Drug interactions
Trimethoprim + Voriconazole
Severity: Moderate
Trimethoprim and Voriconazole: 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
Both drugs have been linked to QT prolongation, though the effect of trimethoprim is weak and mostly reported with sulfamethoxazole combinations. Voriconazole may also modestly raise trimethoprim levels via CYP2C9 inhibition.
What this interaction means in plain words
Trimethoprim and Voriconazole 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.
Trimethoprim belongs to Anti Bacterial; Voriconazole belongs to Anti Fungals.
Why it happens
Possible additive QT prolongation; mechanism for trimethoprim is not well established.
What to do
Monitor ECG and potassium in patients with other QT risk factors such as cardiac disease or other QT-prolonging drugs.
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?
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Other interactions of Voriconazole
- Avanafil + Voriconazole Contraindicated
- Butabarbital + Voriconazole Contraindicated
- Carbamazepine + Voriconazole Contraindicated
- Conivaptan + Voriconazole Contraindicated
- Dihydroergotamine intranasal + Voriconazole Contraindicated
- Dihydroergotamine + Voriconazole Contraindicated
Other interactions of Trimethoprim
Frequently asked questions
Can I take Trimethoprim with Voriconazole?
MediHelp rates the interaction as moderate. Trimethoprim and Voriconazole 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. Both drugs have been linked to QT prolongation, though the effect of trimethoprim is weak and mostly reported with sulfamethoxazole combinations. Voriconazole may also modestly raise trimethoprim levels via CYP2C9 inhibition.
How serious is the interaction between Trimethoprim and Voriconazole?
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 ECG and potassium in patients with other QT risk factors such as cardiac disease or other QT-prolonging drugs.
What other medicines interact with Voriconazole?
MediHelp also lists interactions of Voriconazole with, for example, Avanafil, Butabarbital, Carbamazepine. The full list is on the Voriconazole page.
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