Pharmacokinetics of metronidazole in hospitalized patients

The recently expanded indications of metronidazole increase the use of the drug in the hospitalized patients. However, most of the pharmacokinetic information on metronidazole was derived from normal subjects. The pharmacokinetics of metronidazole was, therefore, evaluated in nine hospitalized patients who have no evidence of liver or kidney failure. The patients received the drug for prophylaxis or treatment of infectious conditions. Serial blood samples were obtained from the patients and serum metronidazole concentrations were determined by high performance liquid chromatography. The following pharmacokinetic parameters (mean +/- standard deviation) were obtained: half-life = 10.2 +/- 3.1 hours, elimination rate constant = 0.075 +/- 0.026 hour-1, volume of distribution = 0.65 +/- 0.25 l kg-1, and total body clearance = 0.048 +/- 0.024 l h-1 kg-1. The mean value of these parameters are not substantially different from those obtained in the normal subjects. However, a higher interpatient variation was found in the hospitalized patients. The heterogeneity of health condition, body composition, fluid balance, hemodynamics and nutritional status may all contribute to the variability in pharmacokinetic characteristics.