Phenylalanine
Essential aromatic amino acid, dietary precursor to dopamine and noradrenaline.
Pharmacology
Contents
WHAT IS PHENYLALANINE?
Detailed overview
Phenylalanine is an essential aromatic alpha-amino acid the body cannot synthesize, so it must come from diet or supplementation. The L-form is converted by phenylalanine hydroxylase into tyrosine, which is the starting point of the catecholamine pathway (L-DOPA, dopamine, noradrenaline, adrenaline) as well as thyroid hormones and melanin, giving it its dopaminergic and mood relevance. The DL-form (a mix of the D- and L-isomers) showed antidepressant effects in small controlled studies from the 1970s, and the D-form is thought to inhibit enkephalinase. In phenylketonuria (PKU) it is absolutely contraindicated, because the missing enzyme lets phenylalanine build up to toxic levels.
Mechanism
Catecholamine precursor (tyrosine, dopamine, noradrenaline)
Evidence
Moderate (small human trials, mood and vitiligo)
Legal status
Essential amino acid / dietary supplement
Receptor profile
- Phenylalanine hydroxylase (substrate)Strong
- Catecholamine synthesis (tyrosine, L-DOPA, dopamine, noradrenaline)Moderate
- Phenylethylamine (PEA) formationModerate
- Enkephalinase inhibition (D-form)Weak
Safety
Side effects, stop signs, contraindications
Side effects · 4
- Restlessness, anxiety or insomnia, especially at higher doses or late dosing (catecholamine stimulation)
- Headache, and possible migraine trigger in migraine-prone individuals
- Mild rise in blood pressure at high doses
- Stomach upset, nausea, heartburn
Contraindications · 5
- Phenylketonuria (PKU): absolute contraindication, phenylalanine cannot be metabolized and its accumulation causes neurological damage
- MAO-inhibitor therapy: risk of hypertensive crisis due to increased catecholamine synthesis
- Pregnancy and breastfeeding: safety at supplemental doses not established, avoid
- Anxiety disorder, uncontrolled hypertension, arrhythmia: the stimulant effect may worsen them
- History of melanoma or pigment tumor: theoretical concern via the melanin pathway
Related Nootropics
Same therapeutic category
Studies
Related research and clinical findings
DL-phenylalanine versus imipramine: a double-blind controlled study
Beckmann H, et al.
DL-phenylalanine as an antidepressant. Open study
Beckmann H, et al.
DL-phenylalanine in depressed patients: an open study
Beckmann H, et al.
Treatment of vitiligo with phenylalanine and UV-A
Treatment of vitiligo using phenylalanine and UVA irradiation
FAQ
FAQ
Essential aromatic amino acid, dietary precursor to dopamine and noradrenaline.
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Structure & chemistry
The information here is strictly for educational and scientific purposes. It does not replace medical advice or clinical consultation, and it does not encourage illegal substance or pharmaceutical use. Data is sourced. When in doubt, consult your doctor.