Nafarelin (Synarel): Uses, Side Effects, Dosage, Storage, and Safety

Understanding nafarelin (marketed as Synarel) involves exploring its mechanism, applications, side effects, and safety considerations. This synthetic protein plays a crucial role in managing conditions like endometriosis pain and central precocious puberty.

Mechanism of Action

Nafarelin is a synthetic protein designed to block the effects of gonadotropin-releasing hormone (GnRH), regulating hormone output by the pituitary gland. By suppressing gonadotropins, it induces a reversible state of “menopause,” reducing estrogen production and causing shrinkage of the uterine lining.

Brand Name and Generic Availability

  • Brand Name: Synarel
  • Generic: Not available

Prescription Requirement

Yes, nafarelin requires a prescription for use.

Uses of Nafarelin

  • Management of endometriosis pain
  • Reduction in the size of endometrial implants
  • Treatment of central precocious puberty

Side Effects

Common side effects are linked to the low estrogen state and include hot flashes, vaginal dryness, headaches, mood changes, and reduced interest in sex. Other effects may include acne, muscle pain, reduced breast size, and nasal irritation. Bone thinning is a concern, and patients should discuss this with their doctors, especially if they have risk factors.

Dosage Information

For endometriosis, nafarelin is administered as one spray (200 µg) into each nostril in the morning and evening for six months. Dosage adjustments may be made based on individual responses. In the case of central precocious puberty, daily doses are higher, administered through nasal sprays.

Drug Interactions

Nasal decongestant sprays (e.g., Afrin) may interfere with nafarelin absorption. They should be used at least 2 hours before or after nafarelin.

Pregnancy and Breastfeeding

Nafarelin should not be used during pregnancy or breastfeeding due to potential harm to the fetus, and its safety in these situations is not well-established. Adequate contraception is advised during treatment.

Storage Information

Nafarelin should be stored at room temperature, between 15 to 30 degrees Celsius (59 to 86 degrees Fahrenheit).


Marketed as Synarel, it stands as a valuable therapeutic option for conditions like endometriosis and central precocious puberty. However, its usage requires careful consideration of dosage, potential side effects, and adherence to safety guidelines, especially for pregnant or breastfeeding individuals. Always consult with healthcare professionals for personalized guidance and information.

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