← All peptides
Hormones & TRT
Clinical

Nafarelin

Also known as: Synarel, Nafarelin acetate

An intranasal GnRH agonist used for endometriosis and central precocious puberty. FDA-approved as Synarel nasal spray. Prescription medication.

Last updated

Mechanism of Action

Nafarelin is a synthetic decapeptide GnRH agonist with a naphthylalanine substitution that makes it far more potent than native GnRH. Given as a nasal spray, it first stimulates LH and FSH release; with repeated twice-daily dosing the pituitary GnRH receptors become desensitized and gonadotropin secretion falls. Estradiol drops to postmenopausal levels in women with endometriosis, and sex steroids return toward prepubertal levels in children with precocious puberty. The effect reverses after the spray is stopped.

Half-life
~3 hours
Administration Routes
Intranasal
Research Status
Clinical

Reported Benefits

  • Management of endometriosis, including pain relief and lesion reduction
  • Treatment of central precocious puberty in children
  • Used historically for pituitary suppression in IVF protocols

Potential Side Effects

  • Hot flashes, decreased libido and vaginal dryness
  • Headache, emotional lability and nasal irritation
  • Loss of bone mineral density with treatment beyond 6 months
  • In children: transient breast enlargement, vaginal bleeding or acne early in treatment
  • Psychiatric events and seizures reported with GnRH agonists (label warnings)

Common Dosing

For endometriosis the labeled regimen is a low daily intranasal dose split into morning and evening sprays, for no more than 6 months because of bone loss; precocious puberty uses a substantially higher daily dose. Sneezing during or right after dosing and nasal decongestants can reduce absorption. Dosing is set and supervised by the prescribing clinician.

The dosing information above is aggregated from research literature and anecdotal community reports for educational purposes only. It is not a recommendation, prescription, or medical advice. Peptides are sold as research chemicals only and are not intended for human use.

Contraindications

  • Pregnancy or breastfeeding
  • Undiagnosed abnormal vaginal bleeding
  • Hypersensitivity to GnRH, GnRH agonists or any component

No documented stacking partners for Nafarelin yet.

  • Nafarelin for endometriosis: a large-scale, danazol-controlled trial of efficacy and safety, with 1-year follow-up. The Nafarelin European Endometriosis Trial Group (NEET)

    1992

    View

  • Prospective randomized double-blind trial of 3 versus 6 months of nafarelin therapy for endometriosis associated pelvic pain

    1995

    View

  • Intranasal nafarelin: an LH-RH analogue treatment of gonadotropin-dependent precocious puberty

    1986

    View

Yes. Nafarelin was approved by FDA in 1990 as Synarel nasal spray (Pfizer) and is labeled for endometriosis and central precocious puberty. As of 2026, FDA's Drugs@FDA database still lists Synarel as a marketed prescription product, although supply has been interrupted at times in other countries, including UK and Canadian shortages.

Suppressing estrogen causes bone mineral density loss, which is only partly reversible. The label limits a course to 6 months, and retreatment is generally not recommended without assessing bone density.

All three are GnRH agonists that suppress estrogen after an initial flare. Nafarelin is a twice-daily nasal spray, while leuprolide and goserelin are given as long-acting injections or implants.

PeptideChat is for educational and research purposes only. Nothing on this site constitutes medical advice. Peptides are sold as research chemicals only and are not intended for human use. These statements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. PeptideChat is an independent educational resource — not a pharmacy, compounding, or 503A/503B outsourcing facility — and does not sell products or provide medical advice.