Brand Name(s):

  • Kuvan®

WHY is this medicine prescribed?

Sapropterin is used along with a restricted diet to control blood phenylalanine levels in people who have phenylketonuria (PKU; an inborn condition in which phenylalanine may build up in the blood and causes decreased intelligence and a decreased ability to focus, remember, and organize information). Sapropterin will only work for some people who have PKU, and the only way to tell if sapropterin will help a particular patient is to give the medication for a period of time and see whether his or her phenylalanine level decreases. Sapropterin is in a class of medications called cofactors. It works by helping the body to break down phenylalanine so it will not build up in the blood.

HOW should this medicine be used?

Sapropterin comes as a tablet to dissolve in water or apple juice and take by mouth. It is usually taken once a day with food. Take sapropterin at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take sapropterin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Place the number of sapropterin tablets you were told to take in a cup that contains 4 to 8 ounces (1/2 to 1 cup or 120 to 240 milliliters) of water or apple juice. Stir the mixture or crush the tablets with a spoon to dissolve the tablets. The tablets may not dissolve completely; there may still be small pieces of tablet floating at the top of the liquid. When the tablets are mostly dissolved, drink the entire mixture. If pieces of tablets remain in the cup after you drink the mixture, pour more water or apple juice into the cup and drink it to be sure you swallow all the medication. Be sure to drink the entire mixture within 15 minutes after you prepare it.

Even if sapropterin tablets are stored properly, the color of the tablets may change to light yellow over time. This is normal and it is safe to take tablets that have changed color.

Your doctor will start you on an average dose of sapropterin and will check your blood phenylalanine level regularly. If your phenylalanine level does not decrease, your doctor will increase your dose of sapropterin. If your phenylalanine level does not decrease after one month of treatment with the higher dose of sapropterin, you and your doctor will know that your condition does not respond to sapropterin. Your doctor will tell you to stop taking the medication.

Sapropterin may help to control blood phenylalanine levels, but it will not cure PKU. Continue to take sapropterin even if you feel well. Do not stop taking sapropterin without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.

Are there OTHER USES for this medicine?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before taking sapropterin,

  • tell your doctor and pharmacist if you are allergic to sapropterin or any other medications.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: levodopa (in Sinemet, in Stalevo); methotrexate (Trexall); and PDE5 inhibitors such as sildenafil (Revatio, Viagra), tadalafil (Cialis), and vardenafil (Levitra). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you have or have ever had anorexia (an eating disorder in which a person eats too little and/or exercises too much to maintain even the minimum body weight considered normal for his/her age and height) or any other condition that causes you to be poorly nourished, or liver or kidney disease.
  • tell your doctor if you have a fever or if you get sick at any time during your treatment. Fever and illness may affect your phenylalanine level, so your doctor may need to adjust your dose of sapropterin.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking sapropterin, call your doctor.

What SPECIAL DIETARY instructions should I follow?

You must continue to follow a low phenylalanine diet while you are taking sapropterin. Follow your doctor and nutritionist's directions carefully. Do not change your diet in any way without talking to your doctor or nutritionist.

What should I do IF I FORGET to take a dose?

If you remember the missed dose later the same day, take the missed dose as soon as you remember it. However, if you do not remember until the next day, skip the missed dose and continue your regular dosing schedule. Do not take more than one dose in one day or take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Sapropterin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • diarrhea
  • nausea
  • vomiting
  • stomach pain
  • headache
  • cough, throat pain, or cold symptoms
  • rash

Sapropterin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at Web Site] or by phone [1-800-332-1088].

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it in a cool, dry place, away from excess heat and moisture (not in the bathroom or car). Do not remove the desiccant (small packet included with medication to absorb moisture). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

What should I do in case of OVERDOSE?

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

Symptoms of overdose may include:

  • headache
  • dizziness

What OTHER INFORMATION should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to sapropterin.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Last Reviewed: February 1, 2009.