EFFECT OF PREGNANCY ON PLASMA PHENOBARBITAL CONCENTRATIONS IN RATS

We examined the pharmacokinetics of phenobarbital before and during pr egnancy in rats. Animals were divided into four groups: (a) control, ( b) pregnant, (c) phenobarbital-treated, and (d) phenobarbital-treated pregnant groups. The increase in body weight of nonpregnant or pregnan t rats was not influenced by long-term phenobarbital treatment. Plasma phenobarbital concentrations during the period of long-term phenobarb ital treatment with a fixed dosage by body weight were not significant ly affected by pregnancy. Furthermore, pregnancy did not affect pharma cokinetic parameters of phenobarbital between 0.25 and 24 h after admi nistration. These results suggest that pregnancy does not influence on the pharmacokinetics of longterm phenobarbital treatment at a fixed d osage by body weight.