Cetrorelix vs Triptorelin
Fast-acting GnRH antagonist that stops premature ovulation during IVF cycles
GnRH agonist that helps manage prostate cancer, endometriosis, and early puberty by controlling sex hormones
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Cetrorelix
3–3 mg
Triptorelin
11.25–11.25 mg
Frequency
Cetrorelix
Once daily
Triptorelin
Once daily
Administration
Cetrorelix
Subcutaneous injection
Triptorelin
Intramuscular injection
Cycle length
Cetrorelix
Ongoing/indefinite
Triptorelin
Ongoing/indefinite
Onset speed
Cetrorelix
Moderate (1-2 weeks)
Triptorelin
Moderate (1-2 weeks)
Evidence level
Cetrorelix
Strong human trials (Phase 3 or FDA approved)
Triptorelin
Strong human trials (Phase 3 or FDA approved)
Benefit ratings
Ovulation Control
Cycle Flexibility
Side Effect Profile
Hormone Regulation
Cancer Management
Endometriosis Relief
Compound specifications
Cetrorelix
Molecular formula
C70H92ClN17O14
Molecular weight
1431.06 Da
Half-life
Approximately 2-6 hours (varies by route of administration)
Bioavailability
~85% (subcutaneous injection)
CAS number
100885-89-0
Triptorelin
Molecular formula
C64H82N18O13
Molecular weight
1311.4 g/mol
Half-life
2-3 hours (free peptide); 2-4 weeks (depot pamoate formulations)
Bioavailability
~100% (intramuscular/subcutaneous injection)
CAS number
57773-63-4
Dosing compared
Cetrorelix
Subcutaneous
0.25 mg
Once every 24 hours · From stimulation day 5-6 until the day of hCG (about 4-9 days)
The FDA-approved multiple-dose plan. A 0.25 mg shot under the skin each day stops an early LH surge during fertility (IVF) ovarian stimulation. [5]
3 mg
Single dose (one injection) · One dose covers at least 4 days; add 0.25 mg daily after if hCG is delayed
The FDA-approved single-dose plan. One 3 mg shot is given when estrogen levels show the follicles are ready (usually stimulation day 7). It protects against an early LH surge for at least 4 days. [5][6]
Triptorelin
Intramuscular injection
3.75 mg
Once every 4 weeks · Ongoing while indicated
FDA-labeled 1-month depot (Trelstar) for advanced prostate cancer; single IM injection into either buttock [5].
11.25 mg
Once every 12 weeks · Ongoing while indicated
FDA-labeled 3-month depot (Trelstar). Strengths are not additive; chosen by desired interval [5].
22.5 mg
Once every 24 weeks · Ongoing while indicated
FDA-labeled 6-month depot (Trelstar for prostate cancer; Triptodur 22.5 mg for central precocious puberty, ages 2+) [5][6].
Best suited for
Cetrorelix
Planning IVF with precise ovulation timing
Cetrorelix is particularly well-suited for individuals focused on planning ivf with precise ovulation timing. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Preventing premature egg release during controlled stimulation
Cetrorelix is particularly well-suited for individuals focused on preventing premature egg release during controlled stimulation. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Managing polycystic ovary syndrome (PCOS) during fertility treatment
Cetrorelix is particularly well-suited for individuals focused on managing polycystic ovary syndrome (pcos) during fertility treatment. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Triptorelin
Managing advanced prostate cancer when combined with other treatments
Triptorelin is particularly well-suited for individuals focused on managing advanced prostate cancer when combined with other treatments. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Relieving severe endometriosis pain and symptoms
Triptorelin is particularly well-suited for individuals focused on relieving severe endometriosis pain and symptoms. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Delaying puberty development in children with early sexual maturation
Triptorelin is particularly well-suited for individuals focused on delaying puberty development in children with early sexual maturation. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Side effects
Cetrorelix
Common
- Injection site reactions (redness, itching, swelling)
- Headache
- Nausea
- Mild abdominal discomfort
- Dizziness
- Allergic reactions (rash, difficulty breathing)
- Ovarian hyperstimulation syndrome (OHSS) if used with other fertility drugs
- Ovarian cysts
- Vaginal bleeding
- Mood changes
- Liver enzyme changes
- Pelvic pain
- Severe allergic reaction
Serious
- Severe allergic reaction
Triptorelin
Safety & evidence
Cetrorelix
Evidence level
Strong human trials (Phase 3 or FDA approved)
FDA status
FDA approved for this use
Safety overview
Cetrorelix is an FDA-approved GnRH antagonist used exclusively in assisted reproductive technology with proven safety in short-term reproductive cycles. Unlike GnRH agonists, cetrorelix lacks the initial testosterone flare, making it well-tolerated for ovarian stimulation. Primary side effects are mild and local—injection site reactions (erythema, bruising) occur in 10-20% of patients. No systemic bone loss, cardiovascular complications, or serious adverse events have been reported in the reproductive context where treatment duration is limited (typically 7-10 days). The short treatment window in IVF protocols minimizes long-term safety concerns. Hypersensitivity reactions are rare but possible.
Contraindications
- Known allergy to cetrorelix or any ingredient
- Pregnancy (it may harm the developing baby)
- Undiagnosed vaginal bleeding
- Severe liver or kidney disease
- Latex allergy (some syringes contain latex)
Triptorelin
Evidence level
Strong human trials (Phase 3 or FDA approved)
FDA status
FDA approved for this use
Safety overview
Triptorelin (GnRH agonist) has extensive FDA-approved safety data spanning decades for prostate cancer, endometriosis, and precocious puberty indications. Initial testosterone surge upon initiation ("flare reaction") can worsen prostate cancer or spinal cord compression symptoms, requiring careful patient monitoring in first 1-2 weeks and use of androgen antagonists in high-risk patients. Hypogonadal effects including hot flashes, sexual dysfunction, and bone loss develop predictably with chronic GnRH suppression; bone density monitoring is recommended in patients on therapy >6 months.
Contraindications
- Pregnancy (can affect fetal development)
- Undiagnosed vaginal bleeding
- Known hypersensitivity to GnRH agonists
- Severe untreated depression
- Active spinal cord compression in prostate cancer (requires urgent decompression)
Which is right for you?
Choose Cetrorelix if...
- Planning IVF with precise ovulation timing
- Preventing premature egg release during controlled stimulation
- Managing polycystic ovary syndrome (PCOS) during fertility treatment
Choose Triptorelin if...
- Managing advanced prostate cancer when combined with other treatments
- Relieving severe endometriosis pain and symptoms
- Delaying puberty development in children with early sexual maturation