Acetylcysteine for treatment of acetaminophen toxicosis in the cat.

Acute acetaminophen intoxication in the cat was studied to characterize the antidotal profile of acetylcysteine. Toxicosis was associated with cyanosis, hyperventilation, depression, and facial edema. Abnormal laboratory findings were methemoglobinemia and elevated serum glutamic-pyruvic transaminase activity. In one trial, each of ten cats was given a 325-mg tablet of acetaminophen, then another after 4 hours. Five of the cats were given antidotal treatment with acetylcysteine (140 mg/kg, per os) at the time of the second dosing with acetaminophen and at 8-hour intervals thereafter for a total of three treatments. All treated cats survived. Two of the untreated cats died. In another trial, doubling each dose of acetaminophen (650 mg) proved fatal in all of four untreated cats. When antidotal therapy was initiated at the time of the second dosing with acetaminophen and repeated at 8- or 4-hour intervals for three treatments, two of four cats in each treatment group survived. Although antidotal therapy was associated with a return of serum glutamic-pyruvic transaminase and methemoglobinemia values toward normal, only the methemoglobin value was a reliable prognostic indicator.