Pharmacokinetics of sulfonamides and trimethoprim in the donkey (Equus asinus).

The research focuses on pharmacokinetics of different sulfonamides and trimethoprim when administered in donkeys, with an attempt to understand body clearance and steady-state distribution. The results were compared to those observed in horses.

Research Overview

• This research was conducted to understand the pharmacokinetics of certain drugs namely sulfadimidine (SDM), sulfadiazine (SDZ), sulfamethoxypyridazine (SMPZ), and a trimethoprim-sulfadimethoxine combination (TMP-SDMX) in donkeys.
• The drugs were administered intravenously in specific doses and their body clearance (ClB) and volume of distribution at a steady state (Vss) were studied.
• The clearance rate was found to be statistically higher for SDZ as compared to other drugs, while the steady-state distribution volume was similar for all sulfonamides.
• Both ClB and Vss for trimethoprim were found to be significantly higher than for the sulfonamides.
• Moreover, assessments were made regarding the hepatic oxidative function and total body water volume considering the ClB and Vss of antipyrine.
• The resultant data was then compared with the data previously reported in horses.

Research Findings

• There was a noticeable variance in the body clearance of the drugs, with SDZ (1.70 +/- 0.14 ml/min/kg) having a significantly higher body clearance when compared to SDM (1.13 +/- 0.18 ml/min/kg), SMPZ (1.10 +/- 0.09 ml/min/kg), and SDMX (0.75 +/- 0.04 ml/min/kg).
• The steady state volume distribution for SDM, SDZ, SMPZ and SDMX was fairly consistent with slight variations: 0.68 +/- 0.08 L/kg, 0.63 +/- 0.07 L/kg, 0.47 +/- 0.06 L/kg, and 0.46 +/- 0.05 L/kg respectively.
• Trimethoprim exhibited significantly higher ClB (4.36 +/- 0.60 ml/min/kg) and Vss (2.71 +/- 0.86 L/kg) values compared to the sulfonamides.
• The ClB and Vss of antipyrine which were used to assess hepatic oxidative function and the total body water volume highlighted either a significant difference (in ClB) or similarity (in Vss) when compared with the values calculated for sulfonamides.
• While comparing these findings with pre-existing data from horses, variations in pharmacokinetics between the two animal species were noted, implying potential differences in metabolism and drug distribution.