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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of antihypertensive medications that work by relaxing vascular smooth muscle and, in some cases, decreasing cardiac contractility and heart rate. They achieve this by blocking the influx of calcium into cells through voltage-gated L-type calcium channels. They are broadly categorized into dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs). ## Primary Indications * Hypertension * Angina pectoris (stable and vasospastic) * Supraventricular tachycardias (rate control) * Raynaud's phenomenon ## Adult Dosing **Dihydropyridines (DHPs)** - Primarily act on vascular smooth muscle. * **Amlodipine:** Start with 5 mg once daily, may increase to 10 mg once daily. * **Nifedipine (extended-release):** Start with 30 mg once daily, may increase to up to 90 mg once daily. * **Felodipine:** Start with 5 mg once daily, may increase to up to 10 mg once daily. **Non-dihydropyridines (non-DHPs)** - Act on both vascular smooth muscle and cardiac conduction. * **Verapamil (immediate-release):** Start with 80 mg three times daily, may increase to up to 160 mg three times daily. * **Verapamil (extended-release):** Start with 180 mg once daily, may increase to up to 480 mg once daily. * **Diltiazem (immediate-release):** Start with 30 mg three to four times daily, may increase to up to 180 mg three to four times daily. * **Diltiazem (extended-release):** Start with 120 mg once or twice daily, may increase to up to 360 mg once or twice daily (formulation dependent). Dosing for specific indications beyond hypertension may vary and should be guided by established clinical protocols. ## Pediatric Dosing Pediatric dosing for CCBs is not well established for many agents and is often based on limited studies or expert consensus. Specific protocols should be followed. * **Amlodipine:** Has been used in children aged 6-17 years for hypertension, with typical doses ranging from 2.5 mg to 5 mg once daily. * **Verapamil:** Has been used for supraventricular tachycardia in neonates and older children, with doses typically ranging from 0.1 mg/kg to 0.3 mg/kg per dose, administered intravenously. ## Dose Adjustments * **Hepatic Impairment:** DHP and non-DHP CCBs are extensively metabolized by the liver. Dose reductions are generally recommended for patients with hepatic impairment. Non-DHP CCBs require more cautious titration. * **Renal Impairment:** Dose adjustments are typically not required for DHPs unless severe renal impairment is present. Non-DHPs generally do not require dose adjustments for renal impairment, but caution is advised. ## Contraindications * Known hypersensitivity to the drug or component. * **Non-DHPs:** Severe hypotension (systolic BP <90 mmHg), cardiogenic shock, sick sinus syndrome, second- or third-degree AV block (unless a functioning pacemaker is present), severe left ventricular dysfunction with pulmonary congestion. * **Dihydropyridines:** Acute myocardial infarction (especially within the first 4 weeks), clinically significant aortic stenosis. ## Adverse Effects Common adverse effects are often dose-related. * **Dihydropyridines:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia. * **Non-dihydropyridines:** Constipation (especially verapamil), bradycardia, AV block, hypotension, dizziness, nausea. Less common but serious adverse effects include gingival hyperplasia, exacerbation of heart failure, and peripheral ischemia. ## Key Drug Interactions * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir) can increase CCB concentrations. Strong CYP3A4 inducers (e.g., rifampin, carbamazepine) can decrease CCB concentrations. * **Beta-Blockers:** Additive effects on heart rate and AV conduction, increasing risk of bradycardia and heart block, especially with non-DHPs. * **Digoxin:** Non-DHP CCBs can increase digoxin levels by decreasing its renal clearance. * **Statins:** Simvastatin and atorvastatin (but not pravastatin or rosuvastatin) have increased concentrations when co-administered with amlodipine; consider lower statin doses. * **Grapefruit Juice:** Can inhibit intestinal CYP3A4, increasing concentrations of some CCBs (e.g., amlodipine, felodipine, verapamil). ## Monitoring * **Blood Pressure:** Regularly monitor for effectiveness and to avoid hypotension. * **Heart Rate and Rhythm:** Particularly important with non-DHPs to detect bradycardia or AV block. * **Electrolytes:** Monitor serum calcium and magnesium, especially in patients with electrolyte imbalances. * **Renal and Hepatic Function:** Periodically assess, especially in patients with pre-existing impairment or those on long-term therapy. * **Signs of Heart Failure:** Monitor for worsening symptoms like dyspnea, orthopnea, and edema. ## Clinical Pearls * Dihydropyridines are generally preferred for isolated hypertension due to their potent vasodilatory effects and lower risk of AV conduction abnormalities. * Non-dihydropyridines (verapamil, diltiazem) are useful for rate control in supraventricular tachycardias and can be used in angina with concomitant hypertension. * Immediate-release nifedipine formulation is generally avoided for chronic hypertension due to risk of reflex tachycardia and precipitating angina or myocardial infarction. * Constipation is a significant side effect of verapamil, particularly in elderly patients. * Peripheral edema is common with DHPs and can be dose-limiting. It is often managed by co-administration with an ACE inhibitor or ARB, or by switching CCB agents. * In cases of overdose, CCB toxicity can be severe and may require aggressive supportive care, including calcium administration, vasopressors, and glucagon. *** **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 administering any medication. Dosing and recommendations may vary based on patient-specific factors and institutional protocols.