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Generic name: fosaprepitant
Brand name: Emend for Injection
Dosage form: intravenous powder for injection (150 mg)
Drug class: NK1 receptor antagonists

Medically reviewed by  A Ras MD.

What is fosaprepitant used for?

Fosaprepitant is a prescription medicine that is used to prevent upset stomach and throwing up from chemo. Fosaprepitant may be given to you for other reasons.


Fosaprepitant for injection is a sterile, white to off white lyophilized cake or powder formulation containing fosaprepitant dimeglumine, a prodrug of aprepitant, a substance P/neurokinin-1 (NK1) receptor antagonist, an antiemetic agent, chemically described as 1-­Deoxy-1-(methylamino)-D-glucitol[3-[[(2R,3S)-2-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3-(4-fluorophenyl)-4-morpholinyl]methyl]-2,5-dihydro-5-oxo-1H-1,2,4-triazol-1-yl]phosphonate (2:1) (salt).

Its molecular formula is C23H22F7N4O6P • 2(C7H17NO5) and its structural formula is:

Fosaprepitant Dimeglumine Chemical Structure

Fosaprepitant dimeglumine is a white to off-white amorphous powder with a molecular weight of 1,004.83. It is freely soluble in water.

Each vial of fosaprepitant for injection for administration as an intravenous infusion contains 150 mg of fosaprepitant (equivalent to 245.3 mg of fosaprepitant dimeglumine) and the following inactive ingredients: edetate disodium (18.8 mg), polysorbate 80 (75 mg), lactose anhydrous (375 mg), sodium hydroxide and/or hydrochloric acid (for pH adjustment).

Mechanism of Action

Fosaprepitant is a prodrug of aprepitant and accordingly, its antiemetic effects are attributable to aprepitant.

Aprepitant is a selective high-affinity antagonist of human substance P/neurokinin 1 (NK1) receptors. Aprepitant has little or no affinity for serotonin (5-HT3), dopamine, and corticosteroid receptors, the targets of existing therapies for chemotherapy-induced nausea and vomiting (CINV). Aprepitant has been shown in animal models to inhibit emesis induced by cytotoxic chemotherapeutic agents, such as cisplatin, via central actions. Animal and human Positron Emission Tomography (PET) studies with aprepitant have shown that it crosses the blood brain barrier and occupies brain NK1 receptors. Animal and human studies have shown that aprepitant augments the antiemetic activity of the 5-HT3-receptor antagonist ondansetron and the corticosteroid dexamethasone and inhibits both the acute and delayed phases of cisplatin-induced emesis.

Before taking fosaprepitant, tell your doctor:

  • If you are allergic to fosaprepitant; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you are taking pimozide.

This is not a list of all drugs or health problems that interact with fosaprepitant.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take fosaprepitant with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take fosaprepitant?

  • Tell all of your health care providers that you take fosaprepitant. This includes your doctors, nurses, pharmacists, and dentists.
  • This medicine interacts with many other drugs. The chance of side effects may be raised or how well fosaprepitant works may be lowered. Check with your doctor and pharmacist to make sure that it is safe for you to take fosaprepitant with all of your other drugs (prescription or OTC, natural products, vitamins).
  • Allergic reactions have happened with fosaprepitant. You will be watched closely while you receive fosaprepitant and for some time after your dose. Talk with your doctor.
  • Birth control pills and other hormone-based birth control may not work as well to prevent pregnancy. Use some other kind of birth control also, like a condom, when taking fosaprepitant and for 1 month after the last dose.
  • Tell your doctor if you are pregnant, plan on getting pregnant, or are breast-feeding. You will need to talk about the benefits and risks to you and the baby.

How is fosaprepitant best taken?

Use fosaprepitant as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • It is given as an infusion into a vein over a period of time.

What do I do if I miss a dose?

  • Call your doctor to find out what to do.

What are the side effects of fosaprepitant that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of a urinary tract infection (UTI) like blood in the urine, burning or pain when passing urine, feeling the need to pass urine often or right away, fever, lower stomach pain, or pelvic pain.
  • Flushing.
  • Dizziness or passing out.
  • Fast or abnormal heartbeat.
  • A burning, numbness, or tingling feeling that is not normal.
  • This medicine may cause tissue damage if the drug leaks from the vein. Tell your nurse if you have any redness, burning, pain, swelling, blisters, skin sores, or leaking of fluid where the drug is going into your body.
  • Low blood cell counts have happened with fosaprepitant. If blood cell counts get very low, this can lead to bleeding problems, infections, or anemia. Call your doctor right away if you have signs of infection like fever, chills, or sore throat; any unexplained bruising or bleeding; or if you feel very tired or weak.

What are some other side effects of fosaprepitant?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Feeling tired or weak.
  • Stomach pain or diarrhea.
  • Heartburn.
  • Pain in arms or legs.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out fosaprepitant?

  • If you need to store fosaprepitant at home, talk with your doctor, nurse, or pharmacist about how to store it.




  • Rx only                  NDC 55150-299-01
    for Injection
    150 mg per vial
    For Intravenous Use Only
    After Reconstitution and Dilution
    Single-Dose Vial
    Discard Unused Portion

PACKAGE LABEL-PRINCIPAL DISPLAY PANEL -150 mg per vial - Container Label




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