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Generic name: selumetinibSEL-ue-MET-i-nib ]
Drug class: Multikinase inhibitors

Medically reviewed by Judith Stewart, BPharm. Last updated on May 30, 2023.

What is Koselugo?

Koselugo inhibits the actions of an enzyme which is often activated in different types of cancers.

Koselugo is a prescription medicine 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.

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


Tell your healthcare provider if you are taking aspirin, blood thinners, or other medicines to treat blood clots. Koselugo contains vitamin E which may increase your risk of bleeding.

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

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

Tell your doctor if your child has ever had:

  • heart problems;

  • vision problems; or

  • liver problems.

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 this medicine.

  • Girls who are able to get pregnant should use effective birth control to prevent pregnancy while taking Koselugo.

  • Boys with female sex partners who are able to get pregnant should also use effective birth control while taking Koselugo.

  • Keep using birth control for at least 1 week after the last dose of Koselugo.

  • Tell your doctor right away if a pregnancy occurs while either the mother or the father is using Koselugo.

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

How should I take Koselugo?

Take Koselugo exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Take Koselugo 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 Koselugo has trouble swallowing the capsule whole.

If you vomit shortly after taking Koselugo, 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.

Koselugo 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.

Koselugo 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.

Koselugo 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.

Dosing information

Usual Pediatric Dose for Fibromatosis:

2 years and older:
25 mg/m2 orally 2 times a day (approximately every 12 hours) until disease progression or unacceptable toxicity

-BSA less than 0.55 mg/m2: No dose recommendation.
-BSA 0.55 to 0.69 m2: 20 mg/m2 orally in the morning and 10 mg/m2 in the evening
-BSA 0.7 to 0.89 m2: 20 mg/m2 orally in the morning and 20 mg/m2 in the evening
-BSA 0.9 to 1.09 m2: 25 mg/m2 orally in the morning and 25 mg/m2 in the evening
-BSA 1.1 to 1.29 m2: 30 mg/m2 orally in the morning and 30 mg/m2 in the evening
-BSA 1.3 to 1.49 m2: 35 mg/m2 orally in the morning and 35 mg/m2 in the evening
-BSA 1.5 to 1.69 m2: 40 mg/m2 orally in the morning and 40 mg/m2 in the evening
-BSA 1.7 to 1.89 m2: 45 mg/m2 orally in the morning and 45 mg/m2 in the evening
-BSA 1.9 mg/m2 or greater: 50 mg orally in the morning and 50 mg/m2 in the evening

Use: Treatment of pediatric patients 2 years 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 to avoid

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.

Koselugo side effects

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

Call your doctor at once if you have:

  • severe or ongoing diarrhea;

  • a skin rash with blistering or peeling, or any rash that covers a large area of skin;

  • heart problems - tiredness, fast heartbeats, cough, wheezing, shortness of breath, swelling in your lower legs;

  • vision changes - blurred vision, vision loss, seeing dark spots or "floaters" in your vision;

  • unexplained muscle pain, tenderness, or weakness (especially if you also have fever, unusual tiredness, or dark colored urine).

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

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

Common Koselugo side effects may include:

  • nausea, vomiting, stomach pain;

  • itching;

  • dry skin, acne, rash;

  • redness around your fingernails;

  • feeling weak or tired;

  • mouth pain or soreness, swollen gums;

  • muscle or bone pain;

  • headache; or

  • fever.

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.

What other drugs will affect Koselugo?

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 interact with 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 Koselugo only for the indication prescribed.

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