Drug interactions
Doxazosin + Phenylephrine
Severity: Moderate
Doxazosin and Phenylephrine: 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
Doxazosin blocks alpha-1 receptors and can reduce the pressor and decongestant effects of phenylephrine. In hypotensive patients, the expected blood pressure response may be diminished.
What this interaction means in plain words
Doxazosin and Phenylephrine 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.
Doxazosin belongs to Genitourinary; Phenylephrine belongs to Respiratory.
Why it happens
Pharmacodynamic antagonism at alpha-1 adrenergic receptors.
What to do
Monitor blood pressure and titrate phenylephrine to effect, using higher doses if needed under supervision. Avoid oral phenylephrine decongestants in patients relying on alpha-blockers for blood pressure control.
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 Phenylephrine
- Isocarboxazid + Phenylephrine Contraindicated
- Phenelzine + Phenylephrine Contraindicated
- Phenylephrine + Tranylcypromine Contraindicated
- Bromocriptine + Phenylephrine Major
- Cocaine + Phenylephrine Major
- Dihydroergotamine intranasal + Phenylephrine Major
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 Phenylephrine?
MediHelp rates the interaction as moderate. Doxazosin and Phenylephrine 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. Doxazosin blocks alpha-1 receptors and can reduce the pressor and decongestant effects of phenylephrine. In hypotensive patients, the expected blood pressure response may be diminished.
How serious is the interaction between Doxazosin and Phenylephrine?
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 titrate phenylephrine to effect, using higher doses if needed under supervision. Avoid oral phenylephrine decongestants in patients relying on alpha-blockers for blood pressure control.
What other medicines interact with Phenylephrine?
MediHelp also lists interactions of Phenylephrine with, for example, Isocarboxazid, Phenelzine, Tranylcypromine. The full list is on the Phenylephrine page.
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