2-amino-3-phenyl-propanoic acid, Acide Alpha-aminohydrocinnamique, Acide Isovalérique de Phénylalanine, Alpha-aminohydrocinnamic Acid, Beta-phenyl-alanine, Bêta-phenyl-alanine, DLPA, D-Phenylalanine, D-Phénylalanine, DL-Phenylalanine, DL-Phénylalanine, D,L-Phenylalanine, D,L-Phénylalanine, Fenilalanina, L-Phenylalanine, L-Phénylalanine, Phenylalanine Ethyl Ester HCl, Phenylalanine Isovaleric Acid, Phenylalanine Methyl Ester HCl.


Overview Information

Phenylalanine is an amino acid, a "building block" of protein. There are three forms of phenylalanine: D-phenylalanine, L-phenylalanine, and the mix made in the laboratory called DL-phenylalanine. D-phenylalanine is not an essential amino acid. Its role in people is not currently understood. L-phenylalanine is an essential amino acid. It is the only form of phenylalanine found in proteins. Major dietary sources of L-phenylalanine include meat, fish, eggs, cheese, and milk.

Phenylalanine is used for a skin disease called vitiligo, depression, attention deficit-hyperactivity disorder (ADHD), Parkinson's disease, multiple sclerosis, pain, acupuncture anesthesia, osteoarthritis, rheumatoid arthritis, weight loss, and alcohol withdrawal symptoms.

Some people apply it directly to the skin for vitiligo and dark spots on the skin due to aging (liver spots).

How does it work?

The body uses phenylalanine to make chemical messengers, but it is not clear how phenylalanine might work.


Uses & Effectiveness?

Possibly Effective for

  • A skin condition called vitiligo. Taking L-phenylalanine by mouth in combination with UVA exposure or applying L-phenylalanine to the skin in combination with UVA exposure seems to be effective for treating vitiligo in adults and in children.

Possibly Ineffective for

  • Attention deficit-hyperactivity disorder (ADHD). Some research suggests that patients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that providing phenylalanine might treat ADHD. However, taking phenylalanine by mouth does not seem to have any effect on ADHD symptoms.
  • Pain. Taking D-phenylalanine by mouth does not need to reduce pain.

Insufficient Evidence for

  • Acupuncture anesthesia. Early research suggests that taking D-phenylalanine by mouth might enhance acupuncture anesthesia while having a tooth pulled. However, it does not seem to improve acupuncture anesthesia for back pain.
  • Aging skin. Early research shows that applying a modified form of phenylalanine called undecylenoyl phenylalanine as a 2% cream twice daily for 12 weeks can reduce the number of age spots.
  • Alcoholism. Early research suggests that taking a combination of D-phenylalanine, L-glutamine, and L-5-hydroxytryptophan for 40 days can improve some symptoms of alcohol withdrawal.
  • Depression. Limited clinical research performed in the 1970s and 1980s suggests L-phenylalanine or DL-phenylalanine might be useful for depression. However, this research needs to be confirmed. Taking D-phenylalanine does not appear to improve symptoms of depression.
  • Multiple sclerosis. Early research suggests that using Cari Loder's regiment, which includes L-phenylalanine, lofepramine, and intramuscular vitamin B12 for 24 weeks, does not improve disability in people with multiple sclerosis.
  • Parkinson's disease. Limited research suggests taking one form of phenylalanine (D-phenylalanine) might decrease symptoms of Parkinson's disease. However, taking another form (DL-phenylalanine) does not seem to work.
  • Phenylalanine deficiency. Early research suggests that taking phenylalanine by mouth might improve phenylalanine deficiency in children with tyrosinemia.
  • Weight loss. Early research shows that phenylalanine does not reduce hunger in people who are obese or overweight.
  • Arthritis.
  • Other conditions.
More evidence is needed to rate the effectiveness of phenylalanine for these uses.

Side Effects

Side Effects & Safety

L-phenylalanine is LIKELY SAFE for most people when taken by mouth in amounts commonly found in foods.

L-Phenylalanine is POSSIBLY SAFE when taken by mouth as medicine or when applied as a cream, short-term.

There is not enough reliable information available about the safety of D-phenylalanine.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Phenylalanine is LIKELY SAFE when consumed in amounts commonly found in foods by pregnant women who have normal phenylalanine levels. However, having too much phenylalanine in the mother's system during pregnancy can increase the chances of birth defects. The risk for facial defects is highest at weeks 10-14, nervous system and growth defects between 3-16 weeks, and heart defects at 3-8 weeks. For women who process phenylalanine normally and have normal levels, it is probably fine to get the amount of phenylalanine found in food, but not in higher doses. Do not take supplements. For women who have high levels of phenylalanine, even normal food amounts are UNSAFE. Additionally, experts recommend a low phenylalanine diet for at least 20 weeks before getting pregnant. This should reduce the risk of birth defects.

Phenylalanine is LIKELY SAFE for breast-feeding mothers whose bodies' process phenylalanine normally to consume the amount of phenylalanine found in food. However, do not take more. Not enough is known about the safety of taking phenylalanine in medicinal amounts during breast-feeding.

Phenylketonuria (PKU) and other conditions that cause high levels of phenylalanine: Phenylalanine should be avoided in people with certain inherited disorders that cause their bodies to build up too much phenylalanine. Phenylketonuria (PKU) is one of these diseases. People with this disorder can develop mental retardation, high blood pressure, stroke, and many other serious health issues if they consume phenylalanine. PKU is so serious that babies are screened at birth to determine whether they have the disorder and will need a special diet to avoid these problems.

Schizophrenia: Use with caution. Phenylalanine can make a movement disorder (tardive dyskinesia) in people with schizophrenia worse.



Major Interaction

Do not take this combination

  • Levodopa interacts with PHENYLALANINE

    Levodopa is used for Parkinson's disease. Taking phenylalanine along with levodopa can make Parkinson's disease worse. Do not take phenylalanine if you are taking levodopa.

Moderate Interaction

Be cautious with this combination

  • Medications for depression (MAOIs) interacts with PHENYLALANINE

    Phenylalanine can increase a chemical in the body called tyramine. Large amounts of tyramine can cause high blood pressure. But the body naturally breaks down tyramine to get rid of it. This usually prevents the tyramine from causing high blood pressure. Some medications used for depression stop the body from breaking down tyramine. This can cause there to be too much tyramine and lead to dangerously high blood pressure.

    Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.

  • Medications for mental conditions (Antipsychotic drugs) interacts with PHENYLALANINE

    Some medications for mental conditions might cause jerky muscle movements. Taking phenylalanine along with some medications for mental conditions might increase the risk of jerky muscle movements.

    Some medications for mental conditions include chlorpromazine (Thorazine), clozapine (Clozaril), fluphenazine (Prolixin), haloperidol (Haldol), olanzapine (Zyprexa), perphenazine (Trilafon), prochlorperazine (Compazine), quetiapine (Seroquel), risperidone (Risperdal), thioridazine (Mellaril), thiothixene (Navane), and others.



The following doses have been studied in scientific research:



  • For a skin condition called vitiligo: 50-100 mg/kg of L-phenylalanine once per day has been used. L-phenylalanine 50 mg/kg three times per week for up to 3 months has also been used.
  • For a skin condition called vitiligo: Applying a 10% phenylalanine cream to the skin has been used.

  • For a skin condition called vitiligo: Phenylalanine 100 mg/kg twice weekly for 3-4 months has been used.

View References


  • Beckmann, H. and Ludolph, E. [DL-phenylalanine as an antidepressant. Open study (author's transl)]. Arzneimittelforschung. 1978;28(8):1283-1284. View abstract.
  • Beckmann, H., Strauss, M. A., and Ludolph, E. Dl-phenylalanine in depressed patients: an open study. J.Neural Transm. 1977;41(2-3):123-134. View abstract.
  • Camacho, F. and Mazuecos, J. Oral and topical L-phenylalanine, clobetasol propionate, and UVA/sunlight--a new study for the treatment of vitiligo. J Drugs Dermatol 2002;1(2):127-131. View abstract.
  • Camacho, F. and Mazuecos, J. Treatment of vitiligo with oral and topical phenylalanine: 6 years of experience. Arch Dermatol 1999;135(2):216-217. View abstract.
  • Cotzias, G. C., Van Woert, M. H., and Schiffer, L. M. Aromatic amino acids and modification of parkinsonism. N Engl.J Med 2-16-1967;276(7):374-379. View abstract.
  • Fischer, E., Heller, B., Nachon, M., and Spatz, H. Therapy of depression by phenylalanine. Preliminary note. Arzneimittelforschung. 1975;25(1):132. View abstract.
  • Kravitz, H. M., Sabelli, H. C., and Fawcett, J. Dietary supplements of phenylalanine and other amino acid precursors of brain neuroamines in the treatment of depressive disorders. J Am Osteopath.Assoc 1984;84(1 Suppl):119-123. View abstract.
  • Mann, J., Peselow, E. D., Snyderman, S., and Gershon, S. D-phenylalanine in endogenous depression. Am.J.Psychiatry 1980;137(12):1611-1612. View abstract.
  • Rucklidge, J. J., Johnstone, J., and Kaplan, B. J. Nutrient supplementation approaches in the treatment of ADHD. Expert.Rev.Neurother. 2009;9(4):461-476. View abstract.
  • Sabelli, H. C., Fawcett, J., Gusovsky, F., Javaid, J. I., Wynn, P., Edwards, J., Jeffriess, H., and Kravitz, H. Clinical studies on the phenylethylamine hypothesis of affective disorder: urine and blood phenylacetic acid and phenylalanine dietary supplements. J Clin Psychiatry 1986;47(2):66-70. View abstract.
  • Schallreuter, K. U., Wood, J. M., Pittelkow, M. R., Gutlich, M., Lemke, K. R., Rodl, W., Swanson, N. N., Hitzemann, K., and Ziegler, I. Regulation of melanin biosynthesis in the human epidermis by tetrahydrobiopterin. Science 3-11-1994;263(5152):1444-1446. View abstract.
  • ten Hoedt, A. E., de Sonneville, L. M., Francois, B., ter Horst, N. M., Janssen, M. C., Rubio-Gozalbo, M. E., Wijburg, F. A., Hollak, C. E., and Bosch, A. M. High phenylalanine levels directly affect mood and sustained attention in adults with phenylketonuria: a randomised, double-blind, placebo-controlled, crossover trial. J Inherit.Metab Dis. 2011;34(1):165-171. View abstract.
  • Wade, D. T., Young, C. A., Chaudhuri, K. R., and Davidson, D. L. A randomised placebo controlled exploratory study of vitamin B-12, lofepramine, and L-phenylalanine (the "Cari Loder regime") in the treatment of multiple sclerosis. J Neurol.Neurosurg.Psychiatry 2002;73(3):246-249. View abstract.
  • Antoniou C, Schulpis H, Michas T, et al. Vitiligo therapy with oral and topical phenylalanine with UVA exposure. Int J Dermatol 1989;28:545-7. View abstract.
  • Baker GB, Bornstein RA, Rouget AC, et al. Phenylethylaminergic mechanisms in attention-deficit disorder. Biol Psychiatry 1991;29:15-22.. View abstract.
  • Baruzzi A, Contin M, Riva R, et al. Influence of meal ingestion time on pharmacokinetics of orally administered levodopa in parkinsonian patients. Clin Neuropharmacol 1987;10:527-37. View abstract.
  • Beckmann H, Athen D, Olteanu M, Zimmer R. DL-phenylalanine versus imipramine: a double-blind controlled study. Arch Psychiatr Nervenkr 1979;227:49-58. View abstract.
  • Birkmayer W, Riederer P, Linauer W, Knoll J. L-deprenyl plus L-phenylalanine in the treatment of depression. J Neural Transm 1984;59:81-7. View abstract.
  • Bornstein RA, Baker GB, Carroll A, et al. Plasma amino acids in attention deficit disorder. Psychiatry Res 1990;33:301-6.. View abstract.
  • Cederbaum S. Phenylketonuria: an update. Curr Opin Pediatr 2002;14:702-6. View abstract.
  • Cejudo-Ferragud, E., Nacher, A., Polache, A., Cercos-Fortea, T., Merino, M., and Casabo, V. G. Evidence of competitive inhibition for the intestinal absorption of baclofen by phenylalanine. Int J of Pharm (Amsterdam) 1996;132:63-69.
  • Cormane RH, Siddiqui AH, Westerhof W, Schutgens RB. Phenylalanine and UVA light for the treatment of vitiligo. Arch Dermatol Res 1985;277:126-30. View abstract.
  • Cotzias GC, Van Woert MH, Schiffer LM. Aromatic amino acids and modification of parkinsonism. N Engl J Med 1967;276:374-9.
  • Eriksson T, Granerus AK, Linde A, et al. "On-off" phenomenon in Parkinson's disease: relationship between dopa and other large neutral amino acids in plasma. Neurology 1988;38:1245-8. View abstract.
  • Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press, 2002. Available at:
  • Fujita T, Nakamura K, Yamazaki A, et al. Effect of L-phenylalanine supplementation and a high-protein diet on pharmacokinetics of cefdinir in healthy volunteers: an exploratory study. J Clin Pharm Ther. 2007;32(3):277-85. View abstract.
  • Gardos G, Cole JO, Matthews JD, et al. The acute effects of a loading dose of phenylalanine in unipolar depressed patients with and without tardive dyskinesia. Neuropsychopharmacology 1992;6:241-7. View abstract.
  • Heller B, Fischer BE, Martin R. Therapeutic action of D-phenylalanine in Parkinson's disease. Arzneimittelforschung 1976;26:577-9. View abstract.
  • Hogewind-Schoonenboom JE, Zhu L, Zhu L, et al. Phenylalanine requirements of enterally fed term and preterm infants. Am J Clin Nutr 2015;101(6):1155-62. View abstract.
  • Jardim LB, Palma-Dias R, Silva LC, et al. Maternal hyperphenylalaninaemia as a cause of microcephaly and mental retardation. Acta Paediatr 1996;85:943-6. View abstract.
  • Jukic T, Rojc B, Boben-Bardutzky D, Hafner M, Ihan A. The use of a food supplementation with D-phenylalanine, L-glutamine and L-5-hydroxytriptophan in the alleviation of alcohol withdrawal symptoms. Coll Antropol 2011;35:1225-30. View abstract.
  • Juncos JL, Fabbrini G, Mouradian MM, et al. Dietary influences on the antiparkinsonian response to levodopa. Arch Neurol 1987;44:1003-5. View abstract.
  • Katoulis AC, Alevizou A, Bozi E, et al. A randomized, double-blind, vehicle-controlled study of a preparation containing undecylenoyl phenylalanine 2% in the treatment of solar lentigines. Clin Exp Dermatol 2010;35(5):473-6. View abstract.
  • Kitade T, Odahara Y, Shinohara S, et al. Studies on the enhanced effect of acupuncture analgesia and acupuncture anesthesia by D-phenylalanine (2nd report)- schedule of administration and clinical effects in low back pain and tooth extraction. Acupunct Electrother Res 1990;15:121-35. View abstract.
  • Kuiters GR, et al. Oral phenylalanine loading and sunlight as source of UVA irradiation in vitiligo on the Caribbean island of Curacao NA. J Trop Med Hyg 1986;89:149-55. View abstract.
  • Lehmann WD, Theobald N, Fischer R, Heinrich HC. Stereospecificity of phenylalanine plasma kinetics and hydroxylation in man following oral application of a stable isotope-labelled pseudo-racemic mixture of L- and D-phenylalanine. Clin Chim Acta 1983;128:181-98. View abstract.
  • Mitchell MJ, Daines GE, Thomas BL. Effect of L-tryptophan and phenylalanine on burning pain threshold. Phys Ther 1987;67:203-5. View abstract.
  • Mosnik DM, Spring B, Rogers K, Baruah S. Tardive dyskinesia exacerbated after ingestion of phenylalanine by schizophrenic patients. Neuropsychopharmacology 1997;16:136-46. View abstract.
  • National Institutes of Health Consensus Development Conference Statement. Phenylketonuria: Screening and Management (Accessed 30 October 2015).
  • Nutt JG, Woodward WR, Hammerstad JP, et al. The "on-off" phenomenon in Parkinson's disease. Relation to levodopa absorption and transport. N Engl J Med 1984;310:483-8. View abstract.
  • PKU - Dietary Treatment of the Untreated Adult PKU. National Society for Phenylketonuria (NSPKU). 1996-2001. Available at:
  • Pohle-Krauza RJ, Navia JL, Madore EY, et al. Effects of L-phenylalanine on energy intake in overweight and obese women: interactions with dietary restraint status. Appetite 2008;51(1):111-9. View abstract.
  • Rouse B, Azen C, Koch R, et al. Maternal phenylketonuria collaborative Study (MPKUCS) offspring: facial anomalies, malformations, and early neurological sequelae. Am J Med Genet 1997;69:89-95. View abstract.
  • Schulpis CH, Antoniou C, Michas T, Strarigos J. Phenylalanine plus ultraviolet light: preliminary report of a promising treatment for childhood vitiligo. Pediatr Dermatol 1989;6:332-5. View abstract.
  • Siddiqui AH, Stolk LM, Bhaggoe R, et al. L-phenylalanine and UVA irradiation in the treatment of vitiligo. Dermatology 1994;88:215-8. View abstract.
  • Silkaitis RP, Mosnaim AD. Pathways linking L-phenylalanine and 2-phenylethylamine with p-tyramine in rabbit brain. Brain Res 1976;114:105-15. View abstract.
  • Sturtevant FM. Use of aspartame in pregnancy. Int J Fertil 1985;30:85-7. View abstract.
  • Thiele B, Steigleder GK. [Repigmentation treatment of vitiligo with L-phenylalanine and UVA irradiation]. Z Hautkr 1987;62:519-23. View abstract.
  • Walsh NE, Ramamurthy S, Schoenfeld L, Hoffman J. Analgesic effectiveness of D-phenylalanine in chronic pain patients. Arch Phys Med Rehabil 1986;67:436-9. View abstract.
  • Wilson CJ, Van Wyk KG, Leonard JV, Clayton PT. Phenylalanine supplementation improves the phenylalanine profile in tyrosinaemia. J Inherit Metab Dis. 2000;23:677-83. View abstract.
  • Wood DR, Reimherr FW, Wender PH. Treatment of attention deficit disorder with DL-phenylalanine. Psychiatry Res 1985;16:21-6.. View abstract.
  • Zametkin AJ, Karoum F, Rapoport JL. Treatment of hyperactive children with D-phenylalanine. Am J Psychiatry 1987;144:792-4.. View abstract.
  • Zhao G. [Inherited metabolic aberration of phenylalanine in the family members of patients with essential hypertension and stroke]. Chung Hua I Hsueh Tsa Chih (Taipei) 1991;71:28, 388-90. View abstract.

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