Signs and symptoms of too much ammonia

Dangers of hyperammonemia

Ammonia doesn't leave your body as it should when you're living with a urea cycle disorder (UCD). When there is too much ammonia in the blood, it's called hyperammonemia (hi-per-am-oh-NEE-me-uh), which can be very dangerous. Signs and symptoms of hyperammonemia that you may experience regularly without even knowing it may include:

  • Confusion
  • Vomiting
  • Being more tired than usual
  • Not being hungry
  • Being irritable/uncooperative

Signs and symptoms of hyperammonemia could mean you're experiencing a hyperammonemic crisis, which is a medical emergency that can lead to coma or death. RAVICTI® (glycerol phenylbutyrate) is not used for the treatment of acute hyperammonemia in people with UCDs.

Even if you've never had a hyperammonemic crisis, it doesn't mean you are safe from the effects of high ammonia. Ammonia levels can go up and down throughout the day, and if they go up just a little, over time, long-term damage to the body or brain is possible.

graph of ammonia levels and potential symptons

*This table is for reference only. Symptoms can vary by age.

RAVICTI helps control ammonia levels

In clinical studies, people taking RAVICTI had their average blood ammonia levels:

  • Controlled at safe and normal levels for 24 hours
  • Stay within a normal range during the 12 months of treatment


  • 7 out of 51 adults (14%) in the study reported a total of 10 hyperammonemic crises
  • 5 out of 26 children aged 6 to 17 years of age (19%) in the study reported a total of 5 hyperammonemic crises

Important Safety information

Ravicti® (glycerol phenylbutyrate) oral liquid indications and usage

Approved Uses for RAVICTI® (glycerol phenylbutyrate) Oral Liquid

RAVICTI is a prescription medicine used in adults and children 2 months of age and older for long-term management of high levels of ammonia in the blood (hyperammonemia) caused by a condition called a urea cycle disorder (UCD). RAVICTI must be used along with a low-protein diet and, in some cases, dietary supplements. RAVICTI should only be used if the UCD cannot be managed with a low-protein diet and dietary supplements alone.

RAVICTI is not used to treat extremely high levels of ammonia in the blood (hyperammonemic crises) in people with UCDs as they may require rapidly acting medication.

It is not known if RAVICTI is safe and effective for the treatment of N-acetylglutamate synthase (NAGS) deficiency.

It is not known if RAVICTI is safe and effective for children younger than 2 months.

Detailed Important Safety Information

Who should not take RAVICTI:

Children younger than 2 months should not take RAVICTI because they may not be able to digest it.

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

RAVICTI may cause serious side effects:

The breakdown of RAVICTI produces the byproduct phenylacetate, which 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, tiredness; nausea; or vomiting.

What are the possible side effects of RAVICTI?

The most common side effects of RAVICTI in adults include diarrhea, gas, headache, nausea, vomiting, tiredness, decreased appetite, and dizziness.

The most common side effects of RAVICTI in children ages 2 to 17 years include stomach pain, nausea, vomiting, diarrhea, decreased appetite, and headache.

The most common side effects of RAVICTI in children ages 2 months to younger than 2 years include decreased level of a type of white blood cell, vomiting, diarrhea, fever, decreased appetite, cough, nasal congestion, runny nose, and rash.

Tell your doctor if you have any side effect that bothers you or that does not go away. These are not all of the possible side effects of RAVICTI. Call your doctor for medical advice about side effects.

Before you take RAVICTI:

Tell your doctor if you have liver or kidney problems, pancreas or bowel (intestine) problems, or any other medical conditions. Tell your doctor if you are pregnant or plan to become pregnant. It is not known if RAVICTI will harm your unborn baby. Tell your doctor if you 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.

Talk to your doctor about participating in a UCD registry. The purpose of this registry is to collect information about people with UCDs to improve care. For more information about the registry program, call 1-855-823-2595 or visit

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit or call 1-800-FDA-1088.

This information is not comprehensive. To learn more, talk to your healthcare provider or pharmacist. The FDA-approved product labeling, including the Medication Guide can be found at