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Synarel Side Effects

Generic Name: nafarelin

Note: This document contains side effect information about nafarelin. Some of the dosage forms listed on this page may not apply to the brand name Synarel.

For the Consumer

Applies to nafarelin: nasal spray

Along with its needed effects, nafarelin (the active ingredient contained in Synarel) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking nafarelin:

More commonFor adults (female)
  • Breast enlargement
  • light vaginal bleeding between regular menstrual periods, called spotting
  • longer or heavier menstrual periods
  • vaginal bleeding between regular menstrual periods, called breakthrough bleeding
For children (male)
  • Body odor
  • growth of pubic hair
For children (female)
  • Body odor
  • breast enlargement
  • growth of pubic hair
  • light vaginal bleeding between regular menstrual periods, called spotting
  • longer or heavier menstrual periods
  • vaginal bleeding between regular menstrual periods, called breakthrough bleeding
Less common
  • Chest pain
  • rash, hives or welts, itching
  • redness of the skin
Less common or rareFor adults (female)
  • Fast or irregular heartbeat
  • numbness or tingling of the hands or feet
  • pain in the eyes or joints
  • patchy brown or dark brown discoloration of the skin
  • pelvic bloating or tenderness
  • unexpected or excess milk flow from the breasts
  • unusual tiredness or weakness
Incidence not knownFor adults (female)
  • Cough
  • difficulty with speaking
  • dizziness or lightheadedness
  • double vision
  • fainting
  • fast heartbeat
  • inability to move the arms, legs, or facial muscles
  • inability to speak
  • nausea
  • pain or discomfort in the arms, jaw, back, or neck
  • pain, redness, or swelling in the arm or leg
  • slow speech
  • sweating
  • troubled breathing
  • vomiting
  • yellow eyes or skin
Incidence not known

Some side effects of nafarelin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More commonFor adults (female)
  • Acne
  • dandruff
  • hot flashes
  • increase or decrease in sexual desire
  • increased hair growth, often abnormally distributed
  • mood swings
  • muscle pain
  • oily skin
  • pain during sexual intercourse
  • rapid weight gain
  • reduced breast size
  • stopping of menstrual periods
  • swelling of the feet or lower legs
  • vaginal dryness
For children (male)
  • Acne
  • dandruff
  • mood swings
  • oily skin
For children (female)
  • Acne
  • dandruff
  • hot flashes
  • mood swings
  • oily skin
Less common or rareFor adults (female)
  • Breast pain
  • headache (mild and transient)
  • irritated or runny nose
  • mental depression (mild and transient)
For children (male)
  • Irritated or runny nose
For children (female)

For Healthcare Professionals

Applies to nafarelin: nasal spray


Hot flashes occurred commonly in adult women who were treated for endometriosis. Approximately 3% of children developed transient hot flashes.[Ref]

Very common (10% or more): Hot flashes/hot flush (up to 90%)
Common (1% to 10%): Chest pain, edema, hyper/hypotension
Frequency not reported: Palpitations
Postmarketing reports: Arterial thromboembolism, deep vein thrombosis, myocardial infarction, venous thromboembolism[Ref]


Very common (10% or more): Decreased libido (up to 23%), emotional/affect lability (up to 15%)
Common (1% to 10%): Depression, increased libido, insomnia
Postmarketing reports: Aggression, anger, impatience, irritability, suicidal ideation, suicide attempt[Ref]


Very common (10% or more): Vaginal dryness (up to 19%)
Common (1% to 10%): Transient breast enlargement, breast atrophy/decreased breast size, vulvovaginal dryness, artificial menopause, uterine hemorrhage, vaginal bleeding, white/brown vaginal discharge
Uncommon (0.1% to 1%): Ovarian cyst
Frequency not reported: Ovarian hyperstimulation syndrome[Ref]

Nervous system

Very common (10% or more): Headache (up to 18%)
Common (1% to 10%): Paresthesia
Frequency not reported: Migraines
Postmarketing reports: Convulsions, stroke, transient ischemic attack[Ref]


Very common (10% or more): Acne (up to 14%)
Common (1% to 10%): Transient increase in pubic hair, body odor, seborrhea, pruritus, rash, urticaria, hirsutism
Uncommon (0.1% to 1%): Alopecia[Ref]


Common (1% to 10%): Rhinitis, dyspnea, nasal irritation
Frequency not reported: Shortness of breath
Postmarketing reports: Interstitial pneumonitis, pulmonary embolism, pulmonary fibrosis[Ref]


Common (1% to 10%): Myalgia, decreased bone mineral density
Uncommon (0.1% to 1%): Arthralgia
Postmarketing reports: Arthritic symptoms[Ref]


Common (1% to 10%): Estrogen deficiency
Frequency not reported: Pituitary enlargement/asymmetry/pituitary gland changes (size and shape)
Postmarketing reports: Pituitary apoplexy[Ref]


Common (1% to 10%): Increased/decreased weight
Frequency not reported: Increased serum alkaline phosphatase, increased total cholesterol/triglycerides[Ref]


Common (1% to 10%): Drug hypersensitivity[Ref]


Frequency not reported: Adrenal rest tumor of the testis, pituitary gland adenoma[Ref]

A patient with congenital adrenal hyperplasia developed an adrenal rest tumor 8 months after discontinuing treatment; however, correlation to treatment is unlikely.

Pituitary gland adenomas have been observed in a few children receiving treatment; however, the relationship to treatment is unknown.[Ref]


Frequency not reported: Increased AST/ALT, serious liver injury[Ref]


Frequency not reported: Blurred vision[Ref]


Postmarketing reports: Crying


1. "Product Information. Synarel (nafarelin)." Roche Laboratories, Nutley, NJ.

2. Cerner Multum, Inc. "Australian Product Information." O 0

3. "Product Information. Synarel (nafarelin nasal)." Pfizer U.S. Pharmaceuticals Group, New York, NY.

4. "Product Information. Synarel Nasel Solution (nafarelin nasal)." Searle, Chicago, IL.

5. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Further information

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

Some side effects may not be reported. You may report them to the FDA.