Comparative pharmacokineticsof various sulfadoxine-trimethoprim preparations used on dogs in veterinary medicine

Twenty-eight mix-breed male dogs of approximately 3 years of age and with similar body weights were used in the study. Four groups, each including 7 animals, were established. The animals included in the first, second, third, and fourth groups were administered formulations A, B, C, and D, respectively, containing 200 mg sulfadoxine and 40 mg trimethoprim per millilitre, at a dose of 25 mg/kg body weight sulfadoxine by intramuscular route at the same site of the body. Subsequently, blood samples were collected at 0.083, : 0.25, 0.50, 1.0, 1.5, 2.0, 4.0, 6.0, 12 and 24 hours. The levels of sulfadoxine-trimethoprim in the plasma samples were measured by means of a HPLC device. Pharmacokinetic calculations were performed in compliance with the two-compartment open model. According to statistical analyses, amongst the parameters evaluated, significant differences were determined to exist between the groups only with respect to the mathematical coefficients (A2*), hybrid rate constant for terminal elimination phase (β), half life at α phase (t1/2α), half life at β phase (t1/2α) and mean residence time (MRT) values for sulfadoxine, and with respect to the A1*, first order absorption rate constant (k a), β and MRT values for trimethoprim (p