Doxazosin and Avanafil: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Avanafil
Doxazosin
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
Increased risk of hypotension
Interaction Deep Dive
Concomitant use of avanafil and doxazosin may increase the risk of symptomatic hypotension due to additive vasodilation. Standing and supine blood pressures were decreased when avanafil was coadministered with doxazosin in a study of healthy subjects. When concomitant use is necessary, initiate avanafil at a dose of 50 mg, and initiate it only in patients stable on doxazosin therapy. When initiating doxazosin in patients already receiving avanafil, begin doxazosin at the lowest dose1.
Why it happens (mechanism)
Additive vasodilation
Literature reports
1 report — tap to read
a) Coadministration of avanafil with doxazosin was associated with a mean maximum decrease in supine and standing blood pressure of -6 mmHg (95% CI, -9.1 mmHg to -2.9 mmHg) and -2.5 mmHg (95% CI, -6.5 mmHg to 1.5 mmHg), respectively, compared with doxazosin plus placebo in a randomized, double-blind, crossover trial (n=24). Healthy subjects received doxazosin 1 mg for 1 day, 2 mg for 2 days, 4 mg for 4 days, and 8 mg for 11 days; avanafil 200 mg or placebo was administered on days 15 and 18, 1.3 hours after the doxazosin dose, so that both drugs would reach peak plasma levels at the same time 1.
Common questions
Can I take Doxazosin and Avanafil together?
Increased risk of hypotension Always confirm with your pharmacist or prescriber before making any change.
How serious is the Doxazosin and Avanafil interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Doxazosin or Avanafil 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: STENDRA(R) oral tablets, avanafil oral tablets. Metuchen Pharmaceuticals LLC (per FDA), Freehold, NJ, 2022. DailyMed
Keep reading about Avanafil
Keep reading about Doxazosin
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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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