Drug interactions
Doxepin + Isoniazid
Severity: Minor
Doxepin and Isoniazid: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Isoniazid has weak, reversible monoamine oxidase inhibiting activity, and combining it with a tricyclic antidepressant such as doxepin could in theory increase serotonergic or noradrenergic effects. Clinically significant serotonin syndrome is rare and reported mainly as isolated cases. Isoniazid may also modestly raise tricyclic levels through enzyme inhibition.
What this interaction means in plain words
Doxepin and Isoniazid have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Doxepin belongs to Dermatology; Isoniazid belongs to Anti Bacterial.
Why it happens
Weak MAO inhibition by isoniazid adds to the reuptake inhibition of doxepin, and isoniazid may slightly inhibit tricyclic metabolism.
What to do
Monitor for agitation, tremor, hyperthermia, and anticholinergic effects when starting the combination. Lower the doxepin dose if toxicity develops.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Isoniazid
Other interactions of Doxepin
- Doxepin + Isocarboxazid Contraindicated
- Doxepin + Phenelzine Contraindicated
- Doxepin + Procarbazine Contraindicated
- Doxepin + Safinamide Contraindicated
- Doxepin + Selegiline Contraindicated
- Doxepin + Tranylcypromine Contraindicated
Frequently asked questions
Can I take Doxepin with Isoniazid?
MediHelp rates the interaction as minor. Doxepin and Isoniazid have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Isoniazid has weak, reversible monoamine oxidase inhibiting activity, and combining it with a tricyclic antidepressant such as doxepin could in theory increase serotonergic or noradrenergic effects. Clinically significant serotonin syndrome is rare and reported mainly as isolated cases. Isoniazid may also modestly raise tricyclic levels through enzyme inhibition.
How serious is the interaction between Doxepin and Isoniazid?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for agitation, tremor, hyperthermia, and anticholinergic effects when starting the combination. Lower the doxepin dose if toxicity develops.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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