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Generic name: ganirelix [ GA-ni-REL-ix ]
Brand names: Ganirelix Acetate, Antagon, Fyremadel
Dosage form: subcutaneous solution (250 mcg/0.5 mL)
Drug class: Gonadotropin-releasing hormone antagonists

Medically reviewed by on May 23, 2023. Written by Cerner Multum.

What is ganirelix?

Ganirelix reduces certain hormones in the body, including estrogen.

Ganirelix is used with other medicines to treat infertility in women.

Ganirelix may also be used for purposes not listed in this medication guide.

Ganirelix side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some women using ganirelix develop ovarian hyperstimulation syndrome (OHSS), a potentially life-threatening condition. Call your doctor right away if you have symptoms of OHSS:

  • stomach pain, bloating, nausea, vomiting, diarrhea;

  • rapid weight gain, especially in your face and midsection;

  • little or no urination; or

  • pain when you breathe, rapid heart rate, feeling short of breath (especially when lying down).

Common side effects of ganirelix may include:

  • stomach pain;

  • headache;

  • vaginal bleeding; or

  • OHSS.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Tell your doctor if you have a severe or active allergy.

Before taking this medicine

You should not use ganirelix if you are allergic to ganirelix or similar medications such as leuprolide, goserelin, or nafarelin.

Tell your doctor if you are allergic to latex rubber, or if you have a severe or active allergy.

May cause birth defects. Do not use if you are pregnant. You may need to have a negative pregnancy test before starting this treatment. Tell your doctor if you become pregnant.

You should not breastfeed while using ganirelix.

How should I use ganirelix?

Ganirelix is injected under the skin, usually once daily for several days in a row during certain phases of your fertility treatment cycle.

Prepare an injection only when you are ready to give it. Read and follow all Instructions for Use. Ask your doctor or pharmacist if you need help.

Do not reuse a needle or syringe. Place them in a puncture-proof "sharps" container and dispose of it following state or local laws. Keep out of the reach of children and pets.

Your blood may need to be tested often. Remain under the care of a doctor while using ganirelix.

Store the prefilled syringe at room temperature, away from heat, moisture and light.

Throw away a prefilled syringe after one use, even if there is still medicine left inside.

Ganirelix dosing information

Usual Adult Dose for Gonadotropin Inhibition:

During the mid to late portion of the follicular phase:
-Administer 250 mcg subcutaneously once a day until the day of human chorionic gonadotropin (hCG) administration

-Follicle stimulating hormone (FSH) therapy should be initiated on day 2 or 3 of the cycle.
-With the assist of ultrasound, hCG should be administered when a sufficient number of follicles of adequate size are present; final maturation of follicles is induced by administering hCG.

Use: For the inhibition of premature luteinizing hormone surges in women undergoing controlled ovarian hyperstimulation.

What happens if I miss a dose?

Call your doctor for instructions if you miss a dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using ganirelix?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

What other drugs will affect ganirelix?

Other drugs may affect ganirelix, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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