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Limited evidenceStress & mood

DLPA (DL-Phenylalanine)

DLPA is a 50/50 racemic mix of L-phenylalanine (a dietary amino acid) and D-phenylalanine (a synthetic isomer claimed to block enkephalin breakdown and relieve chronic pain). The pain evidence is old and largely negative; the mood evidence rests on one 1979 trial versus imipramine with no placebo arm.

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What the science says

  • D-phenylalanine failed to relieve chronic pain in a controlled crossover trial Limited evidence

    The enkephalinase-inhibition theory predicts that D-phenylalanine prolongs endogenous opioid action. Walsh's 1986 double-blind crossover trial in chronic pain patients tested 250 mg D-phenylalanine four times daily and found no significant analgesic effect versus placebo on any pain measure. Small Japanese studies reported that D-phenylalanine enhanced acupuncture analgesia, but these were uncontrolled or partially controlled and have not been replicated.

  • The antidepressant claim comes from a 1979 active-comparator study with no placebo group Limited evidence

    Beckmann's double-blind study compared DL-phenylalanine 150-200 mg/day against imipramine 150-200 mg/day in depressed inpatients over 30 days and reported comparable improvement in both arms. Without a placebo arm, equivalence to an antidepressant in a small short trial cannot establish efficacy — depression trials routinely show 30-40% placebo response. No placebo-controlled replication has been published in the four decades since.

  • Not better than plain L-phenylalanine for anything demonstrated Limited evidence

    Half of a DLPA capsule is ordinary L-phenylalanine, which the body uses normally; the D-isomer is not incorporated into protein and is largely excreted or slowly converted. Because the D-isomer's proposed unique benefit (analgesia) is the claim that failed in controlled testing, the premium over L-phenylalanine buys an ingredient with no proven advantage.

Dosage & safety

Studied doseTrials used 250 mg D-phenylalanine four times daily (1 g/day) for pain and 150-200 mg/day DLPA for depression. Commercial DLPA capsules are usually 500-750 mg, taken 1-3 times daily on an empty stomach — well above the doses in the depression trial and in a range never tested against placebo for pain.
SafetySame absolute contraindication as L-phenylalanine: never use in phenylketonuria. Do not combine with MAO inhibitors — risk of hypertensive reaction. Reported side effects include heartburn, nausea, headache, insomnia and anxiety; higher doses may raise blood pressure. Caution with antipsychotics, in pregnancy and breastfeeding (unstudied), and with existing hypertension or anxiety disorders. DLPA is sometimes marketed for opioid withdrawal — there is no controlled evidence for this and it should not replace medical management. Not banned in sport.

How to take it

TimingMorning to early afternoon; it can be activating and cause insomnia taken later.
With food?On an empty stomach, away from protein-containing meals.
Worth knowingNever in phenylketonuria — the contraindication is absolute, exactly as for L-phenylalanine, and DLPA is sometimes sold without that warning.

Interactions

With medications

  • MAO inhibitors (phenelzine, tranylcypromine, selegiline) and linezolid

    risk of a hypertensive reaction through increased catecholamine and phenylethylamine synthesis do not combine

  • levodopa

    competes with levodopa for intestinal and blood-brain transport, reducing its effect separate by at least 2 hours and tell your neurologist

  • antipsychotics

    case reports of worsened tardive dyskinesia avoid unless your prescriber agrees

With other supplements

  • L-phenylalanine or L-tyrosine

    DLPA already contains L-phenylalanine, and all three compete for the same transporter do not stack them

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does DLPA help chronic pain?

The evidence for DLPA in pain is limited and largely negative: a 1986 double-blind crossover trial of D-phenylalanine at 250 mg four times daily found no significant pain relief versus placebo.

Does DLPA work for depression?

The DLPA depression claim rests on one small 1979 trial comparing it with imipramine and no placebo arm, so the evidence is limited. Depression trials routinely show 30-40% placebo response, and no placebo-controlled replication has been published.

Is DLPA better than L-phenylalanine?

No advantage has been demonstrated. Half of DLPA is ordinary L-phenylalanine, and the D-isomer's proposed unique benefit, pain relief, failed in controlled testing.

Is DLPA safe?

Never use DLPA with phenylketonuria, and do not combine it with MAO inhibitors because of the risk of a hypertensive reaction. Side effects include heartburn, nausea, headache, insomnia and anxiety.

Scientific references

Where to buy

Source Naturals, DLPA, 120 Tablets

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