Nitroglycerin

# Nitroglycerin ## Overview - **Classification**: Organic nitrate, vasodilator - **Mechanism**: Converts to nitric oxide (NO) in vascular smooth muscle, activating guanylyl cyclase, increasing cyclic GMP (cGMP), leading to venodilation (primary) and arterial dilation. ## Primary Indications 1. **Angina Pectoris** - Treatment of acute episodes and prophylaxis of chronic stable angina. 2. **Acute Myocardial Infarction (AMI)** - Management of ischemic pain, hypertension, and congestive heart failure associated with AMI. 3. **Congestive Heart Failure (CHF)** - Adjunctive therapy for acute decompensated heart failure, especially with hypertension or pulmonary congestion. ## Adult Dosing ### Standard Dosing **Acute Angina Pectoris (Sublingual)** - **Dose**: **0.3 mg**, **0.4 mg**, or **0.6 mg** (tablet or spray) - **Frequency**: Repeat every **5 minutes** as needed - **Route**: Sublingual (under the tongue) or Translingual (spray onto/under tongue) - **Duration**: Max **3 doses** within **15 minutes**. If pain persists, seek immediate medical attention. **Prophylaxis of Chronic Stable Angina (Transdermal Patch)** - **Dose**: Start with **0.2 mg/hr** to **0.4 mg/hr** - **Frequency**: Apply **once daily** - **Route**: Transdermal - **Duration**: Remove patch after **12-14 hours** to allow a nitrate-free interval (typically 10-12 hours) to prevent tolerance. **Prophylaxis of Chronic Stable Angina (Ointment)** - **Dose**: **0.5-2 inches** of ointment - **Frequency**: Every **4-8 hours** - **Route**: Topical - **Duration**: Apply for **10-12 hours**, remove for 10-12 hours for nitrate-free interval. **Acute Myocardial Infarction/CHF/Hypertensive Emergency (Intravenous Infusion)** - **Dose**: Initial **5 mcg/min** - **Frequency**: Titrate by **5 mcg/min** every **3-5 minutes** until desired effect or dose response is achieved. If no response at 20 mcg/min, increases of 10-20 mcg/min may be used. - **Route**: Intravenous infusion - **Maximum Dose**: Typically **200 mcg/min** (may go up to 400 mcg/min in some protocols) ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment generally required, but use with caution due to hypotension risk. - **Hepatic Impairment**: No specific dose adjustment generally required, but use with caution. Metabolized by liver. - **Elderly Patients**: Start with lower doses (especially IV) and titrate slowly due to increased sensitivity to hypotensive effects. Monitor closely for orthostatic hypotension. ## Pediatric Dosing **Note**: Nitroglycerin use in pediatrics is **off-label**, typically restricted to **critical care settings** (e.g., cardiac intensive care units) for specific indications like acute systemic hypertension, pulmonary hypertension, or heart failure, and is always under **specialist supervision**. ### Neonates (0-28 days), Infants (1-12 months), Children (1-12 years) - **Indication**: Acute systemic hypertension, heart failure (e.g., post-cardiac surgery) - **Dose**: Initial **0.25-0.5 mcg/kg/min** - **Frequency**: Titrate by **0.25-0.5 mcg/kg/min** increments every **15-30 minutes** - **Route**: Continuous Intravenous Infusion - **Maximum**: Typically **5 mcg/kg/min**, but some sources report up to **10 mcg/kg/min** in refractory cases. - **Special Notes**: Requires continuous hemodynamic monitoring (BP, HR). Use with caution due to limited data and high risk of hypotension. ### Adolescents (13-18 years) - **Approach**: May follow **adult IV dosing** (e.g., 5 mcg/min initial, titrate) based on weight and clinical indication. - **Maximum**: Similar to adult maximum IV doses, up to **200 mcg/min** generally. - **Special Notes**: Sublingual or topical forms are rarely indicated unless for a very specific, rare adolescent cardiac condition that mimics adult angina; expert consultation advised. ## Safety Information ### Contraindications - **Absolute**: Concomitant use with **PDE5 inhibitors** (e.g., sildenafil, tadalafil, vardenafil) within 24-48 hours. - **Absolute**: Severe **hypotension** or uncontrolled shock. - **Absolute**: Pericardial tamponade, constrictive pericarditis. - **Absolute**: Increased intracranial pressure (e.g., head trauma, cerebral hemorrhage). - **Absolute**: Severe anemia. - **Absolute**: Inferior MI with right ventricular involvement (risk of profound hypotension). - **Absolute**: Hypersensitivity to nitrates. ### Common Adverse Effects - **Very Common (>10%)**: **Headache** ("nitrate headache"), **hypotension**, dizziness, flushing. - **Common (1-10%)**: Nausea, vomiting, weakness, lightheadedness, reflex tachycardia. - **Serious but Rare**: Methemoglobinemia (high doses), syncope, severe bradycardia. ### Key Drug Interactions - **PDE5 Inhibitors (sildenafil, tadalafil)**: **Profound, life-threatening hypotension and cardiovascular collapse.** Absolutely contraindicated. - **Antihypertensives (beta-blockers, calcium channel blockers, ACE inhibitors)**: Enhanced hypotensive effect. Monitor BP closely. - **Alcohol**: Exaggerated hypotensive and vasodilator effects. Avoid or limit concurrent use. - **Ergot alkaloids**: Nitrates may antagonize effects of ergot alkaloids. Avoid concomitant use. ## Monitoring & Follow-up - **Before Treatment**: Baseline BP and HR. - **During Treatment**: - **BP & HR**: Routinely monitor, especially at initiation and with dose changes (frequent with IV, less frequent with topical/SL). - **Chest Pain Relief**: Assess effectiveness. - **Headache/Dizziness**: Monitor for common adverse effects. - **IV Infusion**: Continuous ECG and hemodynamic monitoring (BP, HR, CVP, PA pressures if lines present). - **Clinical Signs**: Watch for signs of excessive vasodilation (e.g., profound hypotension, syncope, severe headache). ## Clinical Pearls - 💡 **Nitrate-Free Interval**: For chronic use (patch, ointment), ensure a daily 10-14 hour nitrate-free interval to prevent tolerance and maintain efficacy. - 💡 **Storage**: Sublingual tablets are sensitive to light, heat, and moisture. Keep them in their original dark glass bottle with a metal cap, away from children. Replace open bottles every **6 months**. - 💡 **Administration**: Sublingual tablets should be placed under the tongue and allowed to dissolve completely; do not chew or swallow. Topical ointment should be measured with an applicator and applied to a hairless area, then covered. - 💡 **Headache**: Headache is common and often indicates the drug is working. Patients should be counseled not to discontinue due to headache if it's tolerable; it often subsides with continued use. Acetaminophen may help. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.