Phentolamine mesilate at a glance
Medicine class
Competitive, non-selective alpha-adrenergic receptor blocker
Main role
Controls sudden hypertension caused by phaeochromocytoma before or during surgery
Administration
Given by intravenous or intramuscular injection by healthcare professionals
Key monitoring
Blood pressure and heart rate require close observation
What is Phentolamine mesilate used for?
The selected UK product is licensed for:
Reversal of sudden hypertension caused by phaeochromocytoma before and during surgical treatment.
A diagnostic test for phaeochromocytoma when more specific tests cannot be used or have not provided sufficient results. This is not generally the first choice.
How does Phentolamine mesilate work?
It competitively blocks alpha-1 and alpha-2 adrenergic receptors. This reduces catecholamine-driven narrowing of blood vessels, lowering vascular resistance and blood pressure. Reflex responses and increased noradrenaline release can also raise heart rate.
Phentolamine mesilate preparations and strengths
Injection
Route: Parenteral
Strengths: 10 mg/mL
How to take Phentolamine mesilate
This hospital injection is given into a vein or muscle by a doctor or nurse. Blood pressure is monitored closely, particularly during surgery or diagnostic testing. It is not intended for self-administration.
Phentolamine mesilate side effects
Common or expected effects
- Fast heart rate
- A fall in blood pressure when sitting or standing
- Dizziness
- Flushing
- Blocked nose
- Nausea, vomiting or diarrhoea
- Weakness
Get urgent medical advice
- Severe or prolonged low blood pressure, potentially associated with heart attack or disrupted blood flow to the brain
- Chest pain or angina
- Abnormal heart rhythm
- Rare severe hypersensitivity or bronchospasm caused by sodium metabisulphite
Phentolamine mesilate in pregnancy
Human pregnancy data are very limited, and animal studies found reproductive toxicity. The product is not recommended during pregnancy; a specialist should assess the individual clinical need and available alternatives.
Phentolamine mesilate while breastfeeding
It is unknown whether phentolamine enters human milk. The product information advises stopping breastfeeding during treatment; discuss timing and alternatives with the specialist team.
Phentolamine mesilate interactions
Tell the clinical team about all medicines being used, particularly those affecting blood pressure or adrenergic receptors.
Other antihypertensive medicines
Phentolamine can increase their blood-pressure-lowering effect and the risk of hypotension.
Antipsychotics
These may strengthen the hypotensive effect of alpha blockers.
Non-selective beta agonists, including adrenaline and isoprenaline
Alpha blockade may leave beta-receptor effects unopposed and cause an additional fall in blood pressure.
Common questions about Phentolamine mesilate
Answers are fully visible for fast scanning and source review.
Why is Phentolamine mesilate used during phaeochromocytoma surgery?
Handling the tumour can release catecholamines and cause sudden severe hypertension. Phentolamine blocks alpha receptors to reduce catecholamine-driven blood-vessel constriction.
Is it a first-choice test for phaeochromocytoma?
Usually not. Its licensed diagnostic role is limited to situations where more specific tests cannot be used or have not produced sufficient results.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.