Drug interactions
Fosamprenavir + Theophylline
Severity: Moderate
Fosamprenavir and Theophylline: moderate interaction.
Last updated
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 metabolite of fosamprenavir, inhibits CYP3A4 and may raise theophylline levels modestly. Ritonavir boosting adds a complex effect that may include CYP1A2 induction.
What this interaction means in plain words
Fosamprenavir and Theophylline can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
CYP3A4 inhibition by amprenavir, with possible CYP1A2 induction by ritonavir, changes theophylline clearance.
What to do
Monitor theophylline concentrations when fosamprenavir is started or stopped and adjust the dose.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Theophylline
- Riociguat + Theophylline Contraindicated
- Adenosine + Theophylline Major
- Apalutamide + Theophylline Major
- Bupropion + Theophylline Major
- Carvedilol + Theophylline Major
- Cimetidine + Theophylline Major
Frequently asked questions
Can I take Fosamprenavir with Theophylline?
MediHelp rates the interaction as moderate. Fosamprenavir and Theophylline can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Amprenavir, the active metabolite of fosamprenavir, inhibits CYP3A4 and may raise theophylline levels modestly. Ritonavir boosting adds a complex effect that may include CYP1A2 induction.
How serious is the interaction between Fosamprenavir and Theophylline?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor theophylline concentrations when fosamprenavir is started or stopped and adjust the dose.
What other medicines interact with Theophylline?
MediHelp also lists interactions of Theophylline with, for example, Riociguat, Adenosine, Apalutamide. The full list is on the Theophylline page.
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