Pharmacokinetic studies on tobramycin in horses

Abstract

The objective of the study was to evaluate the pharmacokinetics of tobramycin in plasma and urine in the horse (n = 7) after intravenous administration of a dose of 4 mg/kg b.w. Plasma tobramycin concentrations were assayed microbiologically and by means of HPLC analyses. Pharmacokinetic parameters, calculated on the basis of concentrations determined with the microbiological assay were not statistically different from those obtained when data from HPLC analysis were used, but the microbiological assay was more sensitive in the detection of low plasma and urine values. The values of the total body clearance (Cl(B)) were 101.4 +/- 30.1 and 130.0 +/- 49.9 mL/kg/h, respectively. The overall extraction ratio was 2.9%. The determined capacity of elimination of tobramycin in horses was similar to those for other aminoglycosides. Within 24 h after treatment, 57.6 +/- 12.2% of injected antibiotic was excreted in the urine.

Population Pharmacokinetics of Tobramycin in Horses

“…Availability of userfriendly software can help in introduction of this procedure as a routine practice in clinical care for horses. In our study, using a population approach, experimental data were fitted to a two-compartmental model, in accordance with earlier reports on tobramycin disposition [4,14,15]. Estimated mean value of population for systemic clearance of tobramycin is very close to previously published data in horses [4].…”

“…In our study, using a population approach, experimental data were fitted to a two-compartmental model, in accordance with earlier reports on tobramycin disposition [4,14,15]. Estimated mean value of population for systemic clearance of tobramycin is very close to previously published data in horses [4]. Similar range of values have been reported for humansdsystemic clearance between 0.041 and 0.071 L/hr/kg; Vd ranged from 0.49 to 0.94 L/kg, and V 1 ranged from 0.294 to 0.335 L/kg [16,17].…”

“…Antibiotic concentrations were determined within 2 days after sampling by microbiological assay, as described in the pilot pharmacokinetic study [4]. In comparison with high-performance liquid chromatography analysis, this assay is more sensitive in the detection of low plasma and urine values.…”

“…Plasma concentration curves versus time were interpreted by a two-compartmental model on the basis of knowledge about tobramycin disposition in horses obtained in a previously conducted study [4].…”

“…As an aminoglycoside drug, it exhibits concentration-dependent bactericidal activity. Tobramycin pharmacokinetics was earlier investigated in healthy horses after a single intravenous administration, and it does not differ from the other aminoglycoside antibiotics [4]. Tobramycin shows rapid distribution to most fluids in the body, including peritoneal, pleural, pericardial, and synovial fluids [5].…”