Three cases of intravenous sodium benzoate and sodium phenylacetate toxicity occurring in the treatment of acute hyperammonaemia

Intravenous sodium benzoate and sodium phenylacetate have been used success fully in the treatment of acute hyperammonaemia in patients with urea cycle disorders. They provide alternative pathways for waste nitrogen disposal a nd help maintain nitrogen homeostasis. However, we report three patients wi th hyperammonaemia who received inappropriate doses of intravenous sodium b enzoate and sodium phenylacetate that resulted in severe complications. Amb iguous medical prescriptions and inadequate cross-checking of drug dosage b y physicians, nurses and pharmacists were the main causes of these incident s. All the patients presented with alteration in mental status, Kussmaul re spiration and a partially compensated metabolic acidosis with an increased anion gap. Two patients developed cerebral oedema and hypotension and died. The third survived after haemodialysis. Plasma levels of benzoate and phen ylacetate were excessively high. The possible mechanisms of toxicity, manag ement and safety measures are discussed.