Phenoxybenzamine
DIBENZYLINE
Pronunciation: fen-ox-ee-BEN-za-meen
What it isIrreversible non-selective alpha antagonist; preoperative blockade in phaeochromocytoma.
Why this oneIrreversible blockade cannot be overcome by a catecholamine surge, which is exactly what is needed during tumor handling.
What limits itReflex tachycardia and profound orthostasis; a beta blocker must not be started first. The effect persists for days after stopping.
FDA-approved for
- pheochromocytoma (~1953)
FDA label
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| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Pheochromocytoma (control of hypertension and sweating episodes) | Adults | 10 mg BID | 20–40 mg BID–TID (titrated to BP control) | Undefined |
Titration Every other day
Renal Undefined
Hepatic Undefined
Long-term use not recommended (carcinogenicity). Add a beta-blocker if tachycardia is excessive.
Available strengths
- cap 10 mg
Contraindications
- Conditions where a fall in blood pressure may be undesirable
Cautions
- Unopposed beta stimulation: mixed alpha/beta agonists may cause exaggerated hypotension and tachycardia
Adverse reactions
- Postural hypotension
- Tachycardia
- Inhibition of ejaculation
- Nasal congestion
- Miosis
- GI irritation
- Drowsiness
- Fatigue
Pregnancy No adequate animal reproduction studies; unknown fetal risk — use only if clearly needed.
Lactation Unknown whether excreted in milk; discontinue nursing or drug.
Cost
| Strength | #/mo | generic $/mo | CostPlus | |
|---|---|---|---|---|
| 10 mg | cap | 60 BID | offered |
Generic entry2012
NO BOXED WARNINGS
Principal riskReflex tachycardia and profound orthostasis
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.