Mechanism of Action

Triptorelin is a potent inhibitor of gonadotropin secretion when given continuously and in therapeutic doses. Following the first administration, there is a transient surge in circulating levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, and estradiol (see ADVERSE REACTIONS). After chronic and continuous administration, usually 2 to 4 weeks after initiation of therapy, a sustained decrease in LH and FSH secretion and marked reduction of testicular and ovarian steroidogenesis is observed. In men, a reduction of serum testosterone concentration to a level typically seen in surgically castrated men is obtained. Consequently, the result is that tissues and functions that depend on these hormones for maintenance become quiescent. These effects are usually reversible after cessation of therapy.

Following a single intramuscular (IM) injection of TRELSTAR^TM DEPOT to healthy male volunteers, serum testosterone levels first increased, peaking on day 4, and declined thereafter to low levels by week 4. Similar testosterone profiles were observed in patients with advanced prostate cancer, when injected with TRELSTAR^TM DEPOT. In healthy volunteers, testosterone serum levels returned to near baseline by week 8.

Results of pharmacokinetic investigations conducted in healthy men indicate that after intravenous (IV) bolus administration, trip-torelin is distributed and eliminated according to a 3-compartment model and corresponding half-lives are approximately 6 minutes, 45 minutes, and 3 hours.

Absorption: Triptorelin pamoate is not active when given orally. Intramuscular injection of the depot formulation provides plasma concentrations of triptorelin over a period of 1 month. The pharmacokinetic parameters following a single IM injection of 3.75 mg of TRELSTAR^TM DEPOT to 20 healthy male volunteers are listed in Table 1. The plasma concentrations declined to 0.084 ng/mL at 4 weeks.

¹ Mean ±SD

Brand Name: Trelstar Depot
Generic Name: Triptorelin pamoate

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