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Non-selective irreversible α-blocker

Phenoxybenzamine hydrochloride

Brand names: Dibenyline

A non-selective, irreversible alpha-adrenoceptor blocker used principally for the preoperative control of blood pressure in patients with phaeochromocytoma.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It produces a long-lasting, non-competitive blockade of alpha-1 and alpha-2 adrenoceptors, counteracting the vasoconstriction caused by catecholamine excess.

Prescribing in practice

  • Alpha blockade must be established before any beta-blocker is added in phaeochromocytoma, otherwise unopposed alpha stimulation can precipitate a hypertensive crisis.
  • It commonly causes marked postural hypotension, reflex tachycardia and nasal congestion, and its effect is prolonged because the blockade is irreversible.
  • Adequate dosing requires careful uptitration to control paroxysms and to allow volume expansion before surgery.

Monitoring

Monitor lying and standing blood pressure and heart rate during titration and in the perioperative period.

Counselling the patient

  • Rise slowly from sitting or lying because of the risk of dizziness and fainting.
  • A blocked nose and a fast heartbeat are expected effects of the medicine.
  • Take it as directed in the run-up to your operation and do not stop suddenly.

Evidence & guidelines

Preoperative alpha blockade is the cornerstone of phaeochromocytoma management in endocrine guidelines, with beta blockade added only after adequate alpha blockade.

Reference: UK Endocrine Society; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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