Drug interactions
Doxazosin + Silodosin
Severity: Major
Doxazosin and Silodosin: major interaction.
Last updated Sources: Health Canada product monograph
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 block alpha-1 adrenergic receptors, so combined use increases the risk of orthostatic hypotension, dizziness and syncope. There is generally no added benefit from combining two alpha-blockers.
What this interaction means in plain words
Doxazosin and Silodosin 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; Silodosin belongs to Genitourinary.
Why it happens
Duplicate alpha-1 adrenergic receptor antagonism with additive vasodilation.
What to do
Avoid combining the two and use a single alpha-blocker. If switching, stop one before starting the other and monitor orthostatic 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 Doxazosin
- Alfuzosin + Doxazosin Major
- Amifostine + Doxazosin Major
- Avanafil + Doxazosin Major
- Doxazosin + Dutasteride-tamsulosin Major
- Doxazosin + Phentolamine Major
- Doxazosin + Prazosin Major
Other interactions of Silodosin
- Atazanavir + Silodosin Contraindicated
- Conivaptan + Silodosin Contraindicated
- Darunavir + Silodosin Contraindicated
- Fosamprenavir + Silodosin Contraindicated
- Indinavir + Silodosin Contraindicated
- Itraconazole + Silodosin Contraindicated
Frequently asked questions
Can I take Doxazosin with Silodosin?
MediHelp rates the interaction as major. Doxazosin and Silodosin 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 block alpha-1 adrenergic receptors, so combined use increases the risk of orthostatic hypotension, dizziness and syncope. There is generally no added benefit from combining two alpha-blockers.
How serious is the interaction between Doxazosin and Silodosin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid combining the two and use a single alpha-blocker. If switching, stop one before starting the other and monitor orthostatic blood pressure.
What other medicines interact with Doxazosin?
MediHelp also lists interactions of Doxazosin with, for example, Alfuzosin, Amifostine, Avanafil. The full list is on the Doxazosin page.
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