Drug interactions
Posaconazole + Sulfamethoxazole
Severity: Moderate
Posaconazole and Sulfamethoxazole: 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 agents have been associated with QT prolongation, so combining them may add to arrhythmia risk, including torsades de pointes. The risk is greatest in patients with electrolyte disturbances, structural heart disease or other QT-prolonging drugs.
What this interaction means in plain words
Posaconazole and Sulfamethoxazole 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
Additive effects on cardiac repolarization; the QT effect of sulfamethoxazole is weak and not well established.
What to do
Obtain a baseline ECG and correct potassium and magnesium before and during therapy. Monitor the QTc in patients with additional risk factors.
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 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 Posaconazole with Sulfamethoxazole?
MediHelp rates the interaction as moderate. Posaconazole and Sulfamethoxazole 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 agents have been associated with QT prolongation, so combining them may add to arrhythmia risk, including torsades de pointes. The risk is greatest in patients with electrolyte disturbances, structural heart disease or other QT-prolonging drugs.
How serious is the interaction between Posaconazole and Sulfamethoxazole?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG and correct potassium and magnesium before and during therapy. Monitor the QTc in patients with additional risk factors.
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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