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Sapropterin is used to treat phenylketonuria in certain people. Talk with your health care provider about your diet, and do not change your diet without talking with your health care provider. Keep all appointments to have your blood checked. Common side effects include headache, runny nose, and sore throat. Tell your health care provider right away if you get a fever, nausea, blood in vomit or poop, appetite loss, stomach pain, or trouble swallowing.

Uses

What is sapropterin used for?

Sapropterin is commonly used to treat phenylketonuria in certain people.

Sapropterin may also be used for other conditions as determined by your health care provider.

How does sapropterin work (mechanism of action)?

People with phenylketonuria are unable to break down enough of a normal substance in the body called phenylalanine. Sapropterin helps to activate a protein (enzyme) that breaks down phenylalanine. Use of this medicine may help lower the level of phenylalanine in some people.

How is sapropterin supplied (dosage forms)?

Brands and other names

  • Javygtor
  • Kuvan

Dosage forms and strengths

  • 100 mg oral tablets
  • 100 mg/packet or 500 mg/packet of powder for oral solution 

How should I store sapropterin?

Sapropterin should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Protect it from moisture.

Side Effects

What are the most common side effects of sapropterin?

The most common side effects of sapropterin are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Headache
  • Runny nose or nasal congestion
  • Sore throat
  • Cough
  • Diarrhea
  • Vomiting

There may be other side effects of sapropterin that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of sapropterin?

While less common, the most serious side effects of sapropterin are described below, along with what to do if they happen.

Severe Allergic Reactions. Sapropterin may cause allergic reactions, which can be serious. Stop taking Sapropterin and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown, depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Stomach or Esophagus Inflammation. Sapropterin can cause inflammation of your stomach or esophagus that can be severe. Call your health care provider right away if you have any of the following symptoms.

  • Stomach discomfort or pain
  • Nausea and vomiting
  • Vomit blood
  • Black or tarry poop
  • Trouble swallowing
  • Loss of appetite
  • Sore throat

Hyperactivity. Sapropterin can cause hyperactivity, which is too much or constant activity. Tell your health care provider if you have any of the following symptoms.

  • Fidgeting
  • Moving around too much
  • Talking too much

Low Phenylalanine Levels. Sapropterin may cause the amount of phenylalanine in your body to get too low. The problem may be more likely in children younger than 7 years. Keep all appointments to have your blood checked. Your health care provider will check your blood work to help keep your phenylalanine levels at a normal level.

Warnings & Precautions

Who should not use sapropterin?

Allergies to Ingredients. People who are allergic to any of the following should not take sapropterin.

  • Javygtor
  • Kuvan
  • Sapropterin
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific sapropterin products they stock.

What should I know about sapropterin before using it?

Do not take sapropterin unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share sapropterin with other people, even if they have the same condition as you. It may harm them.

Keep sapropterin out of the reach of children.

Some people with phenylketonuria do not have lower blood levels after treatment with sapropterin. Keep all appointments to have your blood checked. High levels of phenylalanine can cause severe problems. Your health care provider will need to check your blood tests to make sure that the medicine is working. 

Sapropterin should be taken with a meal, preferably at the same time each day. Talk with your health care provider about protein and phenylalanine in your diet. Talk with your health care provider if you want to change your diet. Phenylalanine levels that are either too high or too low can be dangerous.

Tell your health care provider right away if you get a fever or are sick. The dose of sapropterin may need to be changed. 

There are multiple forms of sapropterin available. Read and follow the instructions for the product you have, and make sure you understand how to use it properly. If you have any questions, talk to your health care provider.

Sapropterin oral tablets can be swallowed whole. They can also be dissolved in water or apple juice and taken right away. Or, right before use, the tablets may be crushed and mixed with a small amount of soft food, such as apple sauce or pudding.

If you are using the packets, only open a packet right before taking a dose. Sapropterin powder should be dissolved in water or apple juice, or it can be mixed with a small amount of soft food, such as apple sauce or pudding. Use an accurate measuring device to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist to recommend an appropriate measuring device.

What should I tell my health care provider before using sapropterin?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if sapropterin is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Poor nutrition
  • Loss of appetite

Other Medicines and Supplements. Sapropterin may interact with other medicines and supplements. Before taking Sapropterin, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how sapropterin could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Control of phenylalanine levels is needed during pregnancy. If you become pregnant while taking sapropterin, ask your health care provider about signing up for a pregnancy registry program. Pregnancy registries collect information about your and your baby’s health while you’re taking sapropterin during pregnancy.

Breastfeeding. It is not known if sapropterin passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take sapropterin while breastfeeding.

Interactions

Does sapropterin interact with foods or drinks?

There are no known interactions between sapropterin and foods or drinks. Sapropterin should be taken with a meal.

It is unknown if drinking alcohol will affect sapropterin.

Does sapropterin interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking sapropterin.

  • Levodopa (Inbrija) or a medicine that contains levodopa, which is a medicine for Parkinson’s disease
  • Carbidopa/Levodopa (Crexont, Dhivy, Duopa, Rytary, or Sinemet), which is a medicine for Parkinson’s disease
  • Carbidopa/Levodopa/Entacapone (Stalveo), which is a medicine for Parkinson’s disease
  • Methotrexate (Trexall and others), which is a medicine commonly used for rheumatoid arthritis or certain types of cancer
  • Divalproex sodium, valproate sodium (Depakote and others), or valproic acid, which are medicines used for seizures and other conditions
  • Phenobarbital, which is a medicine that may be used to treat insomnia or seizures
  • Trimethoprim, which is an antibiotic used to treat certain infections
  • A phosphodiesterase-5 (PDE-5) inhibitor, such as avanafil (Stendra), sildenafil (Viagra, Revatio, and others), tadalafil (Cialis and others), or vardenafil (Levitra, Staxyn), which is a medicine used for erectile dysfunction or pulmonary arterial hypertension (PAH)

This may not be a complete list of medicines that can interact with sapropterin. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much sapropterin?

If you or someone else has used too much sapropterin, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of sapropterin?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take two doses on the same day. Do not take double or extra doses.