Glycerol phenylbutyrate (Oral)
Medically reviewed by Drugs.com. Last updated on Sep 4, 2019.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
Therapeutic Class: Hyperammonemia Agent
Uses for glycerol phenylbutyrate
Glycerol phenylbutyrate is used together with a proper diet and supplements to lower high levels of ammonia in the blood caused by urea cycle disorders. Glycerol phenylbutyrate is used in patients who cannot be treated with a low-protein diet and amino acid supplements alone.
Ammonia is formed from the breakdown of protein in the body. If the ammonia cannot be removed by the body, then a buildup may cause serious unwanted effects. Glycerol phenylbutyrate works by helping to remove ammonia (nitrogen) from the body to reduce high levels of ammonia in the blood.
Glycerol phenylbutyrate is available only with your doctor's prescription.
Before using glycerol phenylbutyrate
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For glycerol phenylbutyrate, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to glycerol phenylbutyrate or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of glycerol phenylbutyrate in children. Safety and efficacy have been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of glycerol phenylbutyrate in the elderly. However, elderly patients are more likely to have liver, kidney, or heart problems, which may require caution and an adjustment in the dose for patients receiving glycerol phenylbutyrate.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of glycerol phenylbutyrate. Make sure you tell your doctor if you have any other medical problems, especially:
- Intestinal malabsorption (trouble absorbing food in the bowels) or
- Pancreatic insufficiency (trouble digesting food properly caused by lack of enzymes made by the pancreas)—May not work properly in patients with these conditions.
- Kidney disease or
- Liver disease, moderate to severe—Higher blood levels of glycerol phenylbutyrate may increase the risk of side effects.
- Nerve problems—Use with caution. May make this condition worse.
Proper use of glycerol phenylbutyrate
Take glycerol phenylbutyrate exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may increase the chance of side effects.
Glycerol phenylbutyrate comes with a Medication Guide. Read and follow the instructions carefully. Ask your doctor if you have any questions.
It is important that you or your child follow any special diet instructions from your doctor, such as using a low-protein diet. If you have any questions about this, check with your doctor.
Use an oral syringe or dosing cup to measure your dose. You may also give glycerol phenylbutyrate through a nasogastric tube or gastrostomy tube (g-tube).
To use the oral liquid with a nasogastric tube or g-tube:
- Use an oral syringe to measure your dose and place it on the tip of the nasogastric tube or g-tube.
- Inject the medicine into the tube.
- Flush the tube with 10 milliliters (mL) of water to rinse all of the medicine into the stomach.
- Rinse the tube again with additional 10 mL of water to clear the tube.
The dose of glycerol phenylbutyrate will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of glycerol phenylbutyrate. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (liquid):
- For treatment of urea cycle disorders:
- For patients not on phenylbutyrate treatment:
- Adults and children 2 years of age and older—Dose is based on body size and must be determined by your doctor. The dose is 4.5 to 11.2 milliliters (mL) per square meter (m) per day and divided into 3 equal doses, each rounded up to the nearest 0.5 mL. Your doctor may adjust your dose as needed. However, the dose is usually not more than 17.5 mL per day.
- Children younger than 2 years of age—Dose is based on body size and must be determined by your doctor. The dose is 4.5 to 11.2 milliliters (mL) per square meter (m) per day and divided into 3 or more equal doses, each rounded up to the nearest 0.1 mL. Your doctor may adjust your dose as needed. However, the dose is usually not more than 17.5 mL per day.
- For patients switching from sodium phenylbutyrate powder to Ravicti®:
- Adults and children 2 years of age and older—The dose is the total daily dose of sodium phenylbutyrate that you are already taking multiplied by 0.81 and divided into 3 equal doses, each rounded up to the nearest 0.5 milliliters (mL). Your doctor may adjust your dose as needed. However, the dose is usually not more than 17.5 mL per day.
- Children younger than 2 years of age—The dose is the total daily dose of sodium phenylbutyrate that you are already taking multiplied by 0.81 and divided into 3 or more equal doses, each rounded up to the nearest 0.1 mL. Your doctor may adjust your dose as needed. However, the dose is usually not more than 17.5 mL per day.
- For patients switching from sodium phenylbutyrate tablets to Ravicti®:
- Adults and children 2 years of age and older—The dose is the total daily dose of sodium phenylbutyrate that you are already taking multiplied by 0.86 and divided into 3 equal doses, each rounded up to the nearest 0.5 milliliter (mL). Your doctor may adjust your dose as needed. However, the dose is usually not more than 17.5 mL per day.
- Children younger than 2 years of age—The dose is the total daily dose of sodium phenylbutyrate that you are already taking multiplied by 0.86 and divided into 3 or more equal doses, each rounded up to the nearest 0.1 mL. Your doctor may adjust your dose as needed. However, the dose is usually not more than 17.5 per day.
- For patients not on phenylbutyrate treatment:
- For treatment of urea cycle disorders:
If you miss a dose of glycerol phenylbutyrate, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using glycerol phenylbutyrate
It is very important that your doctor check your or your child's progress at regular visits to make sure that glycerol phenylbutyrate is working properly. Blood tests may be needed to check for unwanted effects.
Check with your doctor right away if you have burning, tingling, numbness or pain in the hands, arms, feet, or legs, headache, lightheadedness, confusion, memory problems, sleepiness or unusual drowsiness, change or loss of taste, hearing loss, or unusual tiredness or weakness. These maybe symptoms of more serious problems.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.
Glycerol phenylbutyrate side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- Black, tarry stools
- bleeding gums
- blood in the urine or stools
- continuing nausea or vomiting
- decreased urination
- dry mouth
- increase in heart rate
- increase in the frequency of seizures
- loss of appetite
- lower back or side pain
- muscle tremors
- painful or difficult urination
- pale skin
- pinpoint red spots on the skin
- rapid breathing
- rapid, deep breathing
- sore throat
- stomach cramps
- sunken eyes
- swollen glands
- troubled breathing with exertion
- ulcers, sores, or white spots in the mouth
- unusual bleeding or bruising
- unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
- wrinkled skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- bloated or full feeling
- excess air or gas in the stomach or bowels
- passing gas
- stomach pain
- stuffy or runny nose
- upper abdominal or stomach pain
- stomach discomfort or upset
Incidence not known
- Abnormal body, skin, hair, and urine odor
- burning sensation in the mouth
- dry heaves
- loss of or change in taste
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
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