Flunixin meglumine given in small doses: pharmacokinetics and prostaglandin inhibition in healthy horses.

The pharmacokinetics and inhibition of prostaglandin synthesis in conscious horses given various dosages of flunixin meglumine were studied. Plasma concentrations of flunixin were measured by high-performance liquid chromatography, and serum thromboxane B2 and 6-keto prostaglandin F1 alpha were quantitated by radioimmunoassay. Within the dosage range studied, linear pharmacokinetics were achieved. After IV administration of flunixin (1.1 mg/kg, 0.25 mg/kg, 0.1 mg/kg), significant suppression of serum thromboxane generation persisted for 12, 4, and 3 hours, respectively. Repeated administrations of flunixin (0.25 mg/kg) once every 8 hours maintained significant suppression of thromboxane generation for the duration of treatment. After treatment with flunixin was stopped, serum thromboxane generation exceeded base line (pretreatment values). Among the groups, significant alteration of 6-keto prostaglandin F1 alpha production was not observed.