Reviewed on 2/22/2023

What Is Nafarelin and How Does It Work?

Nafarelin is a prescription medication used for the treatment of endometriosis and central precocious puberty. 

  • Nafarelin is available under the following different brand names: Synarel.

What Are the Side Effects Associated with Using Nafarelin?

Common side effects of Nafarelin include:

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

Serious side effects of Nafarelin include:

  • hives,
  • difficulty breathing,
  • swelling of the face, lips, tongue, or throat,
  • vaginal spotting,
  • continued menstrual bleeding,
  • pelvic pain or swelling,
  • seizure,
  • sudden headache,
  • confusion,
  • vision changes,
  • vomiting,
  • weak pulse, and
  • slowed breathing
  • Specific to children:
  • anger,
  • aggression,
  • crying,
  • restlessness, and
  • irritable

Rare side effects of Nafarelin include:

  • None 

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out. 

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Are the Dosages of Nafarelin?

Adult and pediatric dosage

Nasal spray

  • 2 mg/mL
  • 200 mcg/spray


Adult dosage

  • 1 spray (200 mcg/spray) in one nostril every morning, 1 spray in the other nostril every night (total 400 mcg/day) on days 2-4 of the menstrual cycle (2 sprays/day)
  • May increase to 800 mcg/day if still menstruating after 2 months: 1 spray in each nostril twice daily

Central Precocious Puberty

Pediatric dosage

  • Aged below 2 years: Safety and efficacy not established
  • Aged above 2 years: 2 sprays (200 mcg/spray) in each nostril twice daily (total 1600 mcg/day)
  • May increase to 1800 mcg/day: 3 sprays (200 mcg/spray) into alternating nostrils thrice daily (total 9 sprays/day)

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Other Drugs Interact with Nafarelin?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Nafarelin has no noted severe interactions with any other drugs.
  • Nafarelin has no noted serious interactions with any other drugs.
  • Nafarelin has no noted moderate interactions with any other drugs.
  • Nafarelin has no noted minor interactions with any other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, health questions, or concerns.

What Are Warnings and Precautions for Nafarelin?


  • Pregnancy, hypersensitivity, lactation, undiagnosed abnormal vaginal bleeding

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Nafarelin?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Nafarelin?”


  • Goal in adult females is to suppress menstruation; the max treatment period 6 mth
  • May cause an increase in bone turnover & decrease in bone mineral content
  • Ovarian cysts may develop within the first 2 months of therapy and occur more commonly in women with polycystic ovarian disease
  • Cases of pituitary apoplexy reported
  • Use caution in patients with risk factors for decreased bone mineral density
  • Irregular or incomplete daily doses may result in stimulation of the pituitary-gonadal axis; counsel caregivers to assure full compliance
  • During the first month of treatment, may initially expect some signs of puberty, e.g., vaginal bleeding or breast enlargement may occur; such changes should resolve soon after the first month; if such resolution does not occur within the first two months of treatment, this may be due to lack of compliance or presence of gonadotropin independent sexual precocity; if both possibilities excluded, the dose may be increased to 1800 mcg/day administered as 600 mcg thrice daily
  • Patients with intercurrent rhinitis should consult their physician for use of topical nasal decongestant; if the use of topical nasal decongestant is required during treatment decongestant should not be used until at least 2 hr after administering therapy; sneezing during or immediately after administering therapy should be avoided, if possible, since may impair drug absorption
  • Convulsions reported in patients receiving GnRH agonists; reports with GnRH agonists have included patients with a history of seizures, epilepsy, cerebrovascular disorders, central nervous system anomalies or tumors, and patients on concomitant medications that have been associated with convulsions such as bupropion and SSRIs; convulsions also reported in patients in the absence of any of the conditions listed
  • Psychiatric events reported in patients taking GnRH agonists; postmarketing reports with this class of drugs include symptoms of emotional lability, such as crying, irritability, impatience, anger, and aggression; monitor for development or worsening of psychiatric symptoms during treatment
  • Depression may occur or worsen during treatment with GnRH agonists; carefully observe women for depression, especially those with a history of depression, and consider whether the risks of continuing therapy outweigh the benefits; women with new or worsening depression should be referred to a mental health professional, as appropriate; inform patients that depression may occur or worsen during treatment with GnRH agonists, especially in patients with a history of depression; advise patients to immediately report thoughts and behaviors of concern to healthcare providers
  • Pseudotumor cerebri (idiopathic intracranial hypertension) reported in pediatric patients receiving GnRH agonists, including leuprolide acetate; monitor patients for signs and symptoms of pseudotumor cerebri, including headache, papilledema, blurred vision, diplopia, loss of vision, pain behind the eye or pain with eye movement, tinnitus, dizziness, and nausea; inform patients and caregivers that reports of pseudotumor cerebri have occurred

Pregnancy and Lactation

  • Do not use it during pregnancy. The risks involved outweigh the potential benefits. Safer alternatives exist.
  • Lactation
    • Excretion in milk unknown, contraindicated

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