Calcium%2525252525252525252525252525252525252520channel%2525252525252525252525252525252525252520blockers

# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of drugs that inhibit the entry of calcium ions into cardiac and vascular smooth muscle cells. This leads to vasodilation and decreased myocardial contractility and heart rate, depending on the specific agent. They are divided into two main classes: dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs). ## Primary Indications * Hypertension * Angina pectoris (stable and variant) * Supraventricular tachycardias (non-DHPs) * Raynaud's phenomenon ## Adult Dosing **Dihydropyridines (e.g., amlodipine, nifedipine, felodipine):** * **Amlodipine:** Start at 5 mg once daily. Usual range: 5-10 mg once daily. Maximum: 10 mg once daily. * **Nifedipine (extended-release):** Start at 30 mg once daily. Usual range: 30-90 mg once daily. Maximum: 120 mg once daily. * **Felodipine (extended-release):** Start at 5 mg once daily. Usual range: 5-10 mg once daily. Maximum: 10 mg once daily. **Non-Dihydropyridines (e.g., verapamil, diltiazem):** * **Verapamil (IR):** Start at 80 mg three times daily. Usual range: 80-160 mg three times daily. Maximum: 320 mg daily (divided doses). * **Verapamil (ER):** Start at 180 mg once daily. Usual range: 180-480 mg once daily. Maximum: 480 mg daily. * **Diltiazem (IR/SR):** Start at 30 mg four times daily (IR) or 60 mg twice daily (SR). Usual range: 180-360 mg daily (divided doses). Maximum: 360 mg daily. * **Diltiazem (ER):** Start at 120-180 mg once daily. Usual range: 120-540 mg once daily. Maximum: 540 mg daily. ## Pediatric Dosing Pediatric dosing for CCBs can vary significantly and is often based on weight and specific indication. Dosing may not be well-established for all agents or age groups. Consult pediatric-specific resources for detailed guidance. * **Amlodipine:** Often initiated at 0.05 mg/kg/day, not to exceed adult maximum. * **Verapamil:** Typically dosed for supraventricular tachycardia; e.g., 0.1-0.2 mg/kg/dose IV up to a maximum of 5 mg/dose in children <1 year, or 10 mg/dose in children >1 year. Oral dosing varies. * **Diltiazem:** Oral dosing varies by formulation and indication. ## Dose Adjustments * **Hepatic Impairment:** Reduced doses are often necessary due to extensive hepatic metabolism. Start at lower doses and titrate carefully. * **Renal Impairment:** Generally, dose adjustments are not required for renal impairment, but caution is advised for severe impairment. ## Contraindications * Severe hypotension (systolic BP < 90 mmHg) * Cardiogenic shock * Acute myocardial infarction with signs of heart failure or pulmonary congestion (non-DHPs) * Second- or third-degree AV block without a functioning pacemaker (non-DHPs) * Sick sinus syndrome without a functioning pacemaker (non-DHPs) * Known hypersensitivity to the drug * Porphyria (primarily for verapamil) ## Adverse Effects Common adverse effects include: * **DHPs:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia. * **Non-DHPs:** Bradycardia, constipation (especially verapamil), AV block, dizziness, headache, hypotension. Serious adverse effects: syncope, heart failure exacerbation. ## Key Drug Interactions * **Beta-blockers:** Additive bradycardia and AV block, particularly with non-DHPs. * **Digoxin:** Increased digoxin levels, especially with verapamil. * **CYP3A4 Inhibitors/Inducers:** May alter CCB concentrations (e.g., grapefruit juice, azole antifungals, rifampin, carbamazepine). * **Aspirin:** May reduce the antiplatelet effect of aspirin (controversial). * **Grapefruit Juice:** Can significantly increase plasma concentrations of some CCBs (especially verapamil, diltiazem, amlodipine, felodipine). ## Monitoring * Blood pressure and heart rate. * Signs of heart failure (e.g., dyspnea, edema). * Electrocardiogram (particularly for non-DHPs to assess for AV block). * Serum electrolytes and renal function if indicated. * For verapamil, monitor for constipation and increase fluid/fiber intake. ## Clinical Pearls * DHPs are generally preferred for hypertension and angina when minimal cardiac effects are desired. * Non-DHPs are useful for rate control in supraventricular tachycardias and may be preferred when both blood pressure and heart rate control are needed. * Onset of action and duration vary significantly by formulation (immediate-release vs. extended-release). * Non-DHP CCBs should be used with caution in patients with impaired left ventricular function. * Constipation is a notable side effect of verapamil and can be managed with dietary modifications and laxatives. --- ***Disclaimer:** This information is intended for educational purposes only and does not constitute medical advice. It is essential to consult the most current prescribing information and clinical guidelines, and to make individualized patient care decisions based on the patient's specific condition and needs.*