Phentolamine Dosage

Usual Adult Dose for Pheochromocytoma

Initial dose: 5 mg injected IV or intramuscularly 1 to 2 hours before surgery and repeated if necessary.
During surgery: 5 mg injected IV as indicated.

Usual Adult Dose for Dermal Necrosis - Treatment

For Prevention: 10 mg/L of solution containing norepinephrine.
For Treatment: 5-10 mg in 10 mL of saline injected into the area of extravasation within 12 hours.

Usual Adult Dose for Pheochromocytoma Diagnosis

IV: 5 mg is dissolved in 1 mL of Sterile Water for Injection. The dose for adults is 5 mg.
Intramuscularly: Preparation is the same as for the IV test. The dose for adults is 5 mg intramuscularly. Blood pressure is recorded every 5 minutes for 30 to 45 minutes following injection.

Usual Adult Dose for Reversal of Anesthesia

Recommended dose: based on the number of cartridges of local anesthetic with vasoconstrictor administered.

1/2 cartridge of local anesthetic administered: dose of phentolamine = 0.2 mg = 1/2 cartridge of phentolamine

1 cartridge of local anesthetic administered: dose of phentolamine = 0.4 mg = 1 cartridge of phentolamine

2 cartridge of local anesthetic administered: dose of phentolamine = 0.8 mg = 2 cartridge of phentolamine

Phentolamine should be administered following the dental procedure using the same location(s) and technique(s) (infiltration or block injection) employed for the administration of the local anesthetic.

Usual Pediatric Dose for Pheochromocytoma Diagnosis

IM or IV: 0.05 to 0.1 mg/kg/dose
Maximum single dose: 5 mg

Usual Pediatric Dose for Pheochromocytoma

Surgery for pheochromocytoma: Hypertension:
IM or IV: 0.05 to 0.1 mg/kg/dose given 1 to 2 hours before procedure; repeat as needed every 2 to 4 hours until hypertension is controlled
Maximum single dose: 5 mg

Usual Pediatric Dose for Reversal of Anesthesia

Use in pediatric patients under 6 years of age or weighing less than 15 kg (33 lbs) is not recommended.

In pediatric patients weighing 15 to 30 kg, the maximum dose of phentolamine recommended is 1/2 cartridge (0.2 mg).

A dose of more than 1 cartridge (0.4 mg) of phentolamine has not been studied in children less than 12 years of age.

Recommended dose: based on the number of cartridges of local anesthetic with vasoconstrictor administered.

1/2 cartridge of local anesthetic administered: dose of phentolamine = 0.2 mg = 1/2 cartridge of phentolamine

1 cartridge of local anesthetic administered: dose of phentolamine = 0.4 mg = 1 cartridge of phentolamine

Phentolamine should be administered following the dental procedure using the same location(s) and technique(s) (infiltration or block injection) employed for the administration of the local anesthetic.

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dialysis

Data not available

Other Comments

The test for pheochromocytoma diagnosis is most reliable in detecting pheochromocytoma in patients with sustained hypertension and least reliable in those with paroxysmal hypertension. False-positive tests may occur in patients with hypertension without pheochromocytoma.
Sedatives, analgesics, and all other medications except those that might be deemed essential (such as digitalis and insulin) are withheld for at least 24 hours, preferably 48-72 hours, prior to the test. Antihypertensive drugs are withheld until blood pressure returns to the untreated, hypertensive level. This test is not performed on a patient who is normotensive.
The patient is kept at rest in the supine position throughout the test, preferably in a quiet, darkened room. Injection of phentolamine is delayed until blood pressure is stabilized, as evidenced by blood pressure readings taken every 10 minutes for at least 30 minutes.
For the IV procedure, the syringe needle is inserted into the vein, and injection is delayed until pressor response to venipuncture has subsided. Phentolamine is injected rapidly. Blood pressure is recorded immediately after injection, at 30-second intervals for the first 3 minutes, and at 60-second intervals for the next 7 minutes.
Interpretation: A positive response, suggestive of pheochromocytoma, is indicated when the blood pressure is reduced more than 35 mm Hg systolic and 25 mm Hg diastolic. A typical positive response is a reduction in pressure of 60 mm Hg systolic and 25 mm Hg diastolic. Usually, maximal effect is evident within 2 minutes after injection. A return to preinjection pressure commonly occurs within 15 to 30 minutes but may occur more rapidly.
A positive response should always be confirmed by other diagnostic procedures, preferably by measurement of urinary catecholamines or their metabolites.
A negative response is indicated when the blood pressure is elevated, unchanged, or reduced less than 35 mm Hg systolic and 25 mm Hg diastolic after injection of phentolamine. A negative response to this test does not exclude the diagnosis of pheochromocytoma, especially in patients with paroxysmal hypertension in whom the incidence of false-negative responses is high.
For the intramuscular injection procedure, blood pressure is recorded every 5 minutes for 30 to 45 minutes following injection. A positive response is indicated when the blood pressure is reduced 35 mm Hg systolic and 25 mm Hg diastolic, or more, within 20 minutes following injection.

Further information

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