Acetyl Cysteine

# Acetyl cysteine ## Overview - **Classification**: Mucolytic agent, Antidote for acetaminophen toxicity - **Mechanism**: Acts as a precursor for **glutathione**, which detoxifies the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI) in acetaminophen overdose. As a mucolytic, it breaks disulfide bonds in mucus. ## Primary Indications 1. **Acetaminophen Overdose**: Prevention or lessening of hepatotoxicity post-ingestion. 2. **Mucolytic Therapy (Inhaled)**: Adjunctive therapy for abnormal, viscid, or inspissated mucus secretions. 3. **Prevention of Contrast-Induced Nephropathy (Off-Label)**: Often given preemptively before contrast studies. ## Adult Dosing ### Standard Dosing **Acetaminophen Overdose (IV Route - 21-hour approach)** - **Load Dose**: **150 mg/kg** in 200 mL D5W - **Load Frequency**: Given over **60 minutes** - **Dose 2**: **50 mg/kg** in 500 mL D5W - **Frequency 2**: Given over **4 hours** - **Dose 3**: **100 mg/kg** in 1000 mL D5W - **Frequency 3**: Given over the **next 16 hours** - **Maximum**: Total dose approximately **300 mg/kg** over 21 hours. **Inhaled Mucolytic Therapy** (Nebulization) - **Dose**: **3–5 mL** of 20% solution or 6–10 mL of 10% solution - **Frequency**: 3 to 4 times daily - **Route**: Inhalation via nebulizer ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment necessary for antidote use. Monitor fluid balance closely. - **Hepatic Impairment**: Used to treat severe hepatic damage from APAP; no dose adjustment needed for the antidote regimen. - **Elderly Patients**: Use standard adult dosing; closely monitor for fluid overload and adverse effects. ## Pediatric Dosing Dosing depends on route and indication. The IV protocol is preferred for APAP overdose. ### Neonates (0-28 days) - **APAP Overdose**: IV dose may be reduced due to immature renal function and fluid sensitivity. - **Dose**: Consult local protocols; often **150 mg/kg total dose** given more slowly (e.g., over 36 hours) or with reduced fluid volumes. - **Special Notes**: Strict fluid management is critical to prevent intracranial hemorrhage. ### Infants (1–12 months) - **APAP Overdose (IV)**: Use standard **3-bag 21-hour protocol (300 mg/kg total)**. - **Fluid Restriction**: Use **smaller fluid bag volumes** (e.g., 50 mL instead of 200 mL) to meet fluid restriction guidelines, but maintain the mg/kg dose. - **Max Dose**: Standard adult total dose is generally not exceeded. ### Children (1–12 years) - **APAP Overdose (IV)**: Standard **3-bag 21-hour protocol** based on weight. - **Dose**: **150 mg/kg load**, then **50 mg/kg** and **100 mg/kg**. - **Maximum**: Do not exceed the **adult dose equivalent** in larger children (>40 kg). ### Adolescents (13–18 years) - **Dose**: Approach **adult dosing and fluid volumes**; calculate based on current weight unless weight exceeds 100 kg, where a **maximum weight of 100 kg** is typically used for dosing calculation. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to acetyl cysteine or excipients. - **Absolute**: Inhaled use contraindicated in patients who may experience exacerbation of asthma (relative). ### Common Adverse Effects - **Very Common (>10%)**: Nausea, Vomiting (especially oral formulation). - **Common (1–10%)**: Flushing, Pruritus, Rash, Hypotension (IV infusion-related). - **Serious but Rare**: **Anaphylactoid reactions** (non-IgE mediated), Angioedema, Bronchospasm (inhaled). ### Key Drug Interactions - **Activated Charcoal**: **Binds oral acetyl cysteine**; give separately or give IV NAC instead. - **Nitroglycerin**: NAC may **potentiate the vasodilatory effects** of sublingual/IV nitroglycerin. - **Metal Solutions (e.g., Iron/Copper)**: NAC reacts with metal; use only **non-reactive materials** (glass, plastic) for preparation. ## Monitoring & Follow-up - **Before Treatment**: Baseline APAP level, LFTs (AST, ALT), INR, BUN, Cr. - **During Treatment (Antidote)**: Monitor vital signs (especially **blood pressure** and respiratory status) hourly during infusion. Monitor LFTs every **24 hours**. - **Clinical Signs**: Watch for allergic-like reactions (flushing, angioedema) and signs of fluid overload or symptomatic hypotension. ## Clinical Pearls - 💡 **Tip 1**: Administer the IV loading dose **slowly** (over 60 mins) to reduce the risk of anaphylactoid reactions (flushing, nausea). - 💡 **Tip 2**: If the patient vomits the oral dose within 1 hour, the dose should be **repeated** or switch to IV protocol. - 💡 **Tip 3**: The unpleasant sulfur odor of the oral solution can be masked by dilution in soda or juice; however, **IV is usually preferred** due to taste/vomiting issues. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.