Amprenavir and Nizatidine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amprenavir
No brand names on recordNizatidine
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Decreased amprenavir serum concentrations (active metabolite of fosamprenavir) and potential reduction of amprenavir efficacy
Interaction Deep Dive
Fosamprenavir is a prodrug of amprenavir (active metabolite). The concurrent administration of ranitidine, an H2-antagonist, with fosamprenavir induced substantial reductions in amprenavir serum concentrations. Fosamprenavir 1400 milligrams (mg) and ranitidine 300 mg were each coadministered as a single dose to healthy subjects (n=30). Amprenavir maximum serum concentration (Cmax) and area under the concentration-time curve (AUC) were reduced by mean of 51% and 30%, respectively. Similarly, concomitant administration of fosamprenavir and nizatidine, an H2 antagonist, may result in decreased amprenavir serum concentrations and a potential loss of amprenavir efficacy. Caution is advised when these two agents are coadministered. Fosamprenavir dose may need to be adjusted. Proton pump inhibitors may be considered as an alternative to nizatidine1.
Why it happens (mechanism)
Unknown
Common questions
Can I take Amprenavir and Nizatidine together?
Decreased amprenavir serum concentrations (active metabolite of fosamprenavir) and potential reduction of amprenavir efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amprenavir and Nizatidine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Amprenavir or Nizatidine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Product Information: LEXIVA(R) oral tablets, fosamprenavir calcium oral tablets. GlaxoSmithKline, Research Triangle Park, NC, 2005. DailyMed
Keep reading about Amprenavir
Keep reading about Nizatidine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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