Clinicopathologic evaluation N-acetylcysteine therapy in acetaminophen toxicosis in the cat.

Acute acetaminophen (ACM) toxicosis was induced in cats and the therapeutic benefit of N-acetylcysteine (NAC) was demonstrated. Groups of 4 adult cats were treated as follows: group A-given ACM only; group B- given ACM and then treated with NAC, starting at 0 hour; group C-given ACM and then treated with NAC, starting at 4 hours; and group D-treated with NAC only. Acetaminophen was given as a single oral dose or 143 mg/kg, and the NAC regimen consisted of 4 oral doses (200 mg/kg, given 3 times and 100 mg/kg, given once) with 2 hours between doses. Group A cats developed increased methemoglobin concentration, depletion of erythrocyte reduced glutathione, and increased Heinz body formation. Group B cats also developed methemoglobinemia, depletion of glutathione, and increased Heinz body formation, but the magnitude of these changes was significantly less (P less than 0.05) than in group A. In group C, the findings were similar to group A through 4 hours, but thereafter, significant hematologic improvement was noted. The level of Heinz bodies in group C was intermediate between the values for groups A and B. In group D cats, no significant changes from base line were noted. Evidence of hepatotoxicity was not seen in any group as based on daily determinations of plasma alanine aminotransferase and sorbitol dehydrogenase activities.