DLPA (DL-Phenylalanine)

Tier 3 — weak evidence · Mood · Pain · Catecholamines

A racemic mixture of L-phenylalanine (a normal amino acid, precursor to tyrosine and catecholamines) and D-phenylalanine (a non-proteinogenic enantiomer that inhibits enkephalinase, potentially extending endogenous opioid action). Small older trials suggested benefit for mild depression and chronic pain, but modern replication is thin. Mechanism for pain is plausible (enkephalinase inhibition) but evidence base is limited. Avoid with MAOIs and in phenylketonuria. Short-term use for pain/mood trial is reasonable.

Dose: 500–1500 mg before breakfast, with a second dose before lunch if well tolerated