Drug interactions
Fosamprenavir + Quetiapine
Severity: Major
Fosamprenavir and Quetiapine: major 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
Fosamprenavir (as amprenavir, boosted or not) inhibits CYP3A4, the main route of quetiapine metabolism, so quetiapine exposure can rise. This may cause excess sedation, orthostatic hypotension and QT prolongation.
What this interaction means in plain words
Fosamprenavir and Quetiapine 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
Inhibition of CYP3A4-mediated quetiapine metabolism by amprenavir, especially when ritonavir-boosted.
What to do
Reduce the quetiapine dose (labeling advises about one sixth of the usual dose with strong CYP3A4 inhibitors) and monitor for sedation, hypotension and QTc. Increase the dose again after the inhibitor is stopped.
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 Quetiapine
- Adagrasib + Quetiapine Major
- Amiodarone + Quetiapine Major
- Amisulpride + Quetiapine Major
- Amoxapine + Quetiapine Major
- Anagrelide + Quetiapine Major
- Apalutamide + Quetiapine Major
Frequently asked questions
Can I take Fosamprenavir with Quetiapine?
MediHelp rates the interaction as major. Fosamprenavir and Quetiapine 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. Fosamprenavir (as amprenavir, boosted or not) inhibits CYP3A4, the main route of quetiapine metabolism, so quetiapine exposure can rise. This may cause excess sedation, orthostatic hypotension and QT prolongation.
How serious is the interaction between Fosamprenavir and Quetiapine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Reduce the quetiapine dose (labeling advises about one sixth of the usual dose with strong CYP3A4 inhibitors) and monitor for sedation, hypotension and QTc. Increase the dose again after the inhibitor is stopped.
What other medicines interact with Quetiapine?
MediHelp also lists interactions of Quetiapine with, for example, Adagrasib, Amiodarone, Amisulpride. The full list is on the Quetiapine page.
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