Drug interactions
Fostemsavir + Itraconazole
Severity: Moderate
Fostemsavir and Itraconazole: 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
Fostemsavir's active moiety, temsavir, is partly cleared by CYP3A4, and itraconazole is a strong CYP3A4 inhibitor that can raise temsavir exposure. Both drugs can prolong the QT interval, and QTc prolongation has been seen with temsavir at supratherapeutic exposures.
What this interaction means in plain words
Fostemsavir and Itraconazole 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.
Fostemsavir belongs to Anti Virals; Itraconazole belongs to Anti Fungals.
Why it happens
Itraconazole inhibits CYP3A4, raising temsavir exposure, and both drugs have additive QT-prolonging potential.
What to do
The standard fostemsavir dose is generally acceptable, but obtain a baseline ECG and monitor QTc, particularly in patients with other QT risk factors. Correct potassium and magnesium abnormalities before starting.
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 Itraconazole
- Alfuzosin + Itraconazole Contraindicated
- Alprazolam + Itraconazole Contraindicated
- Avanafil + Itraconazole Contraindicated
- Conivaptan + Itraconazole Contraindicated
- Dihydroergotamine intranasal + Itraconazole Contraindicated
- Dihydroergotamine + Itraconazole Contraindicated
Other interactions of Fostemsavir
- Apalutamide + Fostemsavir Contraindicated
- Carbamazepine + Fostemsavir Contraindicated
- Enzalutamide + Fostemsavir Contraindicated
- Fostemsavir + Mitotane Contraindicated
- Fostemsavir + Phenytoin Contraindicated
- Fostemsavir + Rifampicin Contraindicated
Frequently asked questions
Can I take Fostemsavir with Itraconazole?
MediHelp rates the interaction as moderate. Fostemsavir and Itraconazole 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. Fostemsavir's active moiety, temsavir, is partly cleared by CYP3A4, and itraconazole is a strong CYP3A4 inhibitor that can raise temsavir exposure. Both drugs can prolong the QT interval, and QTc prolongation has been seen with temsavir at supratherapeutic exposures.
How serious is the interaction between Fostemsavir and Itraconazole?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: The standard fostemsavir dose is generally acceptable, but obtain a baseline ECG and monitor QTc, particularly in patients with other QT risk factors. Correct potassium and magnesium abnormalities before starting.
What other medicines interact with Itraconazole?
MediHelp also lists interactions of Itraconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Itraconazole page.
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