INFLUENCE OF LACTATION ON PLASMA PHENOBARBITAL CONCENTRATIONS IN RATS

The effect of lactation on the pharmacokinetics of phenobarbital (PB) after delivery was studied in female rats. Non-pregnant animals receiv ed PB 20 mg/kg/day twice for 6-7 days before mating, during pregnancy and after delivery. Chronic PB did not significantly influence changes in the body weight of rats after delivery. On the first post-delivery day, the plasma PB concentration in the PB-treated rats was significa ntly higher than that in PB-treated, non-pregnant rats (non-pregnant r ats); and thereafter, it gradually decreased until ablactation on the 20th day. After ablactation, plasma PB concentrations gradually return ed to the level before delivery. In PB-treated rats, pharmacokinetic p arameters (C-max, AUC(0-12)) of PB between 0 and 12 hr after a single oral administration were significantly decreased during lactation. The se results suggest that PB administered during lactation is transferre d in part to offspring through maternal milk.