Alpha-1 Adrenoceptor Antagonist — Hypertension / Raynaud's / BPH Pregnancy: Use with caution — limited data; other agents preferred

Doxazosin

Brand names: Cardura, Doxadura

Adult dose

Dose: Hypertension/Raynaud's: 1 mg once daily; titrate over 4 weeks to 2–4 mg, max 16 mg once daily

Route: Oral (immediate-release or modified-release XL)

Frequency: Once daily (XL) or once daily at bedtime (IR — to minimise first-dose hypotension)

Max: 16 mg/day

First-dose hypotension risk — take first dose at bedtime. XL formulation reduces first-dose effect. Titrate slowly every 1–2 weeks. In Raynaud's: alpha-1 blockade reduces adrenergic-mediated digital vasoconstriction.

Paediatric dose

Route:

Seek specialist opinion — not licensed in paediatrics for vascular indications

Dose adjustments

Renal

No dose adjustment required

Hepatic

Use with caution in moderate-severe hepatic impairment — reduced clearance

Clinical pearls

ALLHAT trial: alpha-blockers (doxazosin) associated with increased heart failure vs chlorthalidone — should not be used as first-line antihypertensive or monotherapy for heart failure
Intraoperative Floppy Iris Syndrome (IFIS): alpha-1 blockade causes poor iris dilation and iris billowing during cataract surgery — must inform ophthalmologist before any eye surgery even if drug stopped weeks earlier
In Raynaud's: less effective than CCBs but useful add-on or if CCB not tolerated
Useful in BPH + hypertension — treats both conditions with single agent

Contraindications

Orthostatic hypotension
History of micturition syncope
Monotherapy for heart failure (ALLHAT — increased heart failure risk)
Concurrent PDE5 inhibitors without BP monitoring

Side effects

First-dose hypotension (orthostatic syncope)
Dizziness
Fatigue
Headache
Oedema
Palpitations
Intraoperative floppy iris syndrome (IFIS — warn ophthalmologist before cataract surgery)

Interactions

PDE5 inhibitors (sildenafil, tadalafil) — additive hypotension — start PDE5 inhibitor at lowest dose
Antihypertensives — additive effect
CYP3A4 inhibitors — may increase doxazosin levels

Monitoring

Blood pressure (lying and standing)
Heart rate
Symptoms of orthostatic hypotension

Reference: BNFc; BNF 90; ALLHAT Trial; MHRA Drug Safety Update (IFIS); BSR/BHPR Raynaud's Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways