Phentolamine
Regitine · OraVerse
Non-selective alpha-adrenergic antagonist
Competitive, reversible α1 + α2 blockade → vasodilation. Short-acting.
Indications
- •Pheochromocytoma hypertensive crisis (intraop)
- •Catecholamine/vasopressor EXTRAVASATION (local infiltration rescue)
- •Cocaine/sympathomimetic hypertensive emergency
- •Reversal of dental soft-tissue anesthesia (OraVerse)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Hypertensive crisis (pheo) | 1–5 mg IV, repeat as needed | — |
| Extravasation rescue | 5–10 mg in 10 mL NS, infiltrate the extravasation site (within ~12 h) | — |
Pharmacokinetics
Onset immediate IV. Short half-life ~19 min.
Side effects
- !Hypotension, reflex tachycardia/arrhythmia
- !Anginal chest pain
Contraindications
- ×Coronary ischemia/recent MI (relative)
Clinical pearls
- ★The antidote for pressor/vasoconstrictor EXTRAVASATION (norepinephrine, dopamine, phenylephrine) — infiltrate the site early.
- ★Intraop pheochromocytoma HTN spikes (tumor manipulation) → phentolamine boluses; α-blockade before any β-blockade.
Other drugs in Others
- Dantrolene
Blocks RYR1 (ryanodine receptor) → ↓ Ca²⁺ release from sarcoplasmic reticulum → muscle relaxation. The only drug for malignant hyperthermia.
- Lipid Emulsion 20%
Theory: 'Lipid sink' sequesters lipophilic drugs (especially LAs), shifts to better Ca²⁺ handling, fatty acid metabolic support.
- Hydroxocobalamin
Vitamin B12a precursor; cyanide binds to cobalt center of hydroxocobalamin → forms cyanocobalamin (B12) → renal excretion. Also scavenges nitric oxide → vasoconstriction.
- Octreotide
Long-acting somatostatin analogue → suppresses splanchnic blood flow, GI/pancreatic secretions, GH, glucagon, insulin, and serotonin/vasoactive-peptide release.
- Alvimopan
Blocks GI mu-opioid receptors WITHOUT crossing the blood-brain barrier → reverses opioid-induced gut slowing while preserving central analgesia. Accelerates return of bowel function.
- Inhaled Nitric Oxide
Inhaled NO diffuses to pulmonary vascular smooth muscle → ↑ cGMP → SELECTIVE pulmonary vasodilation only in VENTILATED lung units (improves V/Q matching). Inactivated by hemoglobin before reaching systemic circulation → no systemic hypotension.
- Digoxin Immune Fab
Ovine Fab fragments bind free digoxin → the complex is renally excreted → rapidly reverses digoxin/digitoxin toxicity.
- Aminophylline
Nonselective PDE inhibition (↑ cAMP) + adenosine-receptor antagonism → bronchodilation, respiratory stimulation, mild inotropy/chronotropy.
Browse all classes: /reference/drugs
Suggested reading
- •Miller's Anesthesia, 9e
- •FDA package insert
