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# Calcium Channel Blockers
## Overview
Calcium channel blockers (CCBs) are a class of drugs that reduce the influx of calcium into cardiac and vascular smooth muscle cells. This leads to vasodilation and/or decreased cardiac contractility and heart rate. They are classified into dihydropyridines (e.g., amlodipine, nifedipine) and non-dihydropyridines (e.g., diltiazem, verapamil).
## Primary Indications
* Hypertension
* Angina pectoris
* Supraventricular tachyarrhythmias (rate control)
* Raynaud's phenomenon
## Adult Dosing
* **Amlodipine:**
* Hypertension/Angina: 5-10 mg orally once daily. Maximum 10 mg daily.
* **Nifedipine (extended-release):**
* Hypertension: 30-60 mg orally once daily. Maximum 120 mg daily.
* Angina: 30-60 mg orally once daily. Maximum 120 mg daily.
* **Diltiazem (extended-release):**
* Hypertension: 180-360 mg orally once daily, divided into 2-3 doses. Maximum 540 mg daily.
* Angina: 180-360 mg orally once daily, divided into 2-3 doses. Maximum 540 mg daily.
* Rate Control: 120-360 mg orally once daily, divided into 2-3 doses. Maximum 540 mg daily.
* **Verapamil (extended-release):**
* Hypertension: 180-480 mg orally once daily, divided into 2-3 doses. Maximum 480 mg daily.
* Angina: 160-480 mg orally once daily, divided into 2-3 doses. Maximum 480 mg daily.
* Rate Control: 160-480 mg orally once daily, divided into 2-3 doses. Maximum 480 mg daily.
Specific dosing for acute treatment of arrhythmias (IV administration) or for rare indications may depend on local protocols.
## Pediatric Dosing
Established pediatric dosing for CCBs is limited and often based on small studies or extrapolated from adult data. Dosing should be individualized and carefully monitored.
* **Amlodipine:**
* Hypertension (6-17 years): 2.5 mg orally once daily. May increase to 5 mg once daily. Maximum 5 mg daily.
* **Nifedipine (extended-release):** Generally not recommended for pediatric use due to lack of established dosing and safety data.
* **Diltiazem:**
* Hypertension (older children): May be considered, but specific guidelines are lacking. Dosing is highly individualized.
* **Verapamil:** Generally not recommended for pediatric use due to lack of established dosing and safety data.
## Dose Adjustments
* **Hepatic Impairment:** Dihydropyridines and non-dihydropyridines are extensively metabolized by the liver. Dose reduction is generally recommended in patients with hepatic impairment. Start with lower doses and titrate cautiously.
* **Renal Impairment:** Dose adjustments are usually not required for dihydropyridines. Non-dihydropyridines may require caution and dose adjustment, especially in severe renal impairment, though data is limited.
## Contraindications
* Hypersensitivity to the drug or its components.
* Cardiogenic shock.
* Severe left ventricular dysfunction (ejection fraction <40%).
* Second- or third-degree atrioventricular (AV) block without a pacemaker (for non-dihydropyridines).
* Sick sinus syndrome without a pacemaker (for non-dihydropyridines).
* Symptomatic hypotension.
* Acute myocardial infarction complicated by hypotension, bradycardia, or left ventricular failure.
* Pulmonary edema associated with mitral stenosis or aortic stenosis (for non-dihydropyridines).
## Adverse Effects
* **Common:** Peripheral edema, headache, flushing, dizziness, fatigue, constipation (more common with verapamil).
* **Cardiovascular:** Bradycardia, AV block, hypotension, exacerbation of heart failure.
* **Gastrointestinal:** Nausea, abdominal pain.
* **Other:** Gingival hyperplasia (rare).
## Key Drug Interactions
* **Beta-blockers:** Additive effects on heart rate and contractility; increased risk of bradycardia and heart failure.
* **CYP3A4 Inhibitors (e.g., azole antifungals, macrolide antibiotics, protease inhibitors):** Can increase CCB levels, leading to increased risk of hypotension and bradycardia.
* **CYP3A4 Inducers (e.g., rifampin, carbamazepine, phenytoin):** Can decrease CCB levels, reducing efficacy.
* **Digoxin:** Non-dihydropyridines can increase digoxin levels.
* **Grapefruit Juice:** Can increase levels of some CCBs (especially amlodipine and felodipine), increasing risk of adverse effects.
* **Statins:** Some statins (simvastatin, atorvastatin) are CYP3A4 substrates; CCBs can increase statin levels, increasing risk of myopathy.
## Monitoring
* **Blood Pressure:** Regularly monitor blood pressure, especially during initiation and titration.
* **Heart Rate and Rhythm:** Monitor for bradycardia and AV block, particularly with non-dihydropyridines.
* **Signs of Heart Failure:** Assess for edema, dyspnea, and weight gain.
* **Electrolytes:** Monitor potassium and magnesium, especially in patients with electrolyte imbalances or those taking diuretics.
* **Renal and Hepatic Function:** Periodic monitoring may be necessary, especially in patients with pre-existing impairment.
## Clinical Pearls
* Dihydropyridines (amlodipine, nifedipine) are primarily vasodilators and have less effect on heart rate and contractility. They are generally preferred for hypertension and Raynaud's.
* Non-dihydropyridines (diltiazem, verapamil) have significant effects on heart rate and contractility and are more useful for rate control in arrhythmias and angina. Verapamil has a stronger negative inotropic effect than diltiazem.
* Peripheral edema is a common dose-limiting side effect of dihydropyridines.
* Constipation is more common with verapamil.
* CCBs should be used with caution in patients with heart failure, especially non-dihydropyridines due to their negative inotropic effects.
* Avoid short-acting nifedipine for hypertension due to risk of reflex tachycardia and rapid BP drops.
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*This information is intended for healthcare professionals and does not replace professional medical advice. Always consult the most current prescribing information and individual patient factors before making treatment decisions.*
