Functional classification: Mucolytic, antidote
Acetylcysteine decreases viscosity of secretions and is used as a mucolytic agent in eyes and in bronchial nebulizing solutions. Acetylcysteine is a sulfhydryl compound and acts to increase synthesis of glutathione in the liver. Glutathione subsequently acts as an antioxidant and facilitates conjugation to toxic metabolites, particularly the toxic metabolites of acetaminophen. The antioxidant effects also have been used to treat conditions associated with oxidative stress.
Indications and Clinical Uses
As a donator of the sulfhydryl group, it is used as an antidote for intoxications (e.g., acetaminophen toxicosis in cats). When treating poisoning, it is important that acetylcysteine be administered as soon as possible for optimum effectiveness. Acetylcysteine also has been used to prevent contrast medium induced nephropathy. Acetylcysteine has been used as a treatment of oxidative stress because it is a scavenger of hydroxyl radicals and hypochlorous acid. Acetylcysteine will reduce cerebral edema.
Adverse Reactions and Side Effects
None reported in animals. Allergic reactions have been reported in people, which resemble anaphylactic reactions when it is given IV. These reactions are manifest as skin reactions, bronchospasm, tachycardia, and hypotension.
Contraindications and Precautions
Acetylcysteine may cause sensitization with prolonged topical administration. It may react with certain materials in nebulizing equipment.
Acetylcysteine acts to donate sulfhydryl groups and may facilitate drug conjugation.
Instructions for Use
Available as agent for decreasing viscosity of respiratory secretions, but most common use is as a treatment for intoxications. In cats, acetylcysteine is used to treat acetaminophen toxicosis. When treating an intoxication, doses are listed here, but consult a poison control center for specific guidelines.
For treatment of oxidative stress, constant rate infusions have been used in which 50 mg/kg is diluted 1:4 in saline solutions and administered IV over the course of 1 hour.
Patient Monitoring and Laboratory Tests
When used to treat acetaminophen toxicity, monitor CBC and liver enzyme concentrations.
Acetylcysteine is available in a 20% solution (200 mg/mL).
Stability and Storage
Acetylcysteine is unstable in air and easily oxidizes. It should be protected from light. Discard open vials after 96 hours.
Small Animal Dosage
Dogs and Cats
• Antidote: 140 mg/kg (loading dose) then 70 mg/kg q4h IV or PO for 5 doses.
• Eye solution: 2% solution topically q2h.
• To prevent contrast-medium nephropathy: 17 mg/kg IV bolus, followed by 17 mg/kg every 12 hours for 48 hours.
• Constant rate infusions have been used to treat oxidative stress (50 mg/kg diluted in saline infused over 1 hour).
Large Animal Dosage
No dose has been reported for large animals.
Trade and other names: Mucomyst and Acetadote. Also referred to as N-acetylcysteine.