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Ammonia scavenger (alternative pathway)

Sodium phenylbutyrate

Brand names: Ammonaps, Pheburane

Sodium phenylbutyrate is a nitrogen-scavenging agent used as adjunctive therapy in the chronic management of urea cycle disorders.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It is metabolised to phenylacetate, which conjugates with glutamine to form phenylacetylglutamine that is excreted renally, providing an alternative route for waste nitrogen elimination.

Prescribing in practice

  • It is used alongside dietary protein restriction and must not replace emergency management of acute hyperammonaemia, which requires urgent specialist treatment.
  • It carries a substantial sodium load, requiring caution in heart failure, hypertension, renal impairment and other states where sodium retention is harmful.
  • Monitor for and manage potential metabolic and electrolyte disturbances; refer to the SPC for guidance.

Monitoring

Plasma ammonia, amino acids, electrolytes and nutritional status are monitored regularly to guide therapy.

Counselling the patient

  • Take this medicine with meals as directed and continue your prescribed low-protein diet.
  • Seek urgent help for vomiting, drowsiness or confusion, which may signal high ammonia.
  • Do not stop treatment suddenly without specialist advice.

Evidence & guidelines

Sodium phenylbutyrate is an established component of urea cycle disorder management supported by long-term clinical experience.

Reference: SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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