The pharmacokinetics of tetroxoprim in the dog

The pharmacokinetics and metabolism of the newly developed antibacterial tetroxoprim (TXP) were investigated in four male beagle dogs using a 2-(14C)-labelled drug. TXP was administered intravenously and orally at doses of 5 mg/kg bodyweight. Counting of the total 14C-radioactivity shows that the drug was absorbed completely and eliminated almost exclusively by the kidneys. The quantitative absorption of TXP from the canine gastro-intestinal tract was ascertained by comparison of the AUC-values and the renal recoveries of unchanged drug following i.v. and oral dosage. The terminal half-lives of non-metabolized compound in plasma were 4.64 and 4.83 for i.v. and oral dosing respectively. Following either i.v. or oral TXP administration, the major route of excretion was renal elimination of the compound as its major metabolite U-1 (81-82.2% of dose) and as unchanged mother substance (11.4-12.3% of dose).