21-day intravenous toxicity study with feline interferon in rats

The toxicity of recombinant feline interferon, a prospective antiviral drug for cats, was examined in a subacute study. Groups of five male and five female Wistar rats were given iv feline interferon in 20 mM-NaCl at doses of 0, 5, 15 and 50 MU/kg body weight/day for 21 consecutive days. Criteria to assess toxicity included clinical observations, ophthalmoscopy, growth, food and water intake, haematology, clinical chemistry, urinalysis, organ weights, gross examination at autopsy and microscopic examination of the liver, kidneys, spleen, adrenals, heart, mesenteric lymph nodes and thymus. No treatment-related were observed even at the highest dose level. The no-observed-adverse-effect level for feline interferon in this study was therefore 50 MU/kg body weight/day.