RELATIVE BIOAVAILABILITY OF MICROGRANULATED SULFADIMIDINE IN VEAL CALVES

The kinetics of free and microgranulated sulfadimidine were compared i n milk-fed calves dosed orally (180 mg/kg) in a crossover study, Micro granulation results in delayed absorption of sulfadimidine and poor bi oavailability, with the area under the plasma concentration-time curve (AUC((0-infinity))) reduced from 7400 to 3781 mu g . h/mL, and maximu m plasma concentration (C-max) reduced from 188.1 +/- 39.0 to 84.41 +/ - 22.6 mu g/mL. It is concluded that sulfadimidine microgranulated wit h long chain fatty acids is not suitable for use in milk-fed calves; t he gastrointestinal transit time is too rapid to allow full release of the drug, markedly limiting its bioavailability. In adult animals, or in the young of other animal species in which digesta transit time is slower than in calves, the bioavailability of microgranulated sulfadi midine may be much greater.