Pharmacokinetics of sulphamethazine and its acetyl metabolite in chickens

The aim of this study was: first, to establish the basic pharmacokinetic ch aracteristics of sulphamethazine following single intravenous, intramuscula r, intracrop and oral dose to chickens; and second, to determine the kineti c behaviour of its main metabolite, N4-acetyl sulphamethazine. Each group o f five Hi-Sex chickens was given a bolus dose of sulphamethazine (100 mg kg (-1)) by the above routes. Blood samples were collected at various time int ervals for up to 48 h after dosing and were assayed spectrophotometrically for the presence of sulphamethazine and its metabolite. The results suggest first, that the blood clearance (approximate to 0.06 L h(-1) kg(-1)) and e limination half-life (approximate to 9 h) of sulphamethazine in chickens ar e independent of the route of administration and second, the extent of acet ylation of sulphamethazine in chickens may be influenced by the route by wh ich the drug is administered and is low for the intramuscular route.