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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that reduce the influx of extracellular calcium ions across the membranes of myocardial and vascular smooth muscle cells. They are classified as either dihydropyridines (DHPs) or non-dihydropyridines (non-DHPs). DHPs primarily affect vascular smooth muscle, while non-DHPs affect both cardiac and vascular smooth muscle. ## Primary Indications * Hypertension * Angina pectoris (stable and vasospastic) * Supraventricular tachyarrhythmias (non-DHPs) * Raynaud's phenomenon ## Adult Dosing Dosing is highly variable based on the specific agent, formulation (immediate vs. extended-release), and indication. Doses should be titrated to effect. * **Dihydropyridines (DHPs):** * **Amlodipine:** 5-10 mg orally once daily. Maximum: 10 mg/day. * **Nicardipine (extended-release):** 30-60 mg orally twice daily. Titrate every 7-14 days. Maximum: 120 mg twice daily. * **Nifedipine (extended-release):** 30-60 mg orally once daily. Titrate weekly. Maximum: 120 mg/day (divided doses for some formulations). * **Felodipine (extended-release):** 5-10 mg orally once daily. Titrate every 2-4 weeks. Maximum: 10 mg/day. * **Non-dihydropyridines (non-DHPs):** * **Diltiazem (extended-release):** 120-180 mg orally once daily initially. Titrate every 7-14 days. Maximum: 360 mg/day (divided doses for some formulations). * **Verapamil:** 80-160 mg orally twice daily initially. Titrate weekly. Maximum: 480 mg/day (divided doses for some formulations). ## Pediatric Dosing Pediatric dosing is less established and often requires careful titration and expert consultation. * **Amlodipine:** Generally 0.1-0.3 mg/kg orally once daily. Maximum doses vary by age and weight but are typically lower than adult maximums. Specific pediatric guidelines should be consulted. * **Diltiazem:** May be used for supraventricular tachyarrhythmias. IV doses are often 0.1-0.3 mg/kg, and oral doses are typically initiated lower and titrated. Consult pediatric cardiology guidelines. ## Dose Adjustments * **Hepatic Impairment:** Dose reduction is often necessary, especially for non-DHPs and amlodipine, as they undergo significant hepatic metabolism. Start with lower doses and titrate cautiously. * **Renal Impairment:** Generally no dose adjustment is needed for most CCBs unless there is coexisting severe hepatic impairment or specific metabolic pathways are affected. ## Contraindications * Severe hypotension * Cardiogenic shock * Acute myocardial infarction (especially with heart failure) * Sick sinus syndrome or AV block (second or third degree) without a functioning pacemaker (non-DHPs) * Known hypersensitivity to the drug ## Adverse Effects * **Common:** Peripheral edema, headache, flushing, dizziness, constipation (especially with verapamil), bradycardia, AV block, hypotension. * **Serious:** Worsening heart failure, gingival hyperplasia, severe hypotension, syncope. ## Key Drug Interactions * **Beta-blockers:** Additive negative chronotropic and inotropic effects, increasing risk of bradycardia, AV block, and heart failure. * **CYP3A4 Inhibitors (e.g., grapefruit juice, ketoconazole, ritonavir):** May increase CCB plasma concentrations, increasing the risk of toxicity. * **CYP3A4 Inducers (e.g., rifampin, carbamazepine):** May decrease CCB plasma concentrations. * **Digoxin:** Non-DHPs can increase digoxin levels. * **Statins:** Some statins (e.g., simvastatin, atorvastatin) may have increased levels when coadministered with CCBs, particularly diltiazem and verapamil. ## Monitoring * Blood pressure and heart rate (regularly) * Signs and symptoms of heart failure (e.g., edema, dyspnea) * ECG for evidence of bradycardia or AV block (especially with non-DHPs) * Electrolytes (especially calcium, though significant changes are rare with oral therapy) ## 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 rate control in atrial fibrillation and for managing certain types of angina due to their negative chronotropic and inotropic effects. * Extended-release formulations are preferred for chronic management to reduce dosing frequency and minimize side effects. * Peripheral edema is a common dose-limiting side effect; it is often managed with dose reduction or coadministration of an ACE inhibitor or ARB. * Verapamil is more likely to cause constipation than diltiazem. *** **Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before initiating or modifying drug therapy. Dosing may vary based on individual patient factors and local protocols.