Phentolamine
Regitin · Rogitine · OraVerse
Non-selective alpha-blocker with onset within minutes and duration under half an hour. A niche drug: catecholamine-induced hypertensive crisis — phaeochromocytoma, cocaine and amphetamine intoxication, MAO inhibitor crisis — and local treatment of skin necrosis after noradrenaline extravasation.
Pure alpha-blockade allows uninhibited beta-stimulation with tachycardia and risk of arrhythmia. Avoid in coronary artery disease without concurrent rate control.
Dosing in adults
| Indication | Regimen | Comment |
|---|---|---|
| Hypertensive crisis in phaeochromocytoma | 5–15 mg iv as bolus every 5–15 minutes | titrated against blood pressure |
| Continuous infusion | Start at 0,1 mg/min iv, increase in steps of 0,1 mg | in severe catecholamine secretion |
| Cocaine- or amphetamine-induced hypertension | 5 mg iv, may be repeated | given before any beta-blockade |
| Noradrenaline extravasation | 5–10 mg diluted in 10 ml NaCl, infiltrated locally into the affected area | within 12 hours of the extravasation |
No established dose adjustment. Titrate to effect.
No established dose adjustment.
0,05–0,1 mg/kg iv as bolus (maximum 5 mg). For extravasation 0,1–0,2 mg/kg locally, maximum 10 mg.
Not a general first-choice drug in hypertensive crisis — reserve for confirmed or strongly suspected catecholamine excess. In ischaemic heart disease, beta-blockade should follow after established alpha-blockade to attenuate the reflex tachycardia.
Pharmacokinetics
- ONSET
- 1–2 minutes
- PEAK EFFECT
- 2 minutes
- DURATION
- 10–30 minutes
- t½
- 19 minutes
- METABOLISM
- Hepatic
- EXCRETION
- Renal (13 % unchanged)
- RECEPTOR
- α₁ and α₂, competitive blockade
- ADMINISTRATION
- iv, im, local infiltration