Full Prescribing Information Important Safety Information

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Today, there are more than 150 Americans with HT-1 who are being treated with Orfadin ® (nitisinone). But taking medication is only one part of the equation. Managing HT-1 is a multi-faceted lifelong journey, and we're here to support you every step of the way.

All individuals featured in this website have experience with Orfadin but may no longer be on treatment.

All about HT-1

What is HT-1?

Tyrosinemia (tahy-ro-si-nee-mee-uh) type 1 (HT-1) is a condition where the body is unable to break down tyrosine (tahy-ruh-seen), one of protein's essential building blocks. When the body cannot break down tyrosine, high levels build up in the blood and form a toxic substance known as succinylacetone (suk-sin-il-as-e-ton). This means that if tyrosinemia isn't treated, it may cause liver and kidney damage, neurological issues, and shorter life expectancy. Watch this short video to learn more.


  • Affects 1 in 100,000 people

  • Is the most severe form of tyrosinemia

  • Must be inherited from both parents

  • Affects males and females equally

All individuals featured in this website have experience with Orfadin but may no longer be on treatment.

Myths + facts about HT-1

Because HT-1 is such a rare condition, finding the right information can be challenging. Here are some common myths about tyrosinemia and its treatment.

Be sure to talk to your doctor before beginning any diet or fitness program, and to learn more about this condition.

Common myths

  • It is possible that my child won't have to worry about HT-1 as an adult.


    No. Those who have HT-1 will likely have to manage it for their entire life.

  • My child can never eat any type of protein.


    While a low-protein diet is required to prevent too much tyrosine from building up in your child's body, they still need small amounts of protein and amino acids. They can eat measured amounts of low-protein foods and protein supplements.

  • Having tyrosinemia means my child will not be able to drink formula, and eventually will have trouble eating bread, pasta, cereal, and cake.


    There are low-protein versions of many foods—including baby formula—that you may be able to order from specialty companies and have delivered directly to your home.

  • I can give my child an occasional break from his diet and he will be fine.


    Not sticking to your child's diet might not have immediate visible consequences, but over time will increase the risk of your child becoming seriously ill.

  • If my child takes Orfadin, they won't have to stick to their low-protein diet.


    Your child must maintain a low-protein diet while taking Orfadin. While Orfadin blocks the breakdown of tyrosine before it can be changed into harmful substances, the tyrosine will remain in the body. Sticking to a low-protein diet helps to minimize the buildup of tyrosine and phenylalanine in the blood.

  • If my child misses taking a dose of Orfadin, I can give them a double dose to make up for it.


    No. If a dose is missed, do not give your child a double dose of Orfadin. Instead, tell their doctor or clinical nurse specialist about it. Your child might need to have an extra blood test to see if there is any change in blood tyrosine level.

  • If my child has no symptoms and doesn't feel sick, they can stop taking Orfadin.


    While they may not feel sick, sticking to their diet and treatment regimen is important. If they neglect their treatment or diet, toxic substances can build up over time in the blood, causing serious problems such as liver failure and kidney dysfunction.

  • My child's daily dose of Orfadin will stay the same throughout their life.


    The dose of Orfadin that your child needs may be adjusted occasionally as their weight changes. That is one of the reasons they need to have blood tests to measure the level of tyrosine in their blood.

    See dosing options
  • The side effects associated with treatment will make my child sick.


    You should talk with your doctor and team if your child experiences any side effects. Some of the side effects that have been seen with Orfadin use include:

    • A reduction in the number of white cells and platelets in the blood

    • Liver cancer

    • Liver failure

    • Conjunctivitis

    • Corneal opacity

    • Inflammation of the cornea

    • Extreme sensitivity to light

All individuals featured in this website have experience with Orfadin but may no longer be on treatment.


Orfadin4U is a comprehensive support program for patients with HT-1 and their caregivers. We offer as little as $0 co-pay, pharmacy services, help navigating insurance and financial needs, low-protein recipes and meal-planning tools, and much more.

When you enroll in Orfadin4U, you'll get:

  • As little as $0 co-pay for eligible patients*

  • Access to a supportive HT-1 community + mentorship program

  • Personalized pharmacy services

  • Help navigating insurance and co-pays

  • HT-1 recipe ideas and lifestyle support

*For eligible commercially insured patients (up to $10,000 per patient annually).

Enroll in Orfadin4U

All individuals featured in this website have experience with Orfadin but may no longer be on treatment.

More from the HT-1 Community

The Network of Tyrosinemia Advocates

A resource for news and events in the community.

Learn more

Tyrosinemia Society

An organization that aims to educate and inspire individuals to improve health outcomes and advocate for adults and children with Tyrosinemia and related disorders.

Learn more

National Organization for Rare Disorders

A patient advocacy organization dedicated to individuals with rare diseases.

Learn more

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Tips, news, information + more


Orfadin is a synthetic reversible inhibitor of 4-hydroxyphenylpyruvate dioxygenase indicated for use as an adjunct to dietary restriction of tyrosine and phenylalanine in the treatment of hereditary tyrosinemia type 1 (HT-1).


Tyrosine levels can increase in the blood if you do not restrict tyrosine and phenylalanine in your diet while taking Orfadin. Too much tyrosine in the blood can cause serious eye problems or other complications.

Do not adjust your Orfadin dosage in order to lower the tyrosine levels in the blood.

A reduction in the number of white cells and platelets in the blood have been observed during treatment with Orfadin. Your platelet and white blood cell counts should be monitored regularly during Orfadin treatment.

The most common adverse reactions to taking Orfadin are elevated tyrosine levels, low platelets or white cells in the blood, and complaints related to the eyes, including conjunctivitis, corneal opacity, inflammation of the cornea, and extreme sensitivity to light.

Tell your physician promptly if you have unexplained eye symptoms, rash, jaundice (yellowing of the skin or whites of the eyes) or excessive bleeding.

Use Orfadin during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nursing women should discontinue either Orfadin or breast-feeding based on the recommendation of your healthcare professional.

Please see full Prescribing Information