Brain phenylalanine concentrations in phenylketonuria: research and treatment of adults.

OBJECTIVE To assess the effects of 2 pharmacologic interventions (amino acid supplements) on the brain levels of phenylalanine (Phe) in adults with phenylketonuria (PKU). METHODS A prospective study was conducted in an outpatient treatment and follow-up setting. The volunteers who were recruited for the first intervention included 4 subjects with classic PKU. The second intervention included 3 adults with classic PKU. The first intervention consisted of dietary supplementation during 1 day with Phlexy 10. Two individuals were given a dose of 0.5 g/kg/d, and 2 were given 1.0 g/kg/d. The second intervention consisted of dietary supplementation with PreKUnil at 0.4 g kg/d over a period of 6 months. Brain Phe was measured by magnetic resonance spectroscopy. The number of the patients involved precluded analysis for significance. RESULTS The first, shorter intervention resulted in a decrease in brain Phe. The second intervention resulted in a 20% decrease in brain Phe, which was maintained after 6 months of treatment. CONCLUSION Dietary supplementation of large neutral amino acids seems to lower the brain Phe in adults who have PKU and have difficulty following their diet.