Phentolamine Mesylate (4 brand names, 2 dosage forms, 2 routes)
Available dosage forms: SOLUTION, INJECTABLE.
Routes of administration: OPHTHALMIC, INJECTION.
Brand Names
- ORAVERSE
- PHENTOLAMINE MESYLATE
- REGITINE
- RYZUMVI
Indications and Usage
RYZUMVI is indicated for the treatment of pharmacologically-induced mydriasis produced by adrenergic agonists (e.g., phenylephrine) or parasympatholytic agents (e.g., tropicamide).
Dosage and Administration
Adults and Pediatric Patients Aged 12 Years or Older: Instill 1 or 2 drops in each dilated eye following the completion of the ophthalmic examination or procedure. If 2 drops are instilled, the second drop should be administered 5 minutes after the first drop. Pediatric Patients Aged 3 to 11 Years: Instill 1 drop in each dilated eye following the completion of the ophthalmic examination or procedure. One single-patient-use vial can be used to dose each dilated eye. Discard the single-patient-use vial immediately after use.
Contraindications
None.
Mechanism of Action
RYZUMVI is a relatively non-selective alpha-1 and alpha-2 adrenergic antagonist. Dilation of the pupil is primarily controlled by the radial iris dilator muscles surrounding the pupil; these muscles are activated by the alpha-1 adrenergic receptors. Phentolamine reversibly binds to these receptors on the iris dilator muscle, thereby reducing pupil diameter. Phentolamine directly antagonizes the mydriatic effect of an α-1 adrenergic agonist, and indirectly reverses mydriasis induced by muscarinic antagonist effects on the iris sphincter muscle.
Overdosage
No deaths due to acute poisoning with phentolamine have been reported. Overdosage with parenterally administered phentolamine is characterized chiefly by cardiovascular disturbances, such as arrhythmias, tachycardia, hypotension, and possibly shock. In addition, the following might occur: excitation, headache, sweating, visual disturbances, nausea, vomiting, diarrhea, or hypoglycemia. There is no specific antidote; treatment consists of appropriate monitoring and supportive care. Substantial decreases in blood pressure or other evidence of shock-like conditions should be treated vigorously and promptly.