Drug interactions
Phenobarbital + Sildenafil
Severity: Moderate
Phenobarbital and Sildenafil: moderate 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
Phenobarbital is an enzyme inducer that can lower sildenafil concentrations and cause loss of efficacy. This is clinically important during chronic phenobarbital therapy.
What this interaction means in plain words
Phenobarbital and Sildenafil can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Phenobarbital induces CYP3A4, accelerating sildenafil clearance.
What to do
Monitor for reduced sildenafil response and titrate the dose cautiously, or use an alternative treatment if efficacy is inadequate.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Phenobarbital and Sildenafil, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
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
Frequently asked questions
Can I take Phenobarbital with Sildenafil?
MediHelp rates the interaction as moderate. Phenobarbital and Sildenafil can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenobarbital is an enzyme inducer that can lower sildenafil concentrations and cause loss of efficacy. This is clinically important during chronic phenobarbital therapy.
How serious is the interaction between Phenobarbital and Sildenafil?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for reduced sildenafil response and titrate the dose cautiously, or use an alternative treatment if efficacy is inadequate.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
