Critical Periods for Diphenylhydantoin and Phenobarbital Administration during Gestation
Pregnant female albino rats were randomly assigned to one of three groups which were administered either 15 mg/kg diphenylhydantoin, 5 mg/kg phenobarbital or an equal volume of distilled water. All administrations occurred daily in one of four time frames, Days 1–7, Days 8–14, Days 15-birth, Days 1-birth. At 75 days of age one male and one female offspring from 48 different litters were tested on avoidance conditioning. Few birth defects were noted in the offspring, and abnormalities were not noted with regard to physical development. The results of avoidance-conditioning testing indicate that the administration of diphenylhydantoin during the third period of pregnancy and the administration of phenobarbital during the first period are most influential in affecting learning in a detrimental direction. Caution seems advisable in the usage of these drugs in pregnancy.