What are the dosing ranges for doxazosin (alpha-blocker)?

Doxazosin Dosing Ranges

The recommended dosing range for doxazosin is 1-16 mg once daily, with specific ranges of 1-8 mg for benign prostatic hyperplasia (BPH) and 1-16 mg for hypertension. 1

Initial Dosing and Titration

• Starting dose: 1 mg once daily (for both BPH and hypertension) 2, 1
• Administration: Can be taken in the morning or evening 1
• Titration schedule:
  • For BPH: Dose may be titrated at 1-2 week intervals 1
  • For hypertension: Daily dosage may be doubled as needed to achieve desired blood pressure reduction 1

Maximum Doses

• BPH: Maximum recommended dose is 8 mg once daily 2, 1
• Hypertension: Maximum dose is 16 mg once daily 1

Monitoring Requirements

• After initial dose and with each dose increase, monitor blood pressure for at least 6 hours 1
• If doxazosin is discontinued for several days, therapy should be restarted using the initial dosing regimen 1
• Routine blood pressure monitoring is recommended for BPH patients 1

Clinical Efficacy

• In BPH treatment, doxazosin significantly improves:

  • Maximum urinary flow rate (increase of 1.9-3.6 ml/second) 3, 4, 5
  • Average urinary flow rate (increase of 1.0-1.4 ml/second) 3, 4
  • Obstructive and irritative symptoms 3, 4

• In hypertensive patients, doxazosin produces:

  • Clinically significant blood pressure reductions (approximately 8/11 mm Hg systolic/diastolic) 3
  • In normotensive BPH patients, blood pressure decreases are not clinically significant (approximately 4-6 mm Hg) 3, 4

Formulation Considerations

• Standard formulation requires multiple titration steps (1 mg → 2 mg → 4 mg → 8 mg) 6, 7
• Controlled-release gastrointestinal therapeutic system (GITS) formulation:
  • Starts at 4 mg once daily
  • May be titrated to 8 mg once daily after 7 weeks if needed
  • Provides comparable efficacy with fewer titration steps 6, 7

Important Precautions

• Alpha blockers like doxazosin are associated with orthostatic hypotension, especially in older adults 2
• Doxazosin is not recommended as a first-line agent for hypertension due to less favorable outcomes for cardiovascular morbidity and mortality compared to ACE inhibitors, ARBs, calcium channel blockers, or thiazide diuretics 8
• May be considered as a second-line agent in patients with concomitant BPH 2

Clinical Pearls

• Nearly half of patients on doxazosin GITS achieve symptom relief at the 4 mg starting dose 6, 7
• If treatment is discontinued for several days, restart at the initial 1 mg dose 1
• Doxazosin is particularly useful in managing patients who have both BPH and hypertension 5