PHARMACOKINETICS OF TETROXOPRIM AND SULFADIAZINE IN VARIOUS SPECIES

Tetroxoprim, a competitive bacterial inhibitor of dihydrofolate reductase is a weak base (pka = 8 25), moderately hydrophilic, and with a protein binding of 13%. ' Administered orally together with sulphadiazine an elimination half-life in the rat of 5 to 8'9 h is observed for tetroxoprim. The total renal excretion of tetroxoprim is 12 8% of the dose after 96 h. Intravenously injected substance shows a 12 4% excretion by the kidneys over same period. Independent of the mode of administration, only one other metabolite appears in the urine in about the same concentrations. Tetroxoprim is quantitatively absorbed. The elimination half-life for sulphadiazine determined in parallel is 12 8 to 7 4 h and is dependent on the dose. The excretion in urine over 24 h is 43% of the dose. © 1979 Oxford University Press.