Drug interactions
Formoterol + Trimethoprim
Severity: Minor
Formoterol 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 drugs have been linked to QT prolongation, so combining them may modestly increase arrhythmia risk. Trimethoprim can also raise potassium, which tends to offset formoterol's potassium-lowering effect.
What this interaction means in plain words
Formoterol 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.
Formoterol belongs to Respiratory; Trimethoprim belongs to Anti Bacterial.
Why it happens
Possible additive QT prolongation; evidence for trimethoprim's effect is limited.
What to do
Routine monitoring is usually unnecessary. In patients with QT risk factors, check electrolytes 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 Formoterol
- Adagrasib + Formoterol Major
- Amiodarone + Formoterol Major
- Amisulpride + Formoterol Major
- Amitriptyline + Formoterol Major
- Amoxapine + Formoterol Major
- Arformoterol + Formoterol Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Formoterol with Trimethoprim?
MediHelp rates the interaction as minor. Formoterol 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 drugs have been linked to QT prolongation, so combining them may modestly increase arrhythmia risk. Trimethoprim can also raise potassium, which tends to offset formoterol's potassium-lowering effect.
How serious is the interaction between Formoterol 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: Routine monitoring is usually unnecessary. In patients with QT risk factors, check electrolytes and consider an ECG.
What other medicines interact with Formoterol?
MediHelp also lists interactions of Formoterol with, for example, Adagrasib, Amiodarone, Amisulpride. The full list is on the Formoterol page.
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