Calcium%2525252525252525252525252525252525252525252525252520channel%2525252525252525252525252525252525252525252525252520blockers

# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce the movement of calcium ions into cardiac and vascular smooth muscle cells. This action leads to vasodilation and decreased myocardial contractility and heart rate, depending on the specific agent. CCBs are broadly classified into dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs). DHPs primarily act on vascular smooth muscle, while non-DHPs affect both cardiac and vascular smooth muscle. ## Primary Indications * Hypertension * Angina pectoris (stable and vasospastic) * Supraventricular tachyarrhythmias (non-DHPs) * Raynaud's phenomenon (DHPs) ## Adult Dosing **Dihydropyridines (DHPs):** * **Amlodipine:** 2.5 mg to 10 mg orally once daily. Maximum 10 mg daily. * **Felodipine:** 5 mg to 10 mg orally once daily. Maximum 10 mg (extended-release) daily. * **Nifedipine (extended-release):** 30 mg to 90 mg orally once daily. Maximum 120 mg daily. * **Nicardipine (IV):** 2.5 mg to 5 mg IV bolus, then infused at 50 mcg/kg/min to 150 mcg/kg/min. Titrate as needed. * **Nimodipine (oral/NG tube):** 60 mg orally or via nasogastric tube every 4 hours for 21 days, often initiated within 96 hours of subarachnoid hemorrhage. **Non-Dihydropyridines:** * **Diltiazem (oral, immediate-release):** 30 mg to 60 mg orally 3-4 times daily. Titrate up to 360 mg daily. * **Diltiazem (oral, extended-release):** 60 mg to 120 mg orally once or twice daily. Titrate up to 360 mg daily. * **Diltiazem (IV):** 0.25 mg/kg IV bolus over 2 minutes. May repeat at 0.35 mg/kg after 15 minutes if needed. Follow with infusion at 5-10 mg/hr, titrating up to 15 mg/hr. * **Verapamil (oral):** 40 mg to 80 mg orally 3 times daily. Titrate up to 480 mg daily. * **Verapamil (IV):** 2.5 mg to 5 mg IV bolus over 2 minutes. May repeat at 5 mg to 10 mg after 15-30 minutes if needed. Not recommended for IV use in patients with heart failure or left ventricular ejection fraction < 40%. Dosing for specific indications like arrhythmias may differ and depend on local protocol. ## Pediatric Dosing Pediatric dosing for CCBs is less established and more variable. * **Amlodipine:** 0.05 mg/kg to 0.1 mg/kg orally once daily, maximum 5 mg daily for children < 12 years old. In adolescents 12-17 years, can use adult doses up to 10 mg daily. * **Diltiazem:** Pediatric dosing is highly variable and should be guided by expert consultation or specific pediatric guidelines. Generally, lower doses are used and titrated carefully. ## Dose Adjustments * **Hepatic Impairment:** Dose reduction is often necessary, especially for non-DHPs, due to extensive hepatic metabolism. Start with lower doses and titrate cautiously. * **Renal Impairment:** Dihydropyridines generally do not require significant dose adjustment in renal impairment, but caution is advised. Non-dihydropyridines may require dose adjustment in severe renal impairment. ## Contraindications * Severe hypotension * Cardiogenic shock * Acute myocardial infarction (certain situations, especially with contraindications to beta-blockers) * Second- or third-degree atrioventricular (AV) block without a pacemaker (non-DHPs) * Sick sinus syndrome without a pacemaker (non-DHPs) * Known hypersensitivity to the drug * Heart failure with reduced ejection fraction (verapamil, diltiazem IV) ## Adverse Effects Common adverse effects include: * **DHPs:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia. * **Non-DHPs:** Bradycardia, constipation (especially verapamil), AV block, dizziness, headache. Serious adverse effects can include severe bradycardia, heart failure exacerbation, and hypotension. ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Concomitant use with strong inhibitors (e.g., ketoconazole, clarithromycin) can increase CCB levels and toxicity. Concomitant use with strong inducers (e.g., rifampin) can decrease CCB levels. * **Beta-blockers:** Additive effects on heart rate and AV conduction, increasing the risk of bradycardia and heart block. Avoid concurrent use of IV verapamil or diltiazem with IV beta-blockers. * **Grapefruit Juice:** Can inhibit intestinal metabolism of some CCBs (e.g., amlodipine, felodipine), increasing plasma concentrations and risk of adverse effects. * **Digoxin:** Non-DHPs can increase digoxin levels by reducing renal clearance and intestinal efflux. * **Systemic Antihypertensives:** Additive hypotensive effects. ## Monitoring * Blood pressure and heart rate (regularly, especially upon initiation and dose changes) * Electrolytes (e.g., potassium) * Renal and hepatic function * ECG for evidence of AV block or significant bradycardia (especially with non-DHPs) * Signs of heart failure ## Clinical Pearls * Start low and titrate gradually, especially in elderly patients or those with hepatic impairment. * DHPs are generally preferred for hypertension and angina due to their potent vasodilatory effects and lower risk of bradycardia. * Non-DHPs (verapamil, diltiazem) are more effective for rate control in supraventricular tachyarrhythmias due to their negative chronotropic and dromotropic effects. * Verapamil is typically more potent for cardiac effects and causes more constipation than diltiazem. * Nimodipine has a specific indication for cerebral vasospasm prophylaxis after subarachnoid hemorrhage. *** **Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information or a qualified healthcare provider for any questions regarding medications.