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Hyperammonemia Follow-up

  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
Updated: Nov 30, 2015

Further Outpatient Care

Outpatient care involves monitoring growth and development of the child that would indicate the adequacy of treatment. Additionally, periodic fasting levels of the following should be determined:

  • Plasma ammonium
  • Plasma glutamine (should be maintained at < 1000 µmol/L)
  • Arginine
  • Total protein

Further Inpatient Care

Patients usually can go back to their dietary regimen and oral medications in 3-4 days. They should be admitted to an intensive care unit initially, and their neurologic status should be monitored carefully.


Inpatient & Outpatient Medications

See the list below:

  • Sodium phenylbutyrate: Patients with CPS, OTC, or AS deficiency should receive sodium phenylbutyrate at a dose of 450-600 mg/kg/day.
  • Citrulline: Patients with CPS or OTC deficiency should receive citrulline (150-200 mg/kg/day for < 20 kg and 3-4 g/m2/day if >20 kg) as a source of arginine; because citrulline is elevated in ASS and ASL deficiencies, it should not be given to patients with an unknown diagnosis. After stabilization, citrulline 170 mg/kg/day is given to patients with OTC and CPS deficiency.
  • Arginine: It is administered IV together with sodium phenylacetate and sodium benzoate solution as part of the initial hyperammonemia treatment. In patients ≤20 kg, CPS and OTC deficiency or if a specific defect in the urea cycle has not been identified, administer arginine hydrochloride bolus 200 mg/kg in patients who weigh less than 20 kg and 4 g/m2 for patients over 20 kg, infused over 90 min; this is followed by a maintenance dose of 200 mg/kg/day in patients under 20 kg and 4 g/m2/day for patients over 20 kg. In ASS and ASL deficiency, the maintenance dose recommended is 600 mg/kg/day if less than 20 kg and 12 g/m2/day if over 20 kg. After stabilization, an arginine base (500 mg/kg/day PO) is recommended for AS and AL deficiency.


Patients should be transferred to a facility having a neonatal or pediatric intensive care unit.



Parents should be educated to take the symptoms of hyperammonemia (ie, lethargy, vomiting, changes in behavior) very seriously. They should contact their physician immediately at the onset of these symptoms. Following dietary recommendations and compliance with medications decreases the frequency of hyperammonemic episodes.

Antenatal diagnosis of urea cycle disorders can be made using several laboratory techniques. Families should be informed about the availability of these tests if they have had an affected infant or if the mother is a carrier of OTC mutation.



See the list below:

  • Cerebral edema
  • Cortical blindness


See the list below:

  • In a previous study of patients with urea cycle defects in Japan, the 5-year survival rate was 22% for the neonatal-onset group and 41% for the late-onset group. Among the survivors of the neonatal-onset group, 90% had moderately severe to severe neurologic deficits, whereas 28% of the survivors of the late-onset group had similar problems.
  • In another study including 260 patients in the United States, the 11-year survival rate was 35% for the neonatal-onset group compared with 87% for the group with onset in late infancy.[10]
  • In previous study, a group of 21 patients with neonatal hyperammonemia was monitored over the long term. Duration of coma was the only reliable sign influencing the short-term outcome. Among the 13 survivors, only 3 had a normal/borderline outcome as far as neurocognitive development was concerned.
  • Suggested guidelines indicate that the most important factor for the neurodevelopmental prognosis is the total duration of coma and peak ammonia levels.[1]

Patient Education

See Deterrence/Prevention.

Contributor Information and Disclosures

Jasvinder Chawla, MD, MBA Chief of Neurology, Hines Veterans Affairs Hospital; Professor of Neurology, Loyola University Medical Center

Jasvinder Chawla, MD, MBA is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Clinical Neurophysiology Society, American Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS Professor Emeritus of Neurology and Psychiatry, Clinical Professor of Medicine, Clinical Professor of Family Medicine, Clinical Professor of Neurosurgery, State University of New York Upstate Medical University; Neuroscience Director, Department of Neurology, Crouse Irving Memorial Hospital

Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS is a member of the following medical societies: American College of International Physicians, American Heart Association, American Stroke Association, American Academy of Neurology, American Academy of Pain Medicine, American College of Forensic Examiners Institute, National Association of Managed Care Physicians, American College of Physicians, Royal College of Physicians, Royal College of Physicians and Surgeons of Canada, Royal College of Surgeons of England, Royal Society of Medicine

Disclosure: Nothing to disclose.

Additional Contributors

J Stephen Huff, MD, FACEP Professor of Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia School of Medicine

J Stephen Huff, MD, FACEP is a member of the following medical societies: American Academy of Neurology, American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Elena Crisan, MD Neurology Staff, Department of Neurology, Edwards Hines Veterans Affairs Hospital; Assistant Professor of Neurology, Loyola University Medical Center

Disclosure: Nothing to disclose.


The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author Kazi Imran Majeed, MD to the development and writing of this article.

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