beta-blockers**: Additive bradycardia, AV block, negative inotropy (especially with non-DHP). - **CYP3A4 inhibitors** (e.g., ketoconazole, macrolides, grapefruit juice): increase CCB levels → toxicity. - **Strong CYP3A4 inducers** (e.g., rifampin, phenytoin): reduce CCB efficacy. - Avoid verapamil/diltiazem with dronedarone, ivabradine, or beta-blockers in heart failure. ## Monitoring - Blood pressure, heart rate, ECG (PR interval for non-DHP), signs of heart failure or edema. Assess hepatic function if on high doses or in hepatic disease. ## Clinical Pearls - Amlodipine is considered safe in heart failure with reduced ejection fraction (HFrEF); non-DHP CCBs are contraindicated in HFrEF. - Verapamil has the highest protein binding; significant drug interactions. - Use extended-release formulations for sustained control and better tolerance. - Grapefruit juice should be avoided with most CCBs due to variable CYP3A4 inhibition. - For hypertensive urgencies, avoid sublingual nifedipine (risk of precipitous hypotension). --- **Disclaimer:** This information is a concise summary and does not replace current prescribing guidelines. Always verify doses, indications, and contraindications against the most recent prescribing information, local protocols, and patient-specific factors before use.