[Hypocarnitinemia in patients affected by a primary defect of ammonia metabolism treated with sodium benzoate].

We have studied the plasma and urinary levels of free and esterified carnitine in 18 patients affected by a primary defect of ammonia metabolism, which had been managed with or without a therapy of sodium benzoate. None of these patients presented with any acute neurologic or digestive symptoms during the study. Our group of non-treated patients showed an increase in the levels of plasma esterified carnitine and an elevation of urinary concentration of free carnitine, while the levels of urinary esterified carnitine clearly approached the superior limits of normal values. The group treated with sodium benzoate showed a more profoundly disturbed plasma and urinary carnitine profile: a significantly lower plasma and urinary free carnitine, accompanied by a clearly increased esterified/free carnitine ratio. We did not find any evidence of a relationship between the plasma levels of free or esterified carnitine and the protein intake or the plasma ammonia concentration. We are proposing a hypothesis to explain the hypocarnitinemia seen in our patients being treated with benzoate, along with other modifications observed in the carnitine profile. We believe that a supplement of carnitine could be beneficial in the management of some of these patients.