Comparative plasma kinetics of orally administered sulfamethazine in clinically parasitized and parasitism-treated lambs

Sulfamethazine was administered at a dosage of 99 mg/kg body weight to lambs with a naturally acquired parasitism and again at 37 days following treatment with an anthelmintic. Blood samples were analyzed for sulfonamides over a 72 h period following sulfamethazine administration in both phases of the study. Pharmacokinetic parameter estimates of the sulfonamide blood data demonstrated significantly lower peak levels, longer times to peak and higher blood levels of the drug as time after dosing increased, in the parasitized as compared with the parasitism-treated lambs.