Drug interactions
Mirtazapine + Posaconazole
Severity: Major
Mirtazapine and Posaconazole: major interaction.
Last updated Sources: UK SmPC
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, and posaconazole may also raise mirtazapine levels through CYP3A4 inhibition. Together they could increase the risk of torsades de pointes, particularly with other risk factors.
What this interaction means in plain words
Mirtazapine and Posaconazole 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.
Mirtazapine belongs to Central Nervous System; Posaconazole belongs to Anti Fungals.
Why it happens
Additive QT prolongation, with CYP3A4 inhibition possibly increasing mirtazapine exposure.
What to do
Avoid if possible; if both are required, obtain baseline and follow-up ECGs, correct potassium and magnesium, and consider a lower mirtazapine 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
- Noxafil 100 mg Gastro-resistant Tablets - SmPC sections 4.3/4.5 (class statement: CYP3A4 substrates; "Posaconazole is a potent inhibitor of CYP3A4. Co-administration of posaconazole with CYP3A4 substrates may result in large increases in exposure to CYP3A4 subst") — electronic medicines compendium (UK SmPC)
Other interactions of Posaconazole
- Artemether + Posaconazole Contraindicated
- Avanafil + Posaconazole Contraindicated
- Cobimetinib + Posaconazole Contraindicated
- Conivaptan + Posaconazole Contraindicated
- Dihydroergotamine intranasal + Posaconazole Contraindicated
- Dihydroergotamine + Posaconazole Contraindicated
Other interactions of Mirtazapine
- Isocarboxazid + Mirtazapine Contraindicated
- Mirtazapine + Phenelzine Contraindicated
- Mirtazapine + Pimozide Contraindicated
- Mirtazapine + Procarbazine Contraindicated
- Mirtazapine + Rasagiline Contraindicated
- Mirtazapine + Selegiline Contraindicated
Frequently asked questions
Can I take Mirtazapine with Posaconazole?
MediHelp rates the interaction as major. Mirtazapine and Posaconazole 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, and posaconazole may also raise mirtazapine levels through CYP3A4 inhibition. Together they could increase the risk of torsades de pointes, particularly with other risk factors.
How serious is the interaction between Mirtazapine and Posaconazole?
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; if both are required, obtain baseline and follow-up ECGs, correct potassium and magnesium, and consider a lower mirtazapine dose.
What other medicines interact with Posaconazole?
MediHelp also lists interactions of Posaconazole with, for example, Artemether, Avanafil, Cobimetinib. The full list is on the Posaconazole page.
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