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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of medications that disrupt the movement of calcium into the cells of the heart and blood vessel walls. This action leads to vasodilation (widening of blood vessels) and decreased heart rate and contractility, thereby reducing blood pressure and myocardial oxygen demand. CCBs are broadly divided into two main classes: * **Dihydropyridines (DHPs):** Primarily affect vascular smooth muscle, causing potent vasodilation. Examples include amlodipine, nifedipine, felodipine. * **Non-dihydropyridines (Non-DHPs):** Affect both vascular smooth muscle and cardiac conduction. Examples include verapamil, diltiazem. ## Primary Indications * Hypertension * Angina Pectoris (stable and vasospastic) * Certain cardiac arrhythmias (e.g., supraventricular tachycardia, atrial fibrillation/flutter rate control - primarily non-DHPs) ## Adult Dosing **Hypertension:** * **Amlodipine:** Initial: 5 mg daily. Maintenance: 2.5-10 mg daily. * **Nifedipine (extended-release):** Initial: 30 mg daily. Maintenance: 30-90 mg daily. * **Felodipine (extended-release):** Initial: 5 mg daily. Maintenance: 5-10 mg daily (max 10 mg/day in some formulations). * **Diltiazem (extended-release):** Initial: 120-180 mg daily. Maintenance: 120-540 mg daily. * **Verapamil (extended-release):** Initial: 180 mg daily. Maintenance: 180-480 mg daily. **Angina:** Dosing is generally similar to hypertension, aiming for symptom control. **Arrhythmias (Non-DHPs):** * **Diltiazem:** IV: 0.25 mg/kg bolus, followed by 5-15 mg/hr infusion. Oral (controlled-release): 30-60 mg TID to QID. * **Verapamil:** IV: 2.5-5 mg bolus, may repeat with 5-10 mg after 15-30 min. Oral (immediate-release): 40-80 mg TID. *Specific dosing for IV administration or complex arrhythmias may depend on local protocols and continuous monitoring.* ## Pediatric Dosing Dosing in pediatrics is less established and often based on weight. **Hypertension (e.g., Amlodipine):** * **Amlodipine:** 1-17 years: 2.5-5 mg once daily. *Dosing for other CCBs in pediatric populations is highly variable and requires expert consultation.* ## Dose Adjustments * **Hepatic Impairment:** Non-DHPs and DHPs require dose reduction and careful monitoring due to increased bioavailability and prolonged half-life. * **Renal Impairment:** Generally, no dose adjustment is needed for most CCBs, but caution is advised. ## Contraindications * Known hypersensitivity to the drug. * **Non-DHPs:** Severe hypotension, sick sinus syndrome, 2nd or 3rd degree AV block (without a pacemaker), severe left ventricular dysfunction (e.g., heart failure with reduced ejection fraction), cardiogenic shock. * **DHPs:** Within 4 weeks after an acute myocardial infarction (some formulations). ## Adverse Effects * **DHP-specific:** Peripheral edema, headache, flushing, reflex tachycardia, dizziness. * **Non-DHP-specific:** Constipation (especially verapamil), bradycardia, AV block, hypotension, dizziness, nausea. * **Both:** Gingival hyperplasia (rare with short-acting nifedipine, more common with long-term amlodipine). ## Key Drug Interactions * **Beta-blockers:** Additive effects on heart rate and contractility, increasing the risk of bradycardia and heart block. * **Digoxin:** CCBs (especially verapamil) can increase digoxin levels. * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Inhibitors (e.g., azole antifungals, macrolide antibiotics, grapefruit juice) can increase CCB levels. Inducers (e.g., rifampin, carbamazepine, St. John's wort) can decrease CCB levels. * **Antihypertensives:** Additive hypotensive effects. * **Aspirin/NSAIDs:** May reduce the hypotensive effects of CCBs. ## Monitoring * Blood pressure (seated, adequate intervals). * Heart rate. * ECG (especially with non-DHPs, or if symptomatic). * Signs of heart failure. * Electrolytes (particularly calcium, though significant changes are rare with therapeutic doses). * Renal and hepatic function. ## Clinical Pearls * DHPs are generally preferred for hypertension and isolated systolic hypertension due to their potent vasodilatory effects with less impact on cardiac conduction. * Non-DHPs are useful when both blood pressure and heart rate/rhythm control are desired, such as in certain arrhythmias or angina with concomitant hypertension. * Avoid short-acting nifedipine for hypertension due to risks of rapid blood pressure drops and reflex tachycardia. Use extended-release formulations. * Gingival hyperplasia is more common with long-term use, especially amlodipine. Good oral hygiene is important. * Non-DHPs can be significantly constipating, particularly verapamil. *** *This information is intended for healthcare professionals and may not reflect all available data. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.*