Drug interactions
Phentolamine + Phenylephrine
Severity: Moderate
Phentolamine 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
Phentolamine is a nonselective alpha-blocker that directly opposes phenylephrine's vasoconstriction. It is used clinically to reverse phenylephrine-induced effects, for example mydriasis or extravasation.
What this interaction means in plain words
Phentolamine 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.
Phentolamine belongs to Cardiovascular; Phenylephrine belongs to Respiratory.
Why it happens
Competitive antagonism at alpha-adrenergic receptors.
What to do
Avoid combining unless reversal is intended. If both are given, monitor blood pressure and heart rate because of possible hypotension and reflex tachycardia.
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 Phentolamine
Frequently asked questions
Can I take Phentolamine with Phenylephrine?
MediHelp rates the interaction as moderate. Phentolamine 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. Phentolamine is a nonselective alpha-blocker that directly opposes phenylephrine's vasoconstriction. It is used clinically to reverse phenylephrine-induced effects, for example mydriasis or extravasation.
How serious is the interaction between Phentolamine 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: Avoid combining unless reversal is intended. If both are given, monitor blood pressure and heart rate because of possible hypotension and reflex tachycardia.
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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