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Generic name: selumetinib [ SEL-ue-MET-i-nib ]
Brand name: Koselugo
Dosage form: oral capsule (10 mg; 25 mg)
Drug class: Multikinase inhibitors

Medically reviewed by on Apr 26, 2024. Written by Cerner Multum.

What is selumetinib?

Selumetinib is used to treat neurofibromatosis (a genetic disorder that causes tumors to develop on the nerves) in children at least 2 years old.

Neurofibromatosis may cause tumors in the brain or spinal cord, learning disabilities, tumors on or under the skin, or bone deformities. Plexiform neurofibromas are large tumors that grow from nerves anywhere in the body and may become cancerous later in life.

Selumetinib is for children with plexiform neurofibromas that cannot be surgically removed.

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

Selumetinib side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

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

Diarrhea is a common side effect of selumetinib. Tell your doctor right away the first time you have diarrhea while taking selumetinib.

Your doses may be delayed or permanently discontinued if you have certain side effects.

Common side effects of selumetinib may include:

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.


Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

Selumetinib should not be given to a child younger than 2 years old.

Tell your doctor if your child has ever had:

A girl who has entered puberty may need to have a negative pregnancy test before starting this treatment.

Selumetinib can harm an unborn baby if the mother or father is using selumetinib.

Do not breastfeed while using this medicine, and for at least 1 week after your last dose.

How should I take selumetinib?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Take selumetinib with a full glass of water on an empty stomach, at least 1 hour before or 2 hours after a meal.

Take the medicine at the same time each day, about every 12 hours. Follow your doctor's dosing instructions very carefully.

Swallow the capsule whole and do not crush, chew, break, or open it.

Tell your doctor if the child taking selumetinib has trouble swallowing the capsule whole.

If you vomit shortly after taking selumetinib, do not take another dose. Wait until your next scheduled dose time to take the medicine again.

Tell your doctor if you start having loose stools. You may be given anti-diarrhea medicine. Keep using this medicine for as long as your doctor has prescribed.

Drink plenty of liquids if you have diarrhea.

Selumetinib can cause your heart to pump less blood than normal. Your heart function will need to be checked every 3 to 6 months while you are taking this medicine.

Selumetinib can also cause eye problems that may lead to blindness. You will need frequent vision exams, and your next dose may be delayed based on the results.

Selumetinib doses are based on body surface area (height and weight). Your dose needs may change if you gain or lose weight or if you are still growing.

Do not change your dose or dosing schedule without your doctor's advice.

Store at room temperature away from moisture and heat. Keep the capsules in their original container, along with the packet or canister of moisture-absorbing preservative.

Selumetinib dosing information

Usual Pediatric Dose for Fibromatosis:

Recommended dosage in pediatric patients ages 2 to 18 years old: 25 mg/m2 orally twice a day (approximately every 12 hours) until disease progression or unacceptable toxicity.

Recommended dosage to achieve 25 mg/m2 twice a day based on body surface area (BSA):
-BSA less than 0.55 mg/m2: No dose recommendation.
-BSA 0.55 to 0.69 m2: 20 mg orally in the morning and 10 mg in the evening
-BSA 0.7 to 0.89 m2: 20 mg orally twice a day
-BSA 0.9 to 1.09 m2: 25 mg orally twice a day
-BSA 1.1 to 1.29 m2: 30 mg orally twice a day
-BSA 1.3 to 1.49 m2: 35 mg orally twice a day
-BSA 1.5 to 1.69 m2: 40 mg orally twice a day
-BSA 1.7 to 1.89 m2: 45 mg orally twice a day
-BSA 1.9 mg/m2 or greater: 50 mg orally twice a day

-Do not administer to patients who are unable to swallow.

Use: For the treatment of pediatric patients 2 years of age and older with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas (PN).

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if your next dose is due in less than 6 hours. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking selumetinib?

Grapefruit may interact with selumetinib and lead to unwanted side effects. Avoid the use of grapefruit products.

Avoid taking an herbal supplement containing St. John's wort.

What other drugs will affect selumetinib?

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.

Other drugs may affect selumetinib, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.