Verapamil

# Verapamil ## Overview - **Classification**: Non-dihydropyridine Calcium Channel Blocker (NDHP CCB), Antiarrhythmic Class IV. - **Mechanism**: Inhibits calcium influx into cardiac and smooth muscle cells, decreasing myocardial contractility, slowing AV nodal conduction, and causing vasodilation. ## Primary Indications 1. **Hypertension** - Management of essential hypertension. 2. **Angina Pectoris** - Chronic stable angina, vasospastic (Prinzmetal's) angina. 3. **Supraventricular Tachycardia (SVT)** - Acute termination of PSVT, rate control in atrial fibrillation/flutter. ## Adult Dosing ### Standard Dosing **Hypertension & Angina Pectoris** (Oral) - **Dose**: **80-120 mg** (initial, immediate release) - **Frequency**: Three times daily (TID) - **Route**: Oral (PO) - **Max Dose**: Up to **480 mg/day** (immediate release), **480 mg/day** (sustained/extended release). **Supraventricular Tachycardia (SVT)** (IV) - **Dose**: **5-10 mg** (initial bolus) - **Frequency**: Over **2 minutes**. May repeat **10 mg** after 30 minutes if needed. - **Route**: Intravenous (IV) push - **Max Dose**: **15-20 mg** total within 30 minutes. ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment needed; use with caution. - **Hepatic Impairment**: Reduce oral dose by **25-50%** due to reduced metabolism. - **Elderly Patients**: Start with lower doses (**40-80 mg PO**) and titrate slowly due to increased bioavailability and reduced clearance. ## Pediatric Dosing ### Neonates (0-28 days) - **Note**: Verapamil is generally **contraindicated** in neonates. - **Special Notes**: High risk of severe hypotension and asystole. Avoid use. ### Infants (1-12 months) - **SVT (IV)**: - **Dose**: **0.05-0.1 mg/kg** (initial bolus) - **Frequency**: Over **2-3 minutes**. - **Maximum**: **2.0-5.0 mg** per dose. May repeat once after 30 minutes if needed. - **Special Notes**: Use with extreme caution. Monitor ECG, heart rate, and blood pressure closely. Resuscitation equipment must be available. ### Children (1-12 years) - **SVT (IV)**: - **Dose**: **0.1-0.3 mg/kg** (initial bolus) - **Frequency**: Over **2-3 minutes**. - **Maximum**: **5 mg** per dose. May repeat once after 30 minutes if needed. - **Hypertension/Angina (Oral, rarely used)**: - **Dose**: **2-5 mg/kg/day** (immediate release, divided doses) - **Frequency**: Two or three times daily (BID or TID) - **Maximum**: **480 mg/day** or adult dose equivalent. ### Adolescents (13-18 years) - **Dose**: Generally follows adult dosing guidelines. - **SVT (IV)**: **5-10 mg** bolus. - **Hypertension/Angina (Oral)**: **80-120 mg** initial, titrate up to **480 mg/day**. - **Maximum**: Adult maximum doses apply. ## Safety Information ### Contraindications - **Absolute**: Severe left ventricular dysfunction, cardiogenic shock. - **Absolute**: Sick sinus syndrome (without pacemaker), 2nd/3rd degree AV block (without pacemaker). - **Absolute**: Hypotension (systolic BP <90 mmHg). - **Absolute**: Wide complex tachycardias (e.g., WPW, LGL syndrome with AFib). - **Absolute**: Concomitant IV beta-blocker administration. - **Relative**: Acute myocardial infarction with pulmonary congestion. ### Common Adverse Effects - **Very Common (>10%)**: Constipation (especially with oral formulations). - **Common (1-10%)**: Headache, dizziness, bradycardia, hypotension, peripheral edema, flushing, nausea. - **Serious but Rare**: High-degree AV block, asystole, heart failure exacerbation, elevated liver enzymes. ### Key Drug Interactions - **Beta-blockers**: Increased risk of bradycardia, AV block, and heart failure. **Avoid concomitant IV use.** - **Digoxin**: Increases digoxin levels by inhibiting renal and P-gp excretion. Reduce digoxin dose by **25-50%** and monitor levels. - **CYP3A4 Inhibitors/Inducers**: Verapamil is a CYP3A4 substrate. Inhibitors (e.g., clarithromycin, grapefruit juice) increase verapamil levels. Inducers (e.g., rifampin) decrease levels. - **Statins (e.g., simvastatin, lovastatin)**: Verapamil inhibits CYP3A4, increasing statin levels. Increased risk of myopathy/rhabdomyolysis. Use lower statin doses or switch to a statin not metabolized by CYP3A4 (e.g., pravastatin, rosuvastatin). - **Grapefruit Juice**: Increases verapamil plasma concentrations. Advise patients to avoid. ## Monitoring & Follow-up - **Before Treatment**: Baseline ECG, blood pressure (BP), heart rate (HR), renal and liver function. - **During Treatment**: - **IV**: Continuous ECG, HR, BP monitoring during and after administration. - **Oral**: Monitor BP and HR regularly. Periodically check renal and liver function. - **Clinical Signs**: Watch for signs of heart failure (e.g., dyspnea, edema), excessive bradycardia, hypotension, or dizziness. ## Clinical Pearls - 💡 **IV Administration**: Administer IV bolus slowly over **2-3 minutes** to minimize risk of severe hypotension/bradycardia. - 💡 **Constipation**: Very common side effect. Counsel patients on hydration, fiber intake, or stool softeners. - 💡 **Extended-release formulations**: Do not crush or chew extended-release tablets. - 💡 **Grapefruit Juice**: Advise patients to avoid grapefruit juice as it can significantly increase verapamil levels. - 💡 **Avoid in WPW**: **Never use IV verapamil for wide-complex tachycardias** (e.g., suspected Wolff-Parkinson-White syndrome with AFib) as it can lead to ventricular fibrillation. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.