Medically reviewed by Drugs.com. Last updated on May 5, 2022.
The Antagon brand name has been discontinued in the U.S. If generic versions of this product have been approved by the FDA, there may be generic equivalents available.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
Therapeutic Class: Endocrine-Metabolic Agent
Pharmacologic Class: Luteinizing Hormone Releasing Hormone Antagonist
Uses for Antagon
Ganirelix injection is used as a fertility medicine to prevent premature luteinizing hormone (LH) surges or ovulation in women undergoing fertility treatment of controlled ovarian hyperstimulation. It may also help reduce the need for follicle-stimulating hormone (FSH), which is also needed for ovulation. Ganirelix is a gonadotropin-releasing hormone (GnRH) antagonist.
This medicine is available only with your doctor's prescription.
Before using Antagon
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
No information is available on the relationship of age to the effects of ganirelix injection in the pediatric population. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of ganirelix injection in the elderly.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Proper use of Antagon
To make using ganirelix as safe and reliable as possible, you should understand how and when to use this medicine and what effects may be expected. A patient information leaflet will be given to you with your filled prescription and will provide many details concerning the use of ganirelix. Read the information carefully and ask your doctor for any additional information or explanation.
Sometimes ganirelix can be given by injection at home. If you are using this medicine at home:
- Understand and use the proper method of safely preparing the medicine if you are going to prepare your own medicine.
- Wash your hands with soap and water and use a clean work area to prepare your injection.
- Make sure you clearly understand and carefully follow your doctor's instructions on how to give yourself an injection, including using the proper needle and syringe.
- Do not inject more or less of the medicine than your doctor ordered.
- Remember to move the site of injection to different areas to prevent skin problems from developing.
- Throw away needles, syringes, bottles, and unused medicine after the injection in a safe manner.
- Tell your doctor when you use your last dose of ganirelix. Your doctor will give you another medicine called human chorionic gonadotrophin (hCG) or arrange for you to get this medicine at the right time.
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For injection dosage form:
- For treatment of female infertility:
- Adults—After receiving FSH treatment on Day 2 or 3 of your menstrual cycle, 250 micrograms (mcg) of ganirelix is injected under the skin once a day during the mid to late follicular phase (about Day 7 or 8 up to Day 12 or 13 of your menstrual cycle).
- Children—Use is not recommended.
- For treatment of female infertility:
Call your doctor or pharmacist for instructions.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Throw away used needles and syringes in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.
Ask your pharmacist, doctor, or nurse about the best way to dispose of any leftover medicine and other supplies.
Precautions while using Antagon
It is very important that your doctor check your progress often at regular visits to make sure that the medicine is working properly and to check for unwanted effects. Your doctor will probably want to follow the developing eggs inside the ovaries by doing an ultrasound examination and measuring hormones in your blood stream.
This medicine may cause serious types of allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Call your doctor right away if you have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you are using this medicine.
The needle cover of the prefilled syringe contains dry natural rubber (a derivative of latex), which may cause allergic reactions in people who are sensitive to latex. Tell your doctor if you have a latex allergy before you start using this medicine.
If your doctor has asked you to record your basal body temperatures (BBTs) daily, make sure that you do this every day. Using a BBT record or some other method, your doctor will help you decide when you are most fertile and when ovulation occurs. It is important that sexual intercourse take place around the time when you are most fertile to give you the best chance of becoming pregnant. Follow your doctor's directions carefully.
If severe abdominal pain occurs with use of ganirelix, discontinue treatment and report the problem to your doctor immediately. Do not receive the injection of human chorionic gonadotropin (hCG) and avoid sexual intercourse.
Antagon side effects
Along with its needed effects, a medicine 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:
- Abdominal or stomach pain
- rapid weight gain
- difficulty with swallowing
- fast heartbeat
- puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
- shortness of breath
- skin rash, hives, or itching
- tightness in the chest
- unusual tiredness or weakness
Some side effects 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:
- redness, pain, or swelling at the injection site
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
More about Antagon (ganirelix)
- Side effects
- Drug interactions
- Dosage information
- During pregnancy
- Drug class: gonadotropin-releasing hormone antagonists
Related treatment guides
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.