How does the urea cycle work?

Breaking down food in the body

The urea cycle is part of the body's process to turn food into energy. Food that isn't used to help the body grow or remain healthy is turned into waste to be removed.

  1. When you eat foods with protein in them—meat, fish, eggs, dairy products, nuts, beans, or soy—your body breaks the protein down
  2. It turns the protein into amino acids
  3. Those amino acids are used to build muscle, skin, blood cells, and more. This is what helps you grow and stay healthy
  4. However, the urea cycle turns the rest of it—what your body doesn't need—into ammonia and other waste products

Too much ammonia can be toxic and harmful to the body. Enzymes in the urea cycle convert this toxic ammonia into a nontoxic substance called urea, which can be eliminated, through urine, from the body.

diagram of protein and the urea cycle

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 years of age and older for long-term management of high blood levels of ammonia (hyperammonemia) caused by a condition called a urea cycle disorder (UCD). RAVICTI should only 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 treatment of acute hyperammonemia in people with UCDs.

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 in children 2 months to less than 2 years of age.

Detailed Important Safety Information

Who should not take RAVICTI:

  • Children less than 2 months of age should not take RAVICTI because it may not be digested in babies less than 2 months of age.
  • Do not take RAVICTI if you are allergic to phenylbutyrate. Call your doctor or go to the nearest hospital emergency room if you get wheezing, shortness of breath, cough, low blood pressure, flushing, nausea, or a rash while taking RAVICTI.

RAVICTI may cause serious side effects:

Phenylacetate, a breakdown product of RAVICTI, may cause nervous system side effects. Call your doctor or get medical help right away if you experience any of these symptoms while taking RAVICTI: sleepiness, weakness, lightheadedness, change in taste, problems with hearing, confusion, problems with memory, worsening neuropathy (numbness, tingling, or burning in your hands or feet), or headache.

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, high blood levels of ammonia, and dizziness.

The most common side effects of RAVICTI in children include upper abdomen (stomach) pain, nausea, vomiting, diarrhea, decreased appetite, high blood levels of ammonia, and headache.

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. RAVICTI may harm your baby, so you and your doctor should decide if you will take RAVICTI or breastfeed.

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 1-855-823-7878 or visit www.ucdregistry.com.

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

This information is not comprehensive. To learn more, talk to your health care provider or pharmacist. For more information about RAVICTI, please see the full Prescribing Information (PDF) and Medication Guide (PDF) for RAVICTI.