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Synarel Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 8/28/2015

Synarel (nafarelin acetate) nasal solution is a man-made form of a protein that is like a hormone and is used to treat precocious puberty in both male and female children. Synarel is also used to treat endometriosis in women who are 18 years of age or older. Common side effects of Synarel in children include nasal irritation, hot flashes, vaginal discharge, or mood changes or mood swings. The same side effects of Synarel along with headaches, decreased sexual interest or changes in sexual desire, muscle pain, vaginal dryness, oily skin or acne, increased body odor, dandruff, increase in pubic hair growth, runny nose, light and occasional menstrual bleeding, or changes in breast size may occur in women.

For the treatment of central precocious puberty (CPP), the recommended daily dose of Synarel is 1600 μg, achieved by two sprays (400 μg) into each nostril in the morning (4 sprays) and two sprays into each nostril in the evening (4 sprays). Synarel may interact with decongestants or other nasal sprays. Tell your doctor all medications and supplements you use. Synarel must not be used during pregnancy. It may harm a fetus. Consult your doctor to discuss birth control. It is recommended that men and women using Synarel use two non-hormonal forms of birth control (e.g., condoms and diaphragm with spermicide) while taking this medication. It is unknown if this medication passes into breast milk. Because of the potential risk to the infant, breastfeeding is not recommended while using this drug.

Our Synarel (nafarelin acetate) nasal solution Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Synarel in Detail - Patient Information: Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • heavy or continued menstrual bleeding;
  • pelvic pain or swelling;
  • increased thirst, increased urination;
  • seizure (convulsions);
  • chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;
  • sudden numbness or weakness, sudden severe headache, confusion, problems with vision, speech, or balance; or
  • nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Less serious side effects may include:

  • changes in breast size;
  • oily skin or acne, increased body odor;
  • dandruff;
  • increase in pubic hair growth;
  • mood changes;
  • runny nose;
  • hot flashes;
  • mild headache, muscle pain;
  • light and occasional menstrual bleeding;
  • white or brownish vaginal discharge;
  • vaginal dryness; or
  • changes in sexual desire.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Synarel (Nafarelin Acetate for Central Precocious Puberty)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Synarel Overview - Patient Information: Side Effects

SIDE EFFECTS: Nasal irritation, hot flashes, vaginal discharge, or mood swings may occur in children. Nasal irritation, hot flashes, headaches, mood swings, decreased sexual interest, muscle pain, vaginal dryness, acne, or decrease in breast size may occur in women. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

For women taking this medication, tell your doctor immediately if any of these unlikely but serious side effects occur: abdominal/lower back pain, bone pain, depression.

For women taking this medication, tell your doctor immediately if any of these rare but very serious side effects occur: fast/pounding heartbeat, numbness/tingling of arms/legs, eye pain.

Rarely, a very serious problem with your pituitary gland (pituitary apoplexy) may occur, usually in the first hour to 2 weeks after your first dose of this medication. Seek immediate medical attention if any of these very serious side effects occur: sudden severe headache, mental/mood changes (e.g., confusion), vision changes, vomiting.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Synarel (Nafarelin Acetate for Central Precocious Puberty)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Synarel FDA Prescribing Information: Side Effects
(Adverse Reactions)


In clinical trials of 155 pediatric patients, 2.6% reported symptoms suggestiv e of drug sensitivity, such as shortness of breath, chest pain, urticaria, rash, and pruritus.

In these 155 patients treated for an average of 41 months and as long as 80 months (6.7 years), adverse events most frequently reported ( > 3% of patients) consisted largely of episodes occurring during the first 6 weeks of treatment as a result of the transient stimulatory action of nafarelin upon the pituitary-gonadal axis:

acne (10%)
transient breast enlargement (8%)
vaginal bleeding (8%)
emotional lability (6%)
transient increase in pubic hair (5%)
body odor (4%)
seborrhea (3%)

Hot flashes, common in adult women treated for endometriosis, occurred in only 3% of treated children and were transient. Other adverse events thought to be drug-related, and occurring in > 3% of patients were rhinitis (5%) and white or brownish vaginal discharge (3%). Approximately 3% of patients withdrew from clinical trials due to adverse events.

In one male patient with concomitant congenital adrenal hyperplasia, and who had discontinued treatment 8 months previously to resume puberty, adrenal rest tumors were found in the left testis. Relationship to SYNAREL is unlikely.

Regular examinations of the pituitary gland by magnetic resonance imaging (MRI) or computer assisted tomography (CT) of children during long-term nafarelin therapy as well as during the post-treatment period has occasionally revealed changes in the shape and size of the pituitary gland. These changes include asymmetry and enlargement of the pituitary gland, and a pituitary microadenoma has been suspected in a few children. The relationship of these findings to SYNAREL is not known.


Pituitary apoplexy: During post-marketing surveillance, rare cases of pituitary apoplexy (a clinical syndrome secondary to infarction of the pituitary gland) have been reported after the administration of gonadotropin-releasing hormone agonists. In a majority of these cases, a pituitary adenoma was diagnosed, with a majority of pituitary apoplexy cases occurring within 2 weeks of the first dose, and some within the first hour. In these cases, pituitary apoplexy has presented as sudden headache, vomiting, visual changes, ophthalmoplegia, altered mental status, and sometimes cardiovascular collapse. Immediate medical attention has been required.

Central/peripheral nervous adverse events: Convulsion.

Read the entire FDA prescribing information for Synarel (Nafarelin Acetate for Central Precocious Puberty)

Synarel - User Reviews

Synarel User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Synarel sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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