Trelstar, Decapeptyl
Evidence Grade A — Regulatory approved. 988 published studies. 40 registered clinical trials.
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Triptorelin (sold as Trelstar) is a hormone-suppressing injectable for advanced prostate cancer, available in one-month, three-month, and six-month depot formulations. It is one of the most commonly used GnRH agonists worldwide and has also been widely used internationally as a puberty blocker in gender-affirming care and central precocious puberty.
988 published studies: 742 human, 79 animal, 132 in-vitro, 75 reviews
Triptorelin is marketed as Trelstar (approved 2000) for advanced prostate cancer, available as intramuscular depot injections in monthly (3.75 mg), three-monthly (11.25 mg), and six-monthly (22.5 mg) formulations. It is also widely used internationally for gender-affirming care and central precocious puberty.
Triptorelin is one of the most commonly used GnRH agonists globally, though it faces the same competitive pressure as other agents in this class from newer oral GnRH antagonists like relugolix, which avoid the initial hormone flare and offer potential cardiovascular advantages. Clinical data demonstrate reliable testosterone suppression comparable to other GnRH agonists in this class.
Triptorelin works through the standard GnRH agonist mechanism: continuous stimulation of the pituitary gland causes an initial brief hormone surge followed by sustained shutdown of sex hormone production. It achieves castrate-level testosterone suppression in over 90% of patients within the first month. The depot injection forms a slow-release reservoir at the injection site, maintaining therapeutic drug levels for one to six months depending on the formulation.
Triptorelin's evidence base is well established, with reliable testosterone suppression comparable to other GnRH agonists in the class. The six-month formulation offers the longest dosing interval among injectable GnRH agonists, reducing clinic visits to just twice yearly. Like all GnRH agonists, triptorelin causes an initial testosterone surge before suppression takes effect, and long-term hormone suppression carries risks of bone density loss, cardiovascular effects, and metabolic changes. The oral GnRH antagonist relugolix (Orgovyx) has emerged as a competitor that avoids the initial hormone surge and offers potential cardiovascular advantages. Triptorelin's use in gender-affirming care for adolescents has been a focus of both clinical research and regulatory discussion across multiple countries.
Efficacy, Safety, and Pharmacokinetics of FP-014, 11.25 mg in Patients With Advanced Prostate Cancer
Efficacy, Safety, and Pharmacokinetics of FP-014, 22.5 mg in Patients With Advanced Prostate Cancer
Intranasal Nafarelin For Triggering Oocyte Maturation
A Study to Assess the Efficacy, Safety, and Pharmacokinetics of Debio 4326 in Pediatric Participants With Central Precocious Puberty (LIBELULA™ Clinical Trial)
Efficacy, Metabolism and BMD of the 3-month TP Compared to the 1-month TP in ICPP
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Histrelin is available as Supprelin LA for central precocious puberty (approved 2007). The Vantas implant for prostate cancer was approved in 2004 but discontinued in 2021. The implant requires a minor surgical procedure for insertion and removal/replacement each year. Supprelin LA's main clinical advantage is its 12-month duration — the longest of any GnRH agonist — which is particularly valuable in paediatric patients where treatment compliance over years is important. Clinical studies demonstrated effective suppression of puberty markers in over 97% of patients. The implant has also seen significant off-label use in gender-affirming care as a puberty blocker, where its annual dosing schedule offers practical benefits for adolescent patients and their families.
Goserelin is marketed as Zoladex by AstraZeneca, available as 3.6 mg monthly and 10.8 mg three-monthly subcutaneous implants. First approved in 1989, it is used in advanced prostate cancer, premenopausal breast cancer, endometriosis, and for thinning the uterine lining before surgical procedures. Goserelin achieves castrate-level testosterone suppression (below 50 ng/dL) within two to four weeks. Its unique implant delivery system means there is no liquid injection, reconstitution, or refrigeration required — a practical advantage in some clinical settings. Like all GnRH agonists, it causes an initial hormone flare before suppression takes effect. Goserelin holds an important niche in breast cancer treatment, where it is used to suppress ovarian function in premenopausal women with hormone-receptor-positive disease, often in combination with aromatase inhibitors.
Nafarelin is marketed as Synarel (approved 1990) for endometriosis and central precocious puberty. It requires administration as one spray in each nostril twice daily — a higher frequency than injectable alternatives but avoids needles entirely, which can be a significant advantage for some patients, particularly children. Clinical trials showed symptom improvement in 75–92% of endometriosis patients. However, absorption can be affected by nasal congestion or concurrent use of nasal decongestants, which can be a practical limitation. As with all GnRH agonists, prolonged use leads to bone density loss, and treatment for endometriosis is typically limited to six months. Nafarelin occupies a niche for patients who prefer non-injectable hormone suppression, though it has become less commonly prescribed as longer-acting depot injections and oral alternatives have become available.
