Antibiotic Concentrations in Ascitic Fluid of Patients with Ascites and Bacterial Peritonitis

Abstract

Paired specimens (36) of serum and ascitic fluid from 21 patients with peritonitis and ascites, most with spontaneous bacterial peritonitis and alcoholic cirrhosis, were assayed for antibiotic content. Antibiotics assayed and number of determinations were gentamincin, 14; tobramycin, 7; ampicillin, 5; clindamycin, 3; penicillin G, 2; cephalothin, 2; chloramphenicol, 2; and cefazolin, 1. In 31 paired specimens the ascitic fluid antibiotic concentration was about 1/2 or more of the simultaneous serum level and in 17 assays exceeded 90% of the serum level. All antibiotics studied penetrated ascitic fluid equally well. Clinical response to antibiotic therapy was good in 12 of 16 patients with culture-proven bacterial peritonitis. Antibiotic levels in ascitic fluid exceeded the minimal inhibitory concentration of the infecting organisms in all but one patient who responded. Direct i.p. instillation of antibiotics does not appear to be necessary routinely, but there may be an initial lag of several hours before antibiotic concentrations in ascites achieve therapeutic levels.