II. Indications
III. Dosing: Adults
-
Hypertensive Crisis in Pheochromocytoma
- Give 5 mg IV/IM for one dose
- Results in profound Blood Pressure drop (e.g. 60/25 mmHg decrease in BP)
-
Vasopressor Extravasation (e.g. Norepinephrine) - Not FDA approved
- Prepare 5-10 mg in 10 ml Normal Saline
- Inject 1 ml SC around extravasation site within 12 hours of extravasation
- In adults may repeat dose up to a total of 5 ml injected around extravasation site
IV. Dosing: Children
-
Hypertensive Crisis in Pheochromocytoma
- Give 0.05 to 0.1 mg/kg (up to 5 mg) IV/IM for one dose
- Results in profound Blood Pressure drop (e.g. 60/25 mmHg decrease in BP)
-
Vasopressor Extravasation (e.g. Norepinephrine) - Not FDA approved
- Prepare 5 mg in 10 ml Normal Saline
- Inject 1 ml SC around extravasation site within 12 hours of extravasation
V. Mechanism
- Synthetic imidazoline acts as a competitive Alpha Adrenergic Antagonist at alpha-1 and alpha-2 receptors resulting in vasodilation
- May block 5-HT receptors
- May stimulate Histamine release from Mast Cells
VI. Adverse Effects
- Hypotension
- Generalized Weakness
VII. Safety
- Pregnancy Category C
- Unknown Safety in Lactation
VIII. Resources
- Phentolamine (DailyMed)