Drug interactions
Nortriptyline + Promethazine
Severity: Moderate
Nortriptyline 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
Both drugs prolong the QT interval and cause sedation and anticholinergic effects, so combined use raises the risk of arrhythmia and anticholinergic toxicity such as confusion, urinary retention and constipation. Promethazine may also modestly inhibit CYP2D6, raising nortriptyline levels.
What this interaction means in plain words
Nortriptyline 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.
Nortriptyline belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive QT prolongation, anticholinergic and sedative effects, with possible CYP2D6-mediated increase in nortriptyline exposure.
What to do
Obtain a baseline ECG and correct potassium and magnesium in patients with cardiac risk factors. Monitor for anticholinergic effects and sedation, especially in older adults.
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
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Nortriptyline
- Disopyramide + Nortriptyline Contraindicated
- Dofetilide + Nortriptyline Contraindicated
- Dronedarone + Nortriptyline Contraindicated
- Ibutilide + Nortriptyline Contraindicated
- Isocarboxazid + Nortriptyline Contraindicated
- Methylene blue + Nortriptyline Contraindicated
Frequently asked questions
Can I take Nortriptyline with Promethazine?
MediHelp rates the interaction as moderate. Nortriptyline 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. Both drugs prolong the QT interval and cause sedation and anticholinergic effects, so combined use raises the risk of arrhythmia and anticholinergic toxicity such as confusion, urinary retention and constipation. Promethazine may also modestly inhibit CYP2D6, raising nortriptyline levels.
How serious is the interaction between Nortriptyline 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: Obtain a baseline ECG and correct potassium and magnesium in patients with cardiac risk factors. Monitor for anticholinergic effects and sedation, especially in older adults.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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