POSSIBLE SIDE EFFECTS

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Side Effects Icon

As with any medicine, it’s possible to experience side effects. Be sure to tell your child’s doctor if your child experiences any side effect that bothers them or does not go away.

Koselugo may cause serious side effects, including:

Heart problems: Koselugo can lower the amount of blood pumped by your heart, which is common and can also be severe. Your child’s healthcare provider will do tests before and during treatment with Koselugo to check how well your child’s heart is working. Tell your child’s healthcare provider right away if your child gets any of the following signs or symptoms:

  • persistent coughing or wheezing
  • tiredness
  • shortness of breath
  • increased heart rate
  • swelling of your child’s ankles and feet

Eye problems: Koselugo can cause eye problems that can lead to blindness. Your child’s healthcare provider will check your child’s vision before and during treatment with Koselugo. Tell your child’s healthcare provider right away if your child gets any of the following signs or symptoms:

  • blurred vision
  • loss of vision
  • dark spots in your child’s vision (floaters)
  • other changes to your child’s vision

Severe diarrhea: Diarrhea is common with Koselugo and can also be severe. Tell your child’s healthcare provider right away the first time that your child gets diarrhea during treatment with Koselugo. Your child’s healthcare provider may give your child medicine to help control diarrhea and may tell them to drink more fluids

Skin rash: Skin rashes are common with Koselugo and can also be severe. Tell your child’s healthcare provider if your child gets any of the following signs or symptoms:

  • rash that covers a large area of your child’s body
  • blisters
  • peeling skin

Muscle problems (rhabdomyolysis): Muscle problems are common with Koselugo and can also be severe. Treatment with Koselugo may increase the level of a muscle enzyme in your child’s blood, which may be a sign of muscle damage. Your child’s healthcare provider should do a blood test to check your child’s muscle enzyme levels before they start taking Koselugo and during treatment. Tell your child’s healthcare provider right away if your child gets any of the following signs or symptoms:

  • muscle aches or pain
  • dark, reddish urine
  • muscle spasms and weakness

Your child’s healthcare provider may change your child’s dose, temporarily stop, or permanently ask your child to stop taking Koselugo if they have any of these side effects.

The most common side effects of Koselugo are:

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  • Vomiting
Stomach pain Icon
  • Stomach pain
Nausea Icon
  • Nausea
Dry skin Icon
  • Dry skin
tiredness Icon
  • Feeling of tiredness, weakness, or lacking energy
Muscle and bone pain Icon
  • Muscle and bone pain
Fever Icon
  • Fever
Inflammation of the mouth Icon
  • Inflammation of the mouth
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  • Headache
Redness around the fingernails Icon
  • Redness around the fingernails
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  • Itching

These are not all the possible side effects of Koselugo

For more information, ask your doctor or pharmacist. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-10881-800-FDA-1088.

Remember, the information on this page does not replace medical guidance or directions from your doctor. Always talk to them about side effects and ways to manage them.

See what people taking Koselugo experienced in a clinical study Learn more

BEFORE STARTING TREATMENT WITH KOSELUGO

Make a list of questions you’d like to ask your child’s doctor and information you’d like to share about your child:

Ask what tests are needed before and during treatment

Share details about pre-existing conditions

Provide names of other medicines your child may be taking

Your child will take 3 tests before taking Koselugo:

  • A test using sound waves to painlessly create pictures of the heart (called an echocardiogram)
  • A blood test for certain enzymes and naturally occurring chemicals
  • An assessment of your child’s eyes

Before taking Koselugo, tell your child’s doctor about all of your child’s medical conditions, including if they:

Have heart problems

Have eye problems

Are pregnant or plan to become pregnant. Koselugo can harm an unborn baby

  • Your child’s healthcare provider should check to see if your child is pregnant before they begin treatment with Koselugo
  • Females who are able to become pregnant should use effective birth control (contraception) during treatment with Koselugo and for 1 week after the last dose
  • Males with female partners who are able to become pregnant should use effective birth control (contraception) during treatment with Koselugo and for 1 week after the last dose
  • Tell your child’s healthcare provider right away if your child becomes pregnant or thinks she may be pregnant during treatment with Koselugo

Are breastfeeding or plan to breastfeed

  • It is not known if Koselugo passes into breast milk
  • Your child should not breastfeed during treatment with Koselugo and for 1 week after the last dose
  • Talk to your child’s healthcare provider about the best way for your child to feed her baby during this time

Tell your child’s healthcare provider about all the medicines your child takes, including prescription and over-the-counter medicines, vitamins, or herbal supplements. Especially tell your child’s healthcare provider if your child is taking aspirin, blood thinners, or other medicines to treat blood clots. Koselugo contains vitamin E, which may increase the risk of bleeding.

Review the treatment journey of patients who took Koselugo in a clinical study Learn more

Important Safety Inforamtion