glycerol phenylbutyrate at a glance
Medicine class
Nitrogen-binding treatment
Usual role
Long-term adjunctive management of specified urea cycle disorders
Administration
Oral liquid measured with a suitable oral syringe and taken with meals or feeds
Diet
Used alongside specialist dietary protein restriction and, when needed, dietary supplements
What is glycerol phenylbutyrate used for?
Licensed as adjunctive chronic treatment when diet and amino-acid supplementation alone do not provide adequate control.
Urea cycle disorders due to carbamoyl phosphate synthetase I deficiency
Ornithine carbamoyltransferase deficiency
Argininosuccinate synthetase deficiency
Argininosuccinate lyase deficiency
Arginase I deficiency
Ornithine translocase deficiency causing HHH syndrome
How does glycerol phenylbutyrate work?
Digestive lipases release phenylbutyrate, which is converted to phenylacetate. Phenylacetate binds glutamine to form phenylacetylglutamine, which is removed in urine and provides another route for eliminating waste nitrogen.
glycerol phenylbutyrate preparations and strengths
Oral liquid
Route: Oral
Strengths: 1.1 g/mL
How to take glycerol phenylbutyrate
Follow the specialist metabolic team's instructions and dietary plan.
Measure the oral liquid with a compatible oral syringe.
Take it with or straight after meals; give during or straight after feeds in young children.
It may be given through a suitable gastrostomy or nasogastric tube when swallowing is not possible, followed by the directed tube flush.
Do not mix it into a large volume of water, juice or another liquid because administration may be incomplete.
It may be mixed with a small amount of apple sauce, ketchup, squash purée or a compatible medical formula and used promptly.
Keep the measuring syringe dry and do not rinse it between administrations.
glycerol phenylbutyrate side effects
Common or expected effects
- Diarrhoea, nausea, vomiting, abdominal pain, indigestion, bloating, constipation or wind
- Headache, dizziness or tremor
- Reduced or increased appetite, or food aversion
- Tiredness or swelling of the hands or feet
- Acne or an unusual skin odour
- Bleeding between menstrual periods
Get urgent medical advice
- New nausea, vomiting or confusion that may indicate rising ammonia
- Marked sleepiness, lethargy or confusion, particularly when ammonia is normal or low, which may indicate phenylacetate toxicity
- Disorientation, memory or hearing changes, or worsening neurological symptoms after excess medicine
glycerol phenylbutyrate in pregnancy
Human pregnancy data are limited, and animal studies showed reproductive toxicity. It should generally not be used during pregnancy unless the woman's clinical condition requires treatment. Contact the specialist team when planning pregnancy or if pregnancy occurs. Effective contraception is required for those who could become pregnant.
glycerol phenylbutyrate while breastfeeding
It is unknown whether glycerol phenylbutyrate or its metabolites enter human milk, and risk to a breastfed infant cannot be excluded. The specialist and patient should decide whether to stop breastfeeding or interrupt treatment after considering the benefits of each.
glycerol phenylbutyrate interactions
Check all medicines with the specialist team because some can raise ammonia or have altered effects.
Corticosteroids
Protein breakdown may increase plasma ammonia, so closer monitoring may be needed.
Valproic acid
May cause hyperammonaemia; monitor ammonia closely if combined use is necessary.
Haloperidol
May cause hyperammonaemia; monitor ammonia closely if combined use is necessary.
Probenecid
May reduce kidney elimination of glycerol phenylbutyrate metabolites.
Common questions about glycerol phenylbutyrate
Answers are fully visible for fast scanning and source review.
Can glycerol phenylbutyrate treat an acute ammonia crisis?
No. It is contraindicated for acute hyperammonaemia because rapid specialist intervention is required.
Why is it used with a low-protein diet?
The diet reduces nitrogen entering the body, while glycerol phenylbutyrate provides another route for removing waste nitrogen.
Can it be mixed with water or juice?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.