Christina Varvatsis is a hospital pharmacist and freelance medical writer committed to educating the public on medication therapy. She strives to promote the safe and effective use of medications.

Femi Aremu, PharmD, is a professional pharmacist with experience in clinical and community pharmacy. He currently practices in Chicago, Illinois.

Synarel (nafarelin ) is a prescription nasal spray used to treat the symptoms of endometriosis in adults and central precocious puberty (early puberty) in children.

Synarel belongs to a group of medications called gonadotropin-releasing hormone (GnRH) agonists. GnRH agonists work by decreasing your body’s production of certain hormones, including estrogen and testosterone.

This medication is available as a nasal solution administered through a nasal spray.

Brand Name(s): Synarel

Controlled Substance: N/A

The U.S. Food and Drug Administration (FDA) approved Synarel to treat:

The tissue that lines the inside of the uterus is called the endometrium. This tissue builds up during a regular menstrual cycle and is shed if you don’t become pregnant, resulting in your period. People with endometriosis have endometrium growing outside their uterus. This tissue may be present on the ovaries, fallopian tubes, or other structures in the pelvis or abdomen.

Because this tissue responds to hormones just like the lining of your uterus, it will build up and bleed during your menstrual cycle, which can cause painful symptoms. Symptoms of endometriosis include severe menstrual cramps, pain during sex, low back pain, and painful bowel movements.

By decreasing estrogen levels, Synarel causes the tissue growth to shrink or disappear and helps improve your symptoms. Because Synarel can weaken your bones, you should not use Synarel for more than six months.

Central precocious puberty, or CPP, is a condition that causes sexual development too early in children—before the age of 8 for girls and before 9 for boys.

Synarel helps stop puberty in children. If Synarel is tolerated, treatment should continue until puberty is desired.

Synarel comes as a nasal spray. To be effective, Synarel must be used twice per day, every day, without missing a dose. When used to treat endometriosis, Synarel should be started two to four days after your period begins. Continue to take Synarel twice per day, every day. The usual treatment duration for endometriosis is six months. For CPP, treatment should be continued until puberty is desired.

Here are some tips for using Synarel:

Synarel should be stored at room temperature (68 F to 77 F). Be sure to keep the bottle upright and protected from light. Do not freeze Synarel. Keep Synarel—and all your medications—in a safe location, up high and out of the reach of children and pets.

If you’re using Synarel to treat endometriosis, you may notice irregular vaginal spotting or bleeding during the first two months of therapy. After two months, your menstrual flow should become lighter or completely stop. Contact your healthcare provider if you still have regular periods after two months.

When Synarel is used for central precocious puberty, certain hormones increase during the first month. This can cause an increase in symptoms, including vaginal bleeding and breast enlargement in girls. Within one month, signs of puberty should begin to stop.

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at fda.gov/medwatch or 800-FDA-1088.

Side effects are common with Synarel. Because Synarel decreases estrogen levels, side effects often resemble symptoms of menopause. People using Synarel to treat endometriosis may experience:

Children taking Synarel to treat CPP may develop:

Be sure to let your healthcare provider know about any side effects that bother you or don’t go away.

Rarely, Synarel may cause severe side effects. Call your healthcare provider immediately if you develop any serious reactions. Call 911 if your symptoms feel life-threatening. Serious side effects include the following:

Seizures have rarely occurred in people taking drugs similar to Synarel. Let your healthcare provider know if you:

Pituitary apoplexy (a very serious pituitary gland problem) has rarely occurred, often within two weeks of starting Synarel. Call your healthcare provider immediately if you experience:

Behavior or mood changes may occur in children. Contact your child’s healthcare provider if you notice any new or worsening symptoms, including:

Seek medical care if you think you are having an allergic reaction. Signs of an allergic reaction include:

Weak bones (osteoporosis) may occur in adults that use Synarel, which may not be reversible. For this reason, Synarel should not be used for longer than six months when used to treat endometriosis.

Ovarian cysts may occur within the first two months of treatment. Your risk of developing ovarian cysts is greater if you have polycystic ovarian syndrome (PCOS). Most ovarian cysts will go away on their own, but discontinuing Synarel or surgically removing the cysts is sometimes required.

Synarel may cause your bones to weaken. In some cases, the effects may be irreversible. For this reason, Synarel should not be used for longer than six months to treat endometriosis.

You may be at increased risk of developing weak bones if you:

Talk with your healthcare provider about your risk factors to determine if Synarel is appropriate.

Synarel may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

It is important not to miss any doses of Synarel. Even one missed dose can cause symptoms to return, including vaginal bleeding. Setting an alarm on your phone can be helpful.

If you miss a dose of Synarel, take it as soon as you remember. If it’s almost time for your next dose, skip the missed dose and resume your regular dosing schedule. Do not double up or take extra Synarel. If you miss two or more doses, call your healthcare provider.

A Synarel overdose is not expected to cause any adverse reactions, but it’s important only to take your prescribed dose. If you’ve taken too much Synarel, call your healthcare provider or the Poison Control Center. If you develop symptoms that feel life-threatening, call 911.

If you think you or someone else may have overdosed on Synarel, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Synarel, call 911 immediately.

It is very important that your doctor check the progress of you or your child at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects. Be sure to keep all appointments.

For female patients: You should not use this medicine if you are pregnant or may become pregnant. Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during treatment with this medicine. If you think you have become pregnant while using the medicine, tell your doctor right away.

For children using nafarelin spray for central precocious puberty (CPP): This medicine can cause a brief increase in blood levels of some hormones. During this time, you may notice more signs of puberty in your child, including light vaginal bleeding and breast enlargement in girls. If your child's symptoms do not improve within 4 weeks, or if they get worse, call your doctor.

For adult women using nafarelin spray for endometriosis:

This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. Make sure the doctor knows if you have trouble sleeping, get upset easily, have a big increase in energy, or start to act reckless. Also tell the doctor if you have sudden or strong feelings, such as feeling nervous, angry, restless, violent, or scared. If you or your caregiver notice any of these side effects, tell your doctor right away.

Using this medicine may increase your risk of having seizures. Check with your doctor right away if you start to have convulsions, muscle spasm or jerking of all extremities, sudden loss of consciousness, or loss of bladder control.

Nafarelin spray can increase your risk of having cysts in the ovaries. Talk to your doctor about this risk.

Before you have any medical tests, tell the medical doctor in charge that you are using this medicine. The results of some tests may be affected by this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Certain conditions increase your risk of developing complications from Synarel. Do not take Synarel if you:

Certain medications may interact with Synarel. Let your healthcare provider and pharmacist know about all your medications, including over-the-counter (OTC) nonprescription products and vitamins or herbal supplements.

Watch out for these common interactions:

This is not a complete list of all the drugs that may interact with Synarel. Keep an up-to-date list of all your medicines and let your healthcare provider and pharmacist know of any changes.

Synarel belongs to a group of medications called gonadotropin-releasing hormone (GnRH) agonists. Other GnRH agonists also used to treat endometriosis and central precocious puberty (CPP) include:

Unlike Synarel, both Lupron and Zoladex are injectable medications. These medications only need to be taken every one to six months, compared with Synarel’s daily dosing. However, Synarel may be a better option for those who are uncomfortable receiving injections.

This is a list of drugs also prescribed to treat endometriosis and CPP. It is NOT a list of drugs recommended to take with Synarel. In fact, you should not take these drugs together. Talk to your healthcare team about any questions or concerns about your treatment.

Synarel is used to treat the painful symptoms of endometriosis, including severe menstrual cramps, pain during sex, low back pain, and painful bowel movements. Synarel is also used in children to treat central precocious puberty (CPP), which causes puberty to start too early.

Synarel works by decreasing certain hormones in your body, including estrogen and testosterone. For people with endometriosis, low estrogen levels cause the endometrial tissue growing outside of the uterus to shrink or disappear, which helps improve symptoms. For children with CPP, decreasing levels of these hormones helps stop puberty.

When used to treat endometriosis, Synarel should reduce menstrual flow or stop your periods altogether by two months. Children with central precocious puberty will begin to notice signs that puberty is stopping within one month.

The most common side effects of Synarel in adults include hot flashes, headaches, vaginal dryness, mood changes, decreased interest in sex, and acne. In children, Synarel may cause acne, body odor, flaky skin, hot flashes, a temporary increase in pubic hair, a stuffy or runny nose, and white or brown vaginal discharge.

No, Synarel is not meant for use to prevent pregnancy. If you miss doses of Synarel, your ovaries may release an egg (ovulation), and you could become pregnant. Becoming pregnant while using Synarel can harm the fetus. You must use a non-hormonal form of birth control (e.g., condoms, IUD, diaphragm with contraceptive jelly) while taking Synarel. Do not take birth control pills.

Synarel is an effective treatment option for endometriosis and central precocious puberty, but you must take it every day without missing a dose for it to work. With all the stressors of daily life, it can be hard to remember your dose or to pick up your refill on time. Follow these tips to ensure you don’t miss a single dose:

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

Pfizer. Synarel- nafarelin acetate spray, metered.

Johns Hopkins Medicine. Precocious puberty.

Strein M, Holton-Burke JP, Smith LR, Brophy GM. Prevention, treatment, and monitoring of seizures in the intensive care unit. J Clin Med. 2019;8(8):1177. doi:10.3390/jcm8081177

TerSera Therapeutics LLC. Zoladex- goserelin implant.

AbbVie Inc. Lupron Depot-Ped- leuprolide acetate.

AbbVie Inc. Lupron Depot- leuprolide acetate.

By Christina Varvatsis, PharmD Christina Varvatsis is a hospital pharmacist and freelance medical writer. She is passionate about helping individuals make informed healthcare choices by understanding the benefits and risks of their treatment options.

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