N Acetyl Cysteine

# N acetyl cysteine ## Overview - **Classification**: Mucolytic, Antioxidant, Antidote - **Mechanism**: Restores hepatic glutathione (APAP overdose), provides cysteine precursor. Disrupts disulfide bonds in mucus proteins, reducing viscosity. ## Primary Indications 1. **Acetaminophen (APAP) Overdose** - Prevention and treatment of hepatotoxicity. 2. **Mucolytic** - Adjunctive therapy for abnormal, viscid, or inspissated mucus secretions in various respiratory conditions. 3. **Prevention of Contrast-Induced Nephropathy (CIN)** - Off-label, evidence is mixed/controversial. ## Adult Dosing ### Standard Dosing **Acetaminophen Overdose (IV - 21-hour protocol)** - **Loading Dose**: **150 mg/kg** in **200 mL D5W** over **60 min** - **Second Dose**: **50 mg/kg** in **500 mL D5W** over **4 hours** - **Third Dose**: **100 mg/kg** in **1000 mL D5W** over **16 hours** - **Route**: Intravenous (IV) - **Total Dose**: **300 mg/kg** over **21 hours** **Acetaminophen Overdose (Oral - 72-hour protocol)** - **Loading Dose**: **140 mg/kg** - **Frequency**: Once - **Maintenance Doses**: **70 mg/kg** - **Frequency**: Every **4 hours** for **17 doses** - **Route**: Oral - **Duration**: **72 hours** **Mucolytic (Inhalation)** - **Dose**: **2-20 mL** of **10%** solution OR **1-10 mL** of **20%** solution - **Frequency**: Every **2-6 hours** as needed - **Route**: Nebulization, direct instillation ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment recommended. Monitor fluid status carefully with IV NAC. - **Hepatic Impairment**: No specific dose adjustment recommended. Continue standard APAP overdose protocol. - **Elderly Patients**: No specific dose adjustment. Consider cautious fluid administration for IV NAC. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: Acetaminophen Overdose (IV) - **Loading Dose**: **150 mg/kg** in **3 mL/kg D5W** over **60 min** - **Second Dose**: **50 mg/kg** in **7 mL/kg D5W** over **4 hours** - **Third Dose**: **100 mg/kg** in **14 mL/kg D5W** over **16 hours** - **Maximum**: Total volume **24 mL/kg** over 21 hours. - **Special Notes**: High risk of fluid overload, hyponatremia. Close monitoring of fluid balance, electrolytes. ### Infants (1-12 months) - **Indication**: Acetaminophen Overdose (IV) - **Loading Dose**: **150 mg/kg** in **3 mL/kg D5W** over **60 min** - **Second Dose**: **50 mg/kg** in **7 mL/kg D5W** over **4 hours** - **Third Dose**: **100 mg/kg** in **14 mL/kg D5W** over **16 hours** - **Maximum**: Total volume **24 mL/kg** over 21 hours. - **Special Notes**: Monitor closely for fluid overload, anaphylactoid reactions. ### Children (1-12 years) - **Indication**: Acetaminophen Overdose (IV) - **Dose**: Same mg/kg dosing as adults/infants. Fluid volume adjusted per weight (e.g., max **100 mL** for 1st bag if <20 kg, max **250 mL** for 2nd bag if <20 kg, max **500 mL** for 3rd bag if <20 kg). - **Maximum**: Adult maximum total dose (e.g., 200 mL, 500 mL, 1000 mL for the 3 bags). - **Special Notes**: Consider IV over oral if vomiting, very young, or if charcoal was administered. ### Adolescents (13-18 years) - **Indication**: Acetaminophen Overdose (IV/Oral) - **Dose**: Follow adult dosing protocols (IV or Oral). - **Maximum**: Adult total dose. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to N-acetylcysteine. ### Common Adverse Effects - **Very Common (>10%)**: Nausea, vomiting (oral), rash, flushing, pruritus, urticaria (IV). - **Common (1-10%)**: Hypotension (IV infusion reaction), angioedema. - **Serious but Rare**: Anaphylactoid reactions (non-IgE mediated), bronchospasm (especially with inhaled NAC), acute liver failure (from APAP). ### Key Drug Interactions - **Activated Charcoal**: May adsorb oral NAC, reducing absorption. Administer charcoal 1-2 hours before oral NAC or use IV NAC. - **Nitroglycerin**: NAC may potentiate the vasodilatory and hypotensive effects of nitrates. Monitor blood pressure closely. - **Some Antibiotics**: May cause inactivation if mixed in IV solutions (e.g., ampicillin, tetracyclines, erythromycin). Do not mix. ## Monitoring & Follow-up - **Before Treatment (APAP Overdose)**: Serum APAP level (4+ hours post-ingestion), AST, ALT, INR, creatinine, electrolytes. - **During Treatment (APAP Overdose)**: AST, ALT, INR, creatinine, glucose, electrolytes every 12-24 hours. Monitor vital signs for infusion reactions (IV). - **Clinical Signs**: Assess for signs of hepatic injury (jaundice, encephalopathy), improving liver function tests. ## Clinical Pearls - 💡 **Tip 1**: Early administration of NAC is crucial for preventing severe hepatotoxicity in APAP overdose. - 💡 **Tip 2**: Anaphylactoid reactions to IV NAC are common but typically managed by slowing or temporarily stopping the infusion. - 💡 **Tip 3**: Oral NAC has a distinct odor and taste; dilute in juice or soda to improve palatability. - 💡 **Tip 4**: IV NAC is preferred in patients who are vomiting, have impaired GI motility, or are severely ill. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.