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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce myocardial oxygen demand and improve myocardial oxygen supply by blocking the influx of calcium ions into cardiac and vascular smooth muscle cells. This leads to vasodilation and decreased heart rate and contractility. They are classified as either dihydropyridines (DHPs), which primarily affect vascular smooth muscle, or non-dihydropyridines (non-DHPs), which affect both cardiac and vascular smooth muscle. ## Primary Indications * Hypertension * Angina pectoris (stable, vasospastic) * Supraventricular tachycardias (rate control, e.g., atrial fibrillation/flutter) ## Adult Dosing Dosing varies significantly by agent and formulation. Examples include: * **Amlodipine (DHP):** * Hypertension: Start with 5 mg orally once daily. Titrate up to 10 mg orally once daily. * Angina: Start with 5 mg to 10 mg orally once daily. * **Diltiazem (Non-DHP):** * Hypertension: Immediate-release: 30-60 mg orally 3-4 times daily. Extended-release: 120-360 mg orally once or twice daily. * Angina: Immediate-release: 30-60 mg orally 3-4 times daily. Extended-release: 120-360 mg orally once or twice daily. * Rate control (AFib/Flutter): Immediate-release: 0.25 mg/kg IV bolus, may repeat after 15 minutes. Continuous infusion: 5-15 mg/hr. Extended-release: 120-360 mg orally once or twice daily. * **Verapamil (Non-DHP):** * Hypertension: Immediate-release: 80-120 mg orally twice daily. Extended-release: 120-180 mg orally once daily. * Angina: Immediate-release: 80-120 mg orally 3-4 times daily. Extended-release: 120-180 mg orally once daily. * Rate control (AFib/Flutter): Immediate-release: 2.5-5 mg IV bolus, may repeat up to 10 mg slow IV. ## Pediatric Dosing Dosing in pediatric populations is less established and should be guided by specific product information and expert consultation. * **Amlodipine:** Hypertension: 0.05 to 0.1 mg/kg orally once daily (max 5 mg/day for <6 years, max 10 mg/day for ≥6 years). * **Diltiazem:** Supraventricular tachycardia: 0.1 to 0.2 mg/kg IV bolus, may repeat up to 0.5 mg/kg. * **Verapamil:** Supraventricular tachycardia: 0.1 to 0.3 mg/kg IV over 2 minutes. ## Dose Adjustments * **Hepatic Impairment:** Non-DHPs (diltiazem, verapamil) generally require dose reduction due to extensive hepatic metabolism. Start with lower doses and titrate cautiously. DHPs are generally less affected, but caution may still be warranted. * **Renal Impairment:** Typically no dose adjustment is needed for most CCBs, but monitor for increased adverse effects. ## Contraindications * Hypersensitivity to the specific agent. * Severe hypotension. * Cardiogenic shock. * Acute myocardial infarction with pulmonary congestion. * Certain heart block conditions (e.g., second or third-degree AV block without a pacemaker) for non-DHPs. * Sick sinus syndrome without a pacemaker for non-DHPs. * Concomitant use of IV beta-blockers with IV non-dihydropyridine CCBs. ## Adverse Effects Common side effects include: * **DHPs:** Peripheral edema, headache, flushing, reflex tachycardia, dizziness. * **Non-DHPs:** Bradycardia, constipation (especially verapamil), AV block, dizziness, headache, nausea. Serious adverse effects may include severe hypotension, heart failure, significant bradycardia or AV block. ## Key Drug Interactions * **Beta-blockers:** Additive negative chronotropic, inotropic, and dromotropic effects, increasing the risk of bradycardia, AV block, and heart failure. Avoid IV combination of non-DHPs and IV beta-blockers. * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Inhibitors (e.g., strong azole antifungals, macrolide antibiotics, grapefruit juice) can increase CCB levels, while inducers (e.g., rifampin, carbamazepine) can decrease them. * **Digoxin:** Non-DHPs can increase digoxin levels. * **Statins:** Diltiazem and verapamil can inhibit CYP3A4, increasing levels of simvastatin and lovastatin. ## Monitoring * Blood pressure and heart rate. * ECG for heart rate, rhythm, and conduction abnormalities (especially with non-DHPs). * Signs and symptoms of heart failure. * Renal and hepatic function, particularly in patients with impairment or those on interacting medications. * For verapamil, monitor for constipation. ## Clinical Pearls * DHPs are preferred for conditions where vasodilation is the primary goal (e.g., hypertension, chronic stable angina) due to their lower risk of cardiotoxicity compared to non-DHPs. * Non-DHPs are useful for managing supraventricular tachycardias and controlling angina in patients who also have supraventricular tachycardias or hypertension. * Parenteral diltiazem and verapamil should be administered with caution in patients with baseline bradycardia or conduction abnormalities. * Constipation is a common and dose-limiting side effect of verapamil, particularly in the elderly. * Extended-release formulations improve adherence and reduce peak-trough fluctuations. *** **Disclaimer:** This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the official prescribing information and relevant clinical guidelines for the most current and comprehensive details before making any treatment decisions.