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How long can I take Trelstar (triptorelin) for prostate cancer?

Medically reviewed by Carmen Fookes, BPharm. Last updated on Nov 8, 2021.

Official answer


Trelstar (triptorelin) can be given for prostate cancer as long as it is tolerated and your doctor believes it is still safe and effective for you, which may be many years. Trelstar is intended as a long-term treatment, and despite the inevitable progression to castration-resistant prostate cancer (CRPC) in most patients receiving androgen deprivation therapies (ADT), such as Trelstar, there may still be benefits in continuing ADT in men in addition to introducing other treatment options for CRPC.

How often is Trelstar given?

For advanced prostate cancer, Trelstar is given intramuscularly (by injection into either buttock) according to the following dosing schedule:

  • 3.75 mg every 4 weeks (about once each month)
  • 11.25 mg every 12 weeks (about once every 3 months)
  • 22.5 mg every 24 weeks (about once every 6 months).

What is Trelstar?

Trelstar may be used in advanced prostate cancer to lower levels of the hormone testosterone in men. Prostate cancer needs the hormone testosterone to grow. Almost all testosterone in men is made by the testicles. Trelstar stops the testicles from making testosterone, reducing testosterone levels, and slowing or stopping the growth of cancer cells. This can help relieve symptoms such as painful or difficult urination.

How does Trelstar work?

Trelstar mimics gonadotropin-releasing hormone (GnRH) and is known as an agonist analog of GnRH. GnRH regulates the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH are known as gonadotropins because they stimulate the gonads (the testes in males and the ovaries in females) to release hormones. Trelstar causes an initial, transient, surge in FSH, LH, and testosterone, which desensitizes the GnRH receptor through a negative feedback loop causing a sustained decrease in FSH and LH and a significant reduction in the production of testosterone 2 to 4 weeks after initiation.

Trelstar belongs to the class of medications known as gonadotropin-releasing hormone agonists. Trelstar causes serum testosterone concentrations to fall to levels typically observed in surgically castrated men.

  • Merseburger AS, Hupe MC. An Update on Triptorelin: Current Thinking on Androgen Deprivation Therapy for Prostate Cancer. Adv Ther. 2016;33(7):1072-1093. doi:10.1007/s12325-016-0351-4
  • Trelstar (triptorelin) Updated 10/2020. Verity Pharmaceuticals Inc.
  • Triptorelin (Decapeptyl® or Gonapeptyl®) Macmillan Cancer Support.,cancer%20or%20stop%20it%20growing.

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