Chemical Identity

Property	Value
Chemical Formula	C70H92ClN17O14
Molecular Weight	1431.04 Da
CAS Number	120287-85-6
Peptide Class	GnRH Antagonist (Decapeptide)
Route	Subcutaneous injection

Structure

Cetrorelix is a synthetic decapeptide GnRH antagonist derived from GnRH by substitution of five amino acids. It contains D-2-naphthylalanine at position 6, D-citrulline at position 3, and N-methylated residues that provide receptor affinity and metabolic stability.

Mechanism of Action

Cetrorelix competitively inhibits GnRH binding to pituitary receptors, immediately suppressing gonadotropin release. In IVF, it prevents the LH surge that would trigger premature ovulation, allowing controlled follicle maturation. The effect is dose-dependent and rapidly reversible.

Clinical Applications

• Controlled ovarian stimulation: Prevention of premature LH surge in IVF
• Prostate cancer: Androgen deprivation therapy
• Uterine fibroids: Pre-surgical shrinkage
• Endometriosis: Hormonal suppression

Pharmacokinetics

• Half-life: 62 hours (0.25 mg dose)
• Tmax: 1-2 hours
• Bioavailability: 85% (subcutaneous)
• Metabolism: Proteolytic cleavage
• Route: Subcutaneous

Safety and Side Effects

Local injection site reactions (redness, swelling), nausea, headache, and ovarian hyperstimulation syndrome (in IVF protocols). Rarely, hypersensitivity reactions. No significant systemic toxicity.

References

• Albano, C., et al. (1997). Cetrorelix in IVF: a prospective randomized study. Fertility and Sterility, 68, 934-939.
• Engel, J.B., & Engel, J.B. (2004). Cetrorelix: a review. Drugs, 64, 1481-1490.