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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) inhibit the influx of calcium ions into cardiac and vascular smooth muscle. They are categorized into two main classes: **Dihydropyridines** (e.g., amlodipine, nifedipine), which act primarily as potent vasodilators, and **Non-dihydropyridines** (e.g., diltiazem, verapamil), which exert significant negative chronotropic and inotropic effects on the myocardium. ## Primary Indications * **Dihydropyridines:** Hypertension, stable angina, Prinzmetal's angina. * **Non-dihydropyridines:** Supraventricular tachycardias (SVT), atrial fibrillation rate control, hypertension, angina. ## Adult Dosing * **Amlodipine:** 2.5 mg to 10 mg PO once daily. Max 10 mg/day. * **Nifedipine (Extended Release):** 30 mg to 90 mg PO once daily. Max 90 mg/day. * **Diltiazem (Extended Release):** 120 mg to 360 mg PO once daily. Max 360 mg/day. * **Diltiazem (IV):** 0.25 mg/kg bolus, followed by 5–15 mg/hr infusion (refer to institutional protocol). * **Verapamil (Extended Release):** 120 mg to 480 mg PO daily in divided doses. Max 480 mg/day. ## Pediatric Dosing *Dosing is highly variable and often off-label; consult current institutional or pediatric references (e.g., Harriet Lane).* * **Amlodipine:** 0.06 to 0.5 mg/kg/day (start low, titrate to effect). Max 10 mg/day. * **Diltiazem:** 1.5 to 3.5 mg/kg/day in 3–4 divided doses (Immediate Release). *Extended release not recommended for small children.* ## Dose Adjustments * **Hepatic Impairment:** Reduce initial doses of diltiazem and verapamil by 50% or more, as they are highly metabolized by the liver. Monitor closely for hypotension. * **Renal Impairment:** No standard dose reduction required; however, monitor for fluid retention in advanced stages. ## Contraindications * **Non-dihydropyridines:** Severe left ventricular dysfunction (HFrEF), second- or third-degree AV block (without pacemaker), sick sinus syndrome, severe hypotension. * **Dihydropyridines:** Cardiogenic shock (caution). ## Adverse Effects * **Dihydropyridines:** Peripheral edema (dose-dependent), reflex tachycardia, flushing, headache, gingival hyperplasia. * **Non-dihydropyridines:** Bradycardia, AV block, constipation (especially verapamil), worsening of heart failure. ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers:** CCBs are CYP3A4 substrates; avoid strong inhibitors (e.g., clarithromycin, ketoconazole) to prevent toxicity. * **Beta-Blockers:** Concomitant use with non-dihydropyridines significantly increases the risk of symptomatic bradycardia and heart block. * **Digoxin:** Verapamil and diltiazem increase serum digoxin concentrations; reduce digoxin dose by 50% upon initiation. ## Monitoring * **Blood Pressure:** Monitor standing and sitting pressures. * **Heart Rate:** Mandatory for non-dihydropyridines. * **EKG:** Monitor PR interval for non-dihydropyridines (risk of heart block). * **Signs of Heart Failure:** Baseline and periodic assessment of respiratory status and lower extremity edema. ## Clinical Pearls * Never use immediate-release nifedipine for acute hypertension; it can cause unpredictable, profound hypotension, reflex tachycardia, and myocardial ischemia. * Diltiazem and verapamil are effectively "negative inotropes." Avoid in patients with clinical evidence of systolic heart failure. * Amlodipine is often the preferred agent for hypertensive patients with comorbid heart failure due to its neutral effect on mortality. *** **Educational Disclaimer:** This information is for educational purposes only. Drug dosing, contraindications, and clinical protocols vary by institution and patient variables. Always verify current prescribing information, package inserts, and local institutional guidelines before administering any medication.