Drug interactions
Promethazine + Trazodone
Severity: Moderate
Promethazine and Trazodone: 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 are sedating and can prolong the QT interval, so combining them may cause marked drowsiness, orthostatic hypotension and arrhythmia risk, particularly with cardiac disease or electrolyte disturbances.
What this interaction means in plain words
Promethazine and Trazodone 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.
Promethazine belongs to Respiratory; Trazodone belongs to Central Nervous System.
Why it happens
Additive CNS depression, alpha-1 blockade and QT prolongation.
What to do
Monitor for sedation and orthostatic hypotension, and check ECG and electrolytes if risk factors for QT prolongation exist. Use the lowest effective doses.
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 Trazodone
- Arsenic trioxide + Trazodone Contraindicated
- Ibutilide + Trazodone Contraindicated
- Isocarboxazid + Trazodone Contraindicated
- Levoketoconazole + Trazodone Contraindicated
- Methylene blue + Trazodone Contraindicated
- Phenelzine + Trazodone Contraindicated
Frequently asked questions
Can I take Promethazine with Trazodone?
MediHelp rates the interaction as moderate. Promethazine and Trazodone 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 are sedating and can prolong the QT interval, so combining them may cause marked drowsiness, orthostatic hypotension and arrhythmia risk, particularly with cardiac disease or electrolyte disturbances.
How serious is the interaction between Promethazine and Trazodone?
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 sedation and orthostatic hypotension, and check ECG and electrolytes if risk factors for QT prolongation exist. Use the lowest effective doses.
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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