Last updated on RxList: 1/14/2021
Synarel Side Effects Center

What Is Synarel?

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.

What Are Side Effects of Synarel?

Common side effects of Synarel in children include:

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.

Tell your doctor if you have unlikely but serious side effects of Synarel including:

  • abdominal or lower back pain,
  • bone pain,
  • depression,
  • fast or pounding heartbeat,
  • numbness or tingling of arms or legs, or
  • eye pain.

Dosage for Synarel

For the management of endometriosis, the recommended daily dose of Synarel is 400 µg.

What Drugs, Substances, or Supplements Interact with Synarel?

Synarel may interact with decongestants. Tell your doctor all medications and supplements you use.

Synarel During Pregnancy and Breastfeeding

Do not use Synarel if you are pregnant. This medication can harm a fetus or cause birth defects. Tell your doctor if you become pregnant during treatment. Use a barrier form of birth control (such as a condom or diaphragm with spermicide). Hormonal contraception (such as birth control pills, injections, implants, skin patches, and vaginal rings) may not be effective to prevent pregnancy during treatment. It is unknown if this drug passes into breast milk or if it could harm a nursing baby. Do not breastfeed while using Synarel.

Additional Information

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.

Synarel Consumer Information

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

Call your doctor at once if you have:

  • vaginal spotting or continued menstrual bleeding;
  • pelvic pain or swelling;
  • a seizure; or
  • signs of a pituitary gland problem--sudden headache, confusion, vision changes, vomiting, weak pulse, slowed breathing.

Some children using nafarelin have had new or worsening mental problems. Call your doctor right away if your child has any unusual changes in mood or behavior (anger, aggression, crying, feeling restless or irritable).

Some side effects can be expected during the first month of using nafarelin nasal and are not a reason to stop using the medicine. Tell your doctor if you have any side effect that is ongoing or bothersome.

Common side effects may include:

  • vaginal bleeding, discharge, or dryness;
  • hot flashes;
  • acne;
  • increase or decrease in breast size;
  • runny nose;
  • headaches, muscle pain;
  • mood changes;
  • decreased interest in sex;
  • itchy, red, or flaky rash;
  • increased body odor; or
  • increase in pubic hair growth.

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)

Synarel Professional Information


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 Patient Information is supplied by Cerner Multum, Inc. and Synarel Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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