Peptide education
Nafarelin
Nafarelin acetate · Synarel
Nafarelin is a prescription GnRH agonist given as a nasal spray. The U.S. Synarel label covers endometriosis and central precocious puberty (CPP), with different daily schedules for the two conditions.
The same nasal spray serves two different conditions, with separate dosing and monitoring.
Overview
Quick answer
One Synarel spray delivers approximately 200 micrograms. The total daily amount is higher in the label's central precocious puberty regimen than in its initial endometriosis regimen.
What is nafarelin used for?
Synarel is labeled for management of endometriosis in adults and for treatment of central precocious puberty in children.
What does the label describe for endometriosis?
The recommended starting amount is 400 micrograms per day, divided between a morning and an evening spray. The label recommends six months of treatment and describes a possible increase for persistent regular menstruation after two months.
How is the central precocious puberty schedule different?
The label describes 1,600 micrograms per day, divided between morning and evening. If suppression is inadequate, it describes a possible increase to 1,800 micrograms per day in three daily doses, after checking adherence and other possible causes. The pediatric team monitors the response.
Does it prevent pregnancy?
Synarel often suppresses ovulation, but the label says contraception is not assured. It recommends nonhormonal contraception during endometriosis treatment and warns of fetal harm.
Evidence
Evidence snapshot
A randomized trial compared two daily nafarelin amounts with danazol over six months in patients with laparoscopically confirmed endometriosis.
The label describes hormone suppression and monitoring in children with a confirmed diagnosis.
The endometriosis label recommends six months and describes bone mineral loss and limited information about repeat treatment.
Claims
Common claims vs evidence
| Claim | Human evidence | Verdict |
|---|---|---|
| The endometriosis and pediatric regimens use the same number of sprays. | The label's initial endometriosis schedule totals 400 micrograms per day. Its recommended central precocious puberty schedule totals 1,600 micrograms per day. | The schedules differ substantially by condition. |
| Nafarelin and danazol had identical effects in every patient. | In a double-blind trial of 213 patients, more than 80% in each group had reduced disease extent at follow-up. The study did not find a statistically significant difference between groups in the reported laparoscopic scores. | Group results do not predict an individual response or prove identical treatment effects. |
| Missing periods means contraception is unnecessary. | For endometriosis, the label says regular use at the labeled dose usually inhibits ovulation, but pregnancy can still occur, particularly if successive doses are missed. | The endometriosis label calls for nonhormonal contraception during treatment. |
Bottom line
Main takeaway
Synarel lowers sex hormone signaling over time, using a measured nasal spray.
The diagnosis determines the schedule, duration, and monitoring plan.
Laparoscopic findings and symptom improvement in the endometriosis trial are distinct outcomes.
Identity
What it is
Nafarelin is a synthetic ten-amino-acid analog of GnRH. Synarel is a metered nasal solution, not an implant or depot injection.
Repeated treatment first stimulates and then suppresses the pituitary signal that drives ovarian or testicular sex hormone production.
Use context
Routes, doses, and cycle patterns
Synarel's label has separate instructions for endometriosis and central precocious puberty. A clinician determines the schedule and monitors the response.
Human studies and product labels
Synarel for endometriosis
- Purpose
- Management of endometriosis, including pain and lesions
- Context
- U.S. adult endometriosis label
- Route
- Intranasal spray
- Amount
- 400 micrograms of nafarelin base per day initially, with a possible increase to 800 micrograms per day under the label's conditions
- Frequency
- One 200 microgram spray in one nostril in the morning and one in the other nostril in the evening at the initial dose
- Duration
- Six months is the labeled recommended duration
The label says to exclude pregnancy and start treatment between days two and four of the menstrual cycle. If regular menstruation persists after two months, it describes a possible increase to one spray in each nostril in the morning and again in the evening. It does not recommend retreatment, but discusses bone-density assessment if further treatment is considered.
Synarel for central precocious puberty
- Purpose
- Suppression of early pubertal hormone signaling
- Context
- U.S. pediatric label
- Route
- Intranasal spray
- Amount
- 1,600 micrograms of nafarelin base per day, with a possible increase to 1,800 micrograms per day if suppression is inadequate
- Frequency
- At 1,600 micrograms, two sprays in each nostril morning and evening; at 1,800 micrograms, three sprays in alternating nostrils three times daily
- Duration
- Treatment continues until resumption of puberty is desired, as determined clinically
The label calls for clinical and hormone monitoring. Before increasing the dose, it describes checking adherence and excluding other causes of early puberty that are independent of gonadotropins.
Endometriosis comparison trial
- Purpose
- Compare treatment of laparoscopically confirmed endometriosis
- Context
- Double-blind randomized study
- Route
- Intranasal spray
- Amount
- Nafarelin 400 or 800 micrograms per day, compared with oral danazol 800 mg per day
- Frequency
- Daily
- Duration
- Six months
The trial measured symptoms and laparoscopic findings after treatment.
What varies
- Sneezing during or immediately after a dose may impair absorption, according to the label.
- The label advises waiting at least two hours after Synarel before using a nasal decongestant when one is needed.
- The spray pump delivers approximately 200 micrograms per actuation after priming.
- For CPP, the label calls for close assessment of hormone suppression and adherence during the first six to eight weeks, with growth and bone-age velocity assessment beginning within three to six months.
Research
Research evidence
A randomized endometriosis trial evaluated nafarelin against danazol for six months. The pediatric label describes hormone suppression and monitoring for central precocious puberty.
| Study / evidence area | Population | Design | Product context | Main outcome | Limitations | Weight |
|---|---|---|---|---|---|---|
| Nafarelin versus danazol | 213 patients with laparoscopically confirmed endometriosis | Multicenter, double-blind randomized trial | Nasal nafarelin 400 or 800 micrograms per day versus oral danazol | More than 80% in each group had reduced laparoscopic disease extent after treatment. | The trial lasted six months; laparoscopic scores and long-term symptoms are different outcomes. | Controlled human study |
| Synarel pediatric label evidence | Children with central precocious puberty | Clinical experience summarized in prescribing information | Intranasal nafarelin | The label describes reduction of stimulated luteinizing hormone (LH) to prepubertal levels during treatment. | Response requires monitoring, and the label says long-term fertility effects are not known. | Human clinical evidence |
Cautions
Safety and unknowns
- The endometriosis label describes hot flashes, vaginal dryness, and bone mineral loss. It recommends a six-month course and does not recommend retreatment because safety data are unavailable.
- Both label sections list pregnancy, breastfeeding, undiagnosed abnormal vaginal bleeding, and specified GnRH-related or product-component hypersensitivities as contraindications. The endometriosis section says pregnancy must be excluded before treatment begins.
- Pediatric warnings include emotional or behavioral changes, convulsions, and increased pressure around the brain. Headache or visual changes should be discussed promptly with the treating clinician.
- The label also warns of severe skin reactions reported with other GnRH agonists and describes what clinicians should do if such a reaction is suspected or confirmed.
- Nasal irritation and rhinitis appear in the product's adverse reaction information.
Product quality
Product identity and quality
Synarel is supplied in a metered pump, with approximately 200 micrograms delivered per spray after priming.
Pump function
The instructions describe cleaning the spray tip because a clogged tip can affect the delivered dose.
Nasal medicines
The label specifies timing for a nasal decongestant when one is needed.
Mechanism
How it is proposed to work
Repeated nafarelin exposure reduces the pituitary signals that stimulate sex hormone production.
Treatment initially stimulates LH and follicle-stimulating hormone (FSH) release before the pituitary response becomes suppressed.
Lower sex steroid levels explain the intended effects and some treatment-related symptoms.
FAQ
Common questions
Is one Synarel spray the daily dose?
No. Each spray delivers approximately 200 micrograms; the total daily dose depends on the condition and prescribed schedule.
Does Synarel provide reliable contraception?
No. The endometriosis label says ovulation suppression does not ensure contraception and discusses nonhormonal contraception during treatment.
How do the central precocious puberty schedules differ?
The label describes 1,600 micrograms daily as two sprays in each nostril morning and evening. If suppression is inadequate after adherence and other causes are assessed, it describes 1,800 micrograms daily as three sprays in alternating nostrils three times a day.
Details
Technical details
Sources
References
- 1.
DailyMed. Synarel nafarelin acetate nasal solution prescribing information
U.S. labeling contains separate instructions for endometriosis and central precocious puberty.
- 2.
PubMed. Randomized comparison of nasal nafarelin and oral danazol for endometriosis
doi:10.1056/NEJM198802253180805 PMID:2963213
Double-blind six-month endometriosis trial comparing two nafarelin doses with danazol.