Drug interactions
Promethazine + Protriptyline
Severity: Major
Promethazine and Protriptyline: major interaction.
Last updated Sources: US FDA label
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 can prolong the QT interval, have anticholinergic activity and cause sedation. Together they increase the risk of arrhythmia, excess drowsiness and anticholinergic adverse effects.
What this interaction means in plain words
Promethazine and Protriptyline can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Additive QT prolongation, antimuscarinic effects and CNS depression.
What to do
Obtain a baseline ECG and correct hypokalemia and hypomagnesemia. Avoid combining in patients with QT risk factors, and monitor for anticholinergic effects and sedation.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Frequently asked questions
Can I take Promethazine with Protriptyline?
MediHelp rates the interaction as major. Promethazine and Protriptyline can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Both drugs can prolong the QT interval, have anticholinergic activity and cause sedation. Together they increase the risk of arrhythmia, excess drowsiness and anticholinergic adverse effects.
How serious is the interaction between Promethazine and Protriptyline?
MediHelp rates it major, 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 hypokalemia and hypomagnesemia. Avoid combining in patients with QT risk factors, and monitor for anticholinergic effects and sedation.
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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