Prostatic fluid and tissue concentrations of ampicillin after administration of hetacillin ester (BL-P1761).

Ampicillin concentrations in prostatic fluid and tissue were studied in dogs after constant intravenous infusion of ampicillin (three dogs) and a lipid-soluble methoxymethyl ester of hetacillin, BL-P1761 (six dogs). Prostatic fluid ampicillin concentrations as determined by bioassay were found to be approximately 15 times higher after administration of hetacillin than after a similar amount of ampicillin. The prostatic fluid concentrations after hetacillin ester administration were approximately one-half of the simultaneous plasma concentrations. This hetacillin ester is thus the first penicillin compound shown to be penetrating the blood-prostatic fluid barrier, resulting in clinically relevant prostatic fluid concentrations.