After subcutaneous administration of 14 C-nafarelin acetate to men, 44–55% of the dose was recovered in urine and –% was recovered in feces. Approximately 3% of the administered dose appeared as unchanged nafarelin in urine. The 14 C serum half-life of the metabolites was about hours. Six metabolites of nafarelin have been identified of which the major metabolite is Tyr-D(2)-Nal-Leu-Arg-Pro-Gly-NH 2 (5–10). The activity of the metabolites, the metabolism of nafarelin by nasal mucosa, and the pharmacokinetics of the drug in hepatically- and renally-impaired patients have not been determined.