Serum gentamicin levels in patients with post-cesarean endomyometritis

Serum gentamicin levels were measured by agar diffusion bioassay in 38 patients undergoing treatment with clindamycin-gentamicin for post-cesarean endomyometritis. Patients received intravenous gentamicin in a dose of 1 mg/kg actual body weight every eight hours. All trough levels were less than 1 microgram/ml. The mean 30-minute postinfusion level was 5.78 +/- 2.43 micrograms/ml (mean +/- SD). The range of postinfusion concentrations was 1 to 12 micrograms/ml. Postinfusion concentrations were less than 5 micrograms/ml in 13 patients, but none of these individuals experienced a clinical failure of antimicrobial therapy. There were no statistically significant differences in mean age, weight, hematocrit, serum creatinine, estimated creatinine clearance, or administered dose in patients with therapeutic gentamicin levels and patients with apparent subtherapeutic levels. The authors conclude that postinfusion gentamicin concentrations fluctuate widely in obstetric patients receiving 1 mg/kg/dose and that apparent subtherapeutic postinfusion levels still may be clinically efficacious, depending upon the antimicrobial susceptibility of the infecting microorganisms.