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Generic name: ganirelix systemic

Brand names: Antagon, Fyremadel

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution Prefilled Syringe, Subcutaneous, as acetate:

Generic: 250 mcg/0.5 mL (0.5 mL)


Mechanism of Action

Competitively blocks the gonadotropin-release hormone receptors on the pituitary gonadotroph and transduction pathway. This suppresses gonadotropin secretion and luteinizing hormone secretion preventing ovulation until the follicles are of adequate size.



SubQ: Rapid


Mean Vd: Single dose: 43.7 L; Multiple dosing: 76.5 L


Hepatic to two primary metabolites (1-4 and 1-6 peptide)


Feces (75%) within 288 hours; urine (22%) within 24 hours

Time to Peak

1.1 hours

Duration of Action

<48 hours

Half-Life Elimination

Single dose: 12.8 hours; Multiple dosing: 16.2 hours

Protein Binding


Use: Labeled Indications

Adjunct to controlled ovarian hyperstimulation: Inhibits premature luteinizing hormone (LH) surges in women undergoing controlled ovarian hyperstimulation.


Hypersensitivity to ganirelix or any component of the formulation; hypersensitivity to gonadotropin-releasing hormone (GnRH) or any other GnRH analog; known or suspected pregnancy

Canadian labeling: Additional contraindications (not in US labeling): Moderate or severe renal impairment; moderate or severe hepatic impairment

Dosage and Administration

Dosing: Adult

Adjunct to controlled ovarian hyperstimulation: SubQ: 250 mcg once daily during the mid-to-late phase after initiating follicle-stimulating hormone on day 2 or 3 of cycle. Treatment should be continued daily until the day of chorionic gonadotropin administration.

Dosing: Geriatric

Refer to adult dosing.


SubQ: Administer SubQ in abdomen (around navel) or upper thigh; rotate injection site.


Store at 25°C (77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F). Protect from light.

Drug Interactions

Indium 111 Capromab Pendetide: Antigonadotropic Agents may diminish the diagnostic effect of Indium 111 Capromab Pendetide. Avoid combination

Adverse Reactions

1% to 10%:

Central nervous system: Headache (3%)

Endocrine & metabolic: Ovarian hyperstimulation syndrome (2%)

Gastrointestinal: Abdominal pain (1%), nausea (1%)

Genitourinary: Pelvic pain (5%), vaginal hemorrhage (2%)

Local: Injection site reaction (1%)

<1%, postmarketing, and/or case reports: Anaphylactoid reaction, hypersensitivity reaction


Concerns related to adverse effects:

  • Hypersensitivity: Hypersensitivity reactions, including anaphylactoid reactions, have been reported; may occur with the first dose; use is not recommended in women with severe allergic conditions. Use with caution in women with signs and symptoms of other allergic conditions.

Special populations:

  • Pregnancy: Exclude pregnancy before beginning treatment.

Dosage form specific issues:

  • Latex: The packaging may contain natural rubber latex.

Other warnings/precautions:

  • Experienced specialists: Should only be prescribed by fertility specialists.

Monitoring Parameters

Ultrasound to assess follicle size


Pregnancy Considerations

Studies in animals have shown evidence of fetal abnormalities, including fetal resorption, and use is contraindicated in women who are pregnant. Fetal resorption is a result of hormonal alterations and could result in fetal loss in humans. Ganirelix is used to treat infertility; pregnancy should be ruled out prior to therapy.

Patient Education

  • Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
  • Patient may experience injection site irritation. Have patient report immediately to prescriber severe vaginal bleeding or signs of ovarian hyperstimulation syndrome (severe abdominal pain or bloating; severe nausea, vomiting, or diarrhea; excessive weight gain; shortness of breath; or change in how much urine is passed) (HCAHPS).
  • Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

Source: Wolters Kluwer Health. Last updated October 9, 2019.