Phase II Study of Sodium Phenylbutyrate, Sodium Benzoate, Sodium Phenylacetate, and Dietary Intervention for Urea Cycle Disorders

PROTOCOL OUTLINE: This protocol describes several clinical studies of pharmacologic and dietary management in patients with urea cycle disorders. Patients with carbamyl phosphate synthetase and ornithine transcarbamylase deficiency are treated with a low-protein diet, essential amino acids (for neonatal onset disease), caloric supplementation, oral sodium phenylbutyrate (now approved as a prescription drug 11/97), and citrulline or arginine free base. Patients with argininosuccinic acid synthetase deficiency are treated with a low-protein diet, caloric supplementation, oral sodium phenylbutyrate (now approved as a prescription drug 11/97), and arginine free base. Patients with argininosuccinic aciduria (AA) are treated with a low-protein diet, caloric supplementation, and arginine free base. (Discontinued 11/97) Any patient who develops hyperammonemia is treated with intravenous sodium benzoate, sodium phenylbutyrate, and arginine hydrochloride; benzoate and phenylbutyrate are not given to patients with AA. If ammonium stabilizes at normal or near normal levels, intravenous medications are gradually replaced by oral medications. If there is no significant decrease in ammonium within 8 hours, patients begin hemodialysis. Concurrent therapy with ondansetron, high caloric intake, and mannitol for elevated intracranial pressure is allowed. Dietary and intravenous nitrogen is prohibited. (Discontinued 11/97)