Ganirelix (Subcutaneous)

Ganirelix is a solution-based medicine injected under the skin (subcutaneously)of women undergoing controlled ovarian hyperstimulation fertility therapy.


Ganirelix injection essentially prevents premature ovulation from occurring. By blocking the release of luteinizing hormone (LH) in the body, the medicine stops an egg from releasing too soon from the ovary, allowing it time to properly develop.

Using this medicine may also reduce the need for follicle-stimulating hormone (FSH), a hormone that controls egg production in the ovaries.

While this medicine treats certain causes of infertility in women, it must not be used to treat a woman who is already pregnant.

Ganirelix is supplied as a solution for injection. In the US, it is sold under the brand name, Antagon, and is sold to patients through a doctor's prescription only.

Condition treated

  • Infertility in women

Type Of Medicine

  • Gonadotropin-releasing hormone (GnRH) antagonist.

Side Effects

Most, if not all, prescription medicines cause side effects. Ganirelix may cause side effects which are expected and required as the medicine works in the body. Other side effects are unwanted and may or may not require medical attention.

Serious allergic reaction

The medicine may cause a serious type of allergic reaction called anaphylaxis. Call your doctor immediately if this occurs. Symptoms of this condition are as follows:

  • Hoarseness
  • Swelling of the mouth/lips, face, or hands
  • Trouble breathing
  • Skin rash
  • Itching
  • Trouble swallowing

A condition known as ovarian hyperstimulation syndrome (OHSS) may result from using this injection. It may occur during or after treatment.

Though rare, a serious case of OHSS causes the following side effects that may be life-threatening. Seek urgent medical attention if you experience any of them.

  • Nausea
  • Vomiting
  • Decrease in the amount of your urine
  • Swelling or pain in the lower abdomen or pelvic area
  • Rapid weight gain (that is sudden)

Call your doctor immediately if you notice any of the side effects on the following list:

Less commonly occur

  • Diarrhea
  • Bloating
  • Rapid weight gain
  • Pain in the stomach or abdomen

Rarely occur

  • Tightness in the chest
  • Swelling or puffiness of the face, lips, tongue, eyelids or area around the eyes
  • Difficulty swallowing
  • Dizziness
  • Shortness of breath
  • Skin rash, hives, or itching
  • Cough
  • Feeling unusually tired or weak
  • Fast heartbeat

The following side effects may occur, but do not usually require medical attention. They tend to go away on their own as the body gets used to the medicine. Tell your doctor if any of them occur but gets worse, bothers you, or does not go away.

Less commonly occur

  • Redness, swelling or pain in the area where the medicine was injected
  • Headache

All of the listed side effects may not occur, or may not occur all at the same time. Some patients may experience other side effects which are not listed here.

Also check with your doctor if you notice any unusual symptom that becomes bothersome or does not go away. You can ask your doctor or health care professional about ways to prevent or reduce side effects.

You may also call the FDA at 1-800-FDA-1088 to report side effects


Ganirelix is supplied as a disposable, pre-filled glass syringe containing 250 mcg/0.5 mL of solution for injection. A sterilized needle is attached and covered with a rubber cap.

Ganirelix injection may be given to you by a nurse or healthcare professional at a hospital or medical clinic. You may also be given the medicine to inject at home.

Carefully read the patient information leaflet that should be given to you, as well as the prescription label.

Your doctor will instruct you on how to prepare and take the injection. If you are not clear on what to do, ask your doctor, pharmacist or healthcare professional to explain.

The following guide may be helpful:

  • Clean your hands by washing them with soap and water, then prepare your injection on a clean surface.
  • Carefully follow all directions your doctor gave you to take the injection.
  • Use only the syringe and needle the medicine was supplied with.
  • Take only the amount of medicine prescribed as your dose.
  • Pick a different spot on your skin to take your medicine each time you inject it. This helps prevent skin problems, such as skin irritation, from developing.
  • After each injection, throw away unused medicines, bottles, needles, and syringes in a safe way.
  • Once you have used your last dose of Ganirelix, tell your doctor. Your doctor should then give you another medicine named human chorionic gonadotrophin (hCG).

The following is an average dosage guide. You should not change your dose to suit this guide. All changes in your dose must be done by your doctor.

For treatment of infertility in women

Adults: After treatment with follicle-stimulating hormone (FSH), and on day 2 or 3 of your menstrual period, inject 250 micrograms (mcg) of Ganirelix under your skin.

Take this dose once a day during the mid to late follicular phase. This will be around Day 7 or 8 up to Day 12 or 13 of your menstrual cycle.

Children: Ganirelix is not indicated for use in children.

Missed dose

If you missed your dose of Ganirelix injection, call your doctor or healthcare professional for instructions.


No data is available relating to overdose in patients using this medicine.


Food, alcohol, and tobacco

Eating during the time of taking a medicine or eating certain foods may cause interaction. The use of alcohol or tobacco may also cause interaction. Your doctor may caution you on the use of foods, alcohol or tobacco if necessary.

Other medicines

Adequate studies have not been done to determine if Ganirelix interacts with other medicines used by patients during treatment with the injection.

This does not mean that no other medicines may interact. Necessary precautions still need to be taken when patients are taking the injection and using other medications.

Tell your doctor about all prescription or over-the-counter medicines (OTC's), vitamins, or herbal supplements you take or plan to take.

Other medical problems

Certain medical conditions may affect or be affected by the use prescription medicines. You must tell your doctor if you are pregnant. Due to the risk of harm to an unborn baby, your doctor should not treat you with this medicine during pregnancy.


  • You should use Ganirelix only if it was prescribed for you. Your doctor will consider your medical history and the potential risks and benefits involved before deciding whether to treat you.
  • This medicine should not be used in children. The safety and efficacy of using Ganirelix in pediatrics have not been established.
  • Studies show that using this medicine during pregnancy may harm an unborn baby. Do not use this medicine if you are pregnant or may become pregnant. Your doctor should test you for pregnancy and should treat you only if the test result is negative.
  • If you become pregnant while being treated with Ganirelix, stop using it immediately and call your doctor right away.
  • Your doctor may direct you to check and record your basal temperatures (BBT's) on a daily basis. Using the record, your doctor will be able to tell you when you are ovulating. During ovulation, you may be most fertile and have a greater chance of being pregnant if you have sexual intercourse during this period.
  • It is important to know that you may become pregnant with more than one fetuses (babies) due to using this medicine.
  • Tell your doctor if you are breastfeeding. Studies done in breastfeeding women have not shown that the medicine can pass through breast milk and harm a breastfeeding infant. Treatment must be determined by a doctor after the potential benefits and risks have been considered.
  • Do not use Ganirelix if you are allergic to it. Tell your doctor if you have had an allergic reaction to Ganirelix or other products that have gonadotropin releasing hormone (GnRH) in it.
  • Let your doctor know if you are allergic to other medicines, foods, preservatives, dyes or animals.
  • Tell your doctor if you are allergic to latex. The cover of the syringe needle used to inject the medication may cause an allergic reaction in patients sensitive to latex.
  • Ganirelix may be safe to use in elderly patients. However, there may be a risk of increased side effects that may be related to your age. Your doctor will determine how to treat you and what precautions to take.
  • Ganirelix may result in a condition called ovarian hyperstimulation syndrome (OHSS). If you develop symptoms of ovarian hyperstimulation syndrome, call your doctor right away. Although side effects are rarely serious, this condition can be life-threatening.
  • Before any medical surgery or dental procedure, tell the person performing the procedure you are taking this medicine.
  • Keep all follow-up doctor's appointments. Your doctor will need to monitor you closely while you are taking this injection. You may also be required to take regular blood tests.
  • Do not share this medicine with anyone else even if they are undergoing a similar treatment.


Keep the medicine in a closed container, away from heat, moisture, and direct light. Keep from freezing.

Keep the medicine out of the reach of children.

Throw away medicine that is expired or no longer needed.

Used syringes and needles should be placed in a hard container. Close the container and keep it away from children and pets.

You may ask your healthcare professional or local waste disposal agency how to safely dispose of unused medicine, needles, and syringes.


Ganirelix is a safe and effective medicine for preventing premature ovulation in adult women receiving controlled ovarian hyperstimulation fertility therapy.

However, this medicine is not safe for use in pregnant women due to the risk of harm to an unborn child.

There are not many side effects caused by using the injection. There is also no known adverse interaction caused by using Ganirelix together with other medicines. It does not mean that there is no possibility for adverse interaction. Therefore, precautions may still need to be taken when treating patients with this fertility medicine.

While side effects are few, the medicine is known to cause a serious, possibly life-threatening, allergic condition known as anaphylaxis. In addition, and although rare, another life-threatening condition called ovarian hyperstimulation syndrome (OHSS) has occurred in patients.

Despite the potential for these adverse effects, patients have become pregnant by using Ganirelix. Multiple births have occurred in some case.