Drug interactions
Dosulepin + Fluphenazine
Severity: Major
Dosulepin and Fluphenazine: 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
Both a phenothiazine and a tricyclic antidepressant can prolong QT, and each has anticholinergic and sedative effects. Combined use increases arrhythmia risk, and fluphenazine may also raise tricyclic levels.
What this interaction means in plain words
Dosulepin and Fluphenazine 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.
Dosulepin belongs to Central Nervous System; Fluphenazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation and anticholinergic effects, with possible CYP2D6 inhibition by fluphenazine.
What to do
Avoid if possible; otherwise monitor ECG and electrolytes and watch for anticholinergic toxicity. Consider a lower dosulepin dose.
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 Fluphenazine
- Arsenic trioxide + Fluphenazine Contraindicated
- Dofetilide + Fluphenazine Contraindicated
- Fluphenazine + Ibutilide Contraindicated
- Fluphenazine + Pimozide Contraindicated
- Adagrasib + Fluphenazine Major
- Alfentanil + Fluphenazine Major
Other interactions of Dosulepin
- Dosulepin + Isocarboxazid Contraindicated
- Dosulepin + Phenelzine Contraindicated
- Dosulepin + Thioridazine Contraindicated
- Dosulepin + Tranylcypromine Contraindicated
- Amitriptyline + Dosulepin Major
- Buprenorphine + Dosulepin Major
Frequently asked questions
Can I take Dosulepin with Fluphenazine?
MediHelp rates the interaction as major. Dosulepin and Fluphenazine 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 a phenothiazine and a tricyclic antidepressant can prolong QT, and each has anticholinergic and sedative effects. Combined use increases arrhythmia risk, and fluphenazine may also raise tricyclic levels.
How serious is the interaction between Dosulepin and Fluphenazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid if possible; otherwise monitor ECG and electrolytes and watch for anticholinergic toxicity. Consider a lower dosulepin dose.
What other medicines interact with Fluphenazine?
MediHelp also lists interactions of Fluphenazine with, for example, Arsenic trioxide, Dofetilide, Ibutilide. The full list is on the Fluphenazine page.
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