Doxazosin is an alpha-1 adrenergic blocker medication prescribed primarily for the management of hypertension (high blood pressure) and the symptomatic treatment of benign prostatic hyperplasia (BPH). It functions by relaxing blood vessels and muscles in the prostate and bladder neck, facilitating smoother blood flow and improved urinary symptoms. This long-acting formulation allows for convenient once-daily dosing, supporting consistent therapeutic effects and patient adherence. As a well-established agent in its class, doxazosin offers a reliable option within comprehensive treatment plans under physician supervision.

Features

• Active ingredient: Doxazosin mesylate
• Drug class: Selective alpha-1 adrenergic receptor antagonist
• Available formulations: Oral tablets in strengths of 1 mg, 2 mg, 4 mg, and 8 mg
• Pharmacokinetics: Peak plasma concentration within 2-3 hours; elimination half-life of approximately 22 hours
• Administration: Once daily, with or without food

Benefits

• Effectively lowers both systolic and diastolic blood pressure, reducing cardiovascular risk.
• Significantly improves urinary flow rates and reduces symptoms of BPH, such as hesitancy and nocturia.
• Provides 24-hour therapeutic coverage with a single daily dose, enhancing convenience.
• Does not adversely affect blood lipid profiles and may offer modest improvements.
• Can be used as monotherapy or in combination with other antihypertensive agents.

Common use

Doxazosin is indicated for the treatment of hypertension, either as monotherapy or in combination with other antihypertensive drugs such as diuretics or beta-blockers. It is also approved for the symptomatic treatment of benign prostatic hyperplasia, helping to alleviate obstructive and irritative symptoms including weak stream, urgency, and frequency. Off-label, it is sometimes utilized in the management of ureteral stones due to its smooth muscle relaxant properties.

Dosage and direction

For hypertension, the initial dose is typically 1 mg once daily, which may be increased to 2 mg, 4 mg, and then up to 8 mg or 16 mg daily based on blood pressure response. Dose adjustments should occur at 1-2 week intervals. For BPH, the starting dose is also 1 mg daily, titrated upwards to 2 mg, 4 mg, and 8 mg as needed for symptom control, with a maximum recommended dose of 8 mg per day. The tablet should be swallowed whole with a glass of water, and can be taken with or without food. The first dose, and each time the dose is increased, should be taken at bedtime to minimize the risk of orthostatic hypotension.

Precautions

Patients should be cautioned about the potential for dizziness, vertigo, or syncope, particularly with the initial dose or following dosage increases. Caution is advised when driving or operating machinery until the individual response is known. Regular monitoring of blood pressure is recommended, especially during the titration phase. Use with caution in patients with hepatic impairment, as doxazosin is extensively metabolized in the liver. Patients with a history of gastrointestinal obstruction should be monitored closely.

Contraindications

Doxazosin is contraindicated in patients with a known hypersensitivity to doxazosin, other quinazolines (such as prazosin or terazosin), or any component of the formulation. It is also contraindicated in patients with a history of orthostatic hypotension and should not be used in combination with other alpha-adrenergic blocking agents due to the increased risk of hypotension.

Possible side effect

Common side effects include dizziness (15.6%), fatigue (8.2%), headache (7.8%), and somnolence (5.1%). Orthostatic hypotension occurs in approximately 0.3-1% of patients. Other reported adverse reactions include edema, dyspnea, nausea, rhinitis, and blurred vision. Less frequently, priapism (a prolonged and painful erection) has been reported, which requires immediate medical attention to avoid permanent damage.

Drug interaction

Doxazosin may potentiate the hypotensive effects of other antihypertensive agents, diuretics, and phosphodiesterase-5 inhibitors (e.g., sildenafil). Concomitant use with strong CYP3A4 inhibitors like ketoconazole or ritonavir may increase doxazosin plasma concentrations. Nonsteroidal anti-inflammatory drugs may reduce the antihypertensive efficacy. Use with other alpha-blockers is contraindicated.

Missed dose

If a dose is missed, it should be taken as soon as remembered on the same day. If it is near the time for the next dose, the missed dose should be skipped and the regular dosing schedule resumed. Doubling the dose to make up for a missed one is not recommended.

Overdose

Symptoms of overdose may include severe hypotension, circulatory collapse, and shock. Supportive measures should be instituted, including placing the patient in a supine position and administering intravenous fluids. Vasopressors may be required, but care should be taken to avoid excessive blood pressure response. Gastric lavage may be considered if ingestion was recent.

Storage

Store at room temperature between 15-30°C (59-86°F), in a tightly closed container, and protect from light and moisture. Keep out of reach of children and pets. Do not use beyond the expiration date printed on the packaging.

Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any new treatment. Do not disregard professional medical advice or delay in seeking it because of something you have read here.

Reviews

Clinical studies and meta-analyses consistently demonstrate doxazosin’s efficacy in reducing blood pressure and improving BPH symptoms. In the ALLHAT trial, while doxazosin was associated with a higher incidence of heart failure compared to chlorthalidone, it remains a valuable option particularly in patients with concomitant BPH. Patient reviews often highlight improved urinary flow and quality of life, though some report dizziness, especially during dose initiation. Overall, it is considered an effective and well-tolerated agent when used appropriately under medical supervision.