Drug interactions
Formoterol + Promethazine
Severity: Moderate
Formoterol and Promethazine: 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
Formoterol, a long-acting beta-agonist, can prolong QTc and cause hypokalemia and tachycardia, while promethazine can also affect QT. Combined use may increase arrhythmia risk, mainly at high doses or in patients with cardiac disease.
What this interaction means in plain words
Formoterol and Promethazine 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.
Formoterol belongs to Respiratory; Promethazine belongs to Respiratory.
Why it happens
Additive QT prolongation, with beta-agonist-induced hypokalemia and tachycardia.
What to do
Monitor for palpitations and check potassium and ECG in patients with heart disease or other QT risk factors. Use the lowest effective formoterol dose.
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 Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Formoterol
- Adagrasib + Formoterol Major
- Amiodarone + Formoterol Major
- Amisulpride + Formoterol Major
- Amitriptyline + Formoterol Major
- Amoxapine + Formoterol Major
- Arformoterol + Formoterol Major
Frequently asked questions
Can I take Formoterol with Promethazine?
MediHelp rates the interaction as moderate. Formoterol and Promethazine 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. Formoterol, a long-acting beta-agonist, can prolong QTc and cause hypokalemia and tachycardia, while promethazine can also affect QT. Combined use may increase arrhythmia risk, mainly at high doses or in patients with cardiac disease.
How serious is the interaction between Formoterol and Promethazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for palpitations and check potassium and ECG in patients with heart disease or other QT risk factors. Use the lowest effective formoterol dose.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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