Effect of single oral dose of sodium benzoate on ureagenesis in healthy men and two patients with late onset citrullinaemia.

Although sodium benzoate therapy is beneficial in patients with inborn error of urea cycle, it has been suggested that an accumulation of benzoyl-CoA would inhibit ureagenesis. In this study, we examined several aspects of ureagenesis after the single oral dosing of sodium benzoate in six healthy subjects who participated in the study previously reported and in two patients with citrullinaemia. Urea nitrogen appearance (UNA) did not change after the doses of 40, 80 and 160 mg.kg-1 of sodium benzoate in the 6 healthy subjects. Sum of UNA and urinary hippurate nitrogen (UHN) increased with increasing the dose. In the 2 patients with late-onset citrullinaemia who benefit from a partially functional urea cycle, no apparent inhibitory effects on the UNA were observed after the administration of 80 mg/kg of sodium benzoate. The precursors of urea (ammonia, glutamate, glutamine and alpha-amino nitrogen) did not increase after the benzoate administration in the 6 normal subjects as well as in the 2 patients with citrullinaemia.