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Infectious Diseases in Obstetrics and Gynecology
Volume 7 (1999), Issue 3, Pages 133-137

Single Daily Dosing of Gentamicin: Pharmacokinetic Comparison of Two Dosing Methodologies for Postpartum Endometritis

1Department of Pharmacy, Detroit Medical Center and Wayne State University, Detroit, MI, USA
2Department of Medicine (Infectious Diseases), Detroit Medical Center and Wayne State University, Detroit, MI, USA
3Department of Obstetrics and Gynecology, Detroit Medical Center and Wayne State University, Detroit, MI, USA
4Department of Obstetrics and Gynecology, Wayne State University-Grace Hospital, 6071 West Outer Drive, Detroit 48235, MI, USA

Received 23 October 1998; Accepted 1 February 1999

Copyright © 1999 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Objective: We compared the pharmacokinetics of two methods for dosing gentamicin for the treatment of postpartum endometritis with the goal of achieving adequate peak serum concentrations (>12 mg/L) and prolonged trough levels below 2 mg/L.

Methods: Group-I subjects (n = 5) received intravenous gentamicin, 5 mg/kg per total body weight over 60 min., with a maximum dose of 500 mg. Group-II subjects (n = 17) were dosed intravenously according to the following formula: Dose = desired peak concentration (fixed at 14 mg/L)* (volume of distribution, i.e., 0.35 L/kg)* adjusted body weight (in kilograms). Serum gentamicin levels were obtained 1 hr. and 8–12 hr. after infusion of the second dose. Pharmacokinetic parameters for the subjects in each group were calculated according to standard formulas.

Results: Subjects in Group I had significantly higher doses and peak drug concentrations (P < 0.01), while in Group II, 76% of patients had peak levels less than desired (<12 mg/L). Both groups maintained trough levels of <2 mg/L in excess of 12 hr.

Conclusions: Changing to the adjusted body weight formula for Group I, while maintaining a dose between 4 and 5 mg/kg, would reduce excessive peak concentrations. Using a calculated volume of distribution of 0.4 L/kg in Group II would improve peak serum concentrations to the desired levels. Both dosing regimens ensure adequate aminoglycoside pharmacokinetic parameters and avoid the need for monitoring serial serum drug concentrations, provided the expected clinical response is also achieved. While the first dosing formula is simpler to calculate, the second dosing formula allows for more individualized dosing considerations. Infect. Dis. Obstet. Gynecol. 7:133–137, 1999.