Sapropterin (By mouth)

Sapropterin (sap-roe-TER-in)

Lowers phenylalanine levels in the blood.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to sapropterin.

How to Use This Medicine:

Liquid, Dissolving Tablet

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
  • Take this medicine at the same time each day. It is best to take this medicine with food or milk.
  • Tablet: Swallow the tablets whole or mix them in 4 to 8 ounces (120 to 240 mL) of water or apple juice. You may stir or crush the tablets to help them dissolve faster. Drink this mixture within 15 minutes. You may also mix the crushed tablets into a small amount of soft food, including applesauce or pudding.
  • Powder for solution: Pour the contents of the 100 mg- or 500 mg- packet in 4 to 8 ounces (120 to 240 mL) of water or apple juice. Mix thoroughly. Drink this mixture within 30 minutes. You may also add the powder to a small amount of soft food, including applesauce or pudding. For infants weighing less than 10 kilograms, you may mix the medicine in as little as 5 mL of water or apple juice and give it to an infant by using an oral dosing syringe.
  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep the bottle tightly closed. Keep the medicine in the original bottle that you were given at the pharmacy.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some foods and medicines can affect how sapropterin works. Tell your doctor if you are using any of the following:
    • Avanafil, levodopa, methotrexate, sildenafil, tadalafil, vardenafil
    • An antifolate medicine

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney problems, liver problems, low blood pressure, brain disease, seizures, or a fever or any illness.
  • This medicine may cause esophagitis or gastritis, which can be severe.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Burning feeling in your chest or stomach, heartburn, upset stomach, vomiting, bloody or black stools
  • Lightheadedness, dizziness, fainting
  • Restlessness, trouble sitting still or focusing
  • Trouble swallowing
  • Warmth or redness in your face, neck, arms, or upper chest

If you notice these less serious side effects, talk with your doctor:

  • Diarrhea
  • Headache
  • Runny or stuffy nose, cough, sore throat

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 11/6/2020

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