This information from Lexicomp® explains what you need to know about this medication, including what it’s used for, how to take it, its side effects, and when to call your healthcare provider.
Brand Names: US
Koselugo
Brand Names: Canada
Koselugo
What is this drug used for?
- It is used to treat neurofibromatosis type 1 (NF1).
What do I need to tell my doctor BEFORE I take this drug?
- If you are allergic to this drug; any part of this drug; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
- If you take any drugs (prescription or OTC, natural products, vitamins) that must not be taken with this drug, like certain drugs that are used for HIV, infections, seizures, and others. There are many drugs that must not be taken with this drug.
- If you are breast-feeding. Do not breast-feed while you take this drug and for 1 week after your last dose.
This is not a list of all drugs or health problems that interact with this drug.
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 this drug 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 this drug?
All products:
- Tell all of your health care providers that you take this drug. This includes your doctors, nurses, pharmacists, and dentists.
- Have your blood work and heart function checked as you have been told by your doctor. You will also need to have eye exams.
- Avoid grapefruit, grapefruit juice, and Seville oranges.
- Diarrhea is common with this drug and can be severe. Talk with your doctor so you will know what to do right away if you have diarrhea or stomach cramps. If diarrhea happens, you will need to drink more liquids to avoid becoming dehydrated.
- This drug may cause harm to an unborn baby or loss of an unborn baby. A pregnancy test will be done before you start this drug to show that you are NOT pregnant.
- If you may become pregnant, use birth control while taking this drug and for 1 week after your last dose. If you get pregnant, call your doctor right away.
- If your sex partner may become pregnant, use birth control while taking this drug and for 1 week after your last dose. If your partner gets pregnant, call the doctor right away.
Capsules:
- Talk with your doctor before you take other sources of vitamin E. This drug has vitamin E in it.
What are some side effects that I need to call my doctor about right away?
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:
All products:
- 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 electrolyte problems like mood changes; confusion; muscle pain, cramps, or spasms; weakness; shakiness; change in balance; an abnormal heartbeat; seizures; loss of appetite; or severe upset stomach or throwing up.
- Signs of skin infection like oozing, heat, swelling, redness, or pain.
- Muscle pain or weakness, dark urine, or trouble passing urine.
- Fever, chills, or sore throat.
- Heart failure (weak heart) has happened with this drug. If you have or have ever had heart failure, talk with your doctor. Get medical help right away if you have signs of heart failure like shortness of breath, a big weight gain, coughing up white or pink mucus, fast heartbeat, waking up at night more than normal, or swelling in the arms or legs while you take this drug.
- Eye problems have happened with this drug. Some of these have been severe like retinal tear or detachment. Call the doctor if you have blurred eyesight or other eyesight changes, including if bright lights bother your eyes. Get medical help right away if objects look distorted, if you start to see halos or bright colors around lights, flashing lights, floaters, a curtain-like shadow coming across the eye, or if you have sudden eyesight loss.
- It is common to get a rash with this drug. Sometimes skin reactions can be severe. Call your doctor right away if you have a rash over a large area, blisters, peeling, or a rash that bothers you or does not go away. Call your doctor right away if you have redness or irritation of the palms of hands or soles of feet.
Capsules:
- Nosebleed.
- Blood in the urine.
- Any unexplained bruising or bleeding.
What are some other side effects of this drug?
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:
- Pimples (acne).
- Dry skin.
- Mouth irritation or mouth sores.
- Change in nails.
- Hair loss.
- Change in color of hair.
- Back, arm, or leg pain.
- Neck pain.
- Feeling tired or weak.
- Headache.
- Stomach pain.
- Constipation, diarrhea, upset stomach, throwing up, and decreased appetite are common with this drug. If these happen, talk with your doctor about ways to lower these side effects. Call your doctor right away if any of these effects bother you, do not get better, or are severe.
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 your national health agency.
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.
How is this drug best taken?
Use this drug as ordered by your doctor. Read all information given to you. Follow all instructions closely.
Capsules:
- Take with or without food.
- Swallow whole. Do not chew, break, open, or dissolve.
- If you have trouble swallowing, talk with your doctor.
Oral granules:
- Do not swallow the capsule whole. Do not chew or crush the granules inside the capsule. Do not chew, crush, dissolve, or swallow the capsule shell after opening.
- Do not take if you open the capsule and granules are clumped together or stuck to the capsule shell. If the granules do not flow freely, do not take them. Call your pharmacist about what to do.
- Sprinkle this drug on a small amount (about 1 to 3 teaspoons) of smooth yogurt or fruit puree containing apple, banana, pear, or strawberry. Do not mix the granules in liquid. Do not mix them with any food that has grapefruit or Seville orange in it.
- Swallow this drug within 30 minutes after mixing. If you do not take it within 30 minutes, throw it away and mix a new dose. If you take only part of the dose within 30 minutes after mixing, throw away the rest and do not make more.
All products:
- Keep taking this drug as you have been told by your doctor or other health care provider, even if you feel well.
- If you throw up after taking a dose, do not repeat the dose. Take your next dose at your normal time.
What do I do if I miss a dose?
- Take a missed dose as soon as you think about it.
- If it is less than 6 hours until the next dose, skip the missed dose and go back to the normal time.
- Do not take 2 doses at the same time or extra doses.
How do I store and/or throw out this drug?
All products:
- Store at room temperature in a dry place. Do not store in a bathroom.
- Store in the original container. Do not take out the antimoisture cube or packet.
- Keep lid tightly closed.
- Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
- Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.
Oral granules:
- Protect from heat. Do not leave this drug at temperatures above 86°F (30°C).
General drug facts
- If your symptoms or health problems do not get better or if they become worse, call your doctor.
- Do not share your drugs with others and do not take anyone else’s drugs.
- Some drugs may have another patient information leaflet. If you have any questions about this drug, please talk with your doctor, nurse, pharmacist, or other health care provider.
- Some drugs may have another patient information leaflet. Check with your pharmacist. If you have any questions about this drug, please talk with your doctor, nurse, pharmacist, or other health care provider.
- 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.
Consumer Information Use and Disclaimer
This generalized information is a limited summary of diagnosis, treatment, and/or medication information. It is not meant to be comprehensive and should be used as a tool to help the user understand and/or assess potential diagnostic and treatment options. It does NOT include all information about conditions, treatments, medications, side effects, or risks that may apply to a specific patient. It is not intended to be medical advice or a substitute for the medical advice, diagnosis, or treatment of a health care provider based on the health care provider’s examination and assessment of a patient’s specific and unique circumstances. Patients must speak with a health care provider for complete information about their health, medical questions, and treatment options, including any risks or benefits regarding use of medications. This information does not endorse any treatments or medications as safe, effective, or approved for treating a specific patient. UpToDate, Inc. and its affiliates disclaim any warranty or liability relating to this information or the use thereof. The use of this information is governed by the Terms of Use, available at https://www.wolterskluwer.com/en/know/clinical-effectiveness-terms.
Last Reviewed Date
2025-12-10
Copyright
© 2025 UpToDate, Inc. and its affiliates and/or licensors. All rights reserved.