sodium phenylbutyrate at a glance
Medicine class
Nitrogen-scavenging metabolic treatment
Usual role
Long-term adjunctive management of specified urea cycle disorders
Diet
Used with a specialist-managed protein-restricted diet
Important limitation
It does not replace emergency treatment for acute hyperammonaemia
What is sodium phenylbutyrate used for?
Selected UK products are licensed as adjunctive therapy for chronic management of urea cycle disorders involving specific enzyme deficiencies.
Carbamylphosphate synthetase deficiency
Ornithine transcarbamylase deficiency
Argininosuccinate synthetase deficiency
Neonatal-onset and late-onset disease with a history of hyperammonaemic encephalopathy
How does sodium phenylbutyrate work?
The body converts sodium phenylbutyrate into phenylacetate. This binds glutamine to form phenylacetylglutamine, which is removed by the kidneys. This provides an alternative route for excreting waste nitrogen and helps lower ammonia and glutamine concentrations.
sodium phenylbutyrate preparations and strengths
Oral solution
Route: Oral
Strengths: 350 mg/mL
Tablet
Route: Oral
Strengths: 500 mg
How to take sodium phenylbutyrate
Use the prescribed formulation exactly as demonstrated by the metabolic team and take it with food as directed.
Swallow tablets with plenty of water; they are unsuitable for people who cannot safely swallow tablets.
Granules may be swallowed with a drink or placed on a small spoonful of suitable soft food and taken immediately. Do not give them through nasogastric or gastrostomy tubes.
Measure oral solution only with the supplied syringe. For oral use, place it in water before drinking; optional supplied flavouring may be added. The solution can also be given through a compatible feeding tube without flavouring.
Continue the specialist-prescribed dietary plan.
sodium phenylbutyrate side effects
Common or expected effects
- Nausea, vomiting, abdominal pain or constipation
- Reduced appetite or altered taste
- Headache, irritability or low mood
- Swelling caused by fluid retention
- Rash
- Irregular or absent menstrual periods
- Changes in blood-cell counts, electrolytes, proteins or liver-test results
Get urgent medical advice
- Persistent vomiting, which may also signal metabolic deterioration
- Fainting or an abnormal heart rhythm
- Severe abdominal pain suggesting pancreatitis or an ulcer
- Rectal bleeding, unusual bruising or other signs of a significant blood disorder
sodium phenylbutyrate in pregnancy
Selected UK products are contraindicated during pregnancy because human evidence is limited and animal studies found reproductive toxicity. Effective contraception is required where pregnancy is possible. Contact the metabolic specialist promptly if pregnancy occurs or is planned so treatment and ammonia control can be reviewed safely.
sodium phenylbutyrate while breastfeeding
Selected UK products are contraindicated during breastfeeding because transfer into human milk is uncertain and harm to the infant cannot be excluded. A metabolic specialist and maternity or infant-feeding team should plan treatment and feeding options.
sodium phenylbutyrate interactions
Check all prescribed, non-prescription and specialist medicines with the metabolic team.
Valproate
May cause or worsen hyperammonaemia, so closer ammonia monitoring is advised if concurrent use is unavoidable.
Haloperidol
Has been associated with hyperammonaemia; closer ammonia monitoring may be required.
Common questions about sodium phenylbutyrate
Answers are fully visible for fast scanning and source review.
Is sodium phenylbutyrate an ammonia scavenger?
Yes. It creates an alternative pathway for removing waste nitrogen, helping reduce ammonia accumulation in urea cycle disorders.
Can sodium phenylbutyrate treat an acute ammonia crisis?
It is not recommended for acute hyperammonaemia. An acute crisis is a medical emergency requiring the person's specialist emergency plan and urgent hospital care.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.