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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 cells and vascular smooth muscle cells. They are broadly classified into dihydropyridines (DHPs) and 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
**Dihydropyridines (DHPs):**
* **Amlodipine:** 2.5 mg to 10 mg once daily.
* **Felodipine:** 2.5 mg to 10 mg once daily (extended-release).
* **Nifedipine (extended-release):** 30 mg to 120 mg once daily.
* **Nicardipine (IV):** 2.5 mcg/kg/min to 15 mcg/kg/min, titrated to blood pressure.
* **Nimodipine:** 0.014 mg/kg (or 1 mg) every 4 hours for 21 days, started 4 days before subarachnoid hemorrhage.
**Non-Dihydropyridines (Non-DHPs):**
* **Diltiazem:**
* Oral (immediate-release): 30 mg to 60 mg three to four times daily.
* Oral (extended-release): 60 mg to 360 mg once or twice daily, depending on formulation.
* IV: 0.25 mg/kg bolus, followed by 0.35 mg/kg if needed, then continuous infusion 5-15 mg/hr.
* **Verapamil:**
* Oral (immediate-release): 80 mg to 160 mg two to three times daily.
* Oral (extended-release): 120 mg to 480 mg once or twice daily, depending on formulation.
* IV: 2.5 mg to 5 mg bolus, followed by 5 mg to 10 mg if needed after 15-30 minutes.
## Pediatric Dosing
* Dosing in pediatric populations is less established and often relies on expert consensus or local protocols.
* **Amlodipine:** Generally 0.1 mg/kg to 0.3 mg/kg once daily (maximum 5 mg to 10 mg daily).
* **Verapamil:** Used for supraventricular tachycardias, generally 0.1 mg/kg to 0.2 mg/kg IV.
* **Diltiazem:** Used for supraventricular tachycardias, generally 0.1 mg/kg to 0.2 mg/kg IV.
## Dose Adjustments
* **Hepatic Impairment:** Reduce dose for verapamil and diltiazem. Use with caution and lower doses for DHPs; monitor blood pressure closely.
* **Renal Impairment:** Generally no dose adjustment needed for most CCBs, but caution and monitoring are advised, especially with verapamil and diltiazem.
## Contraindications
* Hypersensitivity to the drug or excipients.
* Severe hypotension.
* Cardiogenic shock (especially non-DHPs).
* Sick sinus syndrome (non-DHPs, unless pacemaker is in place).
* Second- or third-degree AV block (non-DHPs, unless pacemaker is in place).
* Congestive heart failure with reduced ejection fraction (use non-DHPs with extreme caution or avoid).
* Acute myocardial infarction (especially immediate-release nifedipine).
## Adverse Effects
* **Common:** Peripheral edema, headache, flushing, dizziness, constipation (especially verapamil), nausea, fatigue.
* **Less Common/Serious:** Hypotension, bradycardia, AV block, worsening heart failure, gingival hyperplasia, rash.
## Key Drug Interactions
* **Beta-blockers:** Additive effects on heart rate and contractility, increasing risk of bradycardia and AV block.
* **Digoxin:** Increased digoxin levels (especially with verapamil and diltiazem).
* **CYP3A4 inhibitors/inducers:** Can affect CCB metabolism (e.g., grapefruit juice, azole antifungals, rifampin, carbamazepine).
* **Statins:** Increased risk of myopathy with certain statins (e.g., simvastatin, atorvastatin) when co-administered with diltiazem or verapamil.
* **Antihypertensives:** Additive hypotensive effects.
## Monitoring
* Blood pressure (supine and standing).
* Heart rate.
* Electrocardiogram (ECG) for AV conduction abnormalities and arrhythmias.
* Signs and symptoms of heart failure.
* Renal and hepatic function (periodically).
* Plasma digoxin levels if applicable.
## Clinical Pearls
* Dihydropyridines are generally preferred for isolated hypertension due to their potent vasodilatory effects and lower risk of cardiac depression.
* Non-dihydropyridines are useful for rate control in atrial fibrillation/flutter and for angina with concomitant hypertension.
* Peripheral edema is dose-dependent and often more pronounced with DHPs.
* Constipation is a common and often dose-limiting side effect of verapamil.
* IV administration of CCBs requires close hemodynamic monitoring.
* Dose titrations should be performed cautiously, allowing adequate time for steady-state concentrations to be achieved.
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*This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines before making any treatment decisions.*
