[Antibacterial activity of pefloxacin in the urine during the 7 days following a single 800 mg oral dose].

Antibacterial activity of pefloxacin was studied in the urine after a single 800 mg oral dose in ten healthy female volunteers. Urine was collected in 9 periods: 0-6 h, 6-12 h, 12-24 h, 24-28 h, 48-72 h, 72-96 h, 96-120 h, 120-144 h, 144-168 h. Pefloxacin concentrations were assayed in all samples by a microbiological method and by HPLC. Urine antibacterial activity was determined towards five bacterial strains isolated in urine: 2 E. Coli strains, one sensitive and the other resistant to nalidixic acid (Nal-A), 1 Klebsiella pneumoniae resistant to nalidixic acid (Nal-B), 1 Staphylococcus saprophyticus and 1 Streptococcus faecalis; MIC's of pefloxacin against these strains were respectively 0.015, 0.25, 1, 0.50 and 2 micrograms/ml. Pefloxacin mean concentrations as determined by the microbiological method were 91.8 +/- 11.9, 71.7 +/- 7, 44.5 +/- 4.3, 24.4 +/- 4 and 5.4 +/- 0.8 micrograms/ml in the five first urine samples; low levels were present in the urine until the 7th day in 8 volunteers. HPLC results completed the already known data concerning pefloxacin elimination and metabolism; unchanged pefloxacin was excreted at the highest concentration during the 6 first hours; then demethylpefloxacin was eliminated at higher levels than pefloxacin with a ratio of 2/1 after the 24th hour. These two compounds were detectable in the urine during 5 to 7 days; oxodemethylpefloxacin and N-oxyde-pefloxacin were present in lower amounts and during a shorter period.(ABSTRACT TRUNCATED AT 250 WORDS)