What is Doxazosin Used For?
Doxazosin is FDA-approved for two primary indications: treating the signs and symptoms of benign prostatic hyperplasia (BPH) and treating hypertension to lower blood pressure and reduce cardiovascular risk. 1
Primary Indications
Benign Prostatic Hyperplasia (BPH)
- Doxazosin is indicated for treating both obstructive symptoms (hesitation, intermittency, dribbling, weak urinary stream, incomplete bladder emptying) and irritative symptoms (nocturia, daytime frequency, urgency, burning) associated with BPH 1
- The drug works by selectively blocking alpha-1 adrenoceptors in prostatic smooth muscle, prostatic capsule, and bladder neck, thereby decreasing urethral resistance and relieving obstruction 1
- Clinical trials demonstrate that doxazosin produces statistically significant improvements in maximum urinary flow rate (2.3 to 3.3 mL/sec increase) compared to placebo (0.1 to 0.7 mL/sec) 1
- Symptom relief can be seen as early as one week, with 66-71% of patients showing improvements in both symptoms and maximum urinary flow rate 1
- Long-term efficacy is maintained for up to 2 years of treatment 1
Hypertension
- Doxazosin is indicated for treating hypertension to lower blood pressure, which reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions 1
- The antihypertensive effect results from selective blockade of alpha-1 adrenoceptors, leading to decreased systemic vascular resistance 1
- At doses of 1-16 mg once daily, doxazosin lowers blood pressure by approximately 10/8 mmHg in the standing position and 9/5 mmHg in the supine position compared to placebo 1
- Maximum blood pressure reductions occur 2-6 hours after dosing 1
- Doxazosin may be used alone or in combination with other antihypertensive medications 1
Clinical Considerations for Dual Benefit
Use in Men with Both BPH and Hypertension
- Doxazosin is particularly appropriate for older men with both hypertension and BPH, as it addresses both conditions simultaneously 2
- The European Association of Urology recognizes doxazosin, along with alfuzosin, tamsulosin, and terazosin, as appropriate treatment options for lower urinary tract symptoms secondary to BPH, with all four agents having similar clinical effectiveness 3
Use in Normotensive Men with BPH
- In normotensive men with BPH, doxazosin produces statistically significant but clinically unimportant reductions in blood pressure 4
- The proportion of normotensive BPH patients experiencing sitting systolic BP <90 mmHg and/or diastolic BP <60 mmHg during treatment (6.7%) was not significantly different from placebo (5%) 1
- Doxazosin can be safely introduced for BPH treatment in hypertensive men whose blood pressure is already controlled by another antihypertensive agent without causing clinically significant additional blood pressure reduction 4
Combination Therapy Considerations
- For men with BPH and demonstrable prostatic enlargement (prostate volume >30cc, PSA >1.5 ng/mL, or palpable enlargement on DRE), adding a 5-alpha reductase inhibitor (finasteride or dutasteride) to doxazosin provides superior outcomes and reduces long-term risk of acute urinary retention and need for surgery 3
- The benefits of doxazosin and finasteride may be additive in BPH, especially in men with large prostates 5
Important Safety Considerations
- Doxazosin has a greater effect on blood pressure and heart rate in the standing position compared to supine position, similar to other alpha-1 adrenergic blocking agents 1
- The standard formulation requires titration through multiple steps to minimize first-dose effects, though a gastrointestinal therapeutic system (GITS) formulation requires less titration 5, 6, 7
- Common adverse effects include dizziness and fatigue, which are associated with blood pressure lowering 4