Drug interactions
Diltiazem + Phenoxybenzamine
Severity: Moderate
Diltiazem 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 that causes marked vasodilation and orthostatic hypotension. Adding diltiazem can intensify hypotension and may produce reflex tachycardia or conduction effects.
What this interaction means in plain words
Diltiazem 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 pharmacodynamic hypotensive effects from alpha-adrenergic blockade and calcium channel blockade.
What to do
Monitor supine and standing blood pressure and heart rate when starting or changing doses, and titrate 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 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 Phenoxybenzamine?
MediHelp rates the interaction as moderate. Diltiazem 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 that causes marked vasodilation and orthostatic hypotension. Adding diltiazem can intensify hypotension and may produce reflex tachycardia or conduction effects.
How serious is the interaction between Diltiazem 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: Monitor supine and standing blood pressure and heart rate when starting or changing doses, and titrate gradually.
What other medicines interact with Diltiazem?
MediHelp also lists interactions of Diltiazem with, for example, Flibanserin, Ivabradine, Lomitapide. The full list is on the Diltiazem page.
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