The concentrations of guanidino compounds were determined in urine, plasma and cerebrospinal fluid of two patients with hyperargininemia during dietary therapy. α-Keto-δ-guanidinovaleric acid, N-α-acetylarginine, argininic acid and γ-guanidinobutyric acid were increased in urine. In plasma, these compounds together with creatine, guanidinoacetic acid, arginine and homoarginine were also increased. In cerebrospinal fluid, only arginine, homoarginine and argininic acid were increased. Trace amounts of α-keto-δ-guanidinovaleric acid were found in cerebrospinal fluid of the patient treated with only a low-arginine diet. The concentrations of guanidinosuccinic acid are decreased in urine, plasma and cerebrospinal fluid.

During a low-arginine diet, together with sodium benzoate therapy, the plasma and cerebrospinal fluid arginine values returned to normal. There was also a normalization of plasma guanidinoacetic acid and a marked decrease in plasma N-α-acetylarginine and argininic acid.