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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce the influx of calcium ions into vascular smooth muscle and/or cardiac muscle cells. This leads to vasodilation and/or decreased heart rate and contractility, depending on the specific agent and receptor selectivity. 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 Tachycardias (rate control, particularly non-DHPs) * Raynaud's Phenomenon ## Adult Dosing Specific dosing varies significantly by agent and indication. **Dihydropyridines (e.g., amlodipine, nifedipine, felodipine):** * **Hypertension:** * Amlodipine: 2.5 mg to 10 mg once daily. * Nifedipine (extended-release): 30 mg to 90 mg once daily. * Felodipine (extended-release): 5 mg to 10 mg once daily, may increase to 20 mg daily. * **Angina:** Similar dosing to hypertension, often starting at lower doses. **Non-dihydropyridines (e.g., verapamil, diltiazem):** * **Hypertension:** * Diltiazem (extended-release): 120 mg to 360 mg once or twice daily. * Verapamil (sustained-release): 180 mg to 480 mg once daily. * **Angina:** Similar dosing to hypertension. * **Supraventricular Tachycardia Rate Control:** * Diltiazem IV: 0.25 mg/kg bolus, followed by 0.35 mg/kg bolus if needed. Then, continuous infusion starting at 5 mg/hr, titrate up to 15 mg/hr. * Verapamil IV: 2.5 mg to 5 mg bolus, repeat 5 mg to 10 mg bolus after 15-30 minutes if needed. ## Pediatric Dosing Pediatric dosing is less established and requires careful consideration and often specialized guidelines. * **Hypertension:** * Amlodipine: Generally initiated at 0.1 mg/kg once daily, maximum 5 mg/day. * Nicardipine IV: 1 to 2 mcg/kg/min. Older children may receive higher doses. ## Dose Adjustments * **Renal Impairment:** Generally minimal dose adjustment is needed for most CCBs, though caution is advised. * **Hepatic Impairment:** Dose reduction is often necessary due to reduced metabolism. Start with lower doses and titrate cautiously. * Verapamil: May require up to 50% dose reduction. * Diltiazem: May require up to 50% dose reduction. * Amlodipine: May require dose reduction. ## Contraindications * Hypersensitivity to the drug class or specific agent. * Severe hypotension. * Cardiogenic shock. * Acute myocardial infarction (especially immediate post-MI with certain agents). * Decompensated heart failure (particularly with non-DHPs). * Second- or third-degree AV block, sick sinus syndrome (without a functioning pacemaker) (non-DHPs). * Severe left ventricular outflow tract obstruction (e.g., severe aortic stenosis). ## Adverse Effects Common adverse effects include: * **DHPs:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia, gingival hyperplasia. * **Non-DHPs:** Bradycardia, AV block, constipation (more common with verapamil), nausea, dizziness, hypotension. ## Key Drug Interactions * **Beta-blockers:** Additive effects on heart rate and contractility. Increased risk of bradycardia and AV block. Use with extreme caution, especially non-DHPs with IV beta-blockers. * **Digoxin:** CCBs can increase digoxin levels, particularly verapamil. Monitor digoxin levels. * **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Inhibitors (e.g., grapefruit juice, macrolides, azole antifungals) can increase CCB levels. Inducers (e.g., rifampin, carbamazepine) can decrease levels. * **Statins:** Some statins (simvastatin, atorvastatin) can have increased levels when co-administered with certain CCBs (e.g., amlodipine). * **Antihypertensives:** Additive hypotensive effects. ## Monitoring * Blood pressure and heart rate. * For non-DHPs: Electrocardiogram (ECG) for heart rate and AV conduction. * Renal and hepatic function. * Signs of fluid retention (edema). * For patients on digoxin, digoxin levels. ## Clinical Pearls * DHPs are generally preferred for hypertension and isolated systolic hypertension due to their potent vasodilatory effects and lower risk of bradycardia. * Non-DHPs are useful when heart rate control is also desired (e.g., atrial fibrillation with rapid ventricular response) or for vasospastic angina. * Avoid rapid-acting nifedipine formulations in acute hypertensive emergencies due to risk of precipitous blood pressure drops and reflex tachycardia. * Gingival hyperplasia is a known side effect, especially with long-term use of amlodipine. Advise patients on good oral hygiene. * Non-DHPs should be used with caution in patients with heart failure due to their negative inotropic effects. *** **Disclaimer:** This information is intended for clinical use and does not replace professional medical judgment. Always consult the most current prescribing information and relevant guidelines for definitive dosing and safety recommendations. Pediatric dosing requires particular attention to specific patient factors and available literature.