Medications and Drugs

Salt Shockers: High Sodium Surprises Slideshow Lowering Blood Pressure Slideshow: Tips for Getting Started Healthy Eating: Portion Control

Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: doxazosin mesylate

BRAND NAME: Cardura

DRUG CLASS AND MECHANISM: 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.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

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

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

PRESCRIBED FOR: Doxazosin is used for the treatment of hypertension (high blood pressure) and benign prostatic hyperplasia (BPH).

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

DRUG INTERACTIONS: 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.

PREGNANCY: There are no adequate studies of doxazosin in pregnant women.

NURSING MOTHERS: There are no adequate studies of doxazosin in nursing mothers.

SIDE EFFECTS: Common reactions 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.

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

Reference: FDA Prescribing Information

Report Problems to the Food and Drug Administration   You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088. Need help identifying pills and medications? Use the pill identifier tool on RxList.