FDA Approved Sexual & Reproductive Health

Nafarelin

also known as: Synarel

Pfizer's Synarel — the only FDA-approved intranasal GnRH agonist. Approved for endometriosis and central precocious puberty; offers a depot-free alternative to injectable leuprolide for patients who prefer nasal dosing.

A synthetic GnRH agonist with a 3-(2-naphthyl)-D-alanine substitution at position 6 that increases potency relative to native GnRH while permitting clinically useful intranasal bioavailability. Marketed in the US as Synarel nasal spray (Pfizer, formerly Syntex/Roche). FDA-approved for endometriosis (6 months) and central precocious puberty in children. Offers a needle-free delivery option but requires strict twice-daily adherence.

Mechanism of action

Pituitary GnRHR agonism — produces an initial gonadotropin flare then receptor desensitization and hypogonadism, equivalent in effect to injectable GnRH agonists. Intranasal absorption achieves sufficient plasma concentrations when dosed twice daily.

Primary uses

  • Endometriosis (pain and lesion reduction, maximum 6-month course)
  • Central precocious puberty (pediatric)

Typical dosing

400 (endometriosis); 1600–1800 (CPP) mcg/day twice daily (one spray each nostril BID for endometriosis; higher doses split across multiple sprays for CPP) (intranasal spray)

Endometriosis: one spray (200 mcg) in one nostril in the morning and one spray in the other nostril in the evening (total 400 mcg/day). CPP: two sprays each nostril three times daily (total 1800 mcg/day). Treatment initiated between menstrual days 2 and 4 for endometriosis to avoid mid-cycle ovulation. Nasal decongestants should be delayed at least 30 minutes after dosing.

Regulatory status

FDA-approved as Synarel (nafarelin acetate nasal solution, Pfizer, first approved 1990) for management of endometriosis, including pain relief and reduction of endometriotic lesions (approved for a maximum treatment duration of 6 months); and for treatment of central precocious puberty in children of both sexes.

References

  1. [fda-pi] Synarel (nafarelin acetate) Nasal Solution Prescribing Information. Pfizer.
  2. [pubmed] Henzl MR, et al. "Administration of nasal nafarelin as compared with oral danazol for endometriosis." N Engl J Med, 1988;318:485-489.

Related peptides

Leuprolide

The prototypical long-acting GnRH agonist, FDA-approved across multiple formulations (Lupron Depot, Eligard, Fensolvi, Camcevi) for advanced prostate cancer, endometriosis, central precocious puberty, uterine fibroids, and IVF protocols.

Triptorelin

A widely used long-acting GnRH agonist — FDA-approved as Trelstar for advanced prostate cancer and as Triptodur for pediatric central precocious puberty; approved internationally (Decapeptyl, Gonapeptyl) for endometriosis, uterine fibroids, and female infertility protocols.

Histrelin

Endo Pharmaceuticals' Supprelin LA (pediatric) and Vantas (adult prostate cancer) — a 12-month subcutaneous hydrogel implant delivering histrelin for continuous GnRH-receptor suppression over a full year, minimizing dosing burden for pediatric CPP patients and adult prostate cancer patients alike.

Gonadorelin

The native GnRH decapeptide — the hypothalamic signal that drives LH/FSH release and downstream testosterone/estradiol production. Historically FDA-approved (Factrel, Lutrepulse), now widely used in TRT-adjacent fertility protocols as a testicular-preservation alternative to HCG.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.