Trelstar (22.5 mg triptorelin pamoate) has received FDA marketing approval as a twice-yearly intramuscular gonadotropin-releasing hormone (GnRH) agonist. Trelstar suppresses testosterone production for six months, according to manufacturer Watson Pharmaceuticals. Approval was based on a 12-month, phase III efficacy and safety study of Trelstar given every six months in patients with advanced disease. Trelstar produced a mean testosterone serum level of 12.8 ng/dL from month two through month 12, which was well below castration levels associated with androgen deprivation therapy, according to Watson.
By day 29, 97.5% of the clinical trial patients achieved castrate level, and more than 98% of all patients were below castrate level at month six and month 12. Median prostate-specific antigen (PSA) was also reduced by 96.4% at the end of the study. The most commonly reported adverse event was hot flushes (71.7%).