Acetylcysteine
Common Brand Names: Mucomyst, Mucosil, Acetadote
Therapeutic Class: Mucolytic and Antidote
Common Injectable Dosage Forms: Solution for Injection: 10% and 20% vials
Dosage Ranges:
For the treatment of acetaminophen overdose: 21-hour regimen: Give an IV loading dose of 150 mg/kg in 200 mL D5W over 60 minutes. Maintenance dose is 50 mg/kg in 500 mL D5W over 4 hours, then 100 mg/kg in 1000 mL D5W over 16 hours. 48-hour regimen: Give an IV loading dose of 140 mg/kg (diluted 1:5 in D5W) over 60 minutes. After 4 hours give 70 mg/kg (1:5 in D5W) every 4 hours for 12 doses for a total of 980 mg/kg.
Nephrotoxic Prophylaxis: 1200 mg IV before procedure, followed by 1200 mg orally twice daily for 2 days. No adjustment required for hepatic or renal impairment.
For the treatment of atelectasis by nebulization into a face mask, mouthpiece, or tracheostomy: The usual dose is 3-5 mL of the 20% solution or 6-10 mL of the 10% solution 3-4 times daily. Dosage range is 1-10 mL of the 20% solution or 2-20 mL of the 10% solution every 2-6 hours.
Administration and Stability: Acetylcysteine is a concentrate that must be further diluted in dextrose 5% for IV infusion. The manufacturer recommends the loading dose be added to 200 mL of D5 and infused over 15 minutes. Subsequent first maintenance dose should be mixed in 500 mL D5 and infused over 4 hours. Second maintenance dose should be mixed in a liter of D5 and infused over 16 hours. Total volume must be adjusted for patients <40 kg or in fluid-restricted individuals. Store at room temperature and vials are single use only. Once added to D5, drug is stable for 24 hours at room temperature.
Pharmacology/Pharmacokinetics: Acetylcysteine acts as an antioxidant that scavenges free radicals and enhances nitric oxide by combining with it to form S-nitrosothiol, a potent vasodilator. For hepatotoxicity secondary to acetaminophen overdose, it offers sulfhydryl groups to serve as a substrate for toxic acetaminophen metabolites in place of the liver’s glutathione. Mean half-life is 5.6 hours, clearance is 0.11 L/hr/kg. Renal clearance accounts for 30% of dose. Acetylcysteine that is absorbed systemically deacetylated to cysteine by the liver and intracellularly in most tissues.
Drug and Lab Interactions: Acetylcysteine is a reducing agent that is not compatible with oxidizing agents, therefore, incompatible with rubber and some materials such as iron, copper, and nickel, liberating hydrogen sulfide gas. Use of equipment made of plastic, glass, stainless steel, or nonreactive metal is recommended. Other interactions include nitrates, carbamazepine, and charcoal.
Contraindications/Precautions: Contraindicated in pregnancy, breastfeeding, acute bronchospasm, asthma, biliary cirrhosis, children, gag reflex depression, and vomiting. Pregnancy Category B.
Monitoring Parameters: Blood glucose, LFTs, PT, serum Cr, BUN, serum electrolytes.
Adverse Effects: May cause fever, anaphylaxis, flushing, erythema of skin, nausea, vomiting, urticaria, and angioedema.
Common Clinical Applications: Useful in acute acetaminophen overdose and nephrotoxic prophylaxis. Also used in atelectasis and for prophylactic use along with hydration to prevent nephrotoxicity induced by radiographic contrast agents in high-risk patients.
