Synarel nasal spray contains the active ingredient nafarelin acetate, which is a type of medicine known as a gonadorelin (LHRH) analogue. It acts on the pituitary gland in the brain.

What is it used for?

• Endometriosis.
• Fertility treatment. This medicine is used to prepare the pituitary gland before starting treatment with gonadotrophins (FSH and LH) to artificially stimulate ovulation.

How does it work?

• Synarel nasal spray contains the active ingredient nafarelin acetate, which is a type of medicine known as a gonadorelin (LHRH) analogue. It acts on the pituitary gland in the brain.
• The pituitary gland produces and stores various hormones, including the sex hormones, luteinising hormone (LH) and follicle-stimulating hormone (FSH). In women, FSH and LH cause the production of oestrogen by the ovaries and help control the menstrual cycle.
• The amount of LH and FSH released from the pituitary gland is controlled by another hormone, called gonaderelin (LHRH). Gonadorelin acts on LHRH receptors in the pituitary gland, causing the release of LH and FSH and hence the subsequent production of oestrogen in women.
• Nafarelin is a synthetic form of gonadorelin. It acts on the LHRH receptors in the pituitary gland in the same way as natural gonadorelin.
• Initially, nafarelin causes an increase in the amount of FSH and LH released from the pituitary gland, with resulting increase in oestrogen production. However, chronic administration of nafarelin desensitises the pituitary gland. This means that it produces less and less FSH and LH, which in turn stops the production of oestrogens in women. This reduction in the level of oestrogen is used to treat endometriosis.
• Endometriosis is a condition where tissue resembling the womb or uterus lining (endometrium) grows in other sites in the body. The growth of this tissue is stimulated by oestrogen, so decreasing oestrogen levels with nafarelin will stop the growth of this tissue, thereby relieving symptoms. A six month course of treatment is recommended and this should not be exceeded or repeated.
• Nafarelin is also used in fertility treatment. In women who are infertile due to problems with their natural ovulation, it is used desensitise the pituitary gland and stop the natural production of FSH and LH. Synthetic FSH, LH and hCG (gonadotrophins) are then administered to artificially stimulate ovulation.
• The nafarelin in Synarel nasal spray is absorbed into the bloodstream through the rich supply of blood vessels found in the lining of the nose. The medicine is absorbed even if you have a cold, however if this is the case, you should blow your nose thoroughly before using the spray.

Important information regarding this medicine

• If you sneeze during or immediately after taking a dose from the nasal spray you should repeat that dose, because sneezing may reduce the absorption of the medicine from the nose.

Use with caution in

• Osteoporosis.
• Polycystic ovary syndrome.

Not to be used in

• Allergy to other gonadorelin (LHRH) analogues, eg buserelin, goserelin.
• Vaginal bleeding of unknown cause.
• Pregnancy.
• Breastfeeding.
• Women under the age of 18 years.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

• This medicine should not be used in pregnancy, as it may be harmful to a developing baby. (NB. If you are using this medicine as part of fertility treatment, do not be concerned by this. Treatment with this medicine will be stopped before your ovulation is induced and it will not have any adverse effect on a baby that then results from your fertility treatment.)
• It is not known if this medicine passes into breast milk. There is no information available about the safety of this medicine during breastfeeding. For this reason, the manufacturer states that it should not be used during breastfeeding.

Side effects

• Hot flushes.
• Changes in sex drive.
• Vaginal dryness.
• Headache.
• Mood swings.
• Acne.
• Pain in the muscles (myalgia).
• Reduction in breast size.
• Irritation of the nose.
• Depression.
• Pins and needles sensations.
• Hair loss.
• Migraine.
• Awareness of your heartbeat (palpitations).
• Blurred vision.
• Decrease in the density of bone after six months treatment (reverses after treatment is stopped).
• Shortness of breath or chest pain.
• Skin reactions, such as rash, itching or hives.
• Development of fluid filled sacks (cysts) in the ovaries.
• Alteration in results of liver function tests (raised liver enzymes).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

• Nasal decongestants may decrease the absorption of nafarelin from the nose. If a nasal decongestant is required it should be used at least 30 minutes after using the Synarel nasal spray.

References:

https://www.medicines.org.uk/emc/product/1149/smpc#gref

https://www.netdoctor.co.uk/medicines/during-pregnancy/a7604/synarel-nafarelin/

https://www.webmd.com/drugs/2/drug-6479/synarel-nasal/details

http://www.hpra.ie/img/uploaded/swedocuments/aa4611e6-e47b-4b4f-8ef6-aed091e65fef.pdf

https://www.pfizermedicalinformation.com/en-us/synarel

https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/019886s033s035lbl.pdf

https://www.rxlist.com/synarel-side-effects-drug-center.htm

https://www.medicines.ie/medicines/synarel-nasal-spray-33896/patient-info