What is the recommended dosage of Cardura (doxazosin) for an older adult male patient with Benign Prostatic Hyperplasia (BPH)?

Cardura (Doxazosin) Dosing for BPH

Start doxazosin at 1 mg once daily (morning or evening), then titrate at 1-2 week intervals through 2 mg, 4 mg, up to a maximum of 8 mg once daily based on symptom response and tolerability. 1

Initial Dosing and Titration

• Begin with 1 mg once daily as the FDA-approved starting dose for BPH, which can be taken either in the morning or evening 1
• Titrate upward at 1-2 week intervals to 2 mg, then 4 mg, and finally 8 mg once daily depending on the patient's urodynamic response and symptom improvement 1
• The maximum recommended dose is 8 mg once daily for BPH treatment 1
• Monitor blood pressure for at least 6 hours after the initial dose and each dose increase to detect orthostatic hypotension 1

Important Safety Considerations

• Alpha-blockers like doxazosin are strongly associated with orthostatic hypotension, especially in older adults 2
• Avoid doxazosin in patients with standing systolic blood pressure <110 mmHg or pre-existing orthostatic hypotension 2
• If therapy is discontinued for several days, restart using the initial 1 mg dosing regimen rather than resuming at the previous higher dose 1
• Measure orthostatic blood pressure by having the patient sit/lie for 5 minutes, then measure BP at 1 and 3 minutes after standing 2

Clinical Efficacy Timeline

• Significant symptom improvement typically occurs within 1 month, with further improvements continuing through 3 months of therapy 3, 4
• Mean effective doses in clinical studies were 4 mg daily for normotensive patients and 6.4 mg daily for hypertensive patients 4
• Long-term efficacy is maintained for up to 48 months with sustained improvement in urinary flow rates and symptom scores 4

Alternative Alpha-Blocker Consideration

• Tamsulosin has a significantly lower probability of orthostatic hypotension compared to doxazosin and may be preferred in elderly or frail patients at higher risk for falls 2
• Consider adding a 5-alpha reductase inhibitor (finasteride 5 mg or dutasteride 0.5 mg daily) if prostate volume is >30 cc, as combination therapy may provide additive benefits 5

Common Pitfalls to Avoid

• Do not skip the titration schedule - jumping directly to higher doses significantly increases the risk of first-dose syncope and orthostatic hypotension 1
• Do not use doxazosin as first-line in patients already at high fall risk - the 2021 AUA guidelines recommend alpha-blockers as initial therapy, but clinical judgment should prioritize patient safety in frail elderly patients 5, 2
• Do not combine with another alpha-blocker (like tamsulosin) as this dramatically increases orthostatic hypotension risk without additional BPH benefit 2
• If orthostatic hypotension develops, switch to an alternative agent (like tamsulosin or a 5-ARI) rather than simply reducing the doxazosin dose 2

Blood Pressure Effects

• In hypertensive patients, doxazosin produces clinically significant BP reductions (approximately 8/11 mmHg systolic/diastolic) 4
• In normotensive patients, BP decreases are minimal (approximately 4/2 mmHg) and generally not clinically significant 4, 6
• Doxazosin can be safely added to existing antihypertensive regimens in patients with controlled hypertension without causing excessive BP reduction 6