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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that inhibit the influx of calcium ions into cardiac and vascular smooth muscle cells. This leads to vasodilation and, in some cases, decreased heart rate and contractility. They are broadly classified into dihydropyridines (DHPs), which primarily affect vascular smooth muscle, and non-dihydropyridines (non-DHPs), which affect both cardiac and vascular smooth muscle. ## Primary Indications * Hypertension * Angina Pectoris (stable and vasospastic) * Supraventricular Tachyarrhythmias (non-DHPs) * Raynaud's Phenomenon (DHPs) ## Adult Dosing Dosing varies significantly between specific agents and indications. * **Dihydropyridines (e.g., amlodipine, nifedipine, felodipine):** * **Hypertension:** * Amlodipine: Start at 5 mg orally once daily. Usual range: 5-10 mg once daily. Maximum: 10 mg once daily. * Nifedipine (extended-release): Start at 30-60 mg orally once daily. Usual range: 30-120 mg once daily. Specific maximums depend on formulation. * **Angina:** Dosing similar to hypertension, guided by symptom relief. * **Non-dihydropyridines (e.g., diltiazem, verapamil):** * **Hypertension:** * Diltiazem (extended-release): Start at 120-180 mg orally once daily. Usual range: 120-540 mg once daily. * Verapamil (extended-release): Start at 180 mg orally once daily. Usual range: 180-480 mg once daily. * **Angina:** Dosing similar to hypertension. * **Supraventricular Tachyarrhythmias (IV administration):** * Diltiazem IV: 0.25 mg/kg bolus, followed by 0.35 mg/kg bolus if needed. Infusion: 5-15 mg/hour. * Verapamil IV: 2.5-5 mg bolus, may repeat at 5-10 minute intervals up to 10-15 mg total. ## Pediatric Dosing Pediatric dosing for CCBs is less established and often based on limited studies or extrapolated from adult data. Prescribing should be done with caution and consultation with a pediatric specialist is often necessary. * **Hypertension:** * Amlodipine: Generally initiated at 0.05 mg/kg orally once daily, not to exceed adult maximum doses. * Diltiazem: Various regimens exist, often initiated at lower doses and titrated based on response and tolerability. Specific doses are highly variable by age and indication. ## Dose Adjustments * **Hepatic Impairment:** Dose reduction is generally recommended, especially for non-DHPs, due to extensive hepatic metabolism. Titrate cautiously. * **Renal Impairment:** Dose adjustments are typically not required for most CCBs unless significant renal impairment is present or specific metabolites accumulate. However, always review the specific agent's prescribing information. ## Contraindications * Hypersensitivity to the drug or its components. * **Non-DHPs:** Sick sinus syndrome (without a pacemaker), second- or third-degree AV block (without a pacemaker), severe left ventricular dysfunction (e.g., reduced ejection fraction <35% with verapamil), decompensated heart failure, cardiogenic shock. * **Dihydropyridines:** Use with caution in severe aortic stenosis and in patients with severe heart failure. ## Adverse Effects * **Common (especially DHPs):** Peripheral edema, headache, flushing, dizziness. * **Non-DHPs:** Constipation (especially verapamil), bradycardia, AV block, nausea, fatigue. * **Serious:** Hypotension, worsening heart failure, syncope, gingival hyperplasia (long-term use). ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates for CYP3A4. Concomitant use with strong inhibitors (e.g., azole antifungals, macrolide antibiotics, protease inhibitors) can increase CCB levels, leading to toxicity. Strong inducers (e.g., rifampin, St. John's wort) can decrease CCB levels. * **Beta-Blockers:** Additive effects on heart rate and AV conduction, increasing risk of bradycardia and heart block. Use with extreme caution, especially non-DHPs. * **Digoxin:** Non-DHPs can increase digoxin levels by decreasing its renal and non-renal clearance. * **Grapefruit Juice:** Can inhibit intestinal CYP3A4, increasing levels of some CCBs (especially DHPs). ## Monitoring * **Blood Pressure:** Regular monitoring for efficacy and to detect hypotension. * **Heart Rate and Rhythm:** Especially important with non-DHPs to monitor for bradycardia and AV block. * **Signs of Heart Failure:** Edema, dyspnea, weight gain. * **Electrolytes:** Particularly if co-administered with diuretics. * **Renal and Hepatic Function:** Periodically, especially in patients with pre-existing impairment or those on multiple medications. ## Clinical Pearls * Dihydropyridines are generally preferred for hypertension and angina when vasodilation is the primary goal, due to their lower risk of cardiac depression. * Non-dihydropyridines are useful for hypertension and angina but also have a role in rate control for atrial fibrillation/flutter and other supraventricular tachycardias. * Immediate-release nifedipine is generally avoided due to a risk of rapid blood pressure drops and adverse cardiovascular events. Extended-release formulations are preferred. * Peripheral edema is a common side effect of DHPs, often dose-dependent and more prevalent in women. * Ensure adequate hydration, especially with verapamil, to minimize constipation. *** *Disclaimer: This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information or a qualified healthcare provider for complete drug details, including indications, contraindications, warnings, precautions, adverse reactions, and dosages, particularly for specific patient populations and local protocols.*