Levels of trimethoprim and sulphamethoxazole in human seminal plasma.

An oral dose of the combination trimethophim/sulphamethoxazole (160 and 800 mg, respectively) gave concentrations of trimethoprim in seminal plasma that were equal to or higher than that in blood plasma 2--4 hours after intake. Trimethoprim was excreted by both the prostate and seminal vesicles. With a trimethoprim resistant strain it was possible to demonstrate in three patients with subclinical prostatitis that the concentrations of sulphamethoxazole two hours after the oral intake were 20, 26, and 74 microgram/ml in the blood plasma, respectively. This study was carried out on patients who had been on treatment for 2--5 days prior to investigation. In view of published reports on the pH of the fluids from the human prostate and seminal vesicles, respectively, and the importance of the hydrogen ion concentrations for the excretion of lipid soluble substances into the prostatic fluid it was unexpected to find similar concentrations of trimethoprim in both the "prostatic" and "vesicular" fluids. Preliminary studies on the pH of these fluids indicated, however, that they were in the same order of magnitude, i.e. 7.5 to 8.0. The multiglandular origin of the human seminal plasma must be considered in all studied concerning the excretion of drugs into the semen. Many problems related to the excretion of drugs, e.g. organ specificity, kinetics, and influence on organ and spermatozoal functions remain to be investigated.