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# Calcium Channel Blockers
## Overview
Calcium channel blockers (CCBs) inhibit the influx of calcium ions into cardiac and vascular smooth muscle cells. They are classified into **dihydropyridines** (vasoselective, primarily used for hypertension/angina) and **non-dihydropyridines** (dromotropic/inotropic effects, used for arrhythmias and hypertension).
## Primary Indications
* **Hypertension** (All)
* **Chronic Stable/Vasospastic Angina** (All)
* **Supraventricular Tachyarrhythmias (SVT/A-Fib rate control)** (Non-dihydropyridines only: Diltiazem, Verapamil)
## Adult Dosing
* **Amlodipine (DHP):** 2.5–10 mg PO daily. Max: 10 mg/day.
* **Nifedipine ER (DHP):** 30–90 mg PO daily. Max: 90 mg/day.
* **Diltiazem IR:** 30–90 mg PO QID; **ER/CD:** 120–480 mg PO daily. Max: 480 mg/day.
* **Verapamil IR:** 80–120 mg PO TID; **ER:** 120–480 mg PO daily. Max: 480 mg/day. (Note: dosing for arrhythmias may vary by institutional protocol).
## Pediatric Dosing
* **Amlodipine:** 0.1 mg/kg/day (up to 5 mg) initially, titrated to 0.6 mg/kg/day in older children.
* **Non-dihydropyridines:** Highly variable; typically restricted to specialist settings (pediatric cardiology) for arrhythmias.
* *Note: Dosing is highly weight-dependent and varies by indication. Consult pediatric-specific references (e.g., Harriet Lane) for every order.*
## Dose Adjustments
* **Hepatic Impairment:** Reduce starting doses for diltiazem, verapamil, and amlodipine as they undergo extensive hepatic metabolism.
* **Renal Impairment:** Generally no adjustment required, but monitor for edema.
## Contraindications
* **Non-dihydropyridines:** Severe left ventricular dysfunction (HFrEF), second- or third-degree AV block (without a pacemaker), and sick sinus syndrome (except in patients with a functioning pacemaker).
* **General:** Known severe hypersensitivity. Use caution in hypotension or severe aortic stenosis.
## Adverse Effects
* **Dihydropyridines:** Peripheral edema, reflex tachycardia, flushing, headache, gingival hyperplasia.
* **Non-dihydropyridines:** Bradycardia, AV block, constipation (especially verapamil), exacerbation of Heart Failure with reduced Ejection Fraction (HFrEF).
## Key Drug Interactions
* **CYP3A4 Substrates/Inhibitors:** Diltiazem and verapamil are moderate CYP3A4 inhibitors. Caution with statins (increased risk of myopathy, specifically simvastatin/lovastatin dose caps), cyclosporine, and tacrolimus.
* **Beta-blockers:** Additive effect on slowing AV conduction; high risk of symptomatic bradycardia or heart block when used with non-dihydropyridines.
## Monitoring
* **Blood Pressure** and **Heart Rate** (at baseline and after titration).
* **ECG** (specifically for non-dihydropyridines to assess PR interval).
* **Peripheral Edema.**
* **Signs of HF exacerbation** (dyspnea, weight gain).
## Clinical Pearls
* **Constipation:** Verapamil is well-known for significant constipation; counsel patients on fiber and hydration.
* **Grapefruit Juice:** Avoid or limit consumption, as it can inhibit CYP3A4 and significantly increase systemic levels of CCBs.
* **Dosing Confusion:** Never interchange immediate-release (IR) and extended-release (ER/CD/SR) formulations.
* **Selection:** Use dihydropyridines for pure hypertension; use non-dihydropyridines when comorbid A-fib or SVT is present.
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*Disclaimer: This information is for educational purposes for healthcare professionals. Dosage and local clinical practice protocols can vary significantly. Always verify doses, contraindications, and drug interactions against institutional policies, current FDA-approved labeling, or resources like Lexicomp or Micromedex before prescribing or administering medication.*
