L-Phenylalanine
Essential large neutral amino acid used in protein synthesis and converted by phenylalanine hydroxylase to L-tyrosine. This record represents the natural L-isomer only, not D-phenylalanine or the DLPA racemate. It is not a direct dopamine agonist, and precursor availability does not guarantee a clinically meaningful catecholamine effect. Supplemental phenylalanine is inappropriate in phenylketonuria and can compete with levodopa and other large neutral amino acids for intestinal and blood-brain transport.
Projected serum levels — 500 mg, once daily
Maintenance schedule: 500 mg once daily (oral).
Modeled steady state after ~1 days: peak ≈ 25.9 mg, trough ≈ 3.0 mg body load. Population-based estimate over 15 days for a 500 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.
Key facts
- Category
- Amino Acid
- Route modeled
- Oral
- Model confidence
- inferred
- Half-life
- 28 min
- Common dose
- 500 mg
- Suggested maximum
- 7.5k mg/day
- Reference dose range
- 250–7.5k mg (single dose)
- Suggested cadence
- once daily
- Validated against
- 560 mg oral — Cmax 1 mg/L at 2 h
Research behind this entry
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Studies on Phenylalanine Metabolism by Tracer Techniques. IV. Biotransformation of D- and L-Phenylalanine in Man
A single healthy adult received separate stable-isotope-labeled D- and L-phenylalanine loads at 8 mg/kg. L-phenylalanine reached a much smaller labeled plasma peak at two hours and disappeared with a 0.5-hour half-life;…
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Effect of L-phenylalanine supplementation and a high-protein diet on pharmacokinetics of cefdinir in healthy volunteers
Six healthy men received 7.5 g/day L-phenylalanine for 12 days in a randomized crossover experiment designed around cefdinir disposition. The supplement did not change cefdinir plasma or urinary kinetics and routine…
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Essential Amino Acids and Protein Synthesis
Reanalysis of four tracer studies found that larger peripheral essential amino-acid peaks and changes correlated with muscle and whole-body protein synthesis after varied foods and formulations. Phenylalanine was used…
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Nutrition in phenylketonuria
This review explains that PAH deficiency prevents normal conversion of phenylalanine to tyrosine, allowing neurotoxic accumulation and requiring individualized phenylalanine restriction, medical foods, and sometimes BH4…
5 published studies referenced in the app, each with a plain-language summary.