Drug interactions
Clozapine + Saquinavir
Severity: Major
Clozapine and Saquinavir: 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 saquinavir (boosted with ritonavir) may also raise clozapine levels via CYP3A4 inhibition. This increases the risk of torsades de pointes, and marrow and seizure risks with clozapine may increase.
What this interaction means in plain words
Clozapine and Saquinavir 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 plus possible CYP3A4 inhibition by ritonavir-boosted saquinavir raising clozapine exposure.
What to do
Avoid if possible. If used, obtain a baseline ECG, correct potassium and magnesium, and monitor QTc and clozapine toxicity.
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
- Clozapine Viatris 100 mg Orodispersible Tablets - SmPC sections 4.3/4.5 (class statement: protease inhibitors; "pharmacokinetic interactions with CYP 3A4 inhibitors such as azole antimycotics, cimetidine, erythromycin and protease inhibitors are unlikely, although some ha") — electronic medicines compendium (UK SmPC)
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Clozapine with Saquinavir?
MediHelp rates the interaction as major. Clozapine and Saquinavir 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 saquinavir (boosted with ritonavir) may also raise clozapine levels via CYP3A4 inhibition. This increases the risk of torsades de pointes, and marrow and seizure risks with clozapine may increase.
How serious is the interaction between Clozapine and Saquinavir?
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 used, obtain a baseline ECG, correct potassium and magnesium, and monitor QTc and clozapine toxicity.
What other medicines interact with Clozapine?
MediHelp also lists interactions of Clozapine with, for example, Deferiprone, Irinotecan, Pimozide. The full list is on the Clozapine page.
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