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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of medications that reduce myocardial oxygen demand and increase supply by blocking the influx of calcium into cardiac and vascular smooth muscle cells. This leads to vasodilation and decreased heart rate and contractility. They are broadly classified into dihydropyridines (e.g., amlodipine, nifedipine) and non-dihydropyridines (e.g., verapamil, diltiazem). ## Primary Indications * Hypertension * Angina Pectoris (stable and variant) * Supraventricular Tachycardia (rate control and termination) * Raynaud's Phenomenon ## Adult Dosing Dosing varies significantly by agent and indication. ### Dihydropyridines (e.g., Amlodipine) * **Hypertension:** Initial 5 mg orally once daily, titrate up to 10 mg orally once daily. Maximum 10 mg orally once daily. * **Angina:** Initial 5 mg orally once daily, titrate up to 10 mg orally once daily. Maximum 10 mg orally once daily. ### Non-Dihydropyridines (e.g., Verapamil, Diltiazem) * **Hypertension:** * Verapamil (IR): Initial 80 mg orally twice daily, titrate up to 160-320 mg orally twice daily. * Diltiazem (IR): Initial 30-60 mg orally three to four times daily, titrate up to 360 mg orally daily in divided doses. * Diltiazem (ER): Initial 180 mg orally once daily, titrate up to 360 mg orally once daily. * **Angina (Stable and Variant):** * Verapamil (IR): Initial 80 mg orally three times daily, titrate up to 120-160 mg orally three times daily. * Diltiazem (IR): Initial 30-60 mg orally three to four times daily, titrate up to 360 mg orally daily in divided doses. * Diltiazem (ER): Initial 180 mg orally once daily, titrate up to 360 mg orally once daily. * **Supraventricular Tachycardia (Rate Control):** * Verapamil IV: 2.5 mg to 5 mg administered slowly over 2 minutes; may repeat with 5 mg to 10 mg IV if needed after 15-30 minutes. Maximum 20 mg per 24 hours. * Diltiazem IV: 0.25 mg/kg bolus over 2 minutes; may repeat with 0.35 mg/kg bolus over 2 minutes after 15 minutes. Infusion: 5-15 mg/hr. ## Pediatric Dosing Pediatric dosing is not well-established for many CCBs and should be guided by specialist recommendations and specific protocols. * **Amlodipine:** Generally 0.1 mg/kg/dose orally once daily. Maximum 0.3 mg/kg/day or adult dose. ## Dose Adjustments * **Hepatic Impairment:** Dose reduction is generally recommended due to extensive hepatic metabolism. Start with lower doses and titrate slowly. * **Renal Impairment:** Not typically a primary dose adjustment consideration, but caution is advised, especially with non-dihydropyridines and in severe impairment. ## Contraindications * Severe hypotension (systolic BP < 90 mmHg) * Cardiogenic shock * Acute myocardial infarction (especially with signs of heart failure) * Sick sinus syndrome, sinoatrial (SA) nodal disease, or atrioventricular (AV) block greater than first degree (in patients without a functioning pacemaker) - particularly non-dihydropyridines. * Severe left ventricular dysfunction (non-dihydropyridines) * History of hypersensitivity to the drug or its components. * Porphyria (certain agents). ## Adverse Effects * **Common:** Peripheral edema (especially dihydropyridines), headache, dizziness, flushing, constipation (more common with verapamil), nausea, fatigue. * **Less Common/Serious:** Bradycardia, AV block, hypotension, syncope, gingival hyperplasia, exacerbation of heart failure, hepatotoxicity. ## Key Drug Interactions * **Other Antihypertensives:** Additive hypotensive effect. * **Beta-blockers:** Increased risk of bradycardia, AV block, and heart failure, especially with non-dihydropyridines. * **CYP3A4 Inhibitors/Inducers:** Can alter CCB plasma concentrations (e.g., grapefruit juice, azole antifungals, macrolide antibiotics, rifampin, carbamazepine). * **Digoxin:** May increase digoxin levels (non-dihydropyridines). * **Statins:** Some statins (simvastatin, atorvastatin) may have increased plasma concentrations when co-administered with CCBs. * **Lithium:** May interact, potentially leading to neurotoxicity. ## Monitoring * Blood pressure and heart rate. * Signs and symptoms of heart failure. * Signs and symptoms of AV block or bradycardia. * Electrolytes (especially calcium if IV calcium is being administered). * Renal and hepatic function. * Inquire about side effects such as edema and constipation. ## Clinical Pearls * Dihydropyridines (e.g., amlodipine, nifedipine) are generally preferred for isolated hypertension and angina due to their potent vasodilatory effects with fewer cardiac depressant effects. * Non-dihydropyridines (e.g., verapamil, diltiazem) are useful for rate control in atrial fibrillation and for patients with both hypertension and supraventricular tachycardia or angina. * Avoid non-dihydropyridines in patients with heart failure with reduced ejection fraction. * Sustained-release formulations improve adherence and reduce peak-trough fluctuations, thereby minimizing side effects like reflex tachycardia and hypotension. * Peripheral edema is a common dose-limiting side effect of dihydropyridines and can sometimes be managed by adding an ACE inhibitor or ARB. *** **Disclaimer:** This information is for educational purposes only and does not substitute for professional medical advice. Always verify current prescribing information and consult with a qualified healthcare provider for any health concerns or before making any decisions related to your health or treatment.