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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce the movement of calcium ions into vascular smooth muscle and/or myocardial cells. This leads to vasodilation and/or decreased cardiac contractility and heart rate. They are broadly categorized into dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs). ## Primary Indications * Hypertension * Angina Pectoris (stable, variant) * Supraventricular Tachycardias (PSVT) - primarily non-DHPs * Rate control in atrial fibrillation/flutter - primarily non-DHPs ## Adult Dosing Dosing varies significantly by specific agent and indication. Consult institutional guidelines or specific drug monographs. * **Dihydropyridines (e.g., amlodipine, nifedipine, felodipine):** * Hypertension: Initial doses typically range from 2.5-5 mg once daily, titrated up to a maximum of 10 mg once daily for amlodipine. Nifedipine extended-release may be dosed up to 60-120 mg once daily. * Angina: Similar dosing ranges as hypertension. * **Non-dihydropyridines (e.g., verapamil, diltiazem):** * Hypertension: Verapamil IR 80 mg TID, SR 180-480 mg once daily. Diltiazem IR 30-60 mg TID, SR/ER 60-420 mg once or twice daily. * Angina: Verapamil IR 80 mg TID, SR 180-480 mg once daily. Diltiazem IR 30-60 mg TID, SR/ER 180-480 mg once or twice daily. * Supraventricular Tachycardia: Verapamil IV 2.5-5 mg (max 10 mg) over 2 minutes. Diltiazem IV 0.25 mg/kg over 2 minutes, may repeat 0.35 mg/kg. * Rate control (AF/flutter): Verapamil IR 80-120 mg TID. Diltiazem IR 30-60 mg TID, SR/ER 60-420 mg once or twice daily. ## Pediatric Dosing Pediatric dosing is less established and often requires consultation with a pediatric cardiologist or specialist. Doses are generally weight-based and may differ for DHPs vs. Non-DHPs. * **Amlodipine:** Hypertension: 0.05-0.1 mg/kg/day (max 5 mg/day) for ages 6-17 years. * **Verapamil:** Supraventricular Tachycardia: Neonates: 0.1-0.2 mg/kg IV. Infants: 0.2-0.3 mg/kg IV. Children: 0.2-0.3 mg/kg IV (max 5 mg/dose). * **Diltiazem:** Supraventricular Tachycardia: Neonates: 0.1 mg/kg IV. Infants and children: 0.1-0.2 mg/kg IV (max 5 mg/dose). Rate control: May be dosed orally based on weight, but specific guidelines are limited. ## Dose Adjustments * **Hepatic Impairment:** Dose reduction is generally recommended for all CCBs due to hepatic metabolism. * **Renal Impairment:** DHP CCBs generally do not require significant dose adjustment. Non-DHP CCBs may require caution, especially in severe renal impairment. ## Contraindications * Known hypersensitivity to the drug. * **Non-dihydropyridines:** Severe left ventricular dysfunction (e.g., decompensated heart failure), sick sinus syndrome, second- or third-degree AV block (without a pacemaker), Wolff-Parkinson-White syndrome. * **Dihydropyridines:** Cardiogenic shock. ## Adverse Effects * **Dihydropyridines:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia, gingival hyperplasia. * **Non-dihydropyridines:** Bradycardia, AV block, constipation (more common with verapamil), dizziness, headache, nausea, peripheral edema. * **Both:** Hypotension, hepatic dysfunction. ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Concomitant use with strong inhibitors (e.g., azole antifungals, macrolides, protease inhibitors) can increase CCB levels. Concomitant use with strong inducers (e.g., rifampin, carbamazepine) can decrease levels. * **Beta-blockers:** Additive negative chronotropic and inotropic effects, increasing risk of bradycardia and heart failure. * **Digoxin:** Non-DHP CCBs can increase digoxin levels. * **Statins:** Simvastatin, lovastatin, atorvastatin (CYP3A4 substrates) can have increased levels with verapamil and diltiazem. * **Grapefruit Juice:** Can increase absorption and levels of most CCBs. ## Monitoring * Blood pressure and heart rate. * Electrocardiogram (ECG) for heart rhythm and AV conduction, especially with non-DHPs. * Electrolytes (especially calcium and potassium). * Renal and hepatic function. * Signs and symptoms of heart failure. ## Clinical Pearls * Dihydropyridines are generally preferred for hypertension due to less impact on cardiac conduction and contractility. * Non-dihydropyridines are useful for rate control and in patients with supraventricular tachycardias due to their cardiac effects. * Short-acting nifedipine is generally avoided for hypertension due to risk of precipitating reflex tachycardia and myocardial ischemia. * Constipation is a common and significant side effect of verapamil, particularly in the elderly. * Gingival hyperplasia can occur with chronic use of some CCBs, particularly DHPs. *** **Disclaimer:** This information is intended for healthcare professionals and does not replace professional medical advice. Always consult the most current prescribing information, including package inserts and institutional protocols, for comprehensive details before making any treatment decisions.