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Doxazosin Mesylate

Doxazosin Mesylate

What is 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 is used alone or with other drugs to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This medication works by relaxing blood vessels so blood can flow more easily.

Doxazosin is also used in men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia-BPH). It does not shrink the prostate, but it works by relaxing the muscles in the prostate and part of the bladder. This helps to relieve symptoms of BPH such as difficulty in beginning the flow of urine, weak stream, and the need to urinate frequently or urgently (including during the middle of the night).

how does it work (mechanism of action)?

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.

Doxazosin works by blocking certain chemicals, which helps to widen blood vessels and relax muscles in your prostate and in your bladder.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Heart problems such as chest pain or rapid, pounding, or irregular heartbeat
  • Priapism (painful erection that lasts for hours)
  • Severe allergic reaction. Symptoms may include:
  • wheezing
  • chest tightness
  • itching
  • swelling of your face, lips, tongue, or throat
  • hives
  • Breathing problems or shortness of breath


miss a dose

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

If you miss your doses for several days in a row, call your doctor before restarting the medication. You may need a lower dose.


Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include extreme dizziness or fainting.

Important warnings

Low blood pressure warning: Doxazosin can cause your blood pressure to become low. This may cause dizziness, lightheadedness, and vertigo when you stand up. This is most common with your first dose of medication, but it can also occur when your doctor changes your dosage. To help prevent this problem, your doctor will start you on the lowest dosage and slowly increase it.

Cataract surgery warning: Intraoperative floppy iris syndrome (IFIS) can occur during cataract surgery in people who take or have taken doxazosin. Be sure to tell your doctor if you have a cataract surgery planned.