Fosphenytoin and Phentolamine Mesylate

• Generic Name: fosphenytoin
• Dosage Forms: n.a.
• Other Brand Names: Cerebyx

Fosphenytoin is an anticonvulsant that works by slowing down impulses in the brain that cause seizures.

Fosphenytoin is used to prevent or control seizures. Fosphenytoin is used only for a short time when other forms of phenytoin cannot be given.

Fosphenytoin may also be used for purposes not listed in this medication guide.

• Generic Name: phentolamine
• Dosage Forms: n.a.
• Other Brand Names: OraVerse

Used as an aid in the diagnosis of pheochromocytoma.

Determination of blood catecholamine concentrations, urinary assay of catecholamines, or other biochemical assays are the safest and most reliable diagnostic methods and they have largely replaced phentolamine and other pharmaceutical tests. No test, however, is completely reliable.

May be used when additional confirmatory evidence of pheochromocytoma is required and potential benefits outweigh the possible risks.

Test is more reliable with sustained than with paroxysmal hypertension; no diagnostic value in absence of hypertension at the time of the test.

Sudden and marked reduction in BP following parenteral administration of phentolamine suggests pheochromocytoma; however, false-negative and false-positive responses are frequent.

May be administered immediately prior to or during pheochromocytomectomy to prevent or control paroxysmal hypertension resulting from anesthesia, stress, or operative manipulation of the tumor.

Has been used to manage pheochromocytoma until surgery is performed and for prolonged treatment of hypertension when the tumor is not operable; however, phenoxybenzamine is considered the drug of choice because it has a longer duration of action.

Has been used in the treatment of hypertensive emergencies (severe elevations in BP >180/120 mm Hg accompanied by new or worsening target organ dysfunction) induced by catecholamine excess (e.g., pheochromocytoma, drug interactions with an MAO inhibitor, amphetamine overdosage, cocaine toxicity, clonidine withdrawal).

Used to prevent dermal necrosis and sloughing following IV administration or extravasation of norepinephrine.

Has been used to prevent necrosis after extravasation of dopamine.

Has been used to decrease impedance to left ventricular ejection and the infarct size in patients with MI associated with left ventricular failure.

However, contraindicated in patients with MI, and investigators do not recommend for routine use, since left ventricular function and the ECG must be monitored continuously.

Self-injection of small doses combined with papaverine hydrochloride into the corpus cavernosum has been effective for the treatment of erectile dysfunction (ED, impotence).

Combination has been effective in patients with neurogenic and/or limited vasculogenic impotence or with psychogenic impotence, but efficacy in those with a vasculogenic component of their impotence may be variable depending on the extent and type of vascular dysfunction.

Erection, which can be potentiated by sexual arousal, usually occurs within 10 minutes after injection of the drugs and may persist for 1 to several hours; tolerance to the drugs may occur during long-term use; priapism may occur.

Has been used as an adjunct in the management of cocaine overdose to reverse coronary vasoconstriction.