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Phentolamine
๐ About
Always check the BNF link here for the most up-to-date prescribing advice. Phentolamine mesilate is a short-acting, non-selective alpha-adrenergic antagonist used in the management of phaeochromocytoma and hypertensive crises.
โ๏ธ Mode of Action
- ๐ Competitive, non-selective blockade of ฮฑโ and ฮฑโ adrenergic receptors.
- โฌ๏ธ Causes vasodilation โ reduces blood pressure and counteracts catecholamine-induced vasoconstriction.
- ๐งช May cause reflex tachycardia due to unopposed sympathetic stimulation of the heart.
๐ Indications / Dose
- Phaeochromocytoma surgery ๐ฉธ: 2โ5 mg IV bolus, repeated if necessary.
- Hypertensive emergencies (catecholamine-related): IV bolus or infusion as per specialist guidance.
- Prevention/treatment of dermal necrosis ๐: Sometimes used locally after extravasation of noradrenaline/dopamine.
๐ Interactions
- ๐ See BNF for full list.
- โ ๏ธ Can enhance hypotensive effect of other vasodilators or antihypertensives.
- May interact with sympathomimetic agents (e.g., adrenaline, noradrenaline).
โ ๏ธ Cautions
- โฌ๏ธ Risk of severe hypotension and syncope.
- ๐๏ธ Floppy iris syndrome reported in cataract surgery (similar to other ฮฑ-blockers).
- ๐ Use with caution in patients with coronary artery disease โ may precipitate angina or arrhythmias.
โ Contraindications
- ๐ซ See BNF for full details.
- Known hypersensitivity to phentolamine or excipients.
๐ฌ Side Effects
- โฌ๏ธ Hypotension (including postural).
- โค๏ธ Angina, arrhythmias, palpitations, chest pain.
- ๐ค Headache, dizziness, malaise.
- ๐ฉ GI: Diarrhoea, abdominal pain.
๐ References
- British National Formulary (BNF): Phentolamine
- Endocrine Society Guidelines โ Phaeochromocytoma and Paraganglioma (2020).
๐ Revisions
- Updated September 2025
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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