Peritoneal fluid concentrations of gentamicin in patients with spontaneous bacterial peritonitis.

Simultaneous peritoneal fluid and serum gentamicin assays were performed at 1- or 4-h intervals after the intravenous administration of gentamicin (3 to 5 mg/kg per day) during nine episodes of spontaneous bacterial peritonitis in cirrhotic patients. Mean peritoneal fluid levels were 4.2 micrograms/ml, whereas simultaneous mean serum levels were 6.1 micrograms/ml (mean percent diffusion into ascites of 67.8%). Three additional patients with uninflamed ascites demonstrated lower levels of diffusion. Regression analysis revealed a positive correlation between simultaneous serum and peritoneal fluid levels. We conclude that diffusion of gentamicin from serum into peritoneal fluid during spontaneous peritonitis is therapeutically adequate if sufficient serum levels are maintained.