Genetics of Hyperammonemia Medication

Updated: Sep 20, 2018
  • Author: Karl S Roth, MD; Chief Editor: Maria Descartes, MD  more...
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Medication

Medication Summary

Treatment of hyperammonemia is somewhat dependent on cause. Emergency treatment of life-threatening severe hyperammonemia is hemodialysis. Recommendations for treatment of urea cycle disorders may be found in the specific articles (ie, Ornithine Transcarbamylase Deficiency). (See Differentials and Other Problems to be Considered.)

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Metabolic agents

Class Summary

The use of benzoate and phenylacetate is based on the need to provide alternate routes for disposition of waste nitrogen. 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 2 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 phenylacetate and sodium benzoate (Ammonul)

Benzoate combines with glycine to form hippurate, which is excreted in urine. One mole of benzoate removes 1 mole of nitrogen. Phenylacetate conjugates (via acetylation) glutamine in the liver and kidneys to form phenylacetylglutamine, which is excreted by the kidneys. The nitrogen content of phenylacetylglutamine per mole is identical to that of urea (2 mol of nitrogen). Ammonul must be administered with arginine for CPS, OTC, ASA synthetase, or ASA lyase deficiencies. Indicated as adjunctive treatment of acute hyperammonemia associated with encephalopathy caused by urea cycle enzyme deficiencies. Serves as an alternative to urea to reduce waste nitrogen levels.

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