What kind of interaction is it?

Caution: an interaction that may reduce efficacy or raise side-effect risk and warrants monitoring.

Is this interaction backed by published research?

Yes. NutriStack lists 1 citation row for the 5-HTP + Isoniazid pair, each linking to PubMed by PMID where available. Full sourcing methodology at https://nutristackapp.com/methodology/interactions.

Supplement × Prescription·a caution·Emerging evidence

5-HTP + Isoniazid

Q: Can I take 5-HTP and Isoniazid together?

Possibly, but with caution. 5-HTP and Isoniazid have a documented caution-tier interaction. Isoniazid has weak monoamine oxidase inhibiting activity; 5-HTP could theoretically increase serotonergic adverse-effect risk, although the evidence is much weaker than for linezolid or antidepressant MAOIs.

Q: How does this affect a NutriStack Stack Score?

-5 to your Stack Score per scored caution row.

Caution Emerging evidence

Isoniazid has weak monoamine oxidase inhibiting activity; 5-HTP could theoretically increase serotonergic adverse-effect risk, although the evidence is much weaker than for linezolid or antidepressant MAOIs.

Supplement × Prescription

Open the interaction checker → Read the methodology

From the database

What the row says.

Every entry follows the same shape: what is happening, the mechanism, and the recommendation.

Substances

5-HTP and Isoniazid

Pair type

Caution

Evidence

Emerging

Source citations

Scope

Supplement × Prescription

Last verified

June 4, 2026

CautionEmerging evidence

What is happening. Isoniazid has weak monoamine oxidase inhibiting activity; 5-HTP could theoretically increase serotonergic adverse-effect risk, although the evidence is much weaker than for linezolid or antidepressant MAOIs.

Mechanism. 5-HTP increases serotonin precursor availability, while isoniazid has weak MAO-inhibiting activity and documented tyramine or histamine food interactions.

Recommendation. Avoid nonessential 5-HTP during isoniazid therapy, especially with antidepressants or other serotonergic drugs; counsel on serotonin-toxicity symptoms if use is clinician-approved.

Stack Score

How it moves the number.

Effect on the composite score

If both 5-HTP and Isoniazid are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).

The full algorithm, the clamping rules, and four worked stacks are at /methodology/stack-score.

Sources

Sources, by evidence tier.

Every claim on this page is cited. PMIDs link straight to PubMed.

Reference material

1DailyMed. Isoniazid US prescribing information. 2026.Needs sourceNo link

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