Abstract

To study the effect of sodium benzoate on carnitine metabolism, the acylcarnitine profile in the urine of five normal volunteers and two patients with urea cycle disorders was examined with fast atom bombardment-mass spectrometry. The volunteer subjects were given 5 g of sodium benzoate orally and the two patients with urea cycle disorders (carbamyl phosphate synthetase deficiency type I and ornithine transcarbamylase deficiency) were already undergoing treatment with sodium benzoate and L-carnitine. The amount of benzoylcarnitine excretion depended on the dose of both sodium benzoate and L-carnitine in a reciprocal relation. Increased excretions of acetylcarnitine and propionylcarnitine were also noted after sodium benzoate administration. The alteration of the urinary aclycarnitine profile was consistent with the change of mitochondrial CoA profile predicted by in vitro studies of an animal model. It is suggested that urinary acylcarnitine analysis is important to assess the effect of benzoate administration on mitochondrial function in vivo. Supplementation with carnitine may be necessary to minimise the adverse effects of sodium benzoate treatment in hyperammonaemia.