The influence of pH on antimicrobial substances in canine vaginal and urethral secretions.

Trimethoprim and rosamicin (a new basic macrolide antibiotic) were administered to normal and oophorectomised female dogs by constant intravenous infusion before and after oestrogen and androgen administration. Their concentrations in plasma and in urethral and vaginal secretions were determined by bioassay and correlated with the pH values of vaginal and urethral secretions. Both compounds were concentrated in the vaginal and urethral secretions in reverse correlation with the pH of these fluids. Trimethoprim and rosamicin have antimicrobial spectra well suited for the treatment of bacterial urethritis and vaginitis and require further clinical investigation.