What is the difference between Cetrorelix and Relaxin?

Cetrorelix: Competitive GnRH receptor antagonist; immediately blocks pituitary GnRH receptors; rapidly suppresses LH/FSH without initial flare effect; used for controlled hormonal suppression Relaxin: Binds RXFP1 receptor, activating adenylyl cyclase and cAMP/PKA pathway. Upregulates matrix metalloproteinases (MMPs) to degrade excess collagen. Inhibits TGF-β fibrotic signaling.

Is Cetrorelix FDA approved?

Cetrorelix is FDA approved. This regulatory status is provided for research and educational context only.

Is Relaxin FDA approved?

Relaxin is investigational and not FDA approved. It is discussed for research and educational purposes only, not as medical guidance.

How is Cetrorelix administered in research settings?

In research settings, Cetrorelix is typically administered via the subcutaneous route. PeptideBase does not provide dosing or administration instructions.

How is Relaxin administered in research settings?

In research settings, Relaxin is typically administered via the subcutaneous or intravenous routes. PeptideBase does not provide dosing or administration instructions.

Home›Research›Compare›Cetrorelix vs Relaxin

Peptide Comparison

Cetrorelix vs Relaxin

Both are Reproductive & Hormonal peptides.

Cetrorelix

Cetrotide

Sexual HealthFDA ApprovedPrescription

Half-life: ~62 hours

1 providers listed

Full Cetrorelix profile →

Relaxin

Relaxin-2

Sexual HealthInvestigationalResearch Only

Half-life: ~7–8 h (terminal, serelaxin/rh-relaxin-2)

No providers listed yet

Full Relaxin profile →

Bottom line

Cetrorelix is FDA-approved, while Relaxin is investigational — the clearest structural difference between them.

Quick Verdict

Cetrorelix

Half-life

~62 hours

Relaxin

Half-life

~7–8 h (terminal, serelaxin/rh-relaxin-2)

Which One Should You Choose?

Your goal	Better option
Stronger clinical evidence	Cetrorelix
Further along in FDA review	Cetrorelix
Less frequent dosing (longer half-life)	Cetrorelix
More provider options (1 vs 0)	Cetrorelix

Research summary only — not medical advice. Consult a qualified provider before making any decisions.

Side-by-Side Comparison

Cetrorelix

Relaxin

Mechanism Family

Reproductive & Hormonal

Half-life

~62 hours

~7–8 h (terminal, serelaxin/rh-relaxin-2)

FDA Status

approved

investigational

Admin Routes

subcutaneous

subcutaneous, intravenous

Availability

Prescription

Research Only

Providers

1 listed

None listed

Avail. Notes

FDA-approved GnRH antagonist. Brand: Cetrotide (NDA 021036, Jun 1999). Prevents premature LH surges in controlled ovarian stimulation. Prescription only.

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Research Evidence

Cetrorelix

Meta-analysis · 7 key studies · most recent 2026

Relaxin

RCT · 5 key studies · most recent 2026

Research Citations

Cetrorelix

Meta-analysis2026 · J Coll Physicians Surg Pak

GnRH Agonists and Antagonists in IVF/ICSI Cycles of PCOS Women: A Network Meta-Analysis.

Meta-analysis2023 · Hum Reprod Update

Optimal GnRH antagonist protocol for ovarian stimulation during ART: systematic review and network meta-analy…

Cohort2026 · Int J Reprod Biomed

Efficacy and safety of different cetrorelix doses in the luteal phase for preventing ovarian hyperstimulation…

Cohort2021 · BMC Pregnancy and Childbirth

Effects of half-dose and full-dose GnRH antagonists on IVF-ET outcomes: a retrospective study

+3 more

Relaxin

RCT2026 · Br J Pharmacol

Development of a long-acting relaxin for the treatment of pulmonary hypertension.

RCT2013 · Lancet

Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, place…

Cohort2026 · J Clin Med

Association of Relaxin-1 Levels with Mortality in Sepsis and Septic Shock.

Animal2026 · Life Sci

Serelaxin has greater anti-fibrotic potential than perindopril but maintains its anti-fibrotic efficacy in th…

+1 more

About Cetrorelix

Competitive GnRH receptor antagonist; immediately blocks pituitary GnRH receptors; rapidly suppresses LH/FSH without initial flare effect; used for controlled hormonal suppression

Research Areas

HPG axis suppressionLH/FSH reductioncontrolled ovarian stimulation supporttestosterone management

About Relaxin

Binds RXFP1 receptor, activating adenylyl cyclase and cAMP/PKA pathway. Upregulates matrix metalloproteinases (MMPs) to degrade excess collagen. Inhibits TGF-β fibrotic signaling. Promotes cervical softening and pelvic ligament compliance.

Research Areas

connective tissue remodelinganti-fibroticpelvic floor supportfertility supportcardiac protection

Safety Profile

Information below reflects published research data only — not medical advice. Consult a qualified provider before use.

Cetrorelix

Absolute Contraindications

Pregnancy — contraindicatedLactation — contraindicated

Source: FDA label

Suggested Monitoring

Under clinical review

Being verified by our medical team before we display monitoring guidance for this peptide.

Relaxin

No established clinical contraindications. This is an investigational compound with limited human data and has not been evaluated by the FDA for safety in this context. Consult a qualified clinician.

Find Providers

Where to source these peptides

Providers offering

Cetrorelix

1 listed

Browse directory →

Providers offering

Relaxin

Browse directory →

PeptideBase lists providers for educational research purposes only. Always consult a qualified healthcare professional before obtaining or using any peptide.

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Educational research tools — not medical advice.