Drug interactions
Isoniazid + Sildenafil
Severity: Minor
Isoniazid and Sildenafil: 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 is a weak CYP3A4 inhibitor and may slightly raise sildenafil levels. Clinically meaningful effects are unlikely in most patients.
What this interaction means in plain words
Isoniazid and Sildenafil 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 belongs to Anti Bacterial; Sildenafil belongs to Genitourinary.
Why it happens
Isoniazid weakly inhibits CYP3A4, reducing sildenafil metabolism.
What to do
No dose adjustment is usually needed; monitor for increased sildenafil adverse effects such as headache or hypotension.
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 Sildenafil
- Amyl nitrite + Sildenafil Contraindicated
- Atazanavir + Sildenafil Contraindicated
- Cobicistat + Sildenafil Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Sildenafil Contraindicated
- Glyceryl trinitrate pr + Sildenafil Contraindicated
- Isosorbide dinitrate + Sildenafil Contraindicated
Other interactions of Isoniazid
Frequently asked questions
Can I take Isoniazid with Sildenafil?
MediHelp rates the interaction as minor. Isoniazid and Sildenafil 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 is a weak CYP3A4 inhibitor and may slightly raise sildenafil levels. Clinically meaningful effects are unlikely in most patients.
How serious is the interaction between Isoniazid and Sildenafil?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No dose adjustment is usually needed; monitor for increased sildenafil adverse effects such as headache or hypotension.
What other medicines interact with Sildenafil?
MediHelp also lists interactions of Sildenafil with, for example, Amyl nitrite, Atazanavir, Cobicistat. The full list is on the Sildenafil page.
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