Doxazosin tablets for managing benign prostatic hyperplasia and hypertension

Doxazosin is an oral tablet medication used primarily to treat symptoms of benign prostatic hyperplasia (BPH) and to lower blood pressure in patients with hypertension. It works by selectively blocking alpha1-adrenergic receptors, which relaxes smooth muscles in the prostate and blood vessels. This helps improve urine flow in BPH and reduces systemic vascular resistance to manage hypertension.

Benign Prostatic Hyperplasia (BPH): Doxazosin tablets are prescribed to relieve the signs and symptoms of BPH, such as urinary frequency, nocturia, weak stream, and incomplete bladder emptying.

Hypertension: Doxazosin is used to lower high blood pressure, helping to reduce the risk of cardiovascular events including strokes and myocardial infarctions. It may be used alone or with other antihypertensive agents.

Doxazosin mesylate

Doxazosin selectively blocks alpha1-adrenergic receptors found in the blood vessels and the smooth muscle of the prostate and bladder neck. By blocking these receptors, it causes relaxation of the vascular smooth muscle, leading to decreased systemic vascular resistance and blood pressure. In the prostate, it reduces muscle tone, which decreases urethral resistance and improves urine flow in BPH patients.

Benign Prostatic Hyperplasia (BPH)

The usual starting dose is 1 mg once daily, taken either in the morning or evening. Depending on the patient's response, the dose may be increased at 1 to 2 week intervals to 2 mg, then 4 mg, and up to a maximum of 8 mg once daily. Blood pressure should be routinely monitored during treatment.

Hypertension

Initial dose is 1 mg once daily. Dosage may be increased as needed, up to 16 mg once daily, to achieve blood pressure goals. Blood pressure should be monitored for at least 6 hours after the initial dose and after each dose increase. If therapy is interrupted for several days, treatment should be reinitiated at the starting dose.

Doxazosin is contraindicated in patients with known hypersensitivity to doxazosin, other quinazolines (such as prazosin or terazosin), or any component of the tablets.

• Postural Hypotension: Doxazosin can cause low blood pressure upon standing, which may result in dizziness or fainting, especially after the first dose or when increasing the dose. Patients should be advised to avoid sudden position changes and to report symptoms immediately.
• Intraoperative Floppy Iris Syndrome (IFIS): Patients taking or who have taken alpha1 blockers may experience IFIS during cataract surgery. Surgeons should be informed to prepare for possible surgical modifications. Stopping doxazosin prior to surgery has not been shown to reduce risk.
• Prostate Cancer Screening: Because prostate cancer shares symptoms with BPH, it should be ruled out before starting doxazosin.
• Priapism: Rarely, doxazosin may cause priapism (painful prolonged erection). Immediate medical attention is required to prevent permanent impotence.
• Drug Interactions: Concurrent use with PDE-5 inhibitors can cause additive blood pressure lowering effects and symptomatic hypotension. Use caution and monitor blood pressure.

Common Side Effects

• Dizziness (up to 19% in hypertension, 15.6% in BPH patients)
• Fatigue or malaise (up to 12% in hypertension, 8% in BPH)
• Somnolence (3-5%)
• Edema (up to 2.7% in BPH)
• Dry mouth
• Dyspnea
• Rhinitis
• Palpitations (less common)

Serious or Less Common Reactions (Post-marketing)

• Leukopenia and neutropenia (decreased white blood cells)
• Thrombocytopenia
• Allergic reactions
• Hypoesthesia (reduced sensation)
• Bradycardia
• Bronchospasm aggravation
• Vomiting
• Cholestasis and hepatitis cholestatic
• Urticaria (hives)
• Muscle cramps and weakness
• Hematuria and urinary disorders
• Gynecomastia and priapism

• Strong CYP3A4 inhibitors: May increase doxazosin levels and risk of hypotension; monitor blood pressure and symptoms.
• Phosphodiesterase-5 (PDE-5) inhibitors: Co-administration may cause additive blood pressure lowering effects and symptomatic hypotension; use with caution and monitor.

Pregnancy

There is insufficient human data on the risk of doxazosin during pregnancy. Animal studies showed no major birth defects at exposures several times the human dose. Untreated hypertension during pregnancy poses risks to mother and fetus.

Lactation

Limited data show doxazosin may be present in human milk at very low levels. The effects on the breastfed infant are unknown.

Overdose with doxazosin is rare but can cause significant hypotension. Symptoms may include dizziness, drowsiness, and in severe cases, shock. Treatment involves supportive care with intravenous fluids to maintain blood pressure. Activated charcoal may be used if ingestion is recent. Due to high protein binding, dialysis is not effective.