Drug interactions
Fluvoxamine + Sulfamethoxazole
Severity: Moderate
Fluvoxamine 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 drugs have been linked to QT prolongation, so the combination may add to arrhythmia risk, especially with electrolyte disturbances or heart disease. Sulfamethoxazole also inhibits CYP2C9 and could marginally affect other drugs.
What this interaction means in plain words
Fluvoxamine 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
Possible additive QT interval prolongation.
What to do
Check electrolytes and consider an ECG in patients with QT risk factors; use an alternative antibiotic if the QT lengthens.
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 Fluvoxamine
- Agomelatine + Fluvoxamine Contraindicated
- Alosetron + Fluvoxamine Contraindicated
- Fezolinetant + Fluvoxamine Contraindicated
- Fluvoxamine + Isocarboxazid Contraindicated
- Fluvoxamine + Mavacamten Contraindicated
- Fluvoxamine + Methylene blue Contraindicated
Frequently asked questions
Can I take Fluvoxamine with Sulfamethoxazole?
MediHelp rates the interaction as moderate. Fluvoxamine 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 drugs have been linked to QT prolongation, so the combination may add to arrhythmia risk, especially with electrolyte disturbances or heart disease. Sulfamethoxazole also inhibits CYP2C9 and could marginally affect other drugs.
How serious is the interaction between Fluvoxamine 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: Check electrolytes and consider an ECG in patients with QT risk factors; use an alternative antibiotic if the QT lengthens.
What other medicines interact with Fluvoxamine?
MediHelp also lists interactions of Fluvoxamine with, for example, Agomelatine, Alosetron, Fezolinetant. The full list is on the Fluvoxamine page.
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