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# Calcium Channel Blockers
## Overview
Calcium channel blockers (CCBs) are a class of drugs that reduce the influx of calcium ions into cardiac and vascular smooth muscle cells. They are broadly classified into dihydropyridines (DHPs), which primarily affect vascular smooth muscle, and non-dihydropyridines (non-DHPs), which affect both cardiac and vascular smooth muscle.
## Primary Indications
* Hypertension
* Angina pectoris (stable, variant)
* Supraventricular tachyarrhythmias (e.g., atrial fibrillation rate control - non-DHPs)
* Raynaud's phenomenon
## Adult Dosing
Dosing is highly variable based on the specific agent, formulation (immediate vs. extended-release), and indication.
**Dihydropyridines (DHPs):**
* **Amlodipine:** 2.5-10 mg orally once daily. Max: 10 mg/day.
* **Nifedipine (Extended-release):** 30-180 mg orally once daily. Max: 180 mg/day.
* **Felodipine:** 5-10 mg orally once daily. Max: 10 mg/day.
* **Nicardipine (Extended-release):** 30-60 mg orally twice daily. Max: 120 mg/day.
* **Isradipine:** 2.5-5 mg orally twice daily. Max: 10 mg/day.
**Non-Dihydropyridines (Non-DHPs):**
* **Verapamil:**
* Hypertension: 80-160 mg orally three times daily or 180-240 mg extended-release orally once daily. Max: 480 mg/day.
* Angina/Arrhythmia: 40-80 mg orally three times daily. Max: 480 mg/day.
* IV: 2.5-5 mg IV bolus, may repeat with 5-10 mg IV bolus after 15-30 min. Max: 20 mg in 24 hours.
* **Diltiazem:**
* Hypertension: 30-60 mg orally three times daily or 180-240 mg extended-release orally once daily. Max: 360 mg/day.
* Angina/Arrhythmia: 30-60 mg orally three times daily. Max: 360 mg/day.
* IV: 0.25 mg/kg IV bolus, may repeat with 0.35 mg/kg IV bolus after 15 min. Infusion: 5-10 mg/hr, titrate up to 15 mg/hr.
## Pediatric Dosing
Pediatric dosing for CCBs is generally less well-established and often based on adult data and limited studies. Specific doses should be guided by current pediatric guidelines and institutional protocols.
* **Verapamil:**
* Children 1-15 years: 1-3 mg/kg/day divided into 3-4 doses orally.
* Infants <1 year: 0.5-1 mg/kg/day divided into 3-4 doses orally.
* **Diltiazem:**
* Children 2-14 years: 3-6 mg/kg/day divided into 3-4 doses orally. Max: 240 mg/day.
* **Amlodipine:**
* Children 6-17 years: 2.5 mg orally once daily, may titrate up to 5 mg once daily.
## Dose Adjustments
* **Hepatic Impairment:** Reduce dose, particularly for non-DHPs, due to extensive hepatic metabolism. Non-DHPs are more likely to require dose reduction than DHPs.
* **Renal Impairment:** Generally, dose adjustments are not required for DHPs. Non-DHPs may require cautious titration; severe renal impairment might warrant dose reduction.
## Contraindications
* Severe hypotension (systolic <90 mmHg)
* Cardiogenic shock
* Acute myocardial infarction with pulmonary congestion (for non-DHPs)
* Sick sinus syndrome, AV block (second or third degree) without a pacemaker (especially for non-DHPs)
* Severe left ventricular dysfunction (especially for non-DHPs)
* Known hypersensitivity to the drug
## Adverse Effects
Common adverse effects vary by CCB class:
* **DHPs:** Peripheral edema, headache, flushing, dizziness, reflex tachycardia.
* **Non-DHPs:** Constipation (especially verapamil), bradycardia, AV block, dizziness, headache, hypotension, nausea.
## Key Drug Interactions
* **Beta-blockers:** Additive negative chronotropic and inotropic effects, increasing risk of bradycardia and heart failure. Concurrent use requires caution and close monitoring.
* **Digoxin:** CCBs (especially verapamil) can increase digoxin levels by reducing renal and non-renal clearance.
* **CYP3A4 Inhibitors/Inducers:** Many CCBs are substrates of CYP3A4. Potent inhibitors (e.g., ketoconazole, ritonavir) can increase CCB levels, while inducers (e.g., rifampin, carbamazepine) can decrease them.
* **Grapefruit Juice:** Can inhibit intestinal CYP3A4, increasing levels of some CCBs (especially DHPs).
* **Statins:** Some statins (e.g., simvastatin, atorvastatin) are CYP3A4 substrates. Concurrent use with CCBs can increase statin levels, raising the risk of myopathy.
* **Amiodarone:** Increased risk of bradycardia and AV block when used with non-DHPs.
## Monitoring
* **Blood Pressure:** Regularly monitor blood pressure to assess efficacy and prevent hypotension.
* **Heart Rate:** Monitor heart rate, especially with non-DHPs, for bradycardia or AV block.
* **ECG:** Baseline and periodic ECG may be indicated, especially with non-DHPs, to monitor for conduction abnormalities.
* **Renal and Hepatic Function:** Baseline and periodic monitoring may be necessary, particularly in patients with pre-existing impairment or those on other renally/hepatically cleared medications.
* **Signs of Heart Failure:** Monitor for worsening edema, dyspnea, or weight gain.
## Clinical Pearls
* DHPs are generally preferred for hypertension due to their potent vasodilatory effects and lower risk of cardiac depression.
* Non-DHPs are useful for rate control in atrial fibrillation and for managing supraventricular tachycardias due to their direct cardiac effects.
* Extended-release formulations improve adherence and reduce peak-trough variability, minimizing side effects like reflex tachycardia.
* Calcium channel blockers can worsen GERD symptoms.
* Abrupt discontinuation, especially of high doses, may lead to rebound hypertension or angina.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and clinical guidelines for specific patient care decisions.*
