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Generic name: nafarelin

What is Synarel used for?

  • Synarel is used to treat endometriosis.
  • It is used to delay puberty in children who are maturing too early.
  • Synarel may be given to you for other reasons. Talk to your doctor.

Before taking Synarel, tell your doctor:

  • If you are allergic to Synarel; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you have unexplained vaginal bleeding.
  • If you are pregnant or may be pregnant. Do not take Synarel if you are pregnant.
  • If you are breast-feeding. Do not breast-feed while you take Synarel.

This is not a list of all drugs or health problems that interact with this medicine.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Synarel with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take Synarel?

  • Tell all of your health care providers that you take Synarel. This includes your doctors, nurses, pharmacists, and dentists.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take Synarel.
  • It may take 2 months to see the full effect.
  • This medicine may cause weak bones (osteoporosis) with long-term use. Talk with your doctor to see if you have a higher chance of weak bones or if you have any questions.
  • Use care if you have risks for soft, brittle bones (osteoporosis). Some of these risks include drinking alcohol, smoking, taking steroids, taking drugs to treat seizures, or having family members with osteoporosis. Talk with your doctor about your risks of osteoporosis.
  • Have a bone density test as you have been told by your doctor. Talk with your doctor.
  • Some people have had seizures while taking drugs like this one. The chance of seizures may be raised in people who have had brain or brain blood vessel problems, seizures, or brain tumors. Certain other drugs may also raise the chance of seizures. If you have questions, talk with the doctor.
  • If you have a stuffy nose while using Synarel, talk with your doctor about using a nose decongestant. Do not use a nose decongestant spray within 2 hours after using Synarel.
  • Ovarian cysts may rarely happen in the first 2 months of therapy.
  • Most of the time, Synarel stops you from having a period (menstrual bleeding). This is not a method of birth control. Use a non-hormone type of birth control like condoms to prevent pregnancy while taking Synarel.
  • If you miss doses of Synarel, bleeding between cycles can happen. There may also be a chance of getting pregnant if you miss doses of Synarel. Talk with your doctor.
  • If you are able to get pregnant, a pregnancy test will be done to show that you are NOT pregnant before starting Synarel. Talk with your doctor.
  • This medicine may cause harm to the unborn baby if you take it while you are pregnant. If you are pregnant or you get pregnant while taking Synarel, call your doctor right away.

How is Synarel best taken?

Use Synarel as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • Do not take Synarel by mouth. Use in your nose only. Keep out of your mouth and eyes (may burn).
  • Start taking Synarel between days 2 and 4 of your period (menstrual) cycle.
  • Prime before first use by spraying until you see a fine mist.
  • Blow your nose before use.
  • Do not sneeze during or right after using Synarel.
  • Spray up the nose only. Do not spray onto the wall joining the two nostrils.
  • Keep taking Synarel as you have been told by your doctor or other health care provider, even if you feel well.
  • Clean before and after every use as you have been told by the doctor.

What do I do if I miss a dose?

  • Use a missed dose as soon as you think about it.
  • If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
  • Do not use 2 doses at the same time or extra doses.
  • If you miss 2 doses, call your doctor.

What are the side effects of Synarel that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Chest pain or pressure.
  • Bad nose irritation.
  • Shortness of breath.
  • Belly pain.
  • Swelling in the arms or legs.
  • Vaginal discharge.
  • For women, still having a period.
  • Vaginal bleeding that is not normal.
  • Bone pain.
  • Seizures.
  • A very bad pituitary gland problem (pituitary apoplexy) has rarely happened with Synarel. Most of the time, this has happened within 2 weeks after the first dose. Call your doctor right away if you have a sudden headache, throwing up, passing out, mood changes, eye weakness, not able to move your eyes, or change in eyesight.
  • Behavior and mood changes have happened with the use of drugs like this one in children. This includes acting aggressive, crying, depression, emotional ups and downs, restlessness, and feeling angry and irritable. Call your doctor right away if you have any new or worse behavior or mood changes.

What are some other side effects of Synarel?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

For all patients taking Synarel:

  • Headache.
  • Hot flashes.
  • Pimples (acne).
  • Muscle pain.
  • Weight gain.
  • Nose irritation.
  • Stuffy nose.
  • Runny nose.
  • Not able to sleep.
  • Lowered interest in sex.
  • Vaginal dryness.
  • Vaginal bleeding or spotting.
  • Change in breast size.


  • If your child is taking Synarel to delay puberty, you may see short-term body odor or signs of puberty like vaginal bleeding, enlarged breasts, or more pubic hair during the first month of care. If these last or are very bad, call the doctor.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out Synarel?

  • Store upright at room temperature. Do not freeze.
  • Protect from light.
  • Store in a dry place. Do not store in a bathroom.
  • Throw away any unused portion after 30 days.
  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.

Consumer information use and disclaimer

  • If your symptoms or health problems do not get better or if they become worse, call your doctor.
  • Do not share your drugs with others and do not take anyone else's drugs.
  • This medicine comes with an extra patient fact sheet called a Medication Guide. Read it with care. Read it again each time Synarel is refilled. If you have any questions about Synarel, please talk with the doctor, pharmacist, or other health care provider.
  • If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

This information should not be used to decide whether or not to take Synarel or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to Synarel. This information is not specific medical advice and does not replace information you receive from the healthcare provider. You must talk with the healthcare provider for complete information about the risks and benefits of using this medicine.

Source: Wolters Kluwer Health. Last updated April 5, 2023.