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Ornithine Transcarbamylase Deficiency Treatment & Management

  • Author: Karl S Roth, MD; Chief Editor: Luis O Rohena, MD  more...
Updated: Aug 28, 2015

Medical Care

Immediate temporary discontinuation of protein intake in a symptomatic individual with ornithine transcarbamylase (OTC) deficiency is mandatory, with compensatory increases in carbohydrates and lipids in order to offset any catabolic tendency to draw on muscle amino acids for energy.

In a patient who is comatose with extremely high blood ammonia levels (in some cases exceeding 2000 mg/dL), rapid reduction can be achieved with hemodialysis.

Intravenous administration of sodium benzoate, arginine, and sodium phenylacetate is important; however, only administer these drugs in a large medical facility setting with close laboratory monitoring available. Intravenous sodium benzoate and phenylacetate (Ammonul) was approved in the United States in February 2005.

Glycerol phenylbutyrate is a pre-prodrug that undergoes metabolism to form phenylacetate. Results of a phase 3 study comparing ammonia control in adults showed glycerol phenylbutyrate was noninferior to sodium phenylbutyrate.[11] In a separate study involving young children ages 2 months through 5 years, glycerol phenylbutyrate resulted in a more evenly distributed urinary output of phenylacetylglutamine (PAGN) over 24 hours and accounted for fewer symptoms from accumulation of phenylacetate.[12]

A biochemical geneticist and a highly trained nutritionist should administer long-term outpatient care in a large facility setting with laboratory monitoring available.



Consultations include the following:

  • Medical geneticist
  • Metabolic disease specialist
  • Dietitian


Immediate temporary discontinuation of protein intake in a symptomatic individual is mandatory, with compensatory increases in carbohydrates and lipids in order to offset any catabolic tendency to draw on muscle amino acids for energy.

A highly trained nutritionist should administer long-term outpatient care in a large facility setting with laboratory monitoring available.

Scrupulous adherence to the dietary and medication recommendations is mandatory for survival.

Contributor Information and Disclosures

Karl S Roth, MD Retired Professor and Chair, Department of Pediatrics, Creighton University School of Medicine

Karl S Roth, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Nutrition, American Pediatric Society, American Society for Nutrition, American Society of Nephrology, Association of American Medical Colleges, Medical Society of Virginia, New York Academy of Sciences, Sigma Xi, Society for Pediatric Research, Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Chief Editor

Luis O Rohena, MD Chief, Medical Genetics, San Antonio Military Medical Center; Assistant Professor of Pediatrics, Uniformed Services University of the Health Sciences, F Edward Hebert School of Medicine; Assistant Professor of Pediatrics, University of Texas Health Science Center at San Antonio

Luis O Rohena, MD is a member of the following medical societies: American Academy of Pediatrics, American Chemical Society, American College of Medical Genetics and Genomics, American Society of Human Genetics

Disclosure: Nothing to disclose.

Additional Contributors

Robert D Steiner, MD Chief Medical Officer, Acer Therapeutics; Clinical Professor, University of Wisconsin School of Medicine and Public Health

Robert D Steiner, MD is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American College of Medical Genetics and Genomics, American Society of Human Genetics, Society for Inherited Metabolic Disorders, Society for Pediatric Research, Society for the Study of Inborn Errors of Metabolism

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Acer Therapeutics; Retrophin; Raptor Pharma; Veritas Genetics; Censa Pharma<br/>Received income in an amount equal to or greater than $250 from: Acer Therapeutics; Retrophin; Raptor Pharma; Censa Pharma.

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Compounds that comprise the urea cycle are sequentially numbered, beginning with carbamyl phosphate (1). At this step, the first waste nitrogen is incorporated into the cycle; during this step, N-acetylglutamate exerts its regulatory control on the mediating enzyme, carbamoyl phosphate synthetase (CPS). Compound 2 is citrulline, which is the product of condensation between carbamyl phosphate (1) and ornithine (8); the mediating enzyme is ornithine transcarbamylase. Compound 3 is aspartic acid, which is combined with citrulline to form argininosuccinic acid (ASA) (4); the reaction is mediated by ASA synthetase. Compound 5 is fumaric acid generated in the reaction that converts ASA to arginine (6), which is mediated by ASA lyase.
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