PREPARATIONS: Tablets: 1, 2, 4, and 8 mg. Tablets (Extended Release): 4, 8 mg
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 AND BREASTFEEDING SAFETY: There are no adequate studies of doxazosin in pregnant women.
There are no adequate studies of doxazosin in nursing mothers.
STORAGE: Doxazosin should be stored at room temperature, 15 C - 30 C (59 F - 86 F).
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.
Medically reviewed by Eni Williams, PharmD, PhD
Reference: FDA Prescribing Information
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