Medication·Interactions & depletion·Reviewed June 9, 2026
Isoniazid interactions.
Isoniazid has 4 documented interactions in the NutriStack database. Prolonged use is also associated with lower Vitamin B6, Vitamin B6 (Pyridoxine), and Niacin (Vitamin B3). The full interaction list, depletion table, and replacement suggestions are below. None of this is a substitute for your prescriber's advice.
Isoniazid at a glance.
A quick, data-grounded summary. The full tables are below.
Isoniazid has 4 documented interactions in the NutriStack database. Prolonged use is also associated with lower Vitamin B6, Vitamin B6 (Pyridoxine), and Niacin (Vitamin B3). The full interaction list, depletion table, and replacement suggestions are below. None of this is a substitute for your prescriber's advice.
Substances that interact with isoniazid.
Every supplement and medication in the NutriStack database with a documented interaction with this drug, highest-severity first. Open any pair for the mechanism and sources.
| Substance | Interaction | What happens |
|---|---|---|
| 5-HTP | Caution | Isoniazid has weak monoamine oxidase inhibiting activity; 5-HTP could theoretically increase serotonergic adverse-effect risk, although the evidence... |
| L-Tryptophan | Caution | Isoniazid is a weak, reversible inhibitor of monoamine oxidase. Combining it with high doses of L-tryptophan, a precursor to serotonin, can increase... |
| Milk Thistle | Synergy | Isoniazid carries a recognized risk of hepatotoxicity. Silymarin from milk thistle has been studied as a hepatoprotective adjunct in patients on... |
| Vitamin B6 | Synergy | Isoniazid functionally antagonizes pyridoxine and can cause peripheral neuropathy; vitamin B6 supplementation prevents this in at-risk patients. |
What isoniazid can deplete.
Nutrients this medication is associated with lowering over time, with the mechanism, a suggested replacement where one applies, and the biomarker to monitor. Discuss any replacement with your prescriber first.
| Nutrient | Severity | How it happens | Replace with | Monitor |
|---|---|---|---|---|
| Vitamin B6 | Significant | Isoniazid antagonizes pyridoxine metabolism and increases risk of pyridoxine-responsive peripheral neuropathy. | Vitamin B6 | Clinical neuropathy assessment; pyridoxal 5-phosphate if available |
| Vitamin B6 (Pyridoxine) | Significant | Isoniazid is a hydrazide derivative that reacts directly with pyridoxal and pyridoxal-5'-phosphate to form isoniazid-pyridoxal hydrazones, which are... | Pyridoxine (Vitamin B6) | Plasma pyridoxal-5'-phosphate (PLP); clinical monitoring for signs of peripheral neuropathy (paresthesias, numbness) |
| Niacin (Vitamin B3) | Moderate | Niacin can be synthesized endogenously from the amino acid tryptophan via a pyridoxal-5'-phosphate (vitamin B6)-dependent pathway (the kynurenine... | Niacinamide (Nicotinamide) | Urinary N1-methylnicotinamide and 2-pyridone metabolites; clinical monitoring for pellagra signs (dermatitis, diarrhea, dementia/glossitis) |
The full isoniazid profile.
Uses, typical dosing, side effects, and the cited evidence for this medication.
Common isoniazid questions.
Quick answers drawn from the tables above.
What interacts with Isoniazid?
In the NutriStack database, Isoniazid has 4 documented interactions. The most notable include 5-HTP, L-Tryptophan, Milk Thistle, and Vitamin B6. Check any specific combination before taking it and confirm with your prescriber.
Does Isoniazid deplete any nutrients?
Isoniazid is associated with lowering Vitamin B6, Vitamin B6 (Pyridoxine), and Niacin (Vitamin B3) with prolonged use. Useful biomarkers to monitor include Clinical neuropathy assessment; pyridoxal 5-phosphate if available, Plasma pyridoxal-5'-phosphate (PLP); clinical monitoring for signs of peripheral neuropathy (paresthesias, numbness), and Urinary N1-methylnicotinamide and 2-pyridone metabolites; clinical monitoring for pellagra signs (dermatitis, diarrhea, dementia/glossitis). Ask your prescriber before adding any replacement supplement.
Is it safe to take 5-HTP with Isoniazid?
NutriStack classifies the 5-HTP and Isoniazid pairing as caution: Isoniazid has weak monoamine oxidase inhibiting activity; 5-HTP could theoretically increase serotonergic adverse-effect risk, although the evidence is much weaker than... Avoid nonessential 5-HTP during isoniazid therapy, especially with antidepressants or other serotonergic drugs; counsel on serotonin-toxicity... Always confirm with your prescriber.
Check your whole stack
See how isoniazid fits your supplements.
NutriStack screens your full routine for interactions and depletions, and updates the moment you change it.