Nafarelin
Aliases: Synarel
Last verified: 2026-09-23
The short version
A nasal GnRH agonist — endometriosis and central precocious puberty.
Identity & type
- Molecular type
- analog
- Origin
- A nasal GnRH agonist — endometriosis and central precocious puberty.
Mechanism of action
GnRHR agonism → pituitary desensitization.
Dosing & routes
Official / clinical context
Approved drug — indications, dosing and warnings are defined by the official label. 200–400 mcg nasally twice daily.
Regulator-approved labeling and published study designs — never a recommendation.
Community-reported practice
200–400 mcg nasally twice daily. Synarel nasal: reduces pain in endometriosis; controls the cycle in IVF. Side effects: hypoestrogenic (flashes, dryness).
Unverified self-reports. Not medical advice. Not endorsement.
Expected effects (community)
Synarel nasal: reduces pain in endometriosis; controls the cycle in IVF. Side effects: hypoestrogenic (flashes, dryness).
Protocol — official vs community
Official / label
Synarel (endometriosis): 200 mcg (one spray per nostril) twice daily. Central precocious puberty: 800–1600 mcg/day divided 2–4 nasal doses.
- 01CPP: start 800 mcg/day; titrate upward to 1600 mcg/day by clinical and hormonal response
Duration: Endometriosis: ≤6 months per treatment course because of bone-density loss under hypoestrogenism; CPP: years, until an appropriate pubertal age.
Nasal delivery makes adherence the practical failure mode — missed sprays are missed pharmacology. The hypoestrogenic symptoms are the drug working, not malfunctioning.
Community (anecdotal)
Small gray-market niche: nasal GnRH agonists appear in post-cycle-therapy and fertility-recovery threads, dosed at or below the 200 mcg BID label figure.
- Cycle:
- Weeks, typically alongside hCG/hMG strategies rather than alone.
- Break:
- Suppression is reversed on stopping; community practice treats it as a switch, not a cycle.
The niche is real but minor — the injectable GnRH drugs are cheaper per committed user, and chronic agonist administration without monitoring is exactly the scenario the label warnings describe.
Human evidence
Approved 1990; standard indications.
Preclinical evidence
The preclinical phase was completed and submitted to regulators as part of registration; pharmacology and toxicology details are part of the official label.
Known risks
- Hypoestrogenic symptoms, rhinitis.characterized
Teal: characterized in clinical/labeling contexts. Amber: theoretical or reported outside controlled settings.
Unknowns & evidence gaps
- Real-world data outside controlled trials