Intravenous Combo Successfully Treats Acute Hyperammonemia

The combination of intravenous sodium phenylacetate and sodium benzoate improves survival during episodes of acute hyperammonemia due to urea-cycle disorders, according to a new study.

Researchers from Stanford University (CA, USA) reported on 25 years of experience treating patients with acute hyperammonemia with a combination of sodium phenylacetate and sodium benzoate. The study included 299 patients with urea-cycle disorders treated in 118 hospitals in the United States and Canada between 1980 and 2005. There were 1181 episodes of hyperammonemia in total. Risk factors for reduced survival in addition to age, included comatose condition at admission, peak plasma ammonium level of > 500 mol/l, and failure of ammonium levels to fall upon initiation of treatment. Mortality rates were also affected by which enzyme in the urea cycle was defective, and hence the severity of ammonium accumulation.

Overall survival--defined as survival of all known episodes for each patient--was 84%. Among infants less than 30 days old, survival was 73%, versus 98% among older patients. Before this advance in treatment, survival was only 16% among neonates, and 72% among those with later onset disease. The study was published in the May 31, 2007, edition of the New England Journal of Medicine (NEJM).

"Alternative-pathway therapy for nitrogen excretion uses endogenous biosynthetic pathways to eliminate non-urea-waste nitrogen as a substitute for defective urea synthesis,” explained lead author Dr. Gregory M. Enns and colleagues.


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