FAQs About Kuvan Treatment for Phenylketonuria

FAQs About Kuvan Treatment for Phenylketonuria

Kuvan is a medication by BioMarin for the treatment of phenylketonuria (PKU) in children and adults. The treatment is designed to help lower phenylalanine (Phe) levels in the body for patients already on a low-Phe diet.

What is PKU?

PKU is a rare metabolic disorder caused by mutations in the PAH gene. This gene contains the instructions for cells to make an enzyme called phenylalanine hydroxylase (PAH). The body uses the PAH enzyme to convert Phe into another amino acid, tyrosine. Mutations in the PAH gene in PKU lead to a reduction in the PAH enzyme, which means that phenylalanine from a person’s diet (most protein-containing foods) cannot be metabolized, so it builds up to toxic levels in the bloodstream and body. Having too much phenylalanine can cause brain damage unless a low-Phe diet is started.

How does Kuvan work?

Kuvan works as a synthetic version of a molecule called tetrahydrobiopterin (BH4). BH4 normally binds to PAH and helps stimulate its activity. Kuvan acts similarly to BH4 and causes any existing PAH enzyme the body produces to increase its activity and reduce levels of Phe in the body while increasing Tyr levels.

How do I take it?

Kuvan can be taken as an oral 100 mg tablet, or as a 100 mg or 500 mg powder for oral suspension. You can swallow the oral tablets whole or crush and mix them into soft food such as applesauce. Alternatively, you can dissolve it in water or apple juice. You can also dissolve the powder in water or apple juice or mix it with soft foods.

How often should I take it?

Kuvan is to be taken once a day, preferably at the same time each day, and with a meal. Your doctor will tell you how much to take and when, taking into consideration your age, weight, and other factors.

Can I take Kuvan instead of staying on my diet?

Kuvan does not take the place of a low-Phe diet but should be used in conjunction with the diet.

Does it work in all patients?

Kuvan does not work for everyone. It activates the PAH enzyme your body already produces to break down Phe. However, some patients will not produce PAH naturally or will produce non-functional forms that Kuvan cannot activate.

What are the side effects?

The most common side effects of Kuvan are headache, nasal congestion, runny nose, sore throat, vomiting, cough, and diarrhea. It can also cause serious side effects in some patients, including severe allergic reactions like anaphylaxis, and lead to symptoms such as coughing, trouble breathing, nausea, fainting, and rash.

The medication can cause inflammation to the upper gastrointestinal tract including the stomach and esophagus. This inflammation can cause symptoms such as pain, vomiting, blood in your vomit or stool, black and tarry stool, nausea, loss of appetite, and trouble swallowing.

Kuvan can also cause hyperactivity and low Phe levels in some patients.

Are there reasons I shouldn’t take Kuvan?

You should check with your doctor about taking Kuvan if you have liver or kidney problems as the medication could cause difficulties for these organs. You also should not take Kuvan if you have poor nutrition or lack of appetite.

The effects of Kuvan on pregnancy and breastfeeding are unknown. Consult your physician before starting Kuvan or before becoming pregnant. There is a registry for patients who are pregnant or become pregnant while taking Kuvan in order to assess any effects of the treatment on pregnancy.

You should also let your doctor know about any medications you are taking as they may interact with Kuvan. There have been reported interactions between Kuvan and levodopa resulting in irritability, initiation of seizures, and worsening of seizures. Kuvan may also interact with antifolate medications, and phosphodiesterase inhibitors commonly used for erectile dysfunction such as avanafil, sildenafil, tadalafil, and vardenafil.

How should I store it?

You should store Kuvan in a cool dry place between 68 F and 77 F (20 to 25 C). Make sure you protect the medication from moisture and leave tablets in their original bottles. You should not open packets until you are ready to use them. Once they are open, you should not store them.

Is a generic version available?

Dr. Reddy’s Laboratories announced the launch of its generic form of Kuvan in early October 2020 for adults and children with PKU in the U.S. The generic form is only available in 100 mg tablet form.


Last updated: Nov. 5, 2020


Phenylketonuria News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

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