Kuvan

Pronunciation: COO-van
Generic name: sapropterin dihydrochloride
Dosage form: oral tablets (100 mg), powder for oral solution (100 mg/packet, 500 mg/packet)
Drug class: Miscellaneous metabolic agents

Medically reviewed by Carmen Pope, BPharm. Last updated on Jul 11, 2025.

What is Kuvan?

Kuvan is used to lower blood levels of phenylalanine (Phe) in adults and children one month of age and older with a certain type of phenylketonuria (PKU), called tetrahydrobiopterin (BH4-) responsive phenylketonuria (PKU). Kuvan is used alongside a Phe-restricted diet. Kuvan comes as a tablet or powder for solution that is taken 1 time a day with food.

Kuvan works by helping your body process phenylalanine, which is an amino acid found in many foods. People with PKU (phenylketonuria) have a problem with an enzyme called phenylalanine hydroxylase (PAH) that normally breaks down phenylalanine and converts it into another amino acid called tyrosine. Without this working properly, phenylalanine builds up to dangerous levels in the blood. Kuvan is a synthetic version of BH4, a natural cofactor that PAH requires to function properly. It activates remaining enzyme activity and lowers phenylalanine levels in some PKU patients. Kuvan belongs to the drug class called phenylalanine hydroxylase activators.

Kuvan gained FDA approval on December 13, 2007. A generic is available.

Side effects

The most common side effects of Kuvan are:

• headache
• runny nose and nasal congestion
• sore throat
• diarrhea
• vomiting
• cough.

Serious side effects and warnings

Kuvan can cause the following serious side effects:

• Severe allergic reactions. Stop taking Kuvan and get medical help right away if you develop any of these symptoms of a severe allergic reaction:
  • wheezing or trouble breathing
  • coughing
  • flushing
  • nausea
  • feeling lightheaded or like you might faint
  • rash.

• Inflammation of the lining of the stomach (gastritis) or esophagus (esophagitis). Gastritis or esophagitis can happen with Kuvan and may be severe. Call your doctor right away if you have any of these signs or symptoms:
  • severe upper stomach-area (abdominal) discomfort or pain, nausea, and vomiting
  • blood in your vomit or stools
  • black, tarry stools
  • difficulty swallowing
  • loss of appetite
  • pain in the throat.

• Phe levels that are too low. Some children under the age of 7 years who take high doses of Kuvan each day may experience low Phe levels.

• Too much or constant activity (hyperactivity) can happen with Kuvan. Tell your doctor if you have any signs of hyperactivity, including:
  • fidgeting or moving around too much
  • talking too much.

Tell your doctor if you have any side effect that bothers you or that does not go away. These are not all the possible side effects of Kuvan. 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-1088.

Related/similar drugs

Before taking

Before you take Kuvan, tell your doctor about all your medical conditions, including if you:

• are allergic to sapropterin dihydrochloride or any of the ingredients in Kuvan. See the list of ingredients in Kuvan at the end of this medication guide
• have poor nutrition or have a loss of appetite
• take other medications, including levodopa, antifolate medications, sildenafil (Revatio, Viagra), tadalafil (Adcirca, Cialis), vardenafil (Staxyn, Levitra)
• are pregnant or plan to become pregnant
• are breastfeeding or plan to breastfeed. It is not known if Kuvan passes into your breast milk. Talk to your doctor about the best way to feed your baby if you take Kuvan.

How should I take Kuvan?

Take Kuvan exactly as your doctor tells you. Your doctor should tell you how much Kuvan to take and when to take it. Your doctor may change your dose of Kuvan depending on how you respond to treatment.

• Take Kuvan 1 time each day with a meal. It is best to take Kuvan at the same time each day.

Kuvan comes as a tablet and a powder for oral solution.

• You can swallow Kuvan tablets whole or dissolve the tablets in water or apple juice. You may also crush the tablets and mix in a small amount of soft food, such as apple sauce or pudding, before taking.
• Be sure that you know what dose of Kuvan powder your doctor prescribed and whether you should use Kuvan 100 mg packets, Kuvan 500 mg packets, or both types of packets to prepare your dose.
• Open Kuvan powder packets only when you are ready to use them.
• Kuvan powder for oral solution should be dissolved in water or apple juice. You may also mix the powder for oral solution in a small amount of soft food, such as apple sauce or pudding, before taking.

See the detailed “Instructions for Use” that comes with Kuvan for information about the correct way to dissolve and take a dose of Kuvan tablets or Kuvan powder for oral solution.

• It is not possible to know if Kuvan will work for you until you start taking Kuvan. Your doctor will check your blood Phe levels when you start taking Kuvan to see if the medicine is working.

During treatment with Kuvan:

All patients with PKU who are being treated with Kuvan should also be treated with a Phe-restricted diet, including dietary protein and Phe restriction.

• Any change you make to your diet may affect your blood Phe level. Follow your doctor’s instructions carefully and do not make any changes to your dietary Phe intake without first talking with your doctor. Even if you take Kuvan, if your Phe blood levels are not well controlled, you can develop severe neurologic problems.
• Your doctor should continue to monitor your blood Phe levels often during your treatment with Kuvan, to make sure that your blood Phe levels are not too high or too low.
• If you have a fever or if you are sick, your blood Phe level may go up. Tell your doctor as soon as possible so they can change your dose of Kuvan to help keep your blood Phe levels in the desired range.

What happens if I miss a dose?

If you forget to take your dose of Kuvan, take it as soon as you remember that day. Do not take 2 doses in a day.

What happens if I take too much Kuvan?

If you take too much Kuvan, call your doctor for advice.

Dosing information

All patients with PKU who are being treated with Kuvan should also be treated with a Phe-restricted diet, including dietary protein and Phe restriction.

Dose of Kuvan for BH4-responsive phenylketonuria (Children 1 month to 6 years)

• Starting Dosage: 10 mg/kg taken once daily.
• Dosage Adjustment: Doses of Kuvan may be adjusted in the range of 5 to 20 mg/kg taken once daily.

Monitor blood Phe regularly, especially in pediatric patients.

Dose of Kuvan for BH4-responsive phenylketonuria (Adults and Children 7 years and older)

• Starting dose: 10 to 20 mg/kg taken once daily.
• Dosage Adjustment: Doses of Kuvan may be adjusted in the range of 5 to 20 mg/kg taken once daily.

Monitor blood Phe regularly, especially in pediatric patients.

What other drugs will affect this medicine?

Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins, herbal, and dietary supplements. Kuvan and other medicines may interact with each other. Especially tell your doctor if you take:

• a medicine that contains levodopa
• an antifolate medicine, such as methotrexate, trimethoprim, or pyrimethamine
• sildenafil (Revatio, Viagra), tadalafil (Adcirca, Cialis), vardenafil (Staxyn, Levitra)

Tell your doctor if you are not sure if your medicine is one that is listed above. Know the medicines you take. Keep a list of them to show your doctor and pharmacist when you get a new medicine.

Storage

Store Kuvan at room temperature between 68°F to 77°F (20°C to 25°C).

Keep Kuvan tablets in the original bottle with the cap closed tightly.

Protect from moisture.

Keep out of the reach of children.

Ingredients

Active ingredient: sapropterin dihydrochloride.

Kuvan tablet inactive ingredients: ascorbic acid, crospovidone, dibasic calcium phosphate, D-mannitol, riboflavin, and sodium stearyl fumarate.

Kuvan powder for oral solution inactive ingredients: ascorbic acid, D-mannitol, potassium citrate, and sucralose.

Manufacturer

Kuvan is manufactured by BioMarin Pharmaceuticals Inc., Novato, CA 94949.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer