Drug interactions
Sulfamethoxazole + Venlafaxine
Severity: Minor
Sulfamethoxazole and Venlafaxine: 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/trimethoprim has been linked to QT prolongation and venlafaxine may also prolong QT, mainly at high doses. The combined risk is likely small but may matter in patients with other risk factors.
What this interaction means in plain words
Sulfamethoxazole and Venlafaxine 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 additive QT prolongation.
What to do
No routine action is needed in low-risk patients. Check ECG and electrolytes if other QT-prolonging drugs or cardiac disease are present.
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 Venlafaxine
- Isocarboxazid + Venlafaxine Contraindicated
- Methylene blue + Venlafaxine Contraindicated
- Phenelzine + Venlafaxine Contraindicated
- Procarbazine + Venlafaxine Contraindicated
- Rasagiline + Venlafaxine Contraindicated
- Safinamide + Venlafaxine Contraindicated
Frequently asked questions
Can I take Sulfamethoxazole with Venlafaxine?
MediHelp rates the interaction as minor. Sulfamethoxazole and Venlafaxine 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/trimethoprim has been linked to QT prolongation and venlafaxine may also prolong QT, mainly at high doses. The combined risk is likely small but may matter in patients with other risk factors.
How serious is the interaction between Sulfamethoxazole and Venlafaxine?
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. Check ECG and electrolytes if other QT-prolonging drugs or cardiac disease are present.
What other medicines interact with Venlafaxine?
MediHelp also lists interactions of Venlafaxine with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Venlafaxine page.
Full monographs, dosing and an interaction checker in the MediHelp app
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