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# Calcium Channel Blockers ## Overview Calcium channel blockers (CCBs) are a class of medications that reduce the influx of calcium ions into vascular smooth muscle and/or myocardial cells. This leads to vasodilation and/or decreased myocardial contractility and heart rate. They are generally categorized into dihydropyridines (e.g., amlodipine, nifedipine), which primarily affect vascular smooth muscle, and non-dihydropyridines (e.g., diltiazem, verapamil), which affect both vascular smooth muscle and the heart. ## Primary Indications * Hypertension * Angina pectoris (stable, vasospastic) * Supraventricular tachycardias (rate control with non-dihydropyridines) * Raynaud's phenomenon ## Adult Dosing Dosing is highly variable depending on the specific agent, formulation (immediate-release vs. extended-release), and indication. * **Dihydropyridines (e.g., Amlodipine):** * Hypertension: Start 5 mg orally once daily. Usual range: 5-10 mg orally once daily. Maximum: 10 mg orally once daily. * Angina: Start 5 mg orally once daily, may increase to 10 mg orally once daily. * **Non-dihydropyridines (e.g., Diltiazem IR):** * Hypertension: Start 30 mg orally three to four times daily. Usual range: 180-360 mg orally per day, divided into three to four doses. * Angina: Start 30 mg orally three to four times daily. Usual range: 180-360 mg orally per day, divided into three to four doses. * **Non-dihydropyridines (e.g., Verapamil IR):** * Hypertension: Start 80 mg orally two to three times daily. Usual range: 240-480 mg orally per day, divided into two to three doses. * Angina: Start 80 mg orally three times daily. Usual range: 240-480 mg orally per day, divided into three doses. Extended-release formulations have different starting doses and titration schedules, often once or twice daily. Specific dosing for all CCBs should be confirmed based on the product monograph and clinical context. ## Pediatric Dosing Parenteral CCBs are used for specific indications like supraventricular tachycardia. Oral CCB use in pediatrics is less common and often off-label for general hypertension, with dosing typically based on weight and established protocols. * **Diltiazem (IV):** * SVT: Neonates: 0.1-0.25 mg/kg IV bolus over 2 minutes. Children: 0.1-0.25 mg/kg IV bolus over 2 minutes, may repeat if needed. Continuous infusion: 5-10 mcg/kg/min IV. * **Verapamil (IV):** * SVT: Infants: 0.5-1 mg/kg IV bolus over 2 minutes. Children: 0.1-0.3 mg/kg IV bolus over 2 minutes, may repeat if needed. * **Oral CCBs for Hypertension:** Dosing varies significantly. For example, amlodipine doses in children aged 6-17 years with hypertension may range from 2.5 mg to 5 mg orally once daily. Pediatric dosing is highly specialized and requires consultation with pediatric cardiology or nephrology guidelines. ## Dose Adjustments * **Hepatic Impairment:** Generally, lower starting doses and slower titration are recommended, particularly for non-dihydropyridines, due to hepatic metabolism. * **Renal Impairment:** Dihydropyridines generally require less dose adjustment, but caution is advised. Non-dihydropyridines may require dose adjustments in severe renal impairment. ## Contraindications * Known hypersensitivity to the drug or its components. * **Non-dihydropyridines (diltiazem, verapamil):** Sick sinus syndrome, second- or third-degree AV block (without a pacemaker), severe left ventricular dysfunction, cardiogenic shock. * **Sustained-release verapamil:** Severe congestive heart failure. ## Adverse Effects * **Common:** Peripheral edema (more common with dihydropyridines), headache, flushing, dizziness, constipation (more common with verapamil). * **Cardiovascular:** Hypotension, bradycardia (non-dihydropyridines), AV block (non-dihydropyridines), exacerbation of heart failure. * **Other:** Gingival hyperplasia (rare), rash, nausea. ## Key Drug Interactions * **Beta-blockers:** Additive effect on AV conduction and myocardial contractility; increased risk of bradycardia and heart failure. Avoid concurrent use of non-dihydropyridines with IV beta-blockers. * **CYP3A4 Inhibitors/Inducers:** CCBs (especially diltiazem and verapamil) are substrates for CYP3A4. * *Inhibitors* (e.g., azole antifungals, macrolide antibiotics, grapefruit juice) can increase CCB levels, raising risk of toxicity. * *Inducers* (e.g., rifampin, carbamazepine, phenytoin) can decrease CCB levels. * **Digoxin:** CCBs can increase serum digoxin levels. * **Statins:** Some statins (e.g., simvastatin, atorvastatin) are substrates of CYP3A4; CCBs can increase statin levels. * **Erythromycin and other macrolides:** Can inhibit CCB metabolism, increasing plasma concentrations. ## Monitoring * **Blood Pressure:** Regularly monitor for therapeutic effect and hypotension. * **Heart Rate and Rhythm:** Especially with non-dihydropyridines, monitor for bradycardia and AV block (ECG may be indicated). * **Edema:** Assess for peripheral edema, particularly with dihydropyridines. * **Signs of Heart Failure:** Monitor for worsening dyspnea, weight gain, and peripheral edema. * **Renal and Hepatic Function:** Monitor periodically, especially in patients with pre-existing impairment or those on multiple interacting medications. * **Serum Digoxin Levels:** If co-administered with digoxin. ## Clinical Pearls * Dihydropyridines are generally preferred for isolated hypertension or angina without significant heart rate concerns due to their potent vasodilatory effects and lower risk of bradycardia/AV block. * Non-dihydropyridines are useful when rate control is also desired (e.g., atrial fibrillation with rapid ventricular response) or in combination with beta-blockers for angina, though concurrent use requires careful monitoring. * Extended-release formulations should not be crushed or chewed. * Advise patients about the risk of orthostatic hypotension, especially when initiating therapy or increasing the dose. * Non-dihydropyridines can significantly worsen constipation, particularly verapamil. *** _This information is intended for educational purposes only and does not substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider to confirm drug details, indications, dosing, contraindications, interactions, and safety measures before making any treatment decisions. Local protocols and guidelines may vary._