L-phenylalanine may be helpful in some with depression. It may also be useful in the treatment of vitiligo. There is some evidence that L-phenylalanine may exacerbate tardive dyskinesia in some schizophrenic patients and in some who have used neuroleptic drugs. (en)
The mechanism of L-phenylalanine's putative antidepressant activity may be accounted for by its precursor role in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects. <br/>The mechanism of L-phenylalanine's possible antivitiligo activity is not well understood. It is thought that L-phenylalanine may stimulate the production of melanin in the affected skin (en)
L-phenylalanine will exacerbate symptoms of phenylketonuria if used by phenylketonurics. L-phenylalanine was reported to exacerbate tardive dyskinesia when used by some with schizophrenia. (en)
Gerald L. Bachman, "Recovery of L-phenylalanine and L-aspartic acid during preparation of .alpha.-L-aspartyl-L-phenylalanine methyl ester." U.S. Patent US4348317, issued January, 1967. (en)