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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 vascular smooth muscle and/or myocardial cells. This leads to vasodilation and decreased myocardial contractility and heart rate, depending on the specific agent. They are broadly categorized into dihydropyridines (e.g., amlodipine, nifedipine) and non-dihydropyridines (e.g., verapamil, diltiazem). ## Primary Indications * Hypertension * Angina pectoris (stable and vasospastic) * Supraventricular tachyarrhythmias (non-dihydropyridines) * Raynaud's phenomenon ## Adult Dosing Dosing varies significantly by agent and indication. * **Amlodipine:** * Hypertension: 5-10 mg orally once daily. Maximum: 10 mg daily. * Angina: 5-10 mg orally once daily. Maximum: 10 mg daily. * **Nifedipine (extended-release):** * Hypertension: 30-60 mg orally once daily. Maximum: 120 mg daily. * **Verapamil:** * Hypertension: 80-120 mg orally two to three times daily. Maximum: 480 mg daily. * Angina: 80-120 mg orally two to three times daily. Maximum: 480 mg daily. * Supraventricular tachyarrhythmias (IV): 2.5-5 mg IV over 2 minutes, may repeat with 5-10 mg IV after 15-30 minutes for a maximum of 20 mg. * **Diltiazem:** * Hypertension: 30-90 mg orally three to four times daily. Extended-release formulations: 120-360 mg orally once or twice daily. Maximum (immediate-release): 360 mg daily. Maximum (extended-release): 540 mg daily. * Angina: Similar to hypertension dosing. * Supraventricular tachyarrhythmias (IV): 0.25 mg/kg IV bolus over 2 minutes, may repeat with 0.35 mg/kg IV after 15 minutes. Continuous infusion: 5-15 mg/hour. Consult specific drug monographs for exact dosing for other CCBs and indications. ## Pediatric Dosing Pediatric dosing is less established and often requires careful titration based on clinical response and tolerance. Consult specialized pediatric pharmacotherapy resources for specific recommendations. * **Amlodipine:** Hypertension: 0.1-0.2 mg/kg orally once daily (maximum 5 mg daily for children <12 years; maximum 10 mg daily for adolescents). * **Verapamil:** Pediatric use is generally not recommended except in specific, refractory supraventricular tachycardias where expert consultation is advised. IV doses for infants are typically 0.1 mg/kg. Children 1-15 years: IV dose 0.1-0.3 mg/kg (max 5 mg). ## Dose Adjustments * **Hepatic Impairment:** Dose reduction is often necessary as CCBs are extensively metabolized by the liver. Start with lower doses and titrate cautiously. * **Renal Impairment:** Generally do not require routine dose adjustment unless severe renal impairment is present. Dihydropyridines may require caution. ## Contraindications * Known hypersensitivity to the drug or components. * Sick sinus syndrome (except in patients with pacemakers). * Second- or third-degree atrioventricular block (except in patients with pacemakers) for non-dihydropyridines. * Severe aortic stenosis (for non-dihydropyridines, due to risk of reducing cardiac output). * Cardiogenic shock (for non-dihydropyridines). * Acute myocardial infarction with pulmonary congestion (for prolonged-acting nifedipine). ## Adverse Effects * **Common:** Peripheral edema, headache, dizziness, flushing, constipation (especially with verapamil), nausea. * **Cardiovascular:** Bradycardia, hypotension, AV block, heart failure exacerbation, arrhythmias. * **Other:** Rash, gingival hyperplasia. ## Key Drug Interactions * **Beta-blockers:** Increased risk of bradycardia, AV block, and heart failure (especially non-dihydropyridines). * **Grapefruit Juice:** Can significantly increase plasma concentrations of some CCBs (e.g., amlodipine, verapamil, diltiazem), increasing the risk of hypotension. Avoid concurrent use. * **CYP3A4 Inhibitors/Inducers:** Strong inhibitors (e.g., azole antifungals, macrolide antibiotics, protease inhibitors) can increase CCB levels. Strong inducers (e.g., rifampin, carbamazepine) can decrease CCB levels. * **Digoxin:** Non-dihydropyridines can increase digoxin levels. * **Statins:** Some statins (e.g., simvastatin, atorvastatin) can have their metabolism inhibited by CCBs, leading to increased statin levels and risk of myopathy. Consult product labeling for recommended dose adjustments. ## Monitoring * Blood pressure. * Heart rate and rhythm. * Signs and symptoms of heart failure (e.g., dyspnea, edema). * Electrolytes (especially if diuretics are used concurrently). * Renal and hepatic function. ## Clinical Pearls * Dihydropyridines (e.g., amlodipine, nifedipine) are primarily peripheral vasodilators and have less effect on heart rate and contractility. They are generally preferred for hypertension and chronic stable angina. * Non-dihydropyridines (e.g., verapamil, diltiazem) have significant negative chronotropic and inotropic effects and are useful for rate control in supraventricular tachycardias and vasospastic angina. * Because of the risk of excessive negative chronotropic effects, non-dihydropyridines should be used with extreme caution or avoided in patients taking beta-blockers. * Constipation is a common and dose-limiting side effect of verapamil; consider switching agents or utilizing stool softeners. * Rapid-acting oral nifedipine is generally avoided due to risk of reflex tachycardia and precipitating myocardial ischemia or infarction. Extended-release formulations are preferred for chronic use. *** This information is intended for healthcare professionals and does not substitute for the most current prescribing information from the manufacturer or specialized resources. Always verify drug dosages, indications, contraindications, drug interactions, and patient-specific factors before initiating therapy.