Drug interactions
Chlorpromazine + Venlafaxine
Severity: Major
Chlorpromazine and Venlafaxine: major interaction.
Last updated Sources: Health Canada product monograph
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
Venlafaxine is a weak CYP2D6 inhibitor and may modestly raise chlorpromazine exposure. Both drugs can prolong the QTc interval, so the combination raises the risk of ventricular arrhythmias such as torsades de pointes, especially with other risk factors. Additive sedation and hypotension may also occur.
What this interaction means in plain words
Chlorpromazine and Venlafaxine 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.
Chlorpromazine belongs to Central Nervous System; Venlafaxine belongs to Central Nervous System.
Why it happens
Additive QT prolongation combined with weak CYP2D6 inhibition by venlafaxine reducing chlorpromazine clearance.
What to do
Obtain a baseline ECG and repeat it after dose changes, and correct potassium and magnesium abnormalities. Avoid the combination in patients with long QT or other QT-prolonging drugs, or use a lower chlorpromazine dose with monitoring.
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 Venlafaxine
- Isocarboxazid + Venlafaxine Contraindicated
- Methylene blue + Venlafaxine Contraindicated
- Phenelzine + Venlafaxine Contraindicated
- Procarbazine + Venlafaxine Contraindicated
- Rasagiline + Venlafaxine Contraindicated
- Safinamide + Venlafaxine Contraindicated
Other interactions of Chlorpromazine
- Chlorpromazine + Dofetilide Contraindicated
- Chlorpromazine + Dronedarone Contraindicated
- Chlorpromazine + Droperidol Contraindicated
- Chlorpromazine + Ibutilide Contraindicated
- Chlorpromazine + Metrizamide Contraindicated
- Chlorpromazine + Panobinostat Contraindicated
Frequently asked questions
Can I take Chlorpromazine with Venlafaxine?
MediHelp rates the interaction as major. Chlorpromazine and Venlafaxine 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. Venlafaxine is a weak CYP2D6 inhibitor and may modestly raise chlorpromazine exposure. Both drugs can prolong the QTc interval, so the combination raises the risk of ventricular arrhythmias such as torsades de pointes, especially with other risk factors. Additive sedation and hypotension may also occur.
How serious is the interaction between Chlorpromazine and Venlafaxine?
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 repeat it after dose changes, and correct potassium and magnesium abnormalities. Avoid the combination in patients with long QT or other QT-prolonging drugs, or use a lower chlorpromazine dose with monitoring.
What other medicines interact with Venlafaxine?
MediHelp also lists interactions of Venlafaxine with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Venlafaxine page.
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