Doxazosin
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Alpha-1 adrenergic blocker (non-selective), Benign prostatic hyperplasia treatment, Antihypertensive
Doxazosin
Cardura, Cardura XL
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Summary
Classes
Common uses
Benign prostatic hyperplasia (LUTS)0, Hypertension (later-line; first-dose hypotension limits as monotherapy)0, PTSD-related nightmares (off-label, mostly prazosin in practice)0
Pharmacy
Starting dose
IR 1 mg PO at bedtime, titrate weekly; XL 4-8 mg PO daily
Preparations
1, 2, 4, 8 mg IR tablets; 4, 8 mg XL tablets
US FDA Max
16 mg/d (IR); 8 mg/d (XL)
Pharmacology
Routes
Oral
Onset
BP and symptomatic LUTS improvement within 1-2 weeks
Duration
24 hours
Half-life
~22 hours[1]
Bioavailability
~65% (oral)[1]
Pregnancy
Limited data; rarely indicated in pregnancy.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Doxazosin is a non-selective α1 adrenergic receptor antagonist that relaxes vascular smooth muscle (lowering BP) and prostatic/bladder-neck smooth muscle (improving urodynamic flow); unlike tamsulosin, it lacks α1A subtype selectivity, producing more peripheral hypotension and the characteristic first-dose syncope that drives bedtime initiation.0 ALLHAT (2000) showed the doxazosin arm had significantly more heart failure than chlorthalidone, leading to the general practice of using α1 blockers as later-line antihypertensives rather than first-line[1]. Intraoperative floppy iris syndrome is a recognized class effect.
References
edit- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Cardura (doxazosin mesylate), Pfizer, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/019668s032lbl.pdf