Monograph: |
L-Phenylalanine
White odourless crystals, flakes, or crystalline powder. Spar-
ingly soluble in water: very slightly soluble in alcohol and in
methyl alcohol: practically insoluble in ether: dissolves in di-
lute solutions of alkali hydroxides and in dilute mineral acids.
A 1% solution in water has a pH of 5.4 to 6.0. Protect from
light.
Phenylalanine is an aromatic amino acid which is an essential
constituent of the diet. It is used as a dietary supplement.
Phenylalanine intake should be restricted in patients with
phenyiketonuria (see Amino Acid Metabolic Disorders).
Vitiligo. There is no totally effective treatment for vitiligo
(localised hypopigmentation). Oral or topical photo-
chemotherapy with psoralens is generally considered to be
the best available treatment, but experimental therapy in-
cludes UVA phototherapy with either khellin or phenyl-
alanine. Administration of phenylalanine in doses of up to
100 mg per kg body-weight by mouth in conjunction with
UVA/sunlight led to beneficial results in more than 90% of
200 patients with vitiligo. Optimal repigmentation of the
vitiliginous macules was noted in early disease, but prolonged
treatment still induced repigmentation in long-standing cases.
Repigmentation occurred mainly in areas rich in follicles.
Such treatment is contra-indicated in phenylketonuria and in
pregnancy.
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