Interactions between chloramphenicol and intravenous anesthetics

Chloramphenicol has been reported to prolong the action of barbiturate hypnotics by an inhibition of liver mixed function oxidases. We have studied the importance of this interaction for shortacting intravenous anesthetics the effect of which is terminated by distribution rather than metabolic inactivation. Mice were pretreated orally with 50 mg/kg chloramphenicol as the sodium succinate 1 h before the iv. injection of the anesthetics, and the sleeping times were compared to those of untreated controls. The duration of action of methohexital was prolonged when doses of 15 and 20 mg/kg were injected, but not with the lowest dose of 10 mg/kg. After injection of thiopental (30, 40 and 50 mg/kg) only the medium dose was prolonged the effect of etomidate (3 and 5 mg/kg), but not that of propanidid (60 mg/kg) or ketamine (30 and 40 mg/kg). The results show that the experimental finding of an interaction between chloramphenicol and barbiturates cannot be generalized: It will not play a major role with usual clinical induction doses the effect of which is terminated by distribution, but may be of importance when higher doses are administered.