Effect of sodium benzoate on blood ammonia response to oral glutamine challenge in cirrhotic patients: A note of caution

OBJECTIVE: The administration of sodium benzoate provides an alternative pa thway for the disposal of waste nitrogen and this substance has been used t o treat patients with urea cycle defects and more recently cirrhotics with hepatic encephalopathy. The aim of the study was to assess the ammonia-lowe ring effect of benzoate in cirrhotic patients without overt hepatic encepha lopathy. METHODS: Glutamine challenge, a method to induce an increase of blood ammon ia, was performed in six cirrhotics before and after 5 days of benzoate tre atment (10 g/day). Number Connection Test and Posner's Attention Test were also performed before and after benzoate treatment. RESULTS: Blood ammonia increased after the glutamine load both before (from 66 +/- 12 mug/dl to 123 +/- 34 mug/dl and 179 +/- 53 mug/dl after 30 and 6 0 min, respectively; ANOVA p = 0.0004) and after benzoate treatment (from 1 02 +/- 27 mug/dl to 185 +/- 49 mug/dl and 250 +/- 39 mug/dl after 30 and 60 min, respectively; ANOVA p = 0.00001). However, after benzoate treatment, the basal values (102 +/- 27 vs 66 +/- 12 mug/dl; p = 0.01) and peak increm ents of ammonia (166 +/- 56 mug/dl vs 102 +/- 40 mug/dl; p = 0.03) were sig nificantly higher than before. The Number Connection test and the Posner's test were not altered by benzoate treatment. CONCLUSIONS: Benzoate increased both the basal and post-glutamine ammonia l evels. These results confirm what has already been observed in experimental animals and suggest a note of caution in the use of sodium benzoate in cir rhotic patients. (C) 2000 by Am. Cell. of Gastroenterology.