Side Effects of Acetylcysteine in Felines

Under the brand names Mucomyst or Mucosil, acetylcysteine is approved by the Food and Drug Administration for human use and is used off-label by veterinarians. The drug breaks down mucus, and is often administered in nebulizer form. It is generally considered safe for felines, but some side effects have been reported. While usually given to dry up mucus, it is also used for acetaminophen poisoning in cats. Never give acetaminophens, such as Tylenol or generic versions, to felines for pain relief as it is toxic to cats.

  1. Drooling

    • Acetylcysteine is foul-tasting, with a sulfur-like flavor. If given in oral form, it may cause drooling in cats. Although unpleasant in appearance, this side effect is relatively harmless.

    Airway Spasms

    • Acetylcysteine is often used to treat animals suffering upper respiratory infections, as it will dry up the mucous secretions associated with the ailment. However, the drug has been know to cause spasms of the airways, so it should be used cautiously with any cats known to have lung disease, according to Pet Place. If your cat has an upper respiratory infection, discuss this possible side effect with your veterinarian.

    Hives

    • Pet Education states that hives have occasionally been reported as a side effect of acetylcysteine. If your cat has this reaction, the veterinarian may administer antihistamines to control the itching and reduce the swelling of the hives. Do not give a cat any over-the-counter antihistamine without veterinary approval.

    Nausea and Vomiting

    • Because of its bad smell, some pets will react to the administration of acetylcysteine by throwing up or becoming nauseous. Flavoring the medication may prevent this side effect.

    Drug Interactions

    • Acetylcysteine may interfere with the actions of some medications. Check with your veterinarian if your cat is on a medication that could be affected by acetylcysteine administration. Pet Place reports that acetylcysteine may interfere with charcoal, which would be given in the event of acetaminophen poisoning.