Drug interactions
Diltiazem + Fosamprenavir
Severity: Major
Diltiazem and Fosamprenavir: 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
Amprenavir, the active form of fosamprenavir, inhibits CYP3A4 and can raise diltiazem levels, increasing the risk of bradycardia, AV nodal block and hypotension. Diltiazem may also modestly raise amprenavir exposure.
What this interaction means in plain words
Diltiazem and Fosamprenavir 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
Bidirectional CYP3A4 inhibition, with amprenavir reducing diltiazem metabolism.
What to do
Monitor ECG, heart rate and blood pressure when combining, and reduce the diltiazem dose as needed. Consider an alternative antihypertensive if conduction abnormalities occur.
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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Diltiazem with Fosamprenavir?
MediHelp rates the interaction as major. Diltiazem and Fosamprenavir 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. Amprenavir, the active form of fosamprenavir, inhibits CYP3A4 and can raise diltiazem levels, increasing the risk of bradycardia, AV nodal block and hypotension. Diltiazem may also modestly raise amprenavir exposure.
How serious is the interaction between Diltiazem and Fosamprenavir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG, heart rate and blood pressure when combining, and reduce the diltiazem dose as needed. Consider an alternative antihypertensive if conduction abnormalities occur.
What other medicines interact with Diltiazem?
MediHelp also lists interactions of Diltiazem with, for example, Flibanserin, Ivabradine, Lomitapide. The full list is on the Diltiazem page.
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