[Pharmacokinetic investigations of the transfer of antibiotics into amniotic fluid. Part III: Oxacillin (author's transl)].

After intravenous administration of 2 g of Oxacillin to 12 gravidae at the end of their pregnancy short-interval tests were made of the Oxacillin levels in the mothers' serum and -- intra-amnionic catheter in position -- in the amniotic fluid. The following pharmaco-kinetic data were determined: fictitious initial Oxacillin level (79 mcg/ml), elimination constant (1,044 h-1), half-value of elimination (39,88 min), fictitious distribution volume (25,31), distribution coefficient (0,3617 ml/g), total clearance (26,431 l/h) and invasion constant (0,0084 h-1). All given data were statistically confirmed. For the para-placental passage of Oxacillin a permeability factor (chi) of 0,0084 was found. This factor indicates how easy Oxacillin passes trough the fetal membrane into the amniotic fluid. Ampicillin diffuses about 43 times and Cephalotin diffuses about 2,4 times better trough fetal membrane -- permeability factor 0,357 or 0,02 --, probably because of its weaker link to serum albumin. Under our conditions the amnionic levels reached 12 mcg/ml on the average. With 8-12 g Oxacillin daily bactericidal levels in the amniotic fluid are reached.