Sleeping time and mortality of rats administered acetylsalicylic acid and barbiturates

Acetylsalicylic acid was administered orally in doses from 0.2 to 1.9 g/kg with pentobarbital or thiopental, given intraperitoneally 1 h later, in doses ranging from 25 to 55 mg/kg, to overnight-fasted, male, albino rats. Both sleeping time and mortality were significantly increased with acetylsalicylic acid – barbiturate combinations. A dose-response relationship was observed in both sleeping time and mortality after acetylsalicylic acid and thiopental but only with the former after acetylsalicylic acid and pentobarbital. Starvation prolonged thiopental sleeping time. At equal doses, thiopental was more toxic than pentobarbital, when given separately and in combination with acetylsalicylic acid.