Drug interactions
Fluoxetine + Trimethoprim
Severity: Minor
Fluoxetine and Trimethoprim: 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
Both agents have been linked to QT prolongation, so the combination may modestly add to arrhythmia risk. Trimethoprim can also cause hyperkalemia, which may add to cardiac risk in susceptible patients.
What this interaction means in plain words
Fluoxetine and Trimethoprim have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Fluoxetine belongs to Central Nervous System; Trimethoprim belongs to Anti Bacterial.
Why it happens
Possible additive QT prolongation; the evidence for trimethoprim's QT effect is limited.
What to do
No routine action is needed in low-risk patients. In those with cardiac disease, electrolyte disturbance or renal impairment, check potassium and consider an ECG.
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
Other interactions of Trimethoprim
Frequently asked questions
Can I take Fluoxetine with Trimethoprim?
MediHelp rates the interaction as minor. Fluoxetine and Trimethoprim have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Both agents have been linked to QT prolongation, so the combination may modestly add to arrhythmia risk. Trimethoprim can also cause hyperkalemia, which may add to cardiac risk in susceptible patients.
How serious is the interaction between Fluoxetine and Trimethoprim?
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 action is needed in low-risk patients. In those with cardiac disease, electrolyte disturbance or renal impairment, check potassium and consider an ECG.
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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