Peptide Profile
Cetrorelix
Fast-acting GnRH antagonist that stops premature ovulation during IVF cycles
Dose Range
0.25 mg-3 mgmg
Frequency
Once daily
Route
Subcutaneous injection
Cycle Length
Ongoing/indefinite
Onset
Moderate (1-2 weeks)
Evidence
Strong
Compound Profile
Scientific & Efficacy Data
C70H92ClN17O14
Molecular Formula
1431.06 Da
Molecular Weight
Approximately 2-6 hours (varies by route of administration)
Half-Life
~85% (subcutaneous injection)
Bioavailability
100885-89-0
CAS #
25074887
PubChem ID ↗
Developed By · 1993
Aeterna Zentaris Research Team
Aeterna Zentaris (formerly Arpida/Zentaris)
Primary Benefits
Cetrorelix gives you and your doctor almost perfect control over when ovulation happens, which is the whole point of IVF.
You can start cetrorelix mid-cycle or adjust dosing based on how your body responds, making treatment adaptable to your specific needs.
Most women tolerate cetrorelix really well compared to older hormone treatments. Injection site redness is the main complaint, not serious symptoms.
Amino Acid Sequence
Ac-D-2-Nal-D-4-Cl-Phe-D-3-Pal-Ser-Tyr-D-Cit-Leu-Lys-Pro-D-Ala-NH2Dosing
How much
do I take?
Timing
Best time to take
Administer Cetrorelix at the same time each day (or on the same day each week for weekly injections). Many users prefer morning or evening administration. Pick a time you'll remember consistently.
With food?
Cetrorelix injections can be given regardless of meal timing. However, if GI effects occur, administering on an empty stomach or with a light meal may help reduce discomfort.
If stacking
Cetrorelix should be used as directed by your healthcare provider. If combining with other medications or supplements, discuss potential interactions with your provider. Avoid combining with compounds that have overlapping mechanisms unless specifically guided by a medical professional.
Adjusting Your Dose
Increase if
- +You've tolerated the current dose for the recommended period without significant side effects
- +Therapeutic goals haven't been met at the current dose level
- +Your healthcare provider recommends dose escalation based on your response
- +Lab work or clinical assessments support a higher dose
Decrease if
- -Side effects are bothersome or impacting daily life despite management strategies
- -You experience any signs of an adverse reaction
- -Lab results indicate the need for dose reduction
- -Your healthcare provider recommends a lower dose based on your response
Signs of right dose
- ✓Therapeutic goals being met with minimal side effects
- ✓Stable and consistent response to treatment
- ✓Lab values or clinical markers trending in the right direction
- ✓Good tolerance with manageable or absent side effects
Dosing Calculator
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Suitability
Is this
right for me?
Best For
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.
Consider Alternatives If
Who Should Avoid
Do not use if
- ×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)
Use with caution if
- !You are taking other medications—discuss potential interactions with your healthcare provider
- !You have a history of liver or kidney disease
- !You are elderly or have multiple medical conditions
- !You are planning surgery in the near future—inform your surgeon about Cetrorelix use
- !You have any chronic health conditions that require regular monitoring
Administration
How do I
use it?
Reconstitution
What you need
- •Cetrorelix vial (lyophilized powder or solution)
- •Bacteriostatic water or sterile sodium chloride for reconstitution
- •Alcohol swabs for cleaning vial tops and injection sites
- •Appropriately sized syringes with fine-gauge needles (27-30 gauge)
- •Sharps disposal container
Injection
Route
Subcutaneous injection (into the fatty tissue just under the skin)—allows for consistent absorption and can be self-administered at home after proper training
Best sites
- •Abdomen (stomach area)—at least 2 inches from the belly button, most popular choice for self-injection
- •Front of thighs—middle to upper portion of the outer leg
- •Back of upper arm—outer area (may need assistance from another person)
Technique
- 1.Wash your hands thoroughly with soap and water before handling supplies
- 2.Clean the injection site with an alcohol swab and let it air dry completely
- 3.Pinch a fold of skin at the chosen injection site
- 4.Insert the needle at a 45-90 degree angle (depending on needle length and body composition)
- 5.Inject the medication slowly and steadily over 5-10 seconds
- 6.Release the skin fold and remove the needle, applying gentle pressure with a clean swab
- 7.Rotate injection sites to prevent tissue irritation or lipodystrophy
- 8.Dispose of the needle safely in a sharps container—never recap or reuse needles
Storage
Signs of degradation
Sample Daily Schedule
Safety
Is it
safe?
Safety Profile
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.
Cetrorelix was studied through Phase 3 clinical trials specifically for IVF applications, with large multicenter randomized trials demonstrating safety and efficacy. Regulatory approval in the U.S. and Europe was based on comprehensive Phase 2 and Phase 3 data in infertile patients undergoing controlled ovarian hyperstimulation. Long-term safety data beyond the typical 1-2 week treatment cycle is limited because the drug is not used for chronic applications.
Common Side Effects
Experienced by some users
Injection site reactions (redness, itching, swelling)
Injection site reactions (redness, itching, swelling)
Management: Consult your healthcare provider for guidance.
Headache
Headache
Management: Consult your healthcare provider for guidance.
Nausea
Nausea
Management: Consult your healthcare provider for guidance.
Mild abdominal discomfort
Mild abdominal discomfort
Management: Consult your healthcare provider for guidance.
Dizziness
Dizziness
Management: Consult your healthcare provider for guidance.
Allergic reactions (rash, difficulty breathing)
Allergic reactions (rash, difficulty breathing)
Management: Consult your healthcare provider for guidance.
Ovarian hyperstimulation syndrome (OHSS) if used with other fertility drugs
Ovarian hyperstimulation syndrome (OHSS) if used with other fertility drugs
Management: Consult your healthcare provider for guidance.
Ovarian cysts
Ovarian cysts
Management: Consult your healthcare provider for guidance.
Vaginal bleeding
Vaginal bleeding
Management: Consult your healthcare provider for guidance.
Mood changes
Mood changes
Management: Consult your healthcare provider for guidance.
Liver enzyme changes
Liver enzyme changes
Management: Consult your healthcare provider for guidance.
Pelvic pain
Pelvic pain
Management: Consult your healthcare provider for guidance.
Severe allergic reaction
Severe allergic reaction
Management: Consult your healthcare provider for guidance.
Stop and Seek Help If
- ×Severe or worsening side effects that don't improve with dose adjustment or supportive care
- ×Signs of an allergic reaction—rash, hives, swelling, or difficulty breathing
- ×Your healthcare provider recommends discontinuation based on your clinical response
- ×Development of any new medical condition that may be contraindicated with Cetrorelix
- ×Pregnancy or planning to become pregnant (unless specifically approved for use during pregnancy)
- ×Abnormal lab results or clinical markers that suggest adverse effects
Cetrorelix should only be started, adjusted, or discontinued under medical supervision. This information is for educational purposes only and does not replace professional medical advice. Never stop a prescribed treatment without consulting your healthcare provider first, as abrupt discontinuation may have consequences.
Interactions
With other peptides
- ✓FSH stimulates your ovaries to grow multiple follicles while cetrorelix prevents premature ovulation—they work together perfectly.
- ✓This combination hormone provides both FSH and LH stimulation while cetrorelix blocks the unwanted LH surge.
- ✓After egg retrieval, progesterone prepares your uterus for implantation while cetrorelix has done its job preventing ovulation.
With medications
- !GnRH Agonists (Lupron, Buserelin) - Both affect GnRH signaling. Using both together would be like fighting yourself—they work against each other.
- !Certain hormone contraceptives - Birth control pills taken right before cetrorelix can interfere with how well the antagonist works. Your doctor will tell you when to stop birth control.
With supplements
- ✓Multivitamins - Generally safe to take alongside Cetrorelix. Space doses apart if taking oral formulations to ensure optimal absorption.
- ✓Electrolyte supplements - Helpful if experiencing any GI side effects that could lead to dehydration. Safe to combine.
Effectiveness
Does it
work?
Evidence Level
Strong human trials
What to Expect
Within 1-2 hours
What you might notice
- •Peak blood levels reached
- •The medication is absorbed quickly under the skin and spreads through your bloodstream.
What's normal
- •Initial response to Cetrorelix is beginning at the cellular level
- •Different individuals experience Cetrorelix's onset at different rates
- •Transient systemic effects from initial Cetrorelix exposure are common
What's next
- →Maintain consistent Cetrorelix administration as prescribed
- →Document subjective effects and physical markers daily
- →Schedule a check-in with your provider about initial observations
Within 8 hours
What you might notice
- •LH surge prevention begins
- •Your pituitary stops responding to your body's natural GnRH signals.
What's normal
- •Cetrorelix is achieving sufficient receptor engagement
- •Initial mechanism of Cetrorelix is taking effect
- •Early transient effects from Cetrorelix administration are resolving
What's next
- →Maintain consistent Cetrorelix administration as prescribed
- →Document subjective effects and physical markers daily
- →Schedule a check-in with your provider about initial observations
24-48 hours after last dose
What you might notice
- •Normal hormone signaling returns
- •Once cetrorelix is out of your system, your pituitary can respond to GnRH again.
What's normal
- •Cetrorelix is achieving sufficient receptor engagement
- •Initial mechanism of Cetrorelix is taking effect
- •Early transient effects from Cetrorelix administration are resolving
What's next
- →Maintain consistent Cetrorelix administration as prescribed
- →Document subjective effects and physical markers daily
- →Schedule a check-in with your provider about initial observations
3-5 days into treatment
What you might notice
- •Eggs are ready for retrieval
- •During this time, your eggs are maturing while cetrorelix prevents them from being released too early.
What's normal
- •Cetrorelix response patterns are emerging
- •Initial Cetrorelix response is consistent with mechanism expectations
- •Early tolerance development to Cetrorelix is not expected
What's next
- →Assess whether Cetrorelix response aligns with expectations
- →Plan next steps based on initial Cetrorelix tolerance and response
- →Establish baseline monitoring for Cetrorelix response tracking
Signs It's Working
Treatment Response
- ✓Improvement in the primary symptoms or condition being treated
- ✓Positive changes in relevant lab values or clinical markers
- ✓Consistent, stable response to Cetrorelix over time
- ✓Reduction in symptom frequency or severity
General Well-being
- ✓Improved energy levels and daily functioning
- ✓Better quality of life related to the treated condition
- ✓Manageable or absent side effects indicating good tolerance
- ✓Positive feedback from healthcare provider during check-ups
Not Seeing Results?
Common reasons
- •Not at therapeutic dose yet—initial doses are for building tolerance, not maximum effect
- •Insufficient time at target dose—most compounds need several weeks to show full benefits
- •Inconsistent dosing schedule—regular, consistent use is crucial for optimal results
- •Individual variation in response—genetics, metabolism, and other factors affect outcomes
- •Underlying conditions or medications interfering with absorption or effectiveness
- •Improper storage leading to degraded product—always verify proper storage conditions
Key Research
"Elagolix Represents a Less Invasive and Cheaper Option Than Injectable GnRH Antagonist for Ovulation Suppression in IVF"
Research investigators, 2025
Finding: Cetrorelix achieves robust LH suppression comparable to newer oral GnRH antagonists in IVF cycles, with similar oocyte retrieval and fertilization rates, confirming its continued efficacy as a standard fertility treatment.
View Study"Progestogens for prevention of luteinising hormone (LH) surge in women undergoing controlled ovarian hyperstimulation"
Research investigators, 2023
Finding: Systematic review demonstrates cetrorelix's superior performance in preventing premature LH surges during controlled ovarian hyperstimulation, with consistent clinical efficacy across diverse patient populations.
View Study"Cocktail treatment by GnRH-antagonist, letrozole, and mifepristone for prevention of ovarian hyperstimulation syndrome"
Research investigators, 2023
Finding: Cetrorelix combined with letrozole and mifepristone reduces moderate/severe OHSS from 42.3% to 20.5% in high-risk women, demonstrating its effectiveness as a key component of OHSS prevention strategies.
View Study"GnRH antagonists: expanding indications and improving outcomes in assisted reproductive technology"
Research investigators, 2011
Finding: Comprehensive review establishes cetrorelix and GnRH antagonists as superior alternatives to agonists for preventing premature ovulation, offering immediate LH suppression without the initial hormone flare.
View StudyFrequently Asked Questions