MEDICAL DISCLAIMER: Educational research guidelines only. Lyophilized peptides are investigational chemical compounds and are NOT approved for human consumption, diagnosis, or therapy. Consult a licensed physician before any research application.
Cetrorelix Dosage Chart, Schedule & Reconstitution Protocol
Quickstart Highlights
Cetrorelix (Cetrotide) is a synthetic decapeptide GnRH antagonist that competitively blocks pituitary GnRH receptors, producing an immediate, reversible drop in LH and FSH without the agonist flare effect. In IVF, this prevents a premature LH surge so follicles can be matured and retrieved on schedule. It is given subcutaneously into the lower abdomen, either as 0.25 mg (250 mcg) once daily from stimulation day 5-6 until the hCG trigger, or as a single 3 mg dose that holds the surge for about four days. Onset of LH suppression is within hours, and pituitary responsiveness returns roughly 1-2 days after stopping. Subcutaneous bioavailability is about 85% and peak levels occur within 1-2 hours. Cetrorelix is FDA- and EMA-approved for controlled ovarian stimulation and is used only under physician supervision (PMID 10685535, 12638392).
Reconstitute: Add 3 mL bacteriostatic water → 1 mg/mL concentration.
Typical dose: 0.25 mg (250 mcg)/day SC, or a single 3 mg SC dose
Easy measuring: At 1 mg/mL, 1 unit = 0.01 mL = 0.0100 mg (10 mcg) on a U-100 insulin syringe.
Storage: Commercial single-use vials and the lyophilized powder are stored refrigerated at 2-8 °C, protected from light in the original carton. Once reconstituted, the clinical product is intended for immediate single use; an educational multi-dose reconstituted solution should be kept refrigerated at 2-8 °C and discarded promptly. Do not freeze the reconstituted solution.
Half-life: ~5 hours after a single 0.25 mg dose; ~20 hours with repeated 0.25 mg dosing; ~62-63 hours after a single 3 mg dose.
Route: Subcutaneous injection into the lower abdomen; 0.25 mg daily or a single 3 mg dose.
Status: FDA-approved (2000) and EMA-approved for inhibiting premature LH surges in controlled ovarian stimulation.
About Cetrorelix
Cetrorelix (Cetrotide) is a synthetic decapeptide GnRH antagonist that immediately and reversibly suppresses pituitary LH and FSH release, which is why fertility clinics use it to block premature ovulation during IVF stimulation cycles [1][2]. Unlike many compounds on this site, Cetrorelix is genuinely administered subcutaneously, so the reconstitution figures below closely track its real clinical route; the only difference is that the commercial product ships as a single-use vial with its own sterile-water diluent, whereas the model here treats a vial as an educational multi-dose reference reconstituted with bacteriostatic water.\n\nThere are two established regimens. The multiple-dose protocol uses 0.25 mg (250 mcg) subcutaneously once daily, started on stimulation day 5 or 6 and continued until the day of hCG trigger [1]. The single-dose protocol uses one 3 mg (3000 mcg) subcutaneous injection given in the late follicular phase when estradiol rises, which controls the LH surge for about four days; if hCG is not given within four days, daily 0.25 mg doses are added [1][4][6]. This guide models a 3 mg vial reconstituted with 3 mL of bacteriostatic water (1 mg/mL = 10 mcg per insulin-syringe unit) so the math is clean: 0.25 mg = 25 units (0.25 mL), and a full 3 mg single dose = the whole 3 mL vial.\n\nFrequency: Once daily for the multiple-dose protocol, or a single injection for the 3 mg protocol. Note that clinically Cetrorelix is only used for the ~5-12 day late-follicular window of one IVF cycle, not for the multi-week courses shown in the supply estimates, which follow this site's standard educational convention. Cetrorelix is FDA- and EMA-approved; this page is educational and not medical advice.
Quick Protocol Navigation
Reconstitution Instruction & Mixing Step-by-Step
Lyophilized powder must be reconstituted carefully. Agitating peptide chains can shear disulfide bonds and render the peptide biologically inert.
Draw 3 mL of bacteriostatic water into a sterile syringe (the commercial product instead supplies single-use sterile water for injection in a pre-filled syringe).
Inject the water slowly down the inner wall of the 3 mg Cetrorelix vial; avoid aiming the stream directly at the lyophilized cake and do not shake vigorously.
Gently swirl or roll the vial until the solution is completely clear; this yields a 1 mg/mL concentration, i.e., 10 mcg per U-100 insulin-syringe unit.
Store refrigerated at 2-8 °C and draw the prescribed volume: 0.25 mg = 25 units (0.25 mL); a single 3 mg dose = 300 units, i.e., the entire 3 mL vial.
Swab the lower-abdomen site with alcohol, pinch the skin, insert the needle subcutaneously, inject slowly, and discard sharps safely; the clinical product is single-use, so do not store partially used commercial vials.
Interactive Cetrorelix Syringe Calculator
Currently visualizing the 3 mg vial reconstituted with 3 mL bacteriostatic water. Adjust the target dose to dynamically render syringe units.
Reconstitution Calculation: 3mg dry powder in 3mL water yields 1.00 mg/mL. To evaluate a 250mcg dose, pull to 25.0 units (25 syringe ticks).
U-100 Syringe Representation
Educational reference visual. Assumes standard U-100 insulin syringe where 1.0 mL volume = 100 units.
Titration & Dose Escalation Schedules
| Phase | Dose per injection | Units (per injection) |
|---|---|---|
| Multiple-dose protocol — 0.25 mg SC daily from stimulation day 5-6 until hCG trigger | 250 mcg | 25 units (0.25 mL) |
| Single-dose protocol — one 3 mg SC injection in the late follicular phase | 3000 mcg (3 mg) | 300 units (3.00 mL) |
| Single-dose follow-up — 0.25 mg SC daily if hCG is not administered within 4 days of the 3 mg dose | 250 mcg | 25 units (0.25 mL) |
Administration guidelines: Refer to guidelines | 3 mL Reconstitution
Research Supplies Quantity Planner
Scientific mathematical planning of syringes, bacteriostatic water and dry vials needed for extended research blocks using the 3 mg vial.
Peptide Vials (Cetrorelix, 3 mg each):
- checkEducational multi-dose model: one 3 mg vial provides twelve 0.25 mg daily doses (12 × 0.25 mg = 3 mg).
- check8 weeks at 0.25 mg/day (56 doses) ≈ 5 vials; 12 weeks (84 doses) ≈ 7 vials; 16 weeks (112 doses) ≈ 10 vials.
- checkSingle-dose protocol: one 3 mg vial = one full dose.
- checkClinical reality: real Cetrotide ships as single-use vials (one 0.25 mg vial per daily dose), and the antagonist is used only for the ~5-12 day window of a single IVF cycle, not for multi-week courses.
Insulin Syringes (U-100):
- checkOnce-daily dosing: 7 syringes per week.
- check8 weeks ≈ 56 syringes; 12 weeks ≈ 84 syringes; 16 weeks ≈ 112 syringes.
- checkSingle 3 mg dose (300 units) exceeds one 1 mL syringe and would be split across 3 syringes, or given via the commercial pre-filled single-use device.
Bacteriostatic Water (30 mL bottles): Use 3 mL per 3 mg vial for reconstitution.
- check8 weeks (≈5 vials) ≈ 15 mL ≈ 1 bottle.
- check12 weeks (≈7 vials) ≈ 21 mL ≈ 1 bottle.
- check16 weeks (≈10 vials) ≈ 30 mL ≈ 1 bottle. (Clinically, the commercial product supplies its own sterile water for injection.)
Alcohol Swabs:
- check1-2 swabs per dose (vial top + lower-abdomen injection site).
- check8 weeks ≈ 60-120 swabs; 12 weeks ≈ 90-170 swabs.
- check16 weeks ≈ 120-230 swabs; keep extras for re-swabbing.
Mechanism of Action (MOA)
Cetrorelix is a synthetic decapeptide antagonist of gonadotropin-releasing hormone (GnRH, also called LH-RH). Its structure is the native GnRH backbone modified with multiple D-amino-acid substitutions (acetyl-D-2-naphthylalanine, D-4-chlorophenylalanine, D-3-pyridylalanine, D-citrulline, and D-alanine), which give it high receptor affinity, resistance to enzymatic degradation, and pure antagonist activity [1][7]. It competes with endogenous GnRH for binding to receptors on the gonadotroph cells of the anterior pituitary. Because it occupies the receptor without activating it, Cetrorelix produces an immediate, dose-dependent suppression of LH and FSH secretion and, critically, avoids the transient gonadotropin "flare-up" that occurs in the first days of GnRH-agonist therapy [1][2].\n\nIn women undergoing controlled ovarian stimulation, this rapid suppression delays the endogenous LH surge and prevents premature ovulation/luteinization, so the developing follicles can be matured and retrieved on a controlled schedule. The effect is fully reversible: pituitary responsiveness returns within roughly one to two days of stopping treatment, which is why the antagonist is started only once follicles are well developed and stopped at the hCG trigger [1][3]. At the doses used in stimulation, LH suppression is more pronounced than FSH suppression [1].\n\nPharmacokinetics: Cetrorelix acetate is rapidly absorbed after subcutaneous injection into the lower abdomen, reaching peak plasma concentrations in approximately 1 to 2 hours, with a mean absolute subcutaneous bioavailability of about 85% [1]. The volume of distribution after intravenous dosing is roughly 1 L/kg, and the drug is eliminated largely via biliary/fecal routes after peptidase cleavage into smaller fragments. The terminal half-life is dose-dependent: about 5 hours after a single 0.25 mg dose, rising to roughly 20 hours with multiple 0.25 mg doses and approximately 62-63 hours after a single 3 mg dose, which is what allows one 3 mg injection to control the LH surge for about four days [1][2]. Population PK/PD modeling in healthy premenopausal women described the disposition with a two-compartment model and a terminal half-life near 57 hours, linking plasma exposure directly to the magnitude and duration of LH suppression [2][3].\n\nUnlike most compounds modeled on this site, Cetrorelix is genuinely a subcutaneous peptide, so the reconstitution scheme here closely mirrors clinical practice; the only simplification is treating a single-use vial as an educational multi-dose reference reconstituted with bacteriostatic water. Cetrorelix is approved by the FDA and EMA for inhibition of premature LH surges in controlled ovarian stimulation [1].
Clinical Trial Efficacy Highlights
- starThe FDA-approved Cetrotide label establishes both regimens for inhibiting premature LH surges during controlled ovarian stimulation: 0.25 mg subcutaneously once daily starting on stimulation day 5 or 6 and continued until hCG, or a single 3 mg dose in the late follicular phase, supported by registration trials in women undergoing assisted reproduction [1].
- starOlivennes and colleagues (Human Reproduction, 1998) performed a dose-finding study of single-dose cetrorelix in IVF-embryo transfer comparing 3 mg versus 2 mg in 65 patients, and found that the 3 mg dose more reliably prevented premature LH surges across the stimulation window, establishing 3 mg as the effective single-dose threshold [5].
- starOlivennes and colleagues (Fertility and Sterility, 2000) ran a prospective randomized controlled study comparing a single 3 mg dose of the antagonist cetrorelix with a depot GnRH agonist (triptorelin) in IVF-ET; the cetrorelix single-dose protocol prevented LH surges with comparable oocyte and pregnancy outcomes while requiring far fewer injections and a shorter overall treatment course [4].
- starTwo large multicentre, multinational phase IIIb experiences (reported 2003) evaluated the 3 mg single-dose regimen in routine practice and confirmed that one 3 mg injection effectively and safely prevents premature LH surges, with a meaningful proportion of patients completing the cycle on a single antagonist injection [6].
- starPharmacokinetic/pharmacodynamic modeling by Nagaraja and colleagues (Clinical Pharmacology & Therapeutics, 2000) characterized subcutaneous cetrorelix with a two-compartment model and a terminal half-life of about 56.9 ± 27.1 hours in healthy premenopausal women, directly linking plasma concentration to the depth of LH suppression [2].
- starFollow-up PK/PD modeling by Nagaraja and colleagues (Journal of Clinical Pharmacology, 2003) quantified LH suppression and LH-surge delay after single and multiple cetrorelix doses, demonstrating dose- and concentration-dependent, reversible gonadotropin suppression that underpins both the daily and single-dose protocols [3].
- starThe Cochrane systematic review by Al-Inany and colleagues (2016) pooled randomized trials of GnRH antagonists (including cetrorelix) versus the long GnRH-agonist protocol and found similar live-birth rates with a substantial reduction in ovarian hyperstimulation syndrome, supporting antagonist protocols as equally effective but safer and more patient-friendly [8].
Side Effects & Tolerability Profile
Clinical subjects transiently report mild side effects. Slowly escalating the titration dose represents the single most effective intervention to limit side effects.
- warningInjection-site reactions are the most common local effect, including transient redness, itching, swelling, or mild pain at the lower-abdomen subcutaneous site; these are usually mild and short-lived [1].
- warningOvarian hyperstimulation syndrome (OHSS) was reported in roughly 3.5% of treated cycles in registration data; although antagonist protocols generally lower OHSS risk versus agonist long protocols, OHSS remains a serious potential complication of the underlying ovarian stimulation [1][8].
- warningSystemic adverse reactions are generally infrequent and mild, with nausea (~1.3%) and headache (~1.1%) among the most reported [1].
- warningHypersensitivity and rare anaphylactoid/allergic reactions can occur; Cetrorelix is contraindicated in people with known hypersensitivity to cetrorelix, to extrinsic peptide hormones, to GnRH or any GnRH analog, or to mannitol (an excipient) [1].
- warningIt is contraindicated in known or suspected pregnancy and during lactation, and in severe renal impairment; clinically it is used only within a monitored, physician-directed stimulation cycle [1].
- warningBecause it suppresses LH and FSH, mistimed or off-label use disrupts normal gonadal/reproductive hormone signaling; it must be timed precisely within the stimulation cycle and is not intended for use outside supervised assisted-reproduction care.
- warningCetrorelix is a prescription injectable; sourcing unregulated 'research' material risks impurities, incorrect peptide content, and contamination, and any use outside a clinical fertility program is off-label and unstudied for safety.
- warningRegulatory status: Cetrorelix is FDA-approved (2000) and EMA-approved for inhibition of premature LH surges in controlled ovarian stimulation; the dosing and reconstitution figures here are an educational reference and not a substitute for the prescribing information or medical advice [1].
Subcutaneous Injection Technique
Most research peptides require subcutaneous injection into fatty tissue. Never inject directly into a blood vessel or deep muscle tissue unless clinically detailed.
1. Site Selection
Common locations include the abdomen (2 inches from navel), outer upper arms, or thighs.
2. Sanitization
Thoroughly clean the selected site, stopper and vial top using 70% isopropyl alcohol prep swabs.
3. Angle & Push
Pinch the skin and insert the needle at a 45 to 90-degree angle. Depress plunger smoothly.
4. Site Rotation
Rotate injection sites continuously to avoid lipodystrophy or tissue scarring.
Frequently Asked Questions
What is the typical Cetrorelix dosage?expand_more
Two FDA-approved regimens exist. The multiple-dose protocol is 0.25 mg (250 mcg) injected subcutaneously once daily, started on stimulation day 5 or 6 and continued until the day of the hCG trigger. The single-dose protocol is one 3 mg (3000 mcg) subcutaneous injection given in the late follicular phase, which controls the LH surge for about four days; if hCG is not given within four days, 0.25 mg daily is added. Both are administered into the lower abdomen and used only within a monitored IVF stimulation cycle.
Is Cetrorelix FDA approved?expand_more
Yes. Cetrorelix (brand name Cetrotide) was approved by the U.S. FDA in 2000 and is also approved by the EMA in Europe for the inhibition of premature LH surges in women undergoing controlled ovarian stimulation. It is a prescription injectable used under physician supervision as part of assisted-reproduction care, not an over-the-counter or research-only compound.
How do you reconstitute Cetrorelix?expand_more
The commercial product comes as a lyophilized powder with its own pre-filled syringe of sterile water; you inject the diluent into the vial, swirl gently until clear, and inject the full single-use dose. For the educational model on this page, a 3 mg vial is reconstituted with 3 mL of bacteriostatic water to give 1 mg/mL (10 mcg per U-100 unit), so 0.25 mg = 25 units (0.25 mL) and a 3 mg dose is the whole 3 mL vial. Do not shake vigorously, and keep the solution refrigerated.
What is the half-life of Cetrorelix?expand_more
Cetrorelix has a dose-dependent terminal half-life. After a single 0.25 mg subcutaneous dose it is roughly 5 hours, lengthening to about 20 hours with repeated 0.25 mg dosing, and to approximately 62-63 hours after a single 3 mg dose. This longer half-life at the higher dose is why one 3 mg injection can suppress the LH surge for about four days. Peak plasma levels are reached within 1-2 hours and subcutaneous bioavailability is around 85%.
What are the main Cetrorelix side effects?expand_more
The most common effects are mild, transient injection-site reactions (redness, itching, swelling). Ovarian hyperstimulation syndrome was reported in about 3.5% of cycles, and nausea (~1.3%) and headache (~1.1%) can occur. Rare hypersensitivity reactions are possible. It is contraindicated in pregnancy, lactation, severe renal impairment, and in anyone allergic to GnRH analogs, peptide hormones, or mannitol. It should be used only within a supervised fertility program.
Related Guides & Tools
Step-by-step references for reconstituting, measuring, and storing Cetrorelix, plus the universal dosing calculator.
Academic References & Study Citations
Cetrotide (cetrorelix acetate for injection) Prescribing Information / FDA label, DailyMed (U.S. National Library of Medicine). Dosage (0.25 mg and 3 mg regimens), reconstitution, pharmacokinetics, contraindications, and adverse reactions. View Scientific Paper →
Nagaraja NV, Pechstein B, Erb K, et al. Pharmacokinetic and pharmacodynamic modeling of cetrorelix, an LH-RH antagonist, after subcutaneous administration in healthy premenopausal women. Clin Pharmacol Ther. 2000;68(6):617-625. View Scientific Paper →
Nagaraja NV, Pechstein B, Erb K, et al. Pharmacokinetic/pharmacodynamic modeling of luteinizing hormone (LH) suppression and LH surge delay by cetrorelix after single and multiple doses in healthy premenopausal women. J Clin Pharmacol. 2003;43(3):243-251. View Scientific Paper →
Olivennes F, Belaisch-Allart J, Emperaire JC, et al. Prospective, randomized, controlled study of in vitro fertilization-embryo transfer with a single dose of an LH-RH antagonist (cetrorelix) or a depot LH-RH agonist (triptorelin). Fertil Steril. 2000;73(2):314-320. View Scientific Paper →
Olivennes F, Alvarez S, Bouchard P, et al. The use of a GnRH antagonist (Cetrorelix) in a single dose protocol in IVF-embryo transfer: a dose finding study of 3 versus 2 mg. Hum Reprod. 1998;13(9):2411-2414. View Scientific Paper →
Olivennes F, Diedrich K, Frydman R, et al. Safety and efficacy of a 3 mg dose of the GnRH antagonist cetrorelix in preventing premature LH surges: report of two large multicentre, multinational, phase IIIb clinical experiences. Reprod Biomed Online. 2003;6(4):432-438. View Scientific Paper →
Cetrorelix. Wikipedia (structure, decapeptide sequence, mechanism, and approval history overview). View Scientific Paper →
Al-Inany HG, Youssef MA, Ayeleke RO, Brown J, Lam WS, Broekmans FJ. Gonadotrophin-releasing hormone antagonists for assisted reproductive technology. Cochrane Database Syst Rev. 2016;4(4):CD001750. View Scientific Paper →