Enkel intravenös administrering av trimetoprim-sulfadiazin hos neonatala föl : farmakokinetik samt känslighet hos gramnegativa bakterier från föl med septikemi

Abstract: The retrospective part of this study evaluates the susceptibility patterns of bacteria isolated from blood in critically ill foals in Sweden. The most commonly obtained bacteria were Actinobacillus spp. (38 %) and Escherichia coli (27 %). Trimethoprim-sulphonamide (TMS) had good efficacy against most gram negative bacteria with the exception of Klebsiella spp. Among 17 Escherichia coli isolates 94 % were susceptible to trimethoprim-sulphonamide whereas all 24 isolates of Actinobacillus spp. were susceptible to the same substance. The efficacy against gram positive bacteria was more variable. Two healthy foals (two and three days old) were given a single intravenous (iv) injection of trimethoprim (TMP) – sulphadiazine (SDZ) at a dosage of 2,5 mg TMP/kg bodyweight (bwt) and 12,5 mg SDZ /kg bwt. Blood samples were collected serially during a 24 hour period and plasma concentrations of TMP and SDZ were determined by liquid chromatography tandem mass spectrometry (LCMSMS). The pharmacokinetic parameters of TMP and SDZ from the foals were compared to published data for adult horses. The pharmacokinetic properties of sulphadiazine were equal to those of adult horses with the exception of the area under the curve (AUC0-∞) and the mean residence time (MRT) for the three day old foal. These both values were slightly higher than those of adult horses. The pharmacokinetic parameters of TMP from the foals were also similar compared to earlier published values for adult horses. However, the two day old foal had a higher clearance (Cl) for TMP and therefore a lower half life (t1/2), AUC0-∞ and MRT. The results of the present study indicates that healthy neonatal foals have similar pharmacokinetics of TMP/SDZ as adult horses and it might therefore be possible to use the same dose regimens for foals as for adult horses. However, further studies of more foals are necessary to confirm the result of this pilot study.