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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of antihypertensive agents that work by inhibiting the influx of calcium ions into vascular smooth muscle and myocardial cells, leading to vasodilation and decreased myocardial contractility and heart rate. They are broadly categorized into dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs). ## Primary Indications * Hypertension * Angina pectoris (stable, vasospastic) * Certain arrhythmias (e.g., supraventricular tachycardia, atrial fibrillation rate control - primarily non-DHPs) ## Adult Dosing **Dihydropyridines (DHPs)**: * **Amlodipine**: 2.5 mg to 10 mg orally once daily. Maximum: 10 mg daily. * **Felodipine**: 2.5 mg to 10 mg orally twice daily. Maximum: 10 mg twice daily. * **Nifedipine (Extended-Release)**: 30 mg to 120 mg orally once daily. Maximum: 120 mg daily. (Note: Immediate-release nifedipine is not recommended for hypertension due to risk of rapid BP drop and reflex tachycardia). * **Nicardipine (Infusion)**: 2.5 mg to 15 mg/hour IV. Titrated based on BP response. **Non-Dihydropyridines (Non-DHPs)**: * **Diltiazem**: * Oral (immediate-release): 30 mg to 60 mg orally 3-4 times daily. * Oral (extended-release): 60 mg to 360 mg orally once or twice daily (formulation dependent). Maximum: Typically 360 mg daily, but depends on formulation. * IV: 0.25 mg/kg bolus over 2 minutes. May repeat if needed. Maintenance infusion: 5 mg to 15 mg/hour. * **Verapamil**: * Oral: 80 mg to 120 mg orally 2-3 times daily. * IV: 2.5 mg to 5 mg bolus over 2 minutes. May repeat if needed. *Note: Specific dosing and titrations are highly dependent on the agent, formulation, and patient response. Local protocols may provide further guidance.* ## Pediatric Dosing Pediatric dosing is less established and varies widely by indication, age group, and specific agent. Consult specialized pediatric resources for definitive dosing. * **Amlodipine**: Used in children > 6 years for hypertension. Doses range from 2.5 mg to 5 mg orally once daily. * **Diltiazem**: IV infusions used for supraventricular tachycardia in neonates and infants, often at 0.1-0.2 mg/kg bolus, followed by 15-30 mcg/kg/min infusion. Oral doses for adolescents for hypertension or angina are similar to adult low doses. * **Verapamil**: IV use for supraventricular tachycardia in infants, typically 0.1-0.3 mg/kg bolus. Oral use for older children for angina or hypertension is uncommon and requires expert consultation. ## Dose Adjustments * **Hepatic Impairment**: DHP CCBs generally require caution with reduced doses due to hepatic metabolism. Non-DHP CCBs (verapamil, diltiazem) are extensively metabolized by the liver and generally require significant dose reductions. * **Renal Impairment**: Generally, dose adjustments are not required for CCBs in renal impairment, but caution is advised, particularly with non-DHPs, as metabolites may accumulate. ## Contraindications * Known hypersensitivity to the drug. * **Non-DHPs (Verapamil, Diltiazem)**: Severe left ventricular systolic dysfunction, sick sinus syndrome, second- or third-degree AV block (without a functional pacemaker), Wolff-Parkinson-White syndrome with atrial fibrillation/flutter, cardiogenic shock. * **Dihydropyridines**: Use with caution in severe aortic stenosis. ## Adverse Effects * **Common**: Peripheral edema, headache, flushing, dizziness, hypotension, constipation (especially verapamil). * **Less Common**: Gingival hyperplasia, nausea, rash, fatigue, bradycardia, AV block (more with non-DHPs). * **Serious**: Severe symptomatic hypotension, syncope, worsening heart failure, significant bradyarrhythmias. ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers**: Many CCBs are substrates of CYP3A4. Concurrent use with potent inhibitors (e.g., ketoconazole, ritonavir) can increase CCB levels and toxicity. Concurrent use with potent inducers (e.g., rifampin, carbamazepine) can decrease CCB levels. * **Beta-Blockers**: Additive effects on AV nodal conduction and myocardial contractility; increased risk of bradycardia, AV block, and heart failure. Use with extreme caution or avoid. * **Digoxin**: Non-DHPs (verapamil, diltiazem) can increase digoxin levels by reducing its renal and non-renal clearance. * **Grapefruit Juice**: Can significantly increase serum concentrations of certain CCBs (especially amlodipine, felodipine, verapamil), increasing the risk of adverse effects. * **Statins**: Certain statins (simvastatin, lovastatin, atorvastatin) are CYP3A4 substrates; CCBs can inhibit their metabolism, increasing statin levels and risk of myopathy. ## Monitoring * Blood pressure and heart rate (regularly). * Signs and symptoms of heart failure. * Electrolytes (especially calcium levels, though typically not monitored unless acute toxicity suspected). * Liver function tests (periodically, especially in patients with hepatic impairment). * ECG (especially when initiating non-DHPs or titrating doses, to monitor for AV block or bradycardia). * Signs of gingival hyperplasia. ## Clinical Pearls * Dihydropyridines are generally preferred for their vasodilatory effects and less impact on cardiac conduction. They are potent antihypertensives and antianginals (vasospastic). * Non-dihydropyridines (verapamil, diltiazem) have significant negative chronotropic and inotropic effects, making them useful in rate control for atrial fibrillation and for managing certain arrhythmias, in addition to their antihypertensive and antianginal properties. * Start CCBs at the lowest effective dose and titrate slowly, especially in elderly patients or those with significant comorbidities. * Non-DHPs should generally be avoided in patients with heart failure with reduced ejection fraction. * Peripheral edema is a common dose-limiting side effect of DHPs. It is typically managed by dose reduction, switching to a non-DHP, or adding an ACE inhibitor/ARB. *** **Disclaimer**: This information is intended for educational purposes only and does not substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider for definitive guidance on drug use.