Secretion of metronidazole into the human semen.

The concentration of metronidazole has been studied in blood and in seminal plasma from apparently healthy volunteers and men with subclinical prostatitis. The volunteers took one dose of 500 mg orally and the patients 250 mg twice daily for two to three days. Therapeutic concentrations of metronidazole were found in blood and semen two to three h after intake. In patients the mean concentration was 8.7 micrograms/ml in blood plasma and 7.0 micrograms/ml in seminal plasma. Split ejaculates were collected in four to six fractions and the concentrations of metronidazole in the different fractions were related to those for zinc and fructose. The results indicated that the drug was excreted from prostate, seminal vesicles, and the ampulla ductus deferens.