||alpha antagonist; vasodilator
- alpha blockade in pheochromocytoma (used with a beta blocker)
- antidote for extravasation of alpha stimulants
- antihypertensive agent
- afterload reduction
- useful to treat hypertension in MAO-I overdose
- Bolus dose:
- 0.1mg - 2mg/min (start at lowest dose and titrate to blood pressure). Doses up to 2 mg/min have been used for severe hypertension.
- Antidote for vasoconstrictor extravasation:
- 5-15mg in 10 mL NS infiltrated into the area of extravasation as soon as possible; may be effective up to 12 hours post extravasation of vasoconstrictor
- administer initial dose into interstitial catheter prior to removal to direct phentolamine into area of infiltration
- anticipate need for increased sympathomimetic therapy and/or volume therapy
300mg/500mLdextrose 5%, normal saline 0.9% or Ringer's Lactate
- should be weaned off
- treat hypovolemia concurrently with initiation of drug therapy
- For pheochromocytoma blockade - initiate phentolamine prior to commencing beta blockade; beta blockade may increase peripheral vasoconstriction and worsen hypertension
- increased gastric acid secretion
- tachyphylaxis may occur
- phentolamine + alpha adrenergic agents = decreased alpha effects
- IV site
- blood pressure
- continuous heart rate and ECG rhythm
- urine output
|Adult Critical Care Protocol:
- May be administered IV direct or by IV infusion by a nurse in Adult Critical Care.
- May be titrated by a nurse in Adult Critical Care.
- Administration by central venous access device is preferred.
- Patient requires placement of an arterial line to monitor BP.
- Continuous infusions must be administered by infusion device and the pump library must be enabled.
- Should not be infused via the proximal injectate port (blue) of a pulmonary artery catheter. If this is the only available central venous line, it may be administered through the proximal injectate port but thermodilution cardiac output measurements must not be measured during infusion).