Plasma concentrations, plasma protein binding and residues of sulfamonomethoxine in pigs, horses and cattle.

The protein binding, the plasma half-life and the residue depletion of sulfamonomethoxine (SMM) after intramuscular administration were investigated in pigs, horses and cattle. Protein binding was weakly concentration-dependent. The bound fraction in plasma in the therapeutic range amounted to approximately 45, 40 and 50% for pigs, horses and cattle respectively, and the plasma half-lives were approximately 5.1, 5.7 and 3.1 hours respectively. SMM levels were less than 1 mug/g in muscle tissue after 36, 20 and 12 hours in pigs, horses and cattle respectively. In the kidney SMM levels were not less than 1 mug/g until 48, 60 (extrapolated) and 36 (extrapolated) hours respectively. In pigs and horses SMM residues in the injection site were extremely variable. In cattle, SMM disappearance from the injection site was more regular. SMM concentrations in pig, horse and cattle liver remained more or less constant in the latter part of the period investigated.