Drug interactions
Diltiazem + Doxazosin
Severity: Moderate
Diltiazem and Doxazosin: moderate 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 lower blood pressure by different mechanisms, which can cause additive hypotension and dizziness. Diltiazem inhibits CYP3A4 and may modestly raise doxazosin exposure.
What this interaction means in plain words
Diltiazem and Doxazosin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Diltiazem belongs to Cardiovascular; Doxazosin belongs to Genitourinary.
Why it happens
Additive vasodilation plus possible CYP3A4 inhibition by diltiazem.
What to do
Monitor blood pressure and orthostatic symptoms, and titrate doxazosin gradually.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Diltiazem with Doxazosin?
MediHelp rates the interaction as moderate. Diltiazem and Doxazosin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Both lower blood pressure by different mechanisms, which can cause additive hypotension and dizziness. Diltiazem inhibits CYP3A4 and may modestly raise doxazosin exposure.
How serious is the interaction between Diltiazem and Doxazosin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood pressure and orthostatic symptoms, and titrate doxazosin gradually.
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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