[Effect of orally administered lenampicillin and ampicillin on bacterial flora in human adult feces].

Newly developed lenampicillin (LAPC) which is a prodrug of ampicillin (ABPC), and ampicillin (as the control) were each administered to 6 healthy male volunteers, aged from 21 to 25 years (mean 22.4 years) and weighing 57-78 kg (mean 67.0 kg) to study the effect of LAPC and ABPC on fecal bacterial flora. Each drug was given orally 3 times daily (after meals) with each dose of 250 mg for five days. Changes of the fecal bacterial flora caused by the antibiotic were investigated by determining fecal bacterial counts on the 3rd day before the treatment, 0 (the start of treatment), 3rd and 5th days (the final day of treatment) during treatment, and 3rd, 5th and 10th days after the treatment. Fecal concentrations of LAPC and the metabolites (ABPC, 2-aminobenzyl penicilloic acid (ABPA) and 5S-ABPA) for the LAPC group and ABPC for the ABPC group were assayed. A single dose of 500 mg of LAPC was administered orally after breakfast to additional 6 healthy male volunteers and concentrations of LAPC, metabolites (ABPC, ABPA and 5S-ABPA) in the entire stool were determined daily for 5 successive days after the administration. Clinical adverse reactions and abnormal laboratory-findings caused by either drug were studied in the 18 volunteers. The results obtained are summarized as follows. In the bacterial flora of the 6 volunteers to whom LAPC was administered (the LAPC group), the number of isolated E. coli showed no tend of decrease. Mean bacterial counts obtained 3 days before the treatment and at the day of the treatment were 10(9) and 10(8) cells/g, respectively. These values were compared to the counts obtained on the 3rd and the 5th days during the treatment and were found to be about 10(2)-folds as high as the latter. The decreased counts observed on the 3rd and the 5th days did not last and counts increased again to similar levels observed before the treatment. Klebsiella sp. was isolated from 1 or 2 samples before the treatment. It was isolated from as many as 5-6 cases with mean bacterial counts of 10(7)-10(11) cells/g during and up to 5 days after the treatment. The frequency of isolation then decreased to 4 cases on the 10th day after the treatment.(ABSTRACT TRUNCATED AT 400 WORDS)