Neonatal Drug Therapy Manual

Sodium Phenylacetate/Sodium Benzoate (SPECIAL ACCESS PROGRAM)

Disclaimer: Official controlled document is the CHEO and Ottawa Hospital online copy. It is the responsibility of user to ensure that any paper copy version is the same as the online version before use.

Updated August 28, 2025 - 8:28pm

Alternate Name(s): 
Ammonul®
Classification: 
Urea Cycle Disorder (UCD) Treatment Agent
Original Date: 
Sept 2022
Revised Date: 
August 2025
Indications: 
  • Nitrogen binding agent for treatment of acute hyperammonemia and associated encephalopathy in patients with deficiencies in enzymes of the urea cycle
Administration: 

  • IV Intermittent Infusion: central line 
    Infusion time: 90 minutes

  • IV Continuous Infusion: central line 

Dosage: 
  • Loading: 250 mg/kg/dose IV as a loading dose. Give IV over 90 minutes
  • Maintenance: Followed by 250 mg/kg/day as a continuous IV infusion
Side Effects: 
  • IV infiltration may cause necrosis and phlebitis
  • Nausea, vomiting (especially with loading dose)
  • Hypotension
  • Metabolic acidosis, hyperglycemia, hypokalemia, hypocalcemia, hyperammonemia, hypernatremia
  • Seizure, cerebral edema, agitation
Parameters to Monitor: 

  • Monitor plasma ammonia levels, neurological status, blood gases

  • Electrolytes and glucose 

  • LFTs and renal function (use with caution in renal or hepatic impairment)

Reconstitution and Stability: 

CHEO

  • Vials contain Sodium Phenylacetate 10% and Sodium Benzoate Injection 10% 
  • Diluted product available from pharmacy as a 10 mg/mL solution in D10W, with or without Arginine HCL* added. 

*see monograph for Arginine HCL 

Compatibility: 
  • Solutions Compatible: D10W ONLY
  • Additive/Above Cassette Compatible: arginine HCL
  • Y-site Compatibility: arginine HCL
Notes: 

  • For orders of sodium phenylacetate/sodium benzoate 250 mg/kg + arginine HCL 600 mg/kg, use sodium phenylacetate/sodium benzoate 10 mg/mL with arginine HCL 24 mg/mL in D10W

  • Fluid overload: Use with caution in patients at risk for fluid overload (eg, heart failure, severe renal impairment) or sodium retention edema; contains a significant amount of sodium per vial (

    undiluted solution contains sodium 1.33 mmol/mL [30.5 mg/mL])

  • Caution in neonates: displaces bilirubin from protein-binding site
  • Enhanced potassium excretion may occur with treatment of hyperammonemia, monitor serum potassium concentration closely
References: 
  • Lexi-Comp Online Database, accessed August 2025

  • Sodium phenylacetate/sodium benzoate 10%/10% product monograph (FOSUM PHARMA)

  • Lawrence A. Trissel's Handbook on Injectable Drugs 

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