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# Calcium Channel Blockers
## Overview
Calcium channel blockers (CCBs) are a class of medications that disrupt the movement of calcium ions into muscle cells, including those in the heart and blood vessels. This action leads to vasodilation and decreased heart rate and contractility. They are broadly categorized into dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs).
## Primary Indications
* Hypertension
* Angina pectoris (stable and variant)
* Supraventricular tachyarrhythmias (especially non-DHPs)
* Raynaud's phenomenon
## Adult Dosing
Dosing varies significantly by specific agent and indication. Examples include:
* **Amlodipine (DHP):**
* Hypertension: Start at 5 mg orally once daily, titrate up to 10 mg once daily.
* Angina: Start at 5-10 mg orally once daily.
* **Diltiazem (Non-DHP):**
* Hypertension: Immediate-release 30-60 mg orally 3-4 times daily, or extended-release 120-360 mg orally once daily.
* Angina: Immediate-release 30-90 mg orally 3-4 times daily, or extended-release 120-480 mg orally once daily.
* Rate control (tachyarrhythmias): Immediate-release 0.25 mg/kg IV bolus, may repeat 0.35 mg/kg IV bolus after 15 minutes, followed by continuous infusion of 5-15 mg/hour. Oral immediate-release 30-60 mg 3-4 times daily. Extended-release 180-400 mg once daily.
* **Verapamil (Non-DHP):**
* Hypertension: Immediate-release 80-120 mg orally 2-3 times daily, or extended-release 180-480 mg orally once daily.
* Angina: Immediate-release 80-120 mg orally 3-4 times daily, or extended-release 120-480 mg orally once daily.
* Rate control (tachyarrhythmias): Immediate-release 2.5-5 mg IV bolus, may repeat 5-10 mg IV bolus after 15-30 minutes. Oral immediate-release 80-120 mg 2-3 times daily. Extended-release 180-480 mg once daily.
Maximum doses are agent-specific and should not be exceeded without careful consideration of risks and benefits.
## Pediatric Dosing
Pediatric dosing for CCBs is less established and often requires careful titration based on response and tolerance. Specific doses depend on the agent and indication. Consult specialized pediatric pharmacology resources for detailed regimens.
* **Amlodipine:** Hypertension: 0.05-0.2 mg/kg orally once daily, maximum 5 mg once daily in children <6 years, maximum 10 mg once daily in children 6-12 years.
* **Diltiazem:** Supraventricular Tachycardia: IV loading dose 0.1-0.2 mg/kg per dose, not to exceed 5 mg/kg/day. IV infusion 5-15 mcg/kg/min. Oral: 2-5 mg/kg/day divided into 3-4 doses.
## Dose Adjustments
* **Hepatic Impairment:** Generally requires dose reduction due to metabolism. Start at lower doses and titrate cautiously.
* **Renal Impairment:** DHP CCBs generally do not require significant dose adjustment. Non-DHP CCBs may require caution and dose adjustment due to potential accumulation, especially in severe impairment.
## Contraindications
* Hypersensitivity to the specific drug or its components.
* Decompensated heart failure (especially non-DHPs).
* Second- or third-degree atrioventricular (AV) block or sick sinus syndrome (without a pacemaker) (especially non-DHPs).
* Severe hypotension (systolic BP <90 mmHg).
* Acute myocardial infarction with pulmonary congestion (especially non-DHPs).
* Cardiogenic shock.
## Adverse Effects
Common adverse effects include:
* **DHP:** Peripheral edema, flushing, headache, dizziness, reflex tachycardia.
* **Non-DHP:** Bradycardia, constipation (more common with verapamil), AV block, dizziness, hypotension, nausea.
Serious adverse effects can include: severe hypotension, bradycardia, heart failure, and arrhythmias.
## Key Drug Interactions
* **Beta-blockers:** Additive effects on heart rate and contractility. Use with caution, especially non-DHPs, due to risk of profound bradycardia and AV block.
* **Digoxin:** Non-DHPs can increase digoxin levels by reducing its renal and non-renal clearance.
* **CYP3A4 inhibitors (e.g., ketoconazole, ritonavir, grapefruit juice):** May increase CCB plasma concentrations, increasing risk of toxicity.
* **CYP3A4 inducers (e.g., rifampin, carbamazepine):** May decrease CCB plasma concentrations, reducing efficacy.
* **Statins:** Grapefruit juice interaction with CCBs can also affect concentrations of certain statins (e.g., simvastatin, atorvastatin).
## Monitoring
* Blood pressure (supine and standing)
* Heart rate
* ECG for heart rhythm and AV conduction
* Signs and symptoms of heart failure
* Electrolytes (especially calcium and potassium, in select cases)
* Renal and hepatic function (periodically)
## Clinical Pearls
* DHP CCBs are generally preferred for hypertension and angina management due to their potent vasodilatory effects and lower risk of bradycardia or AV block.
* Non-DHP CCBs are more useful for rate control in supraventricular tachycardias and symptom management in certain types of angina due to their negative chronotropic and inotropic effects.
* Starting CCBs at low doses and titrating slowly is crucial, especially in elderly patients or those with impaired cardiac or hepatic function.
* Non-DHP CCBs can cause significant constipation, particularly verapamil; this may necessitate increased fluid and fiber intake or bowel regimen.
* Grapefruit juice can significantly increase the bioavailability of many CCBs, leading to increased adverse effects; patients should be advised to avoid it.
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***Disclaimer:** This information is intended for healthcare professionals and is not exhaustive. Always consult the most current prescribing information, institutional guidelines, and drug databases for complete and up-to-date information before making therapeutic decisions.*
