Drug interactions
Fluoxetine + Sulfamethoxazole
Severity: Minor
Fluoxetine and Sulfamethoxazole: minor 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
Sulfamethoxazole is partly metabolized by CYP2C9, which fluoxetine can inhibit. Any increase in sulfamethoxazole exposure is likely small and rarely clinically relevant.
What this interaction means in plain words
Fluoxetine and Sulfamethoxazole have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Possible inhibition of CYP2C9-mediated sulfamethoxazole metabolism by fluoxetine.
What to do
No routine dose change is needed; be alert for sulfonamide adverse effects such as rash or cytopenias.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Fluoxetine
- Fluoxetine + Isocarboxazid Contraindicated
- Fluoxetine + Mavacamten Contraindicated
- Fluoxetine + Methylene blue Contraindicated
- Fluoxetine + Phenelzine Contraindicated
- Fluoxetine + Pimozide Contraindicated
- Fluoxetine + Rasagiline Contraindicated
Frequently asked questions
Can I take Fluoxetine with Sulfamethoxazole?
MediHelp rates the interaction as minor. Fluoxetine and Sulfamethoxazole have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Sulfamethoxazole is partly metabolized by CYP2C9, which fluoxetine can inhibit. Any increase in sulfamethoxazole exposure is likely small and rarely clinically relevant.
How serious is the interaction between Fluoxetine and Sulfamethoxazole?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine dose change is needed; be alert for sulfonamide adverse effects such as rash or cytopenias.
What other medicines interact with Fluoxetine?
MediHelp also lists interactions of Fluoxetine with, for example, Isocarboxazid, Mavacamten, Methylene blue. The full list is on the Fluoxetine page.
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