What is the use of Doxazosin (alpha-1 adrenergic blocker)?

From the Guidelines

Doxazosin should be used with caution and only when other treatments for hypertension and heart failure are inadequate due to its inferiority in preventing heart failure compared to other antihypertensive agents, as shown in the ALLHAT trial 1.

Overview of Doxazosin

Doxazosin is an alpha-1 adrenergic blocker used to treat high blood pressure and symptoms of benign prostatic hyperplasia (BPH). For hypertension, the typical starting dose is 1 mg once daily, usually taken at bedtime, which can be gradually increased to 2-4 mg daily if needed, with a maximum dose of 16 mg daily. For BPH, the dosing is similar, starting at 1 mg and potentially increasing to 8 mg daily based on symptom improvement.

Mechanism of Action and Side Effects

Doxazosin works by relaxing blood vessels and smooth muscle in the prostate and bladder neck, improving blood flow and reducing urinary symptoms. Patients should be aware of potential side effects including dizziness, lightheadedness, and first-dose hypotension (a sudden drop in blood pressure when starting the medication or increasing the dose). To minimize these effects, it's recommended to take the first dose at bedtime and rise slowly from sitting or lying positions. Doxazosin may interact with medications for erectile dysfunction and other blood pressure medications, potentially causing excessive blood pressure lowering, so these combinations should be used with caution and proper medical supervision.

Considerations for Use in Hypertension and Heart Failure

The use of doxazosin in patients with hypertension and heart failure should be approached with caution. According to the American Heart Association, drugs to avoid in patients with heart failure and hypertension include nondihydropyridine calcium channel blockers and moxonidine, and doxazosin should only be used if other drugs for the management of hypertension and heart failure are inadequate to achieve blood pressure control at maximum tolerated doses 1. The ALLHAT trial demonstrated that doxazosin was inferior to chlorthalidone for the prevention of heart failure and was associated with a doubling of heart failure risk compared to chlorthalidone 1.

Guidelines and Recommendations

Guidelines from the American Heart Association recommend that the treatment of hypertension in patients with heart failure should include behavioral modification, such as sodium restriction and a closely monitored exercise program, and that thiazide or thiazide-like diuretics can be useful for blood pressure control and to reverse mild volume overload and associated symptoms in symptomatic patients with heart failure 1. The primary recommendation for the treatment of hypertension in patients with heart failure is to use diuretics, ACE inhibitors, β-blockers, and aldosterone receptor antagonists, which have been proven to improve outcomes for patients with heart failure and can lower blood pressure in hypertensive patients 1.

From the FDA Drug Label

1.1 Benign Prostatic Hyperplasia (BPH) Doxazosin tablets, USP are indicated for the treatment of the signs and symptoms of BPH.

1. 2 Hypertension Doxazosin tablets, USP are indicated for the treatment of hypertension, to lower blood pressure.

The main uses of Doxazosin are:

• Treatment of Benign Prostatic Hyperplasia (BPH) symptoms
• Treatment of hypertension to lower blood pressure 2

1. 1 Mechanism of Action Benign Prostatic Hyperplasia (BPH) The symptoms associated with benign prostatic hyperplasia (BPH), such as urinary frequency, nocturia, weak stream, hesitancy, and incomplete emptying are related to two components, anatomical (static) and functional (dynamic)

The mechanism of action for Doxazosin in BPH is the blockade of alpha 1 adrenoceptors, which decreases urethral resistance and relieves obstruction and BPH symptoms 2

From the Research

Efficacy of Doxazosin

• Doxazosin has been shown to be effective in the treatment of benign prostatic hyperplasia (BPH) in multiple studies 3, 4, 5, 6, 7.
• The drug has been found to improve urinary flow rates and symptoms in patients with BPH, with significant increases in maximum and average urinary flow rates observed in several studies 3, 4, 5.
• Doxazosin has also been shown to be effective in reducing blood pressure in hypertensive patients with BPH, with significant decreases in systolic and diastolic blood pressure observed in several studies 4, 5, 6.

Safety and Tolerability of Doxazosin

• Doxazosin has been found to be well tolerated in most patients, with the majority of adverse experiences considered mild or moderate in severity 3, 4, 5, 6.
• The most common adverse events associated with doxazosin include dizziness, headache, and fatigue 3, 4, 5, 6.
• Doxazosin has been shown to be safe and effective for long-term use, with sustained efficacy and safety observed in studies of up to 48 months duration 5.

Patient Populations

• Doxazosin has been found to be effective and safe in both normotensive and hypertensive patients with BPH 3, 4, 5, 6.
• The drug has also been shown to be effective in older patients (≥65 years) and younger patients (45-64 years) with BPH and hypertension 6.
• Doxazosin may be a particularly appropriate therapy for older men with both hypertension and BPH, given its ability to treat both conditions simultaneously 7.