Bottom line
Triptorelin is a synthetic decapeptide GnRH agonist available as long-acting depot intramuscular injections. In the United States, Trelstar is approved for the palliative treatment of advanced prostate cancer and Triptodur is approved for central precocious puberty (CPP) in patients aged 2 years and older. Other triptorelin products have additional jurisdiction-specific indications. Depot strengths and products are not additive or interchangeable — each is formulated for a specific dosing interval. Initial testosterone surge (tumour flare) occurs; label warnings cover cardiovascular, metabolic, seizure, and hypersensitivity risks.
Identity and composition
| Field | Verified information |
|---|---|
| Preferred name | Triptorelin |
| Key aliases | Trelstar (US prostate cancer); Triptodur (US CPP); Decapeptyl (EU/ROW); triptorelin pamoate |
| Molecular/sequence identity | pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2 (decapeptide) |
| Modifications/form | D-Trp at position 6; pamoate salt for depot formulation |
| Stable identifiers | PubChem CID 25074470; UNII 9081Y98W2V |
| Identity caveats | Not interchangeable with other GnRH agonists (leuprolide, goserelin). Trelstar depot strengths are not additive — each is designed for a specific dosing interval |
Development and approval status
| Jurisdiction | Status and indication | Product/source | As of |
|---|---|---|---|
| US (FDA) | Approved: advanced prostate cancer | Trelstar (Verity Pharmaceuticals) | 2000; label revised 03/2025 |
| US (FDA) | Approved: central precocious puberty (CPP) in patients aged ≥2 years | Triptodur (22.5 mg IM every 24 weeks) | Approved June 2017; label revised September 2025 |
| EU (EMA) | Approved: prostate cancer, CPP, endometriosis | Decapeptyl (Ipsen) | Ongoing |
| UK (MHRA) | Approved for multiple indications | Decapeptyl SR | Ongoing |
| Canada (Health Canada) | Approved for prostate cancer, CPP | Trelstar | Ongoing |
Mechanism and pharmacology
GnRH agonist. Continuous depot exposure downregulates pituitary GnRH receptors, suppressing LH/FSH → testosterone castrate levels (less than 50 ng/dL). Initial LH/testosterone surge within 2-4 days. D-Trp substitution at position 6 provides higher potency and longer half-life vs native GnRH. Biodegradable microgranule formulation provides sustained release over 4, 12, or 24 weeks.
Evidence by claim
| Claim/indication | Stage | Grade | Best human evidence | Main result | Important limitations |
|---|---|---|---|---|---|
| Advanced prostate cancer | Approved (FDA) | A | Phase 3 RCTs (Trelstar) | Castrate testosterone maintained in over 95%; equivalent to surgical castration | Tumour flare; no direct comparison with other GnRH agonists |
| Central precocious puberty | Approved (US Triptodur; other products/jurisdictions vary) | A | FDA-reviewed, open-label 50-week pivotal study | Peak stimulated LH was suppressed to prepubertal levels in 93% at month 6 and 98% at month 12 | Single-arm study; approval, formulation, age range, and schedule are product- and jurisdiction-specific |
| Endometriosis | Approved (EU) | A | RCTs | Pain reduction; lesion regression | Limited duration |
Key studies
| Study | Design/population | Exposure studied | Endpoints and result | Limitations |
|---|---|---|---|---|
| Trelstar phase 3 | Open-label; advanced PCa | Trelstar 3.75 mg IM q4w, 11.25 mg q12w, 22.5 mg q24w | Testosterone suppression less than 50 ng/dL: over 95% at Day 29; cumulative maintenance of castration over 90% | Open-label; no active comparator vs other GnRH agonists or antagonists |
Dose and administration evidence
Approved labeled regimen
The label summary below is product-, indication-, and jurisdiction-specific; consult the full current label and a licensed clinician/pharmacist.
Prostate cancer (US Trelstar):
Trelstar 3.75 mg IM q4 weeks
Trelstar 11.25 mg IM q12 weeks
Trelstar 22.5 mg IM q24 weeks
CPP (US Triptodur): 22.5 mg IM every 24 weeks in patients aged ≥2 years.
Route: Single intramuscular injection in either buttock
Note: Dosage strengths are not additive and are not interchangeable across products; select based on desired schedule and indication
Must be administered by a healthcare professional
What is not established
No established or recommended human dose for any unapproved indication.
Safety
Established label risks
Tumour flare (initial weeks) — worsening bone pain, neuropathy, hematuria, urinary obstruction.
Hypersensitivity reactions — anaphylactic shock, angioedema.
Metabolic syndrome — hyperglycemia, diabetes, hyperlipidemia; NAFLD including cirrhosis in post-marketing.
Cardiovascular — MI, sudden cardiac death, stroke risk increased.
Convulsions (post-marketing, including patients with seizure risk factors).
QT interval prolongation (class concern).
Injection site reactions.
Hot flashes.
Unknowns and product-quality risks
Long-term safety in non-oncology indications.
No direct comparative data with leuprolide or goserelin in prostate cancer.
Interactions and special populations
No dose adjustment for renal or hepatic impairment.
Pregnancy: Embryo-fetal toxicity — contraindicated if pregnancy possible.
Lactation: Not recommended.
Regulatory, compounding, and sport notes
US FDA: Prescription only.
WADA: Triptorelin is explicitly prohibited at all times in males under S2.2.1 as a GnRH agonist analogue. GnRH analogues are monitored, not prohibited on that basis, in female athletes under 18 in 2026.
Compounding: Compounded triptorelin not equivalent to Trelstar depot.
Not interchangeable with other GnRH agonists.
Evidence gaps
Head-to-head comparisons with leuprolide, goserelin, and degarelix.
Safety of retreatment in endometriosis.
Optimal sequencing in castration-resistant prostate cancer.
Search notes
Databases and registries: DailyMed, Drugs@FDA, PubMed, EMA
Search terms: triptorelin, Trelstar, Triptodur, Decapeptyl, GnRH agonist, prostate cancer, central precocious puberty
Last searched: 2026-08-06
Inclusion emphasis: FDA label, phase 3 trials
Sources
Trelstar Prescribing Information (Verity, revised 03/2025). https://trelstar.com/wp-content/uploads/2025/03/Trelstar_PI_3-2025.pdf
DailyMed – TRELSTAR. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b1b84d62-a369-a4b7-5c41-dd1f553a18f3
FDA label (accessdata) — Trelstar 2025 update. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/020715s050,021288s045,022437s025lbl.pdf
DailyMed. Triptodur (triptorelin) prescribing information, revised September 2025. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=f41380e7-b830-432d-a5f5-a872932f107e
FDA CDER. Triptodur NDA 208956 clinical review (2017). https://www.accessdata.fda.gov/drugsatfda_docs/nda/2017/208956Orig1s000MedR.pdf
EMA – Decapeptyl product information.
PubChem CID 25074470 (triptorelin). https://pubchem.ncbi.nlm.nih.gov/compound/25074470