Metronidazole Topical and Amprenavir: 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 recordMetronidazole Topical
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
An increased risk of propylene glycol toxicity (seizures, tachycardia, lactic acidosis, renal toxicity, hemolysis)
Interaction Deep Dive
Amprenavir oral solution contains a large amount of propylene glycol in the formulation to achieve adequate solubility of amprenavir. While the acceptable intake of propylene glycol for pharmaceuticals has not been established, certain patient populations may be at risk for propylene glycol accumulation and toxicity, including seizures, stupor, tachycardia, hyperosmolality, lactic acidosis, renal toxicity, and hemolysis. Propylene glycol is metabolized by the alcohol and aldehyde dehydrogenase enzyme pathway, and patients being treated concurrently with metronidazole may not be able to adequately metabolize and eliminate propylene glycol. Therefore, the coadministration of amprenavir oral solution and metronidazole is contraindicated. Patients should receive amprenavir oral solution only when amprenavir capsules or other protease inhibitor formulations are not therapeutic options1.
Why it happens (mechanism)
Saturation of the alcohol and aldehyde dehydrogenase enzyme pathway
Common questions
Can I take Metronidazole Topical and Amprenavir together?
An increased risk of propylene glycol toxicity (seizures, tachycardia, lactic acidosis, renal toxicity, hemolysis) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Metronidazole Topical and Amprenavir interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Metronidazole Topical or Amprenavir 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 a safer alternative to one of these medications for me?
References (1)
- Product Information: Agenerase(R), amprenavir. Glaxo Wellcome Inc. Research Triangle Park, NC, 2000.
Keep reading about Amprenavir
Keep reading about Metronidazole Topical
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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