Oral administration of arginine and citrulline in the treatment of lysinuric protein intolerance.

In two sibling patients with lysinuric protein intolerance (LPI), the therapeutic effect of oral supplement of arginine and citrulline on postprandial hyperammonemia was investigated. Intravenous load of L-alanine (6.6 mmol/kg of body weight), and oral load of L-arginine (0.8 mmol/kg of body weight) or of L-citrulline (1.0 mmol/kg of body weight) during intravenous load of L-alanine were performed to study the preventive effect of arginine or citrulline supplement on hyperammonemia induced by intravenous amino nitrogen load. In the older sibling, the hyperammonemia induced by the intravenous amino nitrogen load was completely prevented by the oral supplement of citrulline, but not completely prevented in the younger sibling. On the other hand, the hyperammonemia was prevented by the oral supplement of arginine only in the younger sibling, but not in the older sibling. In the light of these results, the younger patient received an oral administration of L-arginine and the older patient L-citrulline for the treatment of postprandial hyperammonemia. Two-year observation of each patient revealed that postprandial hyperammonemia and aversion to protein-rich food completely disappeared and that a marked increase of body weight and height was obtained. Furthermore, there was no side effect with these amino acids supplements. The present study suggests that an oral supplement of arginine or citrulline is effective for preventing postprandial hyperammonemia in this disorder.