Drug interactions
Mirtazapine + Thioridazine
Severity: Contraindicated
Mirtazapine and Thioridazine: contraindicated 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
Thioridazine markedly prolongs the QTc interval and carries a risk of torsades de pointes, and mirtazapine can add a smaller QT effect. The pairing increases the likelihood of life-threatening ventricular arrhythmia, especially with electrolyte disturbance or cardiac disease.
What this interaction means in plain words
Mirtazapine and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Mirtazapine belongs to Central Nervous System; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation through cardiac repolarization effects; thioridazine is also CYP2D6-dependent and may raise exposure to other agents.
What to do
Avoid combining; use an antidepressant or antipsychotic with less QT liability. If unavoidable, obtain ECG and correct potassium and magnesium, though safe monitoring is difficult.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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References
Other interactions of Mirtazapine
- Isocarboxazid + Mirtazapine Contraindicated
- Mirtazapine + Phenelzine Contraindicated
- Mirtazapine + Pimozide Contraindicated
- Mirtazapine + Procarbazine Contraindicated
- Mirtazapine + Rasagiline Contraindicated
- Mirtazapine + Selegiline Contraindicated
Other interactions of Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Mirtazapine with Thioridazine?
MediHelp rates the interaction as contraindicated. Mirtazapine and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Thioridazine markedly prolongs the QTc interval and carries a risk of torsades de pointes, and mirtazapine can add a smaller QT effect. The pairing increases the likelihood of life-threatening ventricular arrhythmia, especially with electrolyte disturbance or cardiac disease.
How serious is the interaction between Mirtazapine and Thioridazine?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid combining; use an antidepressant or antipsychotic with less QT liability. If unavoidable, obtain ECG and correct potassium and magnesium, though safe monitoring is difficult.
What other medicines interact with Mirtazapine?
MediHelp also lists interactions of Mirtazapine with, for example, Isocarboxazid, Phenelzine, Pimozide. The full list is on the Mirtazapine page.
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