Drug interactions
Captopril-hydrochlorothiazide + Phenoxybenzamine
Severity: Moderate
Captopril-hydrochlorothiazide and Phenoxybenzamine: 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
Phenoxybenzamine is an irreversible alpha-blocker and, combined with captopril and hydrochlorothiazide, can cause marked hypotension, particularly after the first dose or dose increases. Orthostatic hypotension and syncope may occur.
What this interaction means in plain words
Captopril-hydrochlorothiazide and Phenoxybenzamine 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.
Why it happens
Additive vasodilation from alpha-adrenergic blockade, ACE inhibition and diuretic-induced volume reduction.
What to do
Start phenoxybenzamine at a low dose and monitor blood pressure, including standing readings. Consider lowering the diuretic or ACE inhibitor dose if hypotension develops.
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 Captopril-hydrochlorothiazide
- Aliskiren + Captopril-hydrochlorothiazide Contraindicated
- Captopril-hydrochlorothiazide + Dofetilide Contraindicated
- Captopril-hydrochlorothiazide + Sacubitril / valsartan Contraindicated
- Aceclofenac + Captopril-hydrochlorothiazide Major
- Aldesleukin + Captopril-hydrochlorothiazide Major
- Amifostine + Captopril-hydrochlorothiazide Major
Frequently asked questions
Can I take Captopril-hydrochlorothiazide with Phenoxybenzamine?
MediHelp rates the interaction as moderate. Captopril-hydrochlorothiazide and Phenoxybenzamine 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. Phenoxybenzamine is an irreversible alpha-blocker and, combined with captopril and hydrochlorothiazide, can cause marked hypotension, particularly after the first dose or dose increases. Orthostatic hypotension and syncope may occur.
How serious is the interaction between Captopril-hydrochlorothiazide and Phenoxybenzamine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Start phenoxybenzamine at a low dose and monitor blood pressure, including standing readings. Consider lowering the diuretic or ACE inhibitor dose if hypotension develops.
What other medicines interact with Captopril-hydrochlorothiazide?
MediHelp also lists interactions of Captopril-hydrochlorothiazide with, for example, Aliskiren, Dofetilide, Sacubitril / valsartan. The full list is on the Captopril-hydrochlorothiazide page.
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