Co-trimazine distribution in the canine prostate.

Constant infusion experiments were performed on dogs to determine the concentration levels of co-trimazine (a combination of trimethoprim and sulphadiazine) in the dogs' prostatic secretion, prostatic interstitial fluid, prostatic tissue, urine, and other tissues. Trimethoprim concentrations in prostatic secretion, interstitial fluid and tissue were higher than corresponding serum values, whereas the concentrations of sulphadiazine were far below these values. These results were compared to those of a similar study which combined trimethoprim and sulphamethoxazole (co-trimoxazole). The prostatic secretion to serum ratios of sulphadiazine were lower than those for sulphamethoxazole. Urine concentrations of sulphadiazine, however, were much higher than those of sulphamethoxazole. In serum and urine, only co-trimazine had a trimethoprim/sulphonamide ratio approximating the optimal synergy ratio of 1:20. Neither trimethoprim/sulphonamide combination appears to have any theoretical advantage over the other in the treatment of prostatitis. However, co-trimazine may be more effective in the treatment of urinary tract infections in general because of the high concentrations of sulphadiazine in urine.