Plasma levels of ampicillin in pregnant women following administration of ampicillin and pivampicillin.

A single dose of ampicillin as been reported to produce lower plasma levels in pregnant than in nonpregnant women. In the present study plasma and urine levels oa ampicillin were studied in pregnant women following administration of multiple oral doses as well as single doses of 0.35 Gm. of pivampicillin and 0.5, 1.0, and 2.0 Gm. of ampicillin. Assays for levels of ampicillin were performed by means of a disc-agar-diffusion method. Multiple doses of ampicillin resulted in plasma levels and recovery in urine similar to those after a single dose. Mean plasma levels were low. A dose of 1.0 Gm. of ampicillin resulted in plasma levels in pregnant women comparable to those reported earlier by us in nonpregnant women following a dose of 0.5 Gm. A dose of 0.35 Gm. of pivampicillin resulted in plasma levels considerably lower than those reported by others in nonpregnant subjects, but plasma levels and recovery in urine were as high as those produced in pregnant women by 0.5 Gm. of ampicillin.