Phentolamine mesilate: clinical use

Prescribing considerations

• Reserve the diagnostic test for situations where more specific investigations cannot be used or are inconclusive.
• Use caution with renal impairment because pharmacokinetic studies are unavailable.
• Use caution in gastritis or peptic ulcer disease because gastrointestinal activity and acid secretion may increase.
• Account for sodium metabisulphite, which can rarely cause severe hypersensitivity and bronchospasm.

Contraindications and cautions

• Hypersensitivity to phentolamine, related compounds or sulphites
• Hypotension
• Current or previous myocardial infarction
• Coronary insufficiency, angina or other evidence of coronary artery disease

Monitoring

• Monitor blood pressure closely for excessive or prolonged hypotension.
• Monitor heart rate and rhythm for tachycardia or arrhythmia.
• Remain alert for myocardial or cerebral ischaemic complications, particularly during severe hypotension.

Clinical pharmacology

A competitive, non-selective alpha-1 and alpha-2 antagonist with a relatively short duration of action. Vasodilation lowers systemic vascular resistance, while baroreceptor activation and presynaptic alpha-2 blockade can contribute to tachycardia.

Formulation and product differences

• The selected product is a ready-to-use, sterile, clear solution in single-use ampoules for intravenous or intramuscular injection.
• It contains sodium metabisulphite, is incompatible with alkaline solutions and requires refrigerated, light-protected storage without freezing.

Injection

Route: Parenteral

Strengths: 10 mg/mL