Single dose long-term suppression of testosterone secretion by a gonadotropin-releasing hormone antagonist (antide) in male monkeys

Abstract This study was designed to find the minimal single dose of Antide (Nal-Lys GnRH antagonist) that would provide long-term inhibition of serum testosterone levels in adult male monkeys. At 3 mg/kg (sc), Antide blocked testosterone secretion for only a few days. However, when the dose of Antide was raised to 10 mg/kg, some of the males manifested testosterone inhibition lasting more than 60 days, while shorter durations of action were found in others. These preliminary findings increase our interest in studying Antide as a potential male contraceptive agent, when combined with androgen replacement therapy, as well as for therapeutic applications in men having prostatic carcinoma. Importantly, Antide lacks the sometimes deleterious “flare” effect known to occur when GnRH agonists are used to treat these patients.