At a glance
| Brand | Synarel |
|---|---|
| Drug family | GnRH agonist |
| Delivery | Nasal spray |
| Approved uses | Endometriosis and central precocious puberty |
| Important limitation | Endometriosis treatment duration is restricted |
| Mechanism-related concern | Reduced estrogen and bone mineral loss |
Overview
Nafarelin, marketed as Synarel, provides a noninjectable route for sustained suppression of reproductive hormone signaling. The US label covers central precocious puberty in children of either sex and management of endometriosis, including pain and lesions. The endometriosis experience described in the label is in adults treated for a limited course. Successful treatment depends on consistent absorption and follow-up, not merely possession of a nasal spray. Diagnosis is particularly important in children because early sexual development can have causes outside the central GnRH pathway, which require different investigation and treatment.
How it works
Nafarelin stimulates pituitary GnRH receptors at first, briefly increasing gonadotropins and sex steroids. With repeated exposure, pituitary responsiveness declines, suppressing LH and FSH and lowering ovarian estrogen or testicular testosterone. This can reduce estrogen-driven endometriosis activity or pause premature central pubertal progression. The same mechanism can produce hot flushes, vaginal symptoms and bone effects, even though administration is through the nose.
What conditions does the US label cover?
For endometriosis, nafarelin is used to relieve pain and reduce lesions; the label describes experience in adults over a limited treatment course. For central precocious puberty, diagnosis requires evidence that the central reproductive pathway is active and exclusion of other causes of early development.
Supporting sources [1]
What supports the endometriosis indication?
A multicenter double-blind trial compared nasal nafarelin with oral danazol. Both treatments reduced endometriosis manifestations, with differing adverse-effect patterns. This evidence addresses treatment of established endometriosis rather than a claim that suppressing reproductive hormones improves fertility in people without that diagnosis.
Supporting sources [2]
What should be assessed during treatment?
The label addresses initial hormonal flare, loss of bone mineral density, pregnancy-related harm and hypersensitivity. Pediatric monitoring includes growth and biochemical suppression; warnings also cover psychiatric events, convulsions and intracranial hypertension. Nasal conditions and other intranasal medicines can affect practical administration and should be considered.
Supporting sources [1]
Does lack of menstruation mean reliable contraception?
No. Suppression of menstruation is a treatment effect, not assurance that pregnancy cannot occur. Nafarelin is contraindicated during pregnancy, and the label calls for appropriate pregnancy prevention. Likewise, an apparently convenient nasal route does not justify extending endometriosis treatment beyond the evidence and label limits.
Supporting sources [1]
Reading this profile
Jurisdiction: United States; indications and availability vary by formulation and country.. Molecular class: Synthetic decapeptide GnRH agonist administered intranasally.
This profile was written with AI-assisted research and checked against the linked sources. It has not been represented as a clinician’s review. Evidence summaries describe the cited studies and products; they do not establish that a separately purchased preparation is equivalent.
Sources & references
Follow the original material. Product labels define specific formulations and uses; trial registration describes a study and does not by itself establish benefit.
- Synarel — current US prescribing information ↗Regulatory source · Checked 2026-10-27
- Administration of nasal nafarelin as compared with oral danazol for endometriosis. A multicenter double-blind comparative clinical trial. ↗Original research · Checked 2026-10-27