A pile of pale-orange acetylcysteine pills for dogs and cats.

Acetylcysteine (Mucomyst®) for Dogs and Cats

Acetylcysteine, also known as Mucomyst®, is a derivative of the amino acid cysteine. Though the exact mechanism of action of acetylcysteine is not known, it is believed that the drug reduces sulfide-based links in the proteins of mucus. This results in thinning the mucus, making it easier to be removed from the body by coughing or suction. It is used in dogs and cats as an antidote to acetaminophen toxicity.

Another effect of acetylcysteine is seen in the treatment of acetaminophen poisoning. When acetaminophen is ingested in toxic levels, it will bind to gluathione, resulting in liver damage and the production of abnormal hemoglobin. Acetylcysteine provides an alternate substance for the acetaminophen to bind to, resulting in minimizing liver and hemoglobin damage.

Acetylcysteine is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian. This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names for Acetylcysteine

This drug is registered for use in humans only.

Acetylcysteine is available in 100 mg/ml and 200 mg/ml concentrations in 4 ml, 10 ml and 30 ml vials.

Uses of Acetylcysteine for Dogs and Cats

Acetylcysteine is used as an antidote to acetaminophen toxicity. This drug is also used to reduce excessive production of mucus in the airways and eyes, particularly associated with upper respiratory infections.

Acetylcysteine for Pets: Precautions and Side Effects

While generally safe and effective when prescribed by a veterinarian, acetylcysteine can cause side effects in some animals. Acetylcysteine has a very bad taste and foul sulfur odor. Nausea and vomiting are potential side effects. The bad taste of the drug can also cause drooling. Since acetylcysteine can cause spasms of the lower airways, this drug should be used with caution in animals with lung disease that predisposes to airway spasms.

Acetylcysteine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with acetylcysteine. Such drugs include activated charcoal.

This medication should not be used in animals with known hypersensitivity or allergy to the drug.

Dosing Information for Acetylcysteine in Dogs and Cats

For acetaminophen toxicity, acetylcysteine, diluted to a 50 milligram/milliliter concentration, is given initially at a dose of 70 milligram per pound (140 milligram/kilogram) intravenous or orally. Four hours later, a lower dose of 35 milligram per pound (70 milligram/kilogram) is given intravenous or orally every 4 hours for 3 to 5 total treatments.

For treatment of excessive airway mucus accumulation, acetylcysteine is administered as a nebulization. It is aerosolized and inhaled at a concentration of 50 ml/hour for 30 to 60 minutes, twice a day.

The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse. Medication should never be administered without first consulting your veterinarian.