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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) inhibit the influx of calcium ions into cardiac and vascular smooth muscle cells, leading to vasodilation and/or decreased myocardial contractility and heart rate. They are classified as dihydropyridines (DHPs) or non-dihydropyridines (non-DHPs). ## Primary Indications * Hypertension * Angina Pectoris (stable, variant) * Supraventricular Tachyarrhythmias (rate control) ## Adult Dosing Dosing varies significantly by specific agent and indication. **Dihydropyridines (e.g., amlodipine, nifedipine, felodipine):** * **Hypertension:** * Amlodipine: Start at 5 mg orally once daily. Titrate up to a maximum of 10 mg orally once daily. * Nifedipine (extended-release): Start at 30 mg orally once daily. Titrate up to a maximum of 120 mg orally once daily. * Felodipine (extended-release): Start at 5 mg orally once daily. Titrate up to a maximum of 10 mg orally once daily. * **Angina (stable, variant):** * Amlodipine: Start at 5 mg orally once daily. Titrate up to a maximum of 10 mg orally once daily. * Nifedipine (extended-release): Start at 10-20 mg orally twice daily. Titrate up to a maximum of 180 mg orally daily in divided doses. **Non-Dihydropyridines (e.g., diltiazem, verapamil):** * **Hypertension:** * Diltiazem (extended-release): Start at 180 mg orally once daily. Usual dose is 240-360 mg orally once daily. Max 540 mg/day. * Verapamil (extended-release): Start at 180 mg orally once daily. Usual dose is 240-480 mg orally once daily. Max 540 mg/day. * **Angina:** * Diltiazem (immediate-release): Start at 30 mg orally four times daily. Titrate up to 180-360 mg/day in divided doses. * Verapamil (immediate-release): Start at 80 mg orally three times daily. Titrate up to 320-480 mg/day in divided doses. * **Supraventricular Tachyarrhythmias (rate control):** * Diltiazem (IV): 0.25 mg/kg bolus, may repeat with 0.35 mg/kg bolus after 15 minutes. Continuous infusion may follow at 5-15 mg/hour. * Verapamil (IV): 2.5-5 mg bolus, may repeat with 5-10 mg if needed. ## Pediatric Dosing Pediatric dosing is highly variable and often based on extrapolation from adult data, specific formulations, and is best guided by institutional protocols or specialist consultation. * **Diltiazem (IV for SVT):** Pediatric data is limited. Typical starting dose for children <1 year is 0.1-0.25 mg/kg/min for 1 minute, then 0.05 mg/kg/min for 10 minutes. For children >1 year, 0.1 mg/kg/min for 1 minute, then 0.05 mg/kg/min for 10 minutes. * **Verapamil (IV for SVT):** Pediatric data is limited. Typical starting dose for infants <1 year is 0.1-1 mg/kg/dose over 2 minutes. For children 1-15 years, 0.1-0.3 mg/kg/dose over 2 minutes. ## Dose Adjustments * **Hepatic Impairment:** Dose reduction may be necessary, especially for non-dihydropyridines, due to extensive hepatic metabolism. Start at lower doses and titrate cautiously. * **Renal Impairment:** Generally, CCBs do not require dose adjustment for renal impairment, except for certain metabolites or specific agents with significant renal excretion. Monitor closely. * **Elderly:** Start at lower doses and titrate cautiously due to increased risk of hypotension and bradycardia. ## Contraindications * Severe left ventricular dysfunction (e.g., heart failure with reduced ejection fraction) * Sick sinus syndrome or AV block greater than first degree (except with a functioning pacemaker) * Cardiogenic shock * Hypersensitivity to the drug or its components * Acute myocardial infarction with pulmonary congestion (for verapamil and diltiazem) ## Adverse Effects Common: Peripheral edema, headache, flushing, dizziness, constipation (especially verapamil), bradycardia, hypotension, AV block. Less common: Gingival hyperplasia (especially with amlodipine), rash, nausea, fatigue. ## Key Drug Interactions * **Beta-blockers:** Additive effects on AV conduction and negative inotropy, increasing risk of bradycardia and heart failure. Use with extreme caution. * **Digoxin:** CCBs (especially verapamil) can increase digoxin levels by reducing renal clearance. Monitor digoxin levels. * **CYP3A4 inhibitors (e.g., grapefruit juice, ketoconazole, ritonavir):** May increase CCB plasma concentrations, especially for drugs metabolized by CYP3A4 (e.g., amlodipine, verapamil, diltiazem). * **CYP3A4 inducers (e.g., rifampin, carbamazepine):** May decrease CCB plasma concentrations. * **Antihypertensives:** Additive hypotensive effects. ## Monitoring * Blood pressure and heart rate * ECG for heart rate, rhythm, and AV conduction (especially with non-DHPs) * Signs and symptoms of heart failure (dyspnea, edema) * Electrolytes (if clinically indicated) * Renal and hepatic function (periodically, or if dose adjustments needed) ## Clinical Pearls * Dihydropyridines primarily cause vasodilation and are more effective for blood pressure lowering. * Non-dihydropyridines (verapamil, diltiazem) have significant cardiac effects (negative chronotropy and inotropy) and are useful for rate control in supraventricular tachycardias. * Verapamil is generally the most cardiodepressant and constipating of the CCBs. * Amlodipine is associated with a higher incidence of peripheral edema. * Avoid short-acting nifedipine for hypertension due to risk of reflex tachycardia and rapid, unpredictable blood pressure drops. * Non-dihydropyridine CCBs should be used with caution in patients with pre-existing conduction abnormalities or heart failure. This information is intended for healthcare professionals and does not replace the need to consult the most current prescribing information, institutional guidelines, or manufacturer's product literature for complete details.