Pharmacokinetic interactions between flunixin and sulphadimidine in horses.
The pharmacokinetic aspects of sulphadimidine were studied in clinically healthy (control) and Flunixin-medicated horses after a single intravenous and oral administration of 100 mg/kg body weight. Plasma sulphadimidine concentration were determined by high-performance liquid chromatography (HPLC). Following the intravenous injection, all plasma sulphadimidine data were best approximated by a two-compartment open model using sequential, weight non-linear regression. Flunixin induced a 67% increase in the rate of sulphadimidine return to the central compartment from peripheral tissues (K21) and there were a trend to a 30% increase in K12. The sulphadimidine elimination half-life was decreased 21%, the Vdss was reduced by 18% and MRT was decreased by 20%. Following the oral administration, sulphadimidine was rapidly absorbed in control and Flunixin-medicated horses with absorption half-lives (t1/2 ab) of 0.5 and 0.43 hours respectively. The peak plasma concentration (Cmax) were 93.7 and 109 micrograms/ml attained at (tmax) 2.36 and 1.9 hours respectively. The elimination half-life after oral administration (t1/2 ab) was shorter in flunixin pre-medicated horses than in control ones. The systemic bioavalability percentages (F%) of sulphadimidine after oral administration of 100 mg/kg body weight was 79.3 and 71.2% in control and flunixin medicated horses, respectively. Therefore care should be exercised in the use of sulphadimidine in equine patients concurrently treated with flunixin.
el-Banna
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HA
Pharmacology Department, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt.
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood / Q000493:pharmacokinetics*; D001682:Biological Availability; D003002:Clonixin / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D004347:Drug Interactions; D006207:Half-Life; D006736:Horses; D013418:Sulfamethazine / Q000097:blood / Q000493:pharmacokinetics*
D000894:Anti-Inflammatory Agents, Non-Steroidal; C014557:flunixin; D013418:Sulfamethazine; D003002:Clonixin