Drug interactions
Phenobarbital + Posaconazole
Severity: Major
Phenobarbital and Posaconazole: major 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 can lower posaconazole concentrations enough to cause loss of antifungal protection and breakthrough infection. This is clinically important in prophylaxis and treatment of invasive fungal disease.
What this interaction means in plain words
Phenobarbital and Posaconazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Phenobarbital induces UDP-glucuronosyltransferase and P-glycoprotein, increasing posaconazole elimination.
What to do
Avoid the combination where possible; if unavoidable, measure posaconazole trough levels and increase the dose as needed, or use a different anticonvulsant.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Posaconazole
- Artemether + Posaconazole Contraindicated
- Avanafil + Posaconazole Contraindicated
- Cobimetinib + Posaconazole Contraindicated
- Conivaptan + Posaconazole Contraindicated
- Dihydroergotamine intranasal + Posaconazole Contraindicated
- Dihydroergotamine + Posaconazole Contraindicated
Frequently asked questions
Can I take Phenobarbital with Posaconazole?
MediHelp rates the interaction as major. Phenobarbital and Posaconazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Phenobarbital can lower posaconazole concentrations enough to cause loss of antifungal protection and breakthrough infection. This is clinically important in prophylaxis and treatment of invasive fungal disease.
How serious is the interaction between Phenobarbital and Posaconazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible; if unavoidable, measure posaconazole trough levels and increase the dose as needed, or use a different anticonvulsant.
What other medicines interact with Posaconazole?
MediHelp also lists interactions of Posaconazole with, for example, Artemether, Avanafil, Cobimetinib. The full list is on the Posaconazole page.
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