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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of medications that inhibit the influx of calcium ions into vascular smooth muscle and myocardial cells. This leads to vasodilation and/or decreased cardiac contractility and heart rate, depending on the specific agent. They are broadly categorized into dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs). ## Primary Indications * Hypertension * Angina (stable and vasospastic) * Tachyarrhythmias (supraventricular tachycardias, atrial fibrillation/flutter rate control) - primarily non-DHPs ## Adult Dosing Dosing varies significantly by agent. This is a general overview; specific prescribing information should be consulted. * **Dihydropyridines (e.g., Amlodipine, Nifedipine, Felodipine):** * Amlodipine: 2.5-10 mg once daily. Max 10 mg/day. * Nifedipine (extended-release): 30-90 mg once daily. Max 120 mg/day. * Felodipine (extended-release): 5-10 mg once daily. Max 10 mg/day. * **Non-dihydropyridines (e.g., Verapamil, Diltiazem):** * Verapamil (IR): 80-160 mg three times daily. Max 480 mg/day. * Verapamil (ER): 180-480 mg once daily. Max 480 mg/day. * Diltiazem (IR): 30-60 mg three times daily. Max 360 mg/day. * Diltiazem (ER): Dosing varies by formulation (e.g., 120-540 mg once or twice daily). Max typically 540 mg/day. ## Pediatric Dosing Pediatric dosing is not as well established as adult dosing and often relies on expert consensus or specific institutional protocols. * **Amlodipine:** Generally initiated at lower doses (e.g., 0.1-0.3 mg/kg once daily for hypertension), with maximum doses generally not exceeding adult maximums (e.g., 5 mg for younger children, 10 mg for adolescents). * **Verapamil:** Used for supraventricular tachycardia (SVT) in specific pediatric populations. Intravenous doses are typically 0.1-0.3 mg/kg. Oral dosing is less common and requires careful titration. * **Diltiazem:** Used for rate control in atrial fibrillation/flutter and sometimes for hypertension. Intravenous doses are typically 0.25 mg/kg. Oral doses vary by formulation and age. **Note:** Pediatric dosing is highly variable and requires careful consideration of weight, age, indication, and clinical response. Consult specialized pediatric pharmacology resources or local protocols. ## Dose Adjustments * **Hepatic Impairment:** CCBs are metabolized by the liver. Dose reduction is generally recommended in patients with significant hepatic impairment. Start at the lowest dose and titrate cautiously. * **Renal Impairment:** Dose adjustments are generally not required for DHPs or diltiazem with mild to moderate renal impairment. Verapamil may require caution and monitoring in severe renal impairment due to potential accumulation of metabolites. ## Contraindications * Known hypersensitivity to the drug class or any component. * **Non-DHPs (Verapamil, Diltiazem):** * Sick sinus syndrome or high-grade atrioventricular (AV) block (unless a functioning pacemaker is in place). * Congestive heart failure with reduced ejection fraction (caution, especially with verapamil). * Cardiogenic shock. * **Dihydropyridines (e.g., Amlodipine, Nifedipine):** * Severe aortic stenosis (may worsen hemodynamic status). * Cardiogenic shock. ## Adverse Effects Common adverse effects include: * **DHPs:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia. * **Non-DHPs:** Bradycardia, constipation (more common with verapamil), AV block, dizziness, hypotension, headache. * Gingival hyperplasia (rare but more common with long-term DHP use). ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers:** Many CCBs are CYP3A4 substrates. Concomitant use with strong CYP3A4 inhibitors (e.g., ketoconazole, protease inhibitors) can increase CCB levels, and strong inducers (e.g., rifampin, carbamazepine) can decrease them. * **Beta-Blockers:** Concomitant use of non-DHPs with beta-blockers can lead to additive negative chronotropic and inotropic effects (risk of bradycardia, heart block, heart failure). * **Digoxin:** Non-DHPs (especially verapamil) can increase digoxin levels. * **Grapefruit Juice:** Can significantly increase serum concentrations of some CCBs (e.g., amlodipine, felodipine, verapamil). ## Monitoring * **Blood Pressure:** Regular monitoring, especially after initiation or dose changes. * **Heart Rate & Rhythm:** Particularly important for non-DHPs, monitor for bradycardia and AV block. ECG may be warranted. * **Signs/Symptoms of Heart Failure:** Monitor for dyspnea, edema, weight gain. * **Renal function and Electrolytes:** Especially in patients with pre-existing renal disease or other interacting medications. * **Liver Function Tests:** Consider in patients with hepatic risk factors or prolonged therapy. * **Digoxin Levels:** If co-administered with non-DHPs. ## Clinical Pearls * DHPs are generally preferred for hypertension due to their potent vasodilatory effects and lower risk of cardiac depression. * Non-DHPs are useful for controlling heart rate in supraventricular tachycardias and atrial fibrillation, as well as for angina. * Short-acting nifedipine is generally avoided due to increased risk of MI and adverse cardiovascular events. * Peripheral edema seen with DHPs is dose-related and often managed with diuretic therapy or switching to a non-DHP carefully. * Constipation with verapamil can be dose-limiting; measure bowel movements and consider stool softeners. *** **Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions. Dosing and recommendations may vary based on individual patient factors and local institutional protocols.