By Zaira Salvador BSc, MSc (embryologist) and Neus Ferrando Gilabert BSc, MSc (embryologist).
Last Update: 04/16/2015

Synarel is a medicine composed by a GnRH analogue, more specifically an agonist. GnRH is a gonadotrophin releasing hormone produced by the hypothalamus, which stimulates the pituitary gland, making it produce FSH and LH. Its use as a medicine decreases the body’s normal response to this hormone so that the ovaries produce less estrogen.

This drug is used in genital locations or during ovarian stimulation in an in vitro fertilization (IVF) cycle. The administration of Synarel aims to achieve the development of several follicles during one ovarian cycle so that a greater number eggs can be naturally obtained, and so the probabilities of a pregnancy to be higher.

IVF medicine

Composition and presentation

Synarel is the only medicine used to stimulate the ovary that is administered in the form of a nasal solution. It is the ideal option for women who are afraid of needles or have problems administering medicine through an injection.

The active substance is Nafarelin Acetate, an agonist of gonadotropin-releasing hormones. It is also composed by the following excipients: sorbitol, glacial acetic acid, purified water, and benzalkonium chloride.

Its format is a nasal spray of 200 mcg, which comes in a package of eight millilitres.

Instructions for use

You should follow the doctor’s recommendations and read the information leaflet before using Synarel.

The recommended daily doses is of 800 mg four times a day, administered as one spray in each nostril in the morning and one spray in each nostril in the evening, except if your doctor recommended another dose. The doses can be adjusted according to the woman’s ovarian response. It is important to medically control the stimulation and see how the patient responds to the medication.

How to use Synarel

If the patient sneezes during or after the administration of Synarel, she should repeat the administration since its absorption can be affected.

How to prepare the medicine:

  • Prepare the medicine for the first time: charge the medicine pump. Remove the cap and safety clip. Place 2 fingers on the projections of the valve and your thumb at the base of the bottle.
  • Remove the end of the sprayer and press down firmly until a slight spray appears. The first real spray usually appears after 7-10 sprays.

Once the medicine is prepared, you should follow the following steps during each administration:

  • Use a tissue to softly clean each nostril.
  • Slightly tilt your head forward, insert the spray in one nostril, and cover the other one with your finger.
  • Press the valve and inspire at the same time.
  • Repeat the same steps in the other nostril.


The use of this medicine is not recommended in cases of hypersensitivity to nafarelin, natural GnRH or other excipient components.

This medicine should not be administered in cases of vaginal bleeding of unknown cause. If the woman thinks she might be pregnant or is breastfeeding, Synarel cannot be used.

Synarel cleaner

If you have a history of ovarian cysts, you should inform your doctor because their size and number could increase. However, it’s likely that they will disappear after a few weeks of treatment.

Possible adverse effects

As with every medicine, the administration of Synarel can have secondary effects, which are classified according to their frequency.

Very frequent effects (occur in 1 in 10 patients): headaches, rhinitis, acne, Seborrhoea (excessive production of sebum), muscle pain, hot flashes, decrease in breast size, depression and mood changes.

Frequent effects (at least 1 in 100 patients): tingling sensations, nasal irritation, insomnia, hirsutism (excess hair growth), and increased breast size.

Rare effects (occur in 1 in 1,000 patients): hair loss, blood pressure changes, vaginal bleeding and vaginal secretions.

FAQs from users

Can Synarel (Nafarelin acetate) be used to treat endometriosis?

By Zaira Salvador BSc, MSc (embryologist).

Yes, it is a common hormonal treatment prescribed to relieve the symptoms of endometriosis. It is a nasal spray which main active ingredient is Nafarelin acetate, a GnRH agonist.

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Authors and contributors

 Zaira Salvador
BSc, MSc
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia (UPV). Embryologist specializing in Assisted Procreation, with a Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI). More information
License: 3185-CV
 Neus Ferrando Gilabert
BSc, MSc
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information
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