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glycerol phenylbutyrate

Generic Name: glycerol phenylbutyrate (GLIS er ol FEN il BUE ti rate)
Brand Name: Ravicti

What is glycerol phenylbutyrate?

Glycerol phenylbutyrate binds with other substances in the liver and kidneys to help eliminate nitrogen from the body. Excess nitrogen can cause hyperammonemia (HYE-per-AM-moe-NEE-mee-a), a build-up of ammonia in the blood. Ammonia is very toxic when it circulates in blood and tissues and can cause permanent brain damage, coma, or death.

Glycerol phenylbutyrate helps prevent a build-up of ammonia in the blood in people with urea cycle disorder. This medicine is used in adults and children who are at least 2 years old. Glycerol phenylbutyrate will not treat hyperammonemia.

Glycerol phenylbutyrate is usually given together with a low-protein diet and sometimes dietary supplements.

Glycerol phenylbutyrate may also be used for purposes not listed in this medication guide.

What is the most important information I should know about glycerol phenylbutyrate?

Glycerol phenylbutyrate should not be given to a child under 2 months old.

What should I discuss with my healthcare provider before taking glycerol phenylbutyrate?

You should not use glycerol phenylbutyrate if you are allergic to it.

Glycerol phenylbutyrate should not be given to a child under 2 months old. Do not give this medicine to a child younger than 2 years old without medical advice.

To make sure glycerol phenylbutyrate is safe for you, tell your doctor if you have:

  • liver or kidney disease;

  • pancreas disorder;

  • stomach or intestinal disorder,

  • a condition called NAGS (N-acetylglutamate synthase) deficiency; or

  • if you take haloperidol or probenecid, or if you use a steroid medicine (beclomethasone, dexamethasone, fluticasone, prednisone, and others).

FDA pregnancy category C. It is not known whether glycerol phenylbutyrate will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medicine.

It is not known whether glycerol phenylbutyrate passes into breast milk or if it could harm a nursing baby. You should not breast-feed while using this medicine.

How should I take glycerol phenylbutyrate?

Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Glycerol phenylbutyrate is usually taken 3 times per day. Take with food.

Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

Glycerol phenylbutyrate can also be given through a nasogastric (NG) or gastric feeding tube as follows: After measuring the correct dose in the syringe, attach it to the feeding tube and push the plunger down to empty the syringe into the tube. Then flush the tube with 2 tablespoons of water and allow it to drain. Follow this with 2 more tablespoons of water to wash the contents down.

If you switch from sodium phenylbutyrate to glycerol phenylbutyrate, your dose will not be the same. Follow your doctor's dosing instructions very carefully.

Glycerol phenylbutyrate is only part of a complete program of treatment that may also include a special diet and other medications. It is very important to follow the diet plan created for you by your doctor or nutrition counselor. You should become very familiar with the list of foods you should eat or avoid to help control your condition.

To be sure this medicine is helping your condition and is not causing harmful effects, your blood will need to be tested often. A buildup of ammonia in the blood can quickly cause brain injury or death. Do not miss any follow up visits to your doctor for blood tests. Every person with a urea cycle disorder should remain under the care of a doctor.

Your name may be listed on a Urea Cycle Disorder registry. This is to collect information about people with these disorders and to evaluate the effects of treatment.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking glycerol phenylbutyrate?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Glycerol phenylbutyrate side effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; cough, wheezing, difficult breathing; feeling like you might pass out; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any signs of hyperammonemia:

  • weakness, lack of energy;

  • thinking problems, changes in behavior, feeling irritable;

  • breathing problems;

  • feeding problems; or

  • seizure (convulsions).

Also call your doctor at once if you have:

  • drowsiness, unusual tiredness;

  • a light-headed feeling, like you might pass out;

  • confusion, ongoing headache, vomiting;

  • altered sense of taste; or

  • hearing problems.

Common side effects may include:

  • nausea, vomiting, stomach pain;

  • gas, diarrhea;

  • loss of appetite;

  • dizziness, tired feeling; or

  • occasional headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

Glycerol phenylbutyrate dosing information

Usual Adult Dose for Urea Cycle Disorders:

Phenylbutyrate-Naive Patients:
-Initial dose: 4.5 to 11.2 mL/m2/day (5 to 12.4 g/m2/day) orally in 3 equally divided dosages
-Initial dose when residual enzyme activity is not adequately controlled with dietary restriction: 4.5 mL/m2/day
-Maintenance dose: Adjust dose to produce a fasting plasma ammonia level less than half the upper limit of normal according to age
-Maximum dose: 17.5 mL (19.5 g)

Comments:
-Doses should be rounded up to the nearest 0.5 mL.
- In determining the starting dose, consider the patient's residual urea synthetic capacity, dietary protein requirements, and diet adherence; may consider an initial estimated daily dose of 0.6 mL per gram of dietary protein ingested per 24 hour period.

Patients switching from Sodium Phenylbutyrate should use the following conversion:
-Total daily dose of glycerol phenylbutyrate (mL) should equal the total daily dose of sodium phenylbutyrate (g) x 0.86
Maximum dose: 17.5 mL (19.5 g)

Comments:
-Must use with dietary protein restriction and in some cases, with dietary supplements.
-Not indicated for the treatment of acute hyperammonemia as more rapid interventions should be used.
-Safety and efficacy for treatment of N-acetylglutamate synthase (NAGS) deficiency has not been established.

Use: As a nitrogen-binding agent for chronic management of patients with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone.

Usual Pediatric Dose for Urea Cycle Disorders:

Aged 2 years or older:
Phenylbutyrate-Naive Patients:
-Initial dose: 4.5 to 11.2 mL/m2/day (5 to 12.4 g/m2/day) orally in 3 equally divided dosages
-Initial dose when residual enzyme activity is not adequately controlled with dietary restriction: 4.5 mL/m2/day
-Maintenance dose: Adjust dose to produce a fasting plasma ammonia level less than half the upper limit of normal according to age
-Maximum dose: 17.5 mL (19.5 g)

Comments:
-Doses should be rounded up to the nearest 0.5 mL.
- In determining the starting dose, consider the patient's residual urea synthetic capacity, dietary protein requirements, and diet adherence; may consider an initial estimated daily dose of 0.6 mL per gram of dietary protein ingested per 24 hour period.

Patients switching from Sodium Phenylbutyrate should use the following conversion:
-Total daily dose of glycerol phenylbutyrate (mL) should equal the total daily dose of sodium phenylbutyrate (g) x 0.86
Maximum dose: 17.5 mL (19.5 g)

Comments:
-Must use with dietary protein restriction and in some cases, with dietary supplements.
-Not indicated for the treatment of acute hyperammonemia as more rapid interventions should be used.
-Safety and efficacy for treatment of N-acetylglutamate synthase (NAGS) deficiency has not been established.

Use: As a nitrogen-binding agent for chronic management of pediatric patients 2 years or older with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone.

What other drugs will affect glycerol phenylbutyrate?

Tell your doctor about all medicines you use, and those you start or stop using during your treatment with glycerol phenylbutyrate, especially:

  • divalproex sodium; or

  • valproic acid.

Other drugs may interact with glycerol phenylbutyrate, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Where can I get more information?

  • Your pharmacist can provide more information about glycerol phenylbutyrate.
  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2012 Cerner Multum, Inc. Version: 1.01. Revision Date: 2014-02-12, 8:55:38 AM.

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