Drug interactions
Doxazosin + Tadalafil
Severity: Major
Doxazosin and Tadalafil: major interaction.
Last updated Sources: US FDA label
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 drugs cause vasodilation, and together they can cause symptomatic hypotension, dizziness or syncope. Labeling advises caution, and tadalafil 20 mg is not recommended with doxazosin.
What this interaction means in plain words
Doxazosin and Tadalafil 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; Tadalafil belongs to Genitourinary.
Why it happens
Additive vasodilation from alpha-1 blockade and PDE5 inhibition.
What to do
Ensure the patient is stable on the alpha-blocker before starting tadalafil at the lowest dose. Advise rising slowly and monitor blood pressure.
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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References
Other interactions of Tadalafil
- Amyl nitrite + Tadalafil Contraindicated
- Isosorbide dinitrate + Tadalafil Contraindicated
- Isosorbide mononitrate + Tadalafil Contraindicated
- Nitroglycerin po + Tadalafil Contraindicated
- Nitroglycerin rectal + Tadalafil Contraindicated
- Nitroglycerin sublingual + Tadalafil 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 Tadalafil?
MediHelp rates the interaction as major. Doxazosin and Tadalafil 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 drugs cause vasodilation, and together they can cause symptomatic hypotension, dizziness or syncope. Labeling advises caution, and tadalafil 20 mg is not recommended with doxazosin.
How serious is the interaction between Doxazosin and Tadalafil?
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 the alpha-blocker before starting tadalafil at the lowest dose. Advise rising slowly and monitor blood pressure.
What other medicines interact with Tadalafil?
MediHelp also lists interactions of Tadalafil with, for example, Amyl nitrite, Isosorbide dinitrate, Isosorbide mononitrate. The full list is on the Tadalafil page.
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