Comparison of N-acetylcysteine and methylene blue, alone or in combination, for treatment of acetaminophen toxicosis in cats

Am J Vet Res. 1995 Nov;56(11):1529-33.


Acetaminophen is widely used in human beings for analgesic purposes, but is one of the most frequent causes of poisoning in cats. Acetaminophen-poisoned cats develop methemoglobinemia and sometimes hepatic failure. To determine the benefit of using methylene blue, a treatment for methemoglobinemia, along with N-acetylcysteine (NAC), the recommended treatment for acetaminophen-poisoned cats, groups of 3 male and 3 female cats each were given methylene blue NAC, or both after administration of acetaminophen (120 mg/kg of body weight, PO). Male cats seemed more susceptible than female cats to acetaminophen toxicosis, because 3 males died of hepatic failure (2 cats given acetaminophen/methylene blue and 1 given acetaminophen/NAC/methylene blue). Although NAC alone seemed to elicit the best overall response, methylene blue, alone or in combination with NAC, may be useful in female cats.

MeSH terms

  • Acetaminophen / blood
  • Acetaminophen / poisoning*
  • Acetylcysteine / therapeutic use*
  • Animals
  • Antidotes / therapeutic use*
  • Cat Diseases*
  • Cats
  • Drug Therapy, Combination
  • Female
  • Humans
  • Liver Failure / chemically induced
  • Liver Failure / mortality
  • Liver Failure / veterinary
  • Male
  • Methylene Blue / therapeutic use*
  • Poisoning / veterinary*
  • Sex Characteristics


  • Antidotes
  • Acetaminophen
  • Methylene Blue
  • Acetylcysteine