The pharmacokinetics of intravenous pethidine HC1 in dogs: normal and surgical cases.

The plasma concentration-time profiles of pethidine following a single bolus dose by intravenous injection in normal dogs and in dogs in the immediate postoperative period can be fitted into a biexponential equation, Cp = Ae ^-at+ Be^-βt. The rate of distribution was significantly reduced when a comparatively higher dose rate (3.5 mg/kg) was used in normal dogs but no other differences were seen in the rest of the kinetic parameters. On the other hand using the same dose rate (2 mg/kg) the kinetic constants of both ∝ and β phases in normal and post-surgical dogs were not significantly different, with their respective β half-lives of 36.59 ± 5.98 min and 52.54 ± 11.94 min. However, the distribution volumes and the total body clearance were markedly reduced in surgical as compared to normal dogs. Thus there were differences between the pharmacokinetics of pethidine in normal when compared to dogs undergoing surgical manipulations.