Medication Summary

Intravenous sodium benzoate, sodium phenylacetate, and arginine are important therapeutic avenues for reduction of blood ammonia levels.

Class Summary

The use of benzoate and phenylacetate is based on the need to provide alternate routes for waste nitrogen disposal. Benzoate is transaminated to form hippuric acid, which is rapidly cleared by the kidney. Phenylacetate is converted to phenylacetyl CoA and then conjugated with glutamine to form phenylacetylglutamine. Each of these pathways results in disposition of 1 and 2 molecules of ammonia, respectively. Phenylbutyrate is more acceptable as a form of oral therapy because of a diminished odor but is not available for intravenous use.

Sodium benzoate and sodium phenylacetate (Ucephan, Ammonul)

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Combines with glycine to form hippurate, which is excreted in urine. One mol of benzoate removes 1 mol of nitrogen. The oral product (Ucephan) and IV product (Ammonul) contain a combination of sodium benzoate (10 g) and sodium phenylacetate (10 g per 100 mL; 100 mg of each/mL).

Sodium phenylbutyrate (Buphenyl)

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Prodrug rapidly converted orally to phenylacetylglutamine, which serves as substitute for urea and is excreted in the urine, carrying 2 mol of nitrogen per mol of phenylacetylglutamine, assisting in clearance of nitrogenous waste.

Arginine (R-Gene 10)

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Provides 1 mol of urea plus 1 mol ornithine per mol of arginine when cleaved by arginase. Pituitary stimulant for the release of human growth hormone (HGH). Often induces pronounced HGH levels in patients with intact pituitary function. Available as 10% injection (100 mg/mL).

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Media Gallery

Urea cycle. Compounds that comprise the urea cycle are numbered sequentially, beginning with carbamyl phosphate. At the first step (1), the first waste nitrogen is incorporated into the cycle; also at this step, N-acetylglutamate exerts its regulatory control on the mediating enzyme, carbamyl phosphate synthetase (CPS). Compound 2 is citrulline, 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 (4); the reaction is mediated by argininosuccinate (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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Author

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, The Scientific Research Honor Society, 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

Maria Descartes, MD Professor, Department of Human Genetics and Department of Pediatrics, University of Alabama at Birmingham School of Medicine

Maria Descartes, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Medical Genetics and Genomics, American Medical Association, American Society of Human Genetics, Society for Inherited Metabolic Disorders, International Skeletal Dysplasia Society, Southeastern Regional Genetics Group

Disclosure: Nothing to disclose.

Additional Contributors

Robert D Steiner, MD, FAAP, FACMG Professor (Clinical), Department of Pediatrics, University of Wisconsin School of Medicine and Public Health; Editor-in-Chief, Genetics in Medicine; Chief Medical Officer, PreventionGenetics

Robert D Steiner, MD, FAAP, FACMG 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: PreventionGenetics, ACMG, Acer Therapeutics, Biomarin; Best Doctors, Health Advances, Precision for Health, PTC Therapeutics, CTX Alliance, Aeglea, Eton, Leadiant<br/>Serve(d) as a speaker or a member of a speakers bureau for: France Foundation, Medscape<br/>Received research grant from: Alexion<br/>Received income in an amount equal to or greater than $250 from: Marshfield Clinic, France Foundation, Medscape, PreventionGenetics, ACMG, Acer Therapeutics; Raptor, Retrophin/Travere, Censa; Biomarin; Best Doctors, Health Advances, Precision for Health, PTC Therapeutics, Aeglea, Leadiant<br/>Travel Support for: CTX Alliance.