Phentolamine Mesylate Information
Phentolamine mesylate ()
Phentolamine mesylate () Description
Phentolamine mesylate () for Injection USP, is an antihypertensive, available in vials for intravenous and intramuscular administration. Each vial contains Phentolamine mesylate () USP, 5 mg and mannitol USP, 25 mg in sterile, lyophilized form.
Phentolamine mesylate () is -[-(2-Imidazolin-2-ylmethyl)--toluidino]phenol monomethanesulfonate (salt), and its structural formula is:
Molecular Formula - CHNO•CHOS M.W. - 377.47
Phentolamine mesylate () USP is a white or off-white, odorless crystalline powder. Its solutions are acid to litmus. It is freely soluble in water and in alcohol, and slightly soluble in chloroform. It melts at about 178°C.
Phentolamine mesylate () Clinical Pharmacology
Phentolamine mesylate () produces an alpha-adrenergic block of relatively short duration. It also has direct, but less marked, positive inotropic and chronotropic effects on cardiac muscle and vasodilator effects on vascular smooth muscle.
Phentolamine has a half-life in the blood of 19 minutes following intravenous administration. Approximately 13% of a single intravenous dose appears in the urine as unchanged drug.
Phentolamine mesylate () Indications And Usage
Phentolamine mesylate () for Injection is indicated for the prevention or control of hypertensive episodes that may occur in a patient with pheochromocytoma as a result of stress or manipulation during preoperative preparation and surgical excision.
Phentolamine mesylate () for Injection is indicated for the prevention or treatment of dermal necrosis and sloughing following intravenous administration or extravasation of norepinephrine.
Phentolamine mesylate () for Injection is also indicated for the diagnosis of pheochromocytoma by the phentolamine blocking test.
Phentolamine mesylate () Contraindications
Myocardial infarction, history of myocardial infarction, coronary insufficiency, angina, or other evidence suggestive of coronary artery disease; hypersensitivity to phentolamine or related compounds.
Phentolamine mesylate () Warnings
Myocardial infarction, cerebrovascular spasm, and cerebrovascular occlusion have been reported to occur following the administration of phentolamine, usually in association with marked hypotensive episodes.
For screening tests in patients with hypertension, the generally available urinary assay of catecholamines or other biochemical assays have largely replaced the phentolamine and other pharmacological tests for reasons of accuracy and safety. None of the chemical or pharmacological tests is infallible in the diagnosis of pheochromocytoma. The phentolamine blocking test is not the procedure of choice and should be reserved for cases in which additional confirmatory evidence is necessary and the relative risks involved in conducting the test have been considered.
Phentolamine mesylate () Adverse Reactions
Acute and prolonged hypotensive episodes, tachycardia, and cardiac arrhythmias have been reported. In addition, weakness, dizziness, flushing, orthostatic hypotension, nasal stuffiness, nausea, vomiting, and diarrhea may occur.
Phentolamine mesylate () Overdosage
No deaths due to acute poisoning with phentolamine have been reported.
Oral LD’s (mg/kg): mice, 1000; rats, 1250.
There is no specific antidote.
A decrease in blood pressure to dangerous levels or other evidence of shocklike conditions should be treated vigorously and promptly. The patient’s legs should be kept raised and a plasma expander should be administered. If necessary, intravenous infusion or norepi-nephrine, titrated to maintain blood pressure at the normotensive level, and all available supportive measures should be included. Epinephrine should not be used, since it may cause a paradoxical reduction in blood pressure.
Phentolamine mesylate () Dosage And Administration
The reconstituted solution should be used upon preparation and should not be stored.
If the intramuscular test for pheochromocytoma is preferred, preparation is the same as for the intravenous test. Five milligrams of Phentolamine mesylate () is then dissolved in 1 mL of Sterile Water for Injection. The dose for adults is 5 mg intramuscularly; for children, 3 mg. 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.
Note:
Phentolamine mesylate () How Supplied
Phentolamine mesylate () for Injection USP, 5 mg, for intramuscular or intravenous use, is supplied in a 2mL vial and individually boxed.
The reconstituted solution should be used upon preparation and should not be stored.
Store at controlled room temperature, 15° to 30°C (59° to 86°F).
Manufactured for: Manufactured by:
Bedford Laboratories™ Ben Venue Laboratories™
Bedford, OH 44146 Bedford, OH 44146
May 1999 PHT-P01
Phentolamine mesylate () Vial Label
Phentolamine mesylate () Carton
