Am J Psychiatry. 1987 Jun;144(6):792-4.

Treatment of hyperactive children with D-phenylalanine.

Zametkin AJ, Karoum F, Rapoport JL.

Eleven hyperactive boys were treated for 2 weeks with D-phenylalanine (20 mg/kg per day) and for 2 weeks with placebo in a double-blind crossover study. Tests included parent and teacher behavior ratings, cognitive measures, and blood and urine measures of norepinephrine, amino acids, and trace amines. No significant improvement or deterioration in behavior and no side effects were noted, and only serum phenylalanine was increased by the active treatment phase. This provides reassurance about the toxicity of aspartame, a food additive that contains phenylalanine, but argues against precursor loading treatment of hyperactivity.