Fosaprepitant is used together with other medications to prevent nausea and vomiting that may be caused by chemotherapy in adults and children at least 6 months old.

Fosaprepitant is given ahead of time and will not treat nausea or vomiting that you already have.

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

You should not use fosaprepitant if you also take pimozide. Using these drugs together can cause unwanted or dangerous effects.

Fosaprepitant is given as an infusion into a vein. A healthcare provider will give you this injection.

The first dose of fosaprepitant is usually given on the first day of chemotherapy treatment. This medicine can also be given on the second and third day of chemotherapy treatment.

You may also be given other medicines to further help prevent nausea and vomiting.

Fosaprepitant is not for long-term use.

If you also take warfarin (Coumadin, Jantoven), you may need extra "INR" or prothrombin time tests after you have received fosaprepitant.

You should not be treated with fosaprepitant if you are allergic to fosaprepitant or aprepitant, or if you take another medicine called pimozide (Orap). Fosaprepitant can cause unwanted or dangerous effects when used with pimozide.

Tell your doctor if you have ever had:

• liver disease.

Tell your doctor if you are pregnant or breastfeeding.

Fosaprepitant can make hormonal birth control less effective, including birth control pills, injections, implants, skin patches, and vaginal rings. Use barrier birth control to prevent pregnancy: condom, diaphragm, cervical cap, or contraceptive sponge.

Keep using a barrier form of birth control for at least 1 month after each dose of fosaprepitant.

Fosaprepitant is used as a single dose and does not have a daily dosing schedule.

Since fosaprepitant is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

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

Get emergency medical help if you have signs of an allergic reaction: hives, rash, itching, skin sores or peeling; warmth or tingly feeling; fast or weak heartbeats, severe dizziness; trouble breathing or swallowing; swelling of your face, lips, tongue, or throat.

Fosaprepitant may cause serious side effects. Call your doctor at once if you have:

• pain, redness, swelling, burning, blistering, or skin changes where the chemotherapy medicine was injected;

• a light-headed feeling, like you might pass out;

• pain or burning when you urinate; or

• low blood cell counts--fever, chills, tiredness, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath.

Common side effects of fosaprepitant may include:

• weakness, tired feeling;

• fever;

• low blood cell counts;

• painful urination;

• diarrhea, indigestion; or

• pain, numbness, or weakness in your arms or legs.

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.

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Many drugs can affect fosaprepitant. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.