Milk depletion of dicloxacillin residues in cows and sheep following intramammary administration

The excretion rate of dicloxacillin from milk was studied after intramammar y administration of a suspension of the drug active in vegetable oil. Eight cows and eight sheep, four of each group in low and four in high milk prod uction, were dosed with 200 mg dicloxacillin/quarter in cows and 100 mg dic loxacillin/quarter in sheep, three times at 12 h intervals. The dicloxacill in concentrations in milk were quantified by high performance liquid chroma tography (HPLC). In cows, time until dicloxacillin was undetectable was 48 h and no difference was observed between the groups. In sheep, dicloxacilli n was undetectable 72 h and 84 h after the treatment in low and in high mil k production groups, respectively. The implications of several factors affe cting the possible milk withdrawal period were studied. The results indicat ed that the pharmaceutical vehicle and the coefficient of lipid solubility exerted major effects on depletion time.