N-Acetyl Cystiene

# N-ACETYL CYSTIENE ## Overview - **Classification**: Mucolytic, Antioxidant, Acetaminophen antidote - **Mechanism**: Replenishes hepatic glutathione, detoxifies reactive metabolites in acetaminophen overdose. Breaks disulfide bonds in mucoproteins, reducing mucus viscosity. ## Primary Indications 1. **Acetaminophen Overdose**: Prevention/attenuation of hepatic injury. 2. **Mucolytic Therapy**: Adjuvant in respiratory conditions with viscous secretions (e.g., cystic fibrosis, COPD). 3. **Prevention of Contrast-Induced Nephropathy (Off-label)**: Role is controversial; not routinely recommended. ## Adult Dosing ### Standard Dosing **Acetaminophen Overdose (IV)** - Standard 3-Bag Protocol - **Loading Dose**: **150 mg/kg** in 200 mL D5W over **60 minutes** - **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 infusion - **Maximum Dose**: Total dose **300 mg/kg** over 21 hours - **Special Considerations**: Administer with an infusion pump. Total fluid volume can be adjusted for fluid-restricted patients. **Acetaminophen Overdose (Oral)** - Standard 18-Dose Protocol - **Loading Dose**: **140 mg/kg** - **Frequency**: Single dose - **Route**: Oral (diluted 1:4 with soda, juice, or water) - **Maintenance Doses**: **70 mg/kg** - **Frequency**: Every 4 hours for 17 doses - **Total Doses**: 18 doses over 72 hours - **Special Considerations**: May use nasogastric tube for administration. Administer antiemetics as needed. **Mucolytic (Inhalation)** - **Dose**: **3-5 mL** of 20% solution or **6-10 mL** of 10% solution - **Frequency**: 3-4 times daily - **Route**: Nebulization (face mask, mouthpiece, tracheostomy) - **Special Considerations**: Use bronchodilator prior if patient has reactive airways. ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment for acetaminophen overdose protocol. Use caution, monitor fluid balance closely. - **Hepatic Impairment**: No specific dose adjustment for acetaminophen overdose protocol. Efficacy is reduced in severe hepatic failure. - **Elderly Patients**: No specific dose adjustments; follow standard protocols. Monitor fluid status carefully with IV administration. ## Pediatric Dosing ### Neonates (0-28 days) **Acetaminophen Overdose (IV)** - **Dose**: Same mg/kg protocol as adults: **150 mg/kg**, then **50 mg/kg**, then **100 mg/kg**. - **Frequency**: Over 21 hours (total). - **Maximum**: Total **300 mg/kg**. - **Special Notes**: Crucial to reduce total fluid volume for small infants to prevent fluid overload. Administer in smallest possible diluent (e.g., **D5W 50 mL** for loading, **100 mL** for second, **250 mL** for third dose, or less). ### Infants (1-12 months) **Acetaminophen Overdose (IV)** - **Dose**: Same mg/kg protocol as adults: **150 mg/kg**, then **50 mg/kg**, then **100 mg/kg**. - **Frequency**: Over 21 hours (total). - **Maximum**: Total **300 mg/kg**. - **Special Notes**: Adjust fluid volumes carefully to prevent fluid overload. Use an infusion pump. ### Children (1-12 years) **Acetaminophen Overdose (IV)** - **Dose**: Same mg/kg protocol as adults: **150 mg/kg**, then **50 mg/kg**, then **100 mg/kg**. - **Frequency**: Over 21 hours (total). - **Maximum**: Total **300 mg/kg**. - **Special Notes**: Fluid restriction may be needed in younger, smaller children. **Mucolytic (Inhalation)** - **Dose**: **2-4 mL** of 10% or 20% solution - **Frequency**: 3-4 times daily - **Maximum**: Not to exceed adult dosage. - **Special Notes**: May need to dilute 20% solution further for infants/small children. ### Adolescents (13-18 years) - **Dose**: Follow **adult dosing protocols** for all indications. - **Maximum**: Adult maximum doses apply. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to N-acetylcysteine. - **Relative**: Acute bronchospasm (for inhalation). ### Common Adverse Effects - **Very Common (>10%)**: Nausea, vomiting (oral). - **Common (1-10%)**: Anaphylactoid reactions (flushing, rash, pruritus, angioedema, hypotension, bronchospasm - IV), dyspepsia (oral), stomatitis, rhinitis (inhalation). - **Serious but Rare**: Severe anaphylactoid reactions, status asthmaticus, Stevens-Johnson Syndrome, toxic epidermal necrolysis. ### Key Drug Interactions - **Activated Charcoal**: Adsorbs oral NAC, reducing bioavailability. Separate administration by 1-2 hours. - **Nitroglycerin**: Potentiates vasodilation and hypotensive effects of nitroglycerin. Monitor blood pressure closely. - **Metal Ions**: NAC is incompatible with iron, copper, and rubber. Use plastic/glass for preparation and administration. - **Antibiotics**: NAC may physically interact with some antibiotics (e.g., penicillins, cephalosporins) if mixed directly. Administer separately. ## Monitoring & Follow-up - **Before Treatment (Acetaminophen Overdose)**: Acetaminophen level, LFTs (ALT, AST), PT/INR, serum creatinine, electrolytes. - **During Treatment (Acetaminophen Overdose)**: Repeat LFTs, PT/INR, creatinine every 24 hours. Monitor vital signs for anaphylactoid reactions. - **Clinical Signs**: For IV, observe for flushing, rash, wheezing, hypotension. For oral, monitor for nausea/vomiting. ## Clinical Pearls - 💡 **Timeliness is Key**: For acetaminophen overdose, NAC is most effective when given within **8 hours** of ingestion. - 💡 **Anaphylactoid Reactions**: These are infusion rate-related, not true allergy. Slowing the infusion rate and administering antihistamines can manage symptoms. - 💡 **Oral NAC Palatability**: Has a sulfurous odor and unpleasant taste. Dilute significantly with cola, juice, or water. - 💡 **IV Fluid Volume**: For small children/neonates, judiciously reduce diluent volumes to prevent fluid overload, especially with IV NAC. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.