Serum concentrations of orally administered diphenylhydantoin in dogs.

Diphenylhydantoin was found to have a short half life and poor gastrointestinal absorption in dogs. Consequently, serum content after single or repeated oral dosage of 10 mg/kg of body weight did not exceed a concentration of 2 microgram/ml. To achieve a postulated effective plasma concentration of diphenylhydantoin, oral dosage of at least 35 mg/kg of body weight 3 times daily seems necessary.