Drug interactions
Doxazosin + Sildenafil
Severity: Major
Doxazosin and Sildenafil: major 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
Both agents lower blood pressure, and combining them can produce symptomatic orthostatic hypotension, dizziness or fainting. The effect is more pronounced with higher sildenafil doses and shortly after dosing.
What this interaction means in plain words
Doxazosin and Sildenafil 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.
Doxazosin belongs to Genitourinary; Sildenafil belongs to Genitourinary.
Why it happens
Additive vasodilation from PDE5 inhibition and alpha-1 adrenergic blockade.
What to do
Ensure the patient is stable on doxazosin before starting sildenafil at 25 mg, and avoid doses above 25 mg within 4 hours of the alpha-blocker. Counsel on orthostatic symptoms.
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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Other interactions of Sildenafil
- Amyl nitrite + Sildenafil Contraindicated
- Atazanavir + Sildenafil Contraindicated
- Cobicistat + Sildenafil Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Sildenafil Contraindicated
- Glyceryl trinitrate pr + Sildenafil Contraindicated
- Isosorbide dinitrate + Sildenafil Contraindicated
Other interactions of Doxazosin
- Alfuzosin + Doxazosin Major
- Amifostine + Doxazosin Major
- Avanafil + Doxazosin Major
- Doxazosin + Dutasteride-tamsulosin Major
- Doxazosin + Phentolamine Major
- Doxazosin + Prazosin Major
Frequently asked questions
Can I take Doxazosin with Sildenafil?
MediHelp rates the interaction as major. Doxazosin and Sildenafil 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. Both agents lower blood pressure, and combining them can produce symptomatic orthostatic hypotension, dizziness or fainting. The effect is more pronounced with higher sildenafil doses and shortly after dosing.
How serious is the interaction between Doxazosin and Sildenafil?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Ensure the patient is stable on doxazosin before starting sildenafil at 25 mg, and avoid doses above 25 mg within 4 hours of the alpha-blocker. Counsel on orthostatic symptoms.
What other medicines interact with Sildenafil?
MediHelp also lists interactions of Sildenafil with, for example, Amyl nitrite, Atazanavir, Cobicistat. The full list is on the Sildenafil page.
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