doxazosin mesylate

Doxazosin is an oral drug used for treating high blood pressure and symptoms of benign prostatic hyperplasia (BPH, a noncancerous enlargement of the prostate gland). It belongs to a class of drugs called alpha-1 adrenergic blockers. Other drugs in this class include alfuzosin (Uroxatral), terazosin (Hytrin), tamsulosin (Flomax), silodosin (Rapaflo), and prazosin (Minipress).

Doxazosin prevents norepinephrine that is released by nerves from binding to alpha-1 receptors on smooth muscle surrounding blood vessels and in the prostate and bladder. By blocking the effect of norepinephrine, doxazosin relaxes the smooth muscle. Relaxation of the smooth muscle surrounding blood vessels causes them to enlarge (dilate) and thereby reduces blood pressure. Relaxation of smooth muscle in the prostate and bladder improves the flow of urine and reduces the pain and discomfort characteristic of BPH. The FDA approved doxazosin in November 1990.

WARNING

Doxazosin can cause intraoperative floppy iris syndrome (IFIS) during cataract surgery. Patients should inform their eye surgeon that they are taking doxazosin.

Common side effects of doxazosin include:

• dizziness,
• fatigue,
• headache,
• shortness of breath,
• diarrhea,
• abdominal pain,
• edema (fluid accumulation) and
• low blood pressure.

Doxazosin causes significant reduction in blood pressure after administration of the first dose (first dose effect). This reduction in blood pressure may be associated with dizziness and fainting, especially when rising from a sitting position. To avoid this, patients should rise slowly from a sitting position, start treatment with the 1 mg dose, and then doses should be adjusted upwards slowly. Priapism (painful, prolonged penile erection) and a reduction in white blood cells have been associated with doxazosin.

The recommended dose of doxazosin for hypertension is 1-16 mg daily. The recommended dose for benign prostatic hyperplasia is 1-8 mg daily.

Vardenafil (Levitra) or tadalafil (Cialis) and doxazosin have additive blood pressure lowering effects. Combining vardenafil or tadalafil (Cialis) with doxazosin may cause excessive blood pressure reduction.

There are no adequate studies of doxazosin in pregnant women.

There are no adequate studies of doxazosin in nursing mothers.

What preparations of doxazosin mesylate are available?

Tablets: 1, 2, 4, and 8 mg. Tablets (Extended Release): 4, 8 mg

How should I keep doxazosin mesylate stored?

Doxazosin should be stored at room temperature, 15 C - 30 C (59 F - 86 F).