Skip to Content


Generic Name: nafarelin nasal (NAF a REL in)
Brand Name: Synarel

Medically reviewed by on Nov 11, 2019 – Written by Cerner Multum

What is Synarel?

Synarel is a man-made form of a protein that is like a hormone in the body that helps regulate the menstrual cycle, fertility, and sexual development during puberty.

Synarel is used to treat precocious puberty in both male and female children. It is also used to treat endometriosis in women who are 18 years of age or older.

Synarel may also be used for purposes not listed in this medication guide.

Important Information

Synarel can harm an unborn baby or cause birth defects. Do not use if you are pregnant.

Do not breast-feed while using this medication.

If you are a woman, you should not use Synarel if you have abnormal vaginal bleeding that has not been checked by a doctor.

Before taking this medicine

You should not use Synarel if you are allergic to nafarelin or similar medicines such as leuprolide (Lupron, Eligard, Viadur), goserelin (Zoladex), histrelin (Vantas), or triptorelin (Trelstar).

If you are a woman, you should not use Synarel if you have:

  • abnormal vaginal bleeding that has not been checked by a doctor; or

  • if you are pregnant or breast-feeding.

To make sure Synarel is safe for you, tell your doctor if you have ever had:

  • diabetes, heart disease, high blood pressure, recent weight gain, high cholesterol (especially in men);

  • polycystic ovary disease;

  • low bone mineral density;

  • osteoporosis (in you or a family member);

  • sneezing or a runny nose;

  • a condition for which you take steroids or seizure medication; or

  • if you smoke or drink large amounts of alcohol.

Synarel can harm an unborn baby or cause birth defects. Do not use this medicine if you are pregnant. Tell your doctor right away if you become pregnant during treatment.

Use a barrier form of birth control (condom or diaphragm with spermicide). Hormonal contraception (birth control pills, injections, implants, skin patches, and vaginal rings) may not be effective enough to prevent pregnancy during your treatment.

It is not known whether nafarelin nasal passes into breast milk or if it could harm a nursing baby. Do not breast-feed while using this medication.

How should I use Synarel?

Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Do not miss any doses of this medicine. Skipping doses or not using Synarel correctly may cause a hormonal imbalance that could lead to unwanted side effects.

Synarel is usually given 2 times per day, or once every 12 hours. Use the medicine at the same times each day.

Before your first use, prime the spray bottle by pumping it 5 to 10 times until a fine spray appears.

To use the nasal spray:

  • Blow your nose gently. Keep your head upright and insert the tip of the bottle into one nostril. Press your other nostril closed with your finger. Breathe in quickly and gently spray the medicine into your nose.

  • Tilt your head back for a few seconds to allow the medicine to flow to the back of your nose. Try not to sneeze right after using the nasal spray.

  • If you use more than one spray, wait at least 30 seconds before using the second spray.

  • Do not use the nasal spray in your other nostril unless your doctor has told you to.

  • Do not blow your nose for at least a few minutes after using the nasal spray.

  • If the spray gets in your eyes or mouth or on your skin, rinse with water.

Rinse the tip of the spray bottle with warm water before and after each use.

Do not use a Synarel spray bottle for longer than 30 days, even if it still contains some medicine. After 30 days of regular use, the amount of medicine left in the bottle will not be enough for you to receive a full dose. If your doctor increases your dose, you may need to get a new bottle to be sure you have enough medicine for full doses.

Read all patient information, medication guides, and instruction sheets provided to you. Ask your doctor or pharmacist if you have any questions.

When you first start using Synarel to treat precocious puberty, you may notice an increase in signs of puberty, such as enlarged breasts or vaginal bleeding. These are normal side effects during the first month of use.

Call your doctor if pubertal signs continue for longer than 1 month.

Use Synarel regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

To be sure this medicine is helping your condition and is not causing harmful effects, your doctor will need to check your progress on a regular basis.

Store Synarel in an upright position at room temperature, away from moisture, heat, and light. Do not freeze. Keep the bottle tightly capped when not in use.

What happens if I miss a dose?

Use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

It is very important that you DO NOT MISS A DOSE of Synarel.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking Synarel?

Try not to sneeze or blow your nose just after using the spray. This may decrease the amount of nafarelin your body absorbs.

Avoid using any other nasal sprays within 2 hours after your dose of nafarelin nasal. If you have a stuffy nose, ask your doctor before using a decongestant nasal spray.

Synarel side effects

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

Call your doctor at once if you have:

  • heavy or continued menstrual bleeding;

  • pelvic pain or swelling;

  • a seizure (convulsions); or

  • signs of a pituitary gland problem--sudden headache, confusion, vision changes, vomiting, weak pulse, slowed breathing.

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

Common side effects may include:

  • light vaginal bleeding or spotting;

  • decreased menstrual flow (your periods may stop during treatment);

  • changes in breast size;

  • oily skin or acne, increased body odor;

  • increase in pubic hair growth;

  • headache;

  • hot flashes;

  • mood changes;

  • 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.

What other drugs will affect Synarel?

Other drugs may interact with nafarelin nasal, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.