Antibiotic levels in plasma and peritoneal fluid after amoxycillin, ampicillin, and bacampicillin treatment for pelvic inflammatory disease.

Fifteen patients with pelvic inflammatory disease had a thin polyethylene catheter inserted through the abdominal wall into the pouch of Douglas for sampling of peritoneal fluid. At hourly intervals peritoneal fluid and capillary blood were collected. Five patients each received a single oral dose of either 0.5 g of ampicillin or amoxycillin, or 0.8 g of bacampicillin (approximately equimolar doses). This highest median peak plasma level was observed after bacampicillin. Bacampicillin also showed less variation in individual plasma concentration. The area below the plasma curve was similar for amoxycillin and bacampicillin, whereas that of ampicillin was significantly smaller (p less than 0.01). The rate of penetration into peritoneal fluid was slower for amoxycillin than for bacampicillin, even though the area below the peritoneal fluid curve was similar for the two drugs. Therapeutic levels were maintained for 5--8 hours, longer after amoxycillin than after bacampicillin.