Urea Cycle Disorders are Caused by a Genetic Disorder

Urea cycle disorders (UCDs) are inherited genetic traits. This means they’re usually passed down from parents to children. UCDs can also be caused by an unexpected genetic change. If you have a urea cycle disorder in your family, your children may or may not be born with it. In most cases, it depends on the mix of genes that they get from each parent. Some people may not realize they can have a UCD gene in their bodies.

The role of the X chromosome

A person’s sex (male or female) is decided by his or her chromosomes. Each pair of chromosomes carries genes that decide which traits are passed from parent to child, such as hair and eye color. There are 2 types of sex chromosomes: X chromosomes and Y chromosomes. A female has 2 X chromosomes and a male has 1 X and 1 Y chromosome.

The most common type of UCD is ornithine transcarbamylase (OTC) deficiency. OTC deficiency is usually passed from mother to child through her X chromosome. A mother who has the OTC gene may not know she is a carrier, but also may experience subtle signs and symptoms of a UCD and may need to be treated.

When both parents have a UCD gene (Autosomal Recessive Inheritance)

For all other UCDs except OTC, both parents carry a gene that doesn't work. Review the graphic below to see how a UCD is passed from parent to child.

When both parents have a UCD gene:
Chances of having a child with a UCD

UCD hereditary distribution chart UCD hereditary distribution chart

Father Carrier

Mother Carrier

25%

A 25% chance that their child will develop a UCD by receiving a gene that doesn’t work from each parent

50%

A 50% chance that their child will get one gene that doesn't work from one parent. This child is a carrier

25%

A 25% chance that their child will receive both normal genes and be unaffected

A blood test can find out if you have the UCD gene. If the test shows you have a gene, it means that you could pass it on to your children.

Different UCD genes cause different types of UCDs

The urea cycle is controlled by a series of proteins (enzymes and transporters) that help chemical reactions take place in your body. Eight of these proteins have the job of removing ammonia from the blood stream. In people with urea cycle disorders, one of these proteins is not working correctly. This prevents ammonia from being processed properly so it can safely leave the body.

Different UCD genes cause different types of UCDs. There are 8 types of urea cycle defects. The name of each one identifies the protein that is not working in the urea cycle:

  • Ornithine transcarbamylase deficiency (OTC) — the most common UCD
  • Carbamylphosphate synthetase 1 (CPS1) deficiency
  • Citrullinemia I (CTLN1)
  • Argininosuccinic lyase (ASL)
  • Arginase deficiency (hyperargininemia, ARG)
  • Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome
  • Citrullinemia II (CTLN2)
  • N-acetylglutamate synthetase (NAGS) deficiency*

Who should be tested for a UCD gene?

You can pass a UCD gene to your child without knowing it. Someone who is a carrier of a UCD gene has one normal gene and one UCD gene. Some carriers may not know they have a UCD gene until their child is diagnosed because they may not have the symptoms of a UCD.

Mothers who carry a UCD gene that is part of the OTC subtype, however, may have subtle signs and symptoms, which should not be ignored. Subtle signs and symptoms can include headaches, confusion, and trouble concentrating. If you experience these symptoms, you should talk with your child’s doctor to see if you need treatment.

If you or your child has been diagnosed with a UCD, it’s important to pay attention to other relatives, especially children, who may have similar signs and symptoms. A UCD should be considered in any person with unexplained abnormal behavior that may include:

  • Low appetite
  • Irritability
  • Fogginess
  • Low energy
  • Vomiting
  • Heavy or rapid breathing
  • Aggressive behavior

If one person in a family has been diagnosed with a UCD, other family members should be tested as well, especially parents and siblings. It’s also possible that extended family members may have a UCD and don’t know it. Talk to your doctor and find out if you or other family members should be tested for a UCD.

*Important Limitation of Use:

It is not known if RAVICTI® (glycerol phenylbutyrate) Oral Liquid is safe and effective for the treatment of NAGS deficiency.

About RAVICTI.

The #1 prescribed ammonia-controlling treatment for UCD*.

A liquid medicine that can be taken by mouth that’s FDA-approved to treat most types of UCDs for newborns, babies, children, and adults. See approved uses below.

Find out why

Real Patients. Real Stories.

"I learned I had a urea
cycle disorder
when my
son was diagnosed."

– Patricia | Caregiver
and OTC Patient

Talk to someone who's been there

*According to data sourced from IQVIA and Horizon, between 6/01/2018 to 5/31/2019. Based on the total number of unique patients who had at least one dispense for RAVICTI in the United States.

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USE and IMPORTANT SAFETY INFORMATION

What is the most important safety information I should know about RAVICTI? RAVICTI may cause serious side effects, including: Nervous system side effects (Neurotoxicity) Phenylacetate (PAA), a breakdown product of RAVICTI, may cause nervous system side effects.

USE and IMPORTANT SAFETY INFORMATION

What is the most important safety information I should know about RAVICTI?
RAVICTI may cause serious side effects, including:
Nervous system side effects (Neurotoxicity) Phenylacetate (PAA), a breakdown product of RAVICTI, may cause nervous system side effects. Call your doctor or get medical help right away if you have any of these symptoms while taking RAVICTI:

  • sleepiness
  • lightheadedness
  • change in taste
  • problems with hearing
  • confusion
  • problems with memory
  • worsening of numbness, tingling, or burning in your hands or feet
  • headache
  • feeling very tired (fatigue)
  • nausea
  • vomiting

Your doctor may do blood tests to measure the amount of PAA in your blood during your treatment with RAVICTI.

What is RAVICTI?

  • RAVICTI (glycerol phenylbutyrate) Oral Liquid is a prescription medicine used for long-term management of high blood levels of ammonia (hyperammonemia) caused by a condition called a urea cycle disorder (UCD). RAVICTI should be used if the UCD cannot be managed with a low-protein diet and dietary supplements alone. RAVICTI must be used along with a low-protein diet and in some cases dietary supplements.
  • RAVICTI is not used for the acute treatment of hyperammonemia in people with UCD.
  • It is not known if RAVICTI is safe and effective for the treatment of N-acetylglutamate synthase (NAGS) deficiency.

Do not take RAVICTI if you are allergic to phenylbutyrate. Call your doctor or go to the nearest hospital emergency room if you have wheezing, shortness of breath, cough, low blood pressure, flushing, nausea or a rash while taking RAVICTI.

Before taking RAVICTI, tell your doctor about all of your medical conditions, including if you:

  • have liver or kidney problems
  • have pancreas or bowel (intestine) problems.
  • are pregnant or plan to become pregnant. It is not known if RAVICTI will harm your unborn baby. If you become pregnant during treatment with RAVICTI, call Horizon at 1‐866‐479‐6742 to report the pregnancy.
  • are breastfeeding or plan to breastfeed. It is not known if RAVICTI passes into your breast milk. Breastfeeding is not recommended during treatment with RAVICTI. Talk to your doctor about the best way to feed your baby if you take RAVICTI.

What are possible side effects of RAVICTI?

RAVICTI may cause serious side effects, including:

  • See "What is the most important information I should know about RAVICTI?"

The most common side effects of RAVICTI in adults include:

  • diarrhea
  • gas
  • headache
  • abdomen (stomach) pain
  • vomiting
  • tiredness
  • decreased appetite
  • indigestion or heartburn

The most common side effects of RAVICTI in children 2 years to 17 years of age include:

  • upper abdomen (stomach) pain
  • rash
  • nausea
  • vomiting
  • diarrhea
  • decreased appetite
  • headache

The most common side effects of RAVICTI in children 2 months to less than 2 years of age include:

  • low white blood cell count (neutropenia)
  • vomiting
  • constipation
  • diarrhea
  • fever
  • reduced food intake
  • cough
  • stuffy nose
  • runny nose
  • skin rash
  • small round bumps on the skin

The most common side effects of RAVICTI in children less than 2 months of age include:

  • vomiting
  • rash
  • gastroesophageal reflux
  • increased levels of liver enzymes in the blood
  • decreased appetite and reduced food intake
  • low red blood cell count (anemia)
  • cough
  • loss of too much body fluid (dehydration)
  • too much acid in the blood (acidosis)
  • high blood platelet count (thrombocytosis)
  • low blood platelet count (thrombocytopenia)
  • low blood neutrophil count (type of
    white blood
    cell) (neutropenia)
  • high white blood cell count (lymphocytosis)
  • diarrhea
  • gas
  • constipation
  • fever
  • drowsiness (lethargy)
  • irritability
  • agitation

These are not all of the possible side effects of RAVICTI. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

For additional Important Safety Information, click here for the Medication Guide and discuss with your doctor.

USE and IMPORTANT SAFETY INFORMATION

What is the most important safety information I should know about RAVICTI? RAVICTI may cause serious side effects, including: Nervous system side effects (Neurotoxicity) Phenylacetate (PAA), a breakdown product of RAVICTI, may cause nervous system side effects.

USE and IMPORTANT SAFETY INFORMATION

What is the most important safety information I should know about RAVICTI?
RAVICTI may cause serious side effects, including:
Nervous system side effects (Neurotoxicity) Phenylacetate (PAA), a breakdown product of RAVICTI, may cause nervous system side effects. Call your doctor or get medical help right away if you have any of these symptoms while taking RAVICTI:

  • sleepiness
  • lightheadedness
  • change in taste
  • problems with hearing
  • confusion
  • problems with memory
  • worsening of numbness, tingling, or burning in your hands or feet
  • headache
  • feeling very tired (fatigue)
  • nausea
  • vomiting

Your doctor may do blood tests to measure the amount of PAA in your blood during your treatment with RAVICTI.

What is RAVICTI?

  • RAVICTI (glycerol phenylbutyrate) Oral Liquid is a prescription medicine used for long-term management of high blood levels of ammonia (hyperammonemia) caused by a condition called a urea cycle disorder (UCD). RAVICTI should be used if the UCD cannot be managed with a low-protein diet and dietary supplements alone. RAVICTI must be used along with a low-protein diet and in some cases dietary supplements.
  • RAVICTI is not used for the acute treatment of hyperammonemia in people with UCD.
  • It is not known if RAVICTI is safe and effective for the treatment of N-acetylglutamate synthase (NAGS) deficiency.

Do not take RAVICTI if you are allergic to phenylbutyrate. Call your doctor or go to the nearest hospital emergency room if you have wheezing, shortness of breath, cough, low blood pressure, flushing, nausea or a rash while taking RAVICTI.

Before taking RAVICTI, tell your doctor about all of your medical conditions, including if you:

  • have liver or kidney problems
  • have pancreas or bowel (intestine) problems.
  • are pregnant or plan to become pregnant. It is not known if RAVICTI will harm your unborn baby. If you become pregnant during treatment with RAVICTI, call Horizon at 1‐866‐479‐6742 to report the pregnancy.
  • are breastfeeding or plan to breastfeed. It is not known if RAVICTI passes into your breast milk. Breastfeeding is not recommended during treatment with RAVICTI. Talk to your doctor about the best way to feed your baby if you take RAVICTI.

What are possible side effects of RAVICTI?

RAVICTI may cause serious side effects, including:

  • See "What is the most important information I should know about RAVICTI?"

The most common side effects of RAVICTI in adults include:

  • diarrhea
  • gas
  • headache
  • abdomen (stomach) pain
  • vomiting
  • tiredness
  • decreased appetite
  • indigestion or heartburn

The most common side effects of RAVICTI in children 2 years to 17 years of age include:

  • upper abdomen (stomach) pain
  • rash
  • nausea
  • vomiting
  • diarrhea
  • decreased appetite
  • headache

The most common side effects of RAVICTI in children 2 months to less than 2 years of age include:

  • low white blood cell count (neutropenia)
  • vomiting
  • constipation
  • diarrhea
  • fever
  • reduced food intake
  • cough
  • stuffy nose
  • runny nose
  • skin rash
  • small round bumps on the skin

The most common side effects of RAVICTI in children less than 2 months of age include:

  • vomiting
  • rash
  • gastroesophageal reflux
  • increased levels of liver enzymes in the blood
  • decreased appetite and reduced food intake
  • low red blood cell count (anemia)
  • cough
  • loss of too much body fluid (dehydration)
  • too much acid in the blood (acidosis)
  • high blood platelet count (thrombocytosis)
  • low blood platelet count (thrombocytopenia)
  • low blood neutrophil count (type of
    white blood
    cell) (neutropenia)
  • high white blood cell count (lymphocytosis)
  • diarrhea
  • gas
  • constipation
  • fever
  • drowsiness (lethargy)
  • irritability
  • agitation

These are not all of the possible side effects of RAVICTI. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

For additional Important Safety Information, click here for the Medication Guide and discuss with your doctor.

*According to data sourced from IQVIA and Horizon, between 6/01/2018 to 5/31/2019. Based on the total number of unique patients who had at least one dispense for RAVICTI in the United States.

Back to Top