Drug reference

phentolamine

Nonselective α adrenergic receptor antagonist (competitive) · Antihypertensive, Alpha Blocker

Nonselective α adrenergic receptor antagonist (competitive)Antihypertensive, Alpha BlockerATC C04AB01

CDSCO approvedATC C04AB01

EXCRETION

—

not curated

INTERACTIONS

1 major

SEVERE in our sources

PREGNANCY

FDA category + note

Top interactionssee all 12 →

TizanidineSevereDatabaseDDInter

Mechanism

Phentolamine is a competitive α adrenergic receptor antagonist. It causes a progressive decrease in peripheral resistance due to antagonism of α adrenergic receptors in the vasculature and increases cardiac output due to reflex sympathetic stimulation and enhanced norepinephrine release (due to presynaptic α2 blockade).

Indications

hypertension (short-term control in pheochromocytoma)relieving pseudo-obstruction of bowel (in pheochromocytoma)prevent dermal necrosis after extravasation of α receptor agonisthypertensive crises (after clonidine withdrawal, tyramine-containing foods with MAOIs)sexual dysfunction (buccal or oral for some men)reversing soft tissue local anesthesiaDiagnosis of pheochromocytomaIntraoperative management of pheochromocytomaControl of hypertension due to clonidine withdrawalControl of hypertension due to cheese reactionCounteracting vasoconstriction due to extravasated NA/DA during their i.v. infusionerectile dysfunction (ED) (as part of intracavernosal injection therapy)Hypertensive episodes in pheochromocytomaCheese reactionClonidine withdrawal

Dosing

Adult: 5 mg i.v. repeated as required

Pharmacokinetics

Onset

2 min

Duration

5–15 min

Contraindications

history of peptic ulcer (use with caution)

Side effects

Common

hypotensionreflex tachycardiacardiac arrhythmiasreversible inhibition of ejaculationgastric acid secretion

Serious

severe hypotension (rapid infusions)
cardiac ischemic events (including myocardial infarction)
Tachycardia (may complicate use)
myocardial ischaemia (may complicate use)

Pregnancy & lactation

Pregnancy

Drug interactions

Tizanidine

Severe

Database

Clinical effect not specified

Source: DDInter

Acebutolol

Moderate

Textbook

Management of tachycardia caused by phentolamine.