Drug interactions
Epinephrine + Phentolamine
Severity: Major
Epinephrine and Phentolamine: major 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
Phentolamine blocks alpha-adrenergic receptors, so the beta-mediated effects of epinephrine are unopposed. This can cause marked hypotension from vasodilation and reflex tachycardia.
What this interaction means in plain words
Epinephrine and Phentolamine 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.
Epinephrine belongs to Endocrine; Phentolamine belongs to Cardiovascular.
Why it happens
Alpha-adrenergic blockade by phentolamine leaves epinephrine's beta-2 vasodilation unopposed, causing 'epinephrine reversal'.
What to do
Avoid epinephrine as a pressor in patients who have received phentolamine; use a pure vasoconstrictor such as phenylephrine or norepinephrine if needed. Monitor blood pressure and heart rate continuously.
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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Other interactions of Phentolamine
Other interactions of Epinephrine
- Epinephrine + Isocarboxazid Contraindicated
- Epinephrine + Phenelzine Contraindicated
- Epinephrine + Tranylcypromine Contraindicated
- Acebutolol + Epinephrine Major
- Amitriptyline + Epinephrine Major
- Amoxapine + Epinephrine Major
Frequently asked questions
Can I take Epinephrine with Phentolamine?
MediHelp rates the interaction as major. Epinephrine and Phentolamine 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. Phentolamine blocks alpha-adrenergic receptors, so the beta-mediated effects of epinephrine are unopposed. This can cause marked hypotension from vasodilation and reflex tachycardia.
How serious is the interaction between Epinephrine and Phentolamine?
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 epinephrine as a pressor in patients who have received phentolamine; use a pure vasoconstrictor such as phenylephrine or norepinephrine if needed. Monitor blood pressure and heart rate continuously.
What other medicines interact with Phentolamine?
MediHelp also lists interactions of Phentolamine with, for example, Alfuzosin, Avanafil, Doxazosin. The full list is on the Phentolamine page.
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