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Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 197627
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
INDICATIONS AND USAGE A. Benign Prostatic Hyperplasia (BPH) Doxazosin tablets USP are indicated for the treatment of both the urinary outflow obstruction and obstructive and irritative symptoms associated with BPH: obstructive symptoms (hesitation, intermittency, dribbling, weak urinary stream, incomplete emptying of the bladder) and irritative symptoms (nocturia, daytime frequency, urgency, burning). Doxazosin tablets USP may be used in all BPH patients whether hypertensive or normotensive. In patients with hypertension and BPH, both conditions were effectively treated with doxazosin tablets USP monotherapy. Doxazosin tablets USP provide rapid improvement in symptoms and urinary flow rate in 66 to 71% of patients. Sustained improvements with doxazosin tablets USP were seen in patients treated for up to 14 weeks in double-blind studies and up to 2 years in open-label studies. B. Hypertension Doxazosin tablets USP are indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes, including this drug. Control of high blood pressure should be part of comprehensive cardiovascular risk management, including, as appropriate, lipid control, diabetes management, antithrombotic therapy, smoking cessation, exercise, and limited sodium intake. Many patients will require more than one drug to achieve blood pressure goals. For specific advice on goals and management, see published guidelines, such as those of the National High Blood Pressure Education Program’s Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC). […]
About this medicine
DESCRIPTION Doxazosin mesylate is a quinazoline compound that is a selective inhibitor of the alpha 1 subtype of alpha-adrenergic receptors. The chemical name of doxazosin mesylate is 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(1,4-benzodioxan-2-ylcarbonyl) piperazine methanesulfonate. The empirical formula for doxazosin mesylate is C 23 H 25 N 5 O 5 • CH 4 O 3 S and the molecular weight is 547.6. It has the following structure: Doxazosin mesylate is freely soluble in dimethylsulfoxide, soluble in dimethylformamide, slightly soluble in methanol, ethanol, and water (0.8% at 25°C), and very slightly soluble in acetone and methylene chloride. Doxazosin tablets USP are available as colored tablets for oral use and contains 1 mg (White to off white), 2 mg (Cream to yellow), 4 mg (Cream to yellow) and 8 mg (White to off white) of doxazosin as the free base. The inactive ingredients for all tablets are: lactose monohydrate, microcrystalline cellulose, sodium lauryl sulfate, magnesium stearate and sodium starch glycolate. The 2 mg & 4 mg tablet contains ferric oxide yellow. Chemical Structure
Who should not take it
CONTRAINDICATIONS Doxazosin tablets are contraindicated in patients with a known sensitivity to quinazolines (e.g., prazosin, terazosin), doxazosin, or any of the inert ingredients.
Warnings
WARNINGS Syncope and "First-dose" Effect Doxazosin, like other alpha-adrenergic blocking agents, can cause marked hypotension, especially in the upright position, with syncope and other postural symptoms such as dizziness. Marked orthostatic effects are most common with the first dose but can also occur when there is a dosage increase, or if therapy is interrupted for more than a few days. To decrease the likelihood of excessive hypotension and syncope, it is essential that treatment be initiated with the 1 mg dose. The 2, 4, and 8 mg tablets are not for initial therapy. Dosage should then be adjusted slowly (see DOSAGE AND ADMINISTRATION ), with evaluations and increases in dose every two weeks to the recommended dose. Additional antihypertensive agents should be added with caution. Patients being titrated with doxazosin should be cautioned to avoid situations where injury could result should syncope occur, during both the day and night. In an early investigational study of the safety and tolerance of increasing daily doses of doxazosin in normotensives beginning at 1 mg/day, only 2 of 6 subjects could tolerate more than 2 mg/day without experiencing symptomatic postural hypotension. In another study of 24 healthy normotensive male subjects receiving initial doses of 2 mg/day of doxazosin, seven (29%) of the subjects experienced symptomatic postural hypotension between 0.5 and 6 hours after the first dose, necessitating termination of the study. In this study, 2 of the normotensive subjects experienced syncope. Subsequent trials in hypertensive patients always began doxazosin dosing at 1 mg/day, resulting in a 4% incidence of postural side effects at 1 mg/day with no cases of syncope. In multiple-dose clinical trials in hypertension involving over 1500 hypertensive patients with dose titration every one to two weeks, syncope was reported in 0.7% of patients. None of these events occurred at the starting dose of 1 mg, and 1.2% (8/664) occurred at 16 mg/day. In placebo-controlled clinical trials in BPH, 3 out of 665 patients (0.5%) taking doxazosin reported syncope. […]
Reported side effects
ADVERSE REACTIONS A. Benign Prostatic Hyperplasia (BPH) The incidence of adverse events has been ascertained from worldwide clinical trials in 965 BPH patients. The incidence rates presented below (Table 3) are based on combined data from seven placebo-controlled trials involving once-daily administration of doxazosin in doses of 1 to 16 mg in hypertensives and 0.5 to 8 mg in normotensives. The adverse events when the incidence in the doxazosin group was at least 1% are summarized in Table 3. No significant difference in the incidence of adverse events compared to placebo was seen except for dizziness, fatigue, hypotension, edema, and dyspnea. Dizziness and dyspnea appeared to be dose-related. TABLE 3 ADVERSE REACTIONS DURING PLACEBO-CONTROLLED STUDIES BENIGN PROSTATIC HYPERPLASIA DOXAZOSIN PLACEBO Body System (N=665) (N=300) BODY AS A WHOLE Back Pain 1.8% 2.0% Chest Pain 1.2% 0.7% Fatigue 8.0% p ≤0.05 for treatment differences 1.7% Headache 9.9% 9.0% Influenza-like Symptoms 1.1% 1.0% Pain 2.0% 1.0% CARDIOVASCULAR SYSTEM Hypotension 1.7% 0.0% Palpitation 1.2% 0.3% DIGESTIVE SYSTEM Abdominal Pain 2.4% 2.0% Diarrhea 2.3% 2.0% Dyspepsia 1.7% 1.7% Nausea 1.5% 0.7% METABOLIC AND NUTRITIONAL DISORDERS Edema 2.7% 0.7% NERVOUS SYSTEM Dizziness Includes vertigo 15.6% 9.0% Mouth Dry 1.4% 0.3% Somnolence 3.0% 1.0% RESPIRATORY SYSTEM Dyspnea 2.6% 0.3% Respiratory Disorder 1.1% 0.7% SPECIAL SENSES Vision Abnormal 1.4% 0.7% UROGENITAL SYSTEM Impotence 1.1% 1.0% Urinary Tract Infection 1.4% 2.3% SKIN & APPENDAGES Sweating Increased 1.1% 1.0% PSYCHIATRIC DISORDERS Anxiety 1.1% 0.3% Insomnia 1.2% 0.3% In these placebo-controlled studies of 665 doxazosin patients treated for a mean of 85 days, additional adverse reactions have been reported. These are less than 1% and not distinguishable from those that occurred in the placebo group. Adverse reactions with an incidence of less than 1% but of clinical interest are (doxazosin vs. placebo): Cardiovascular System: angina pectoris (0.6% vs. 0.7%), postural hypotension (0.3% vs. 0.3%), syncope (0.5% vs. 0.0%), tachycardia (0.9% vs. 0.0%); Urogenital System: dysuria (0.5% vs. 1.3%); and Psychiatric Disorders: libido decreased (0.8% vs. […]
Interactions with other medicines
Drug Interactions Most (98%) of plasma doxazosin is protein bound. In vitro data in human plasma indicate that doxazosin has no effect on protein binding of digoxin, warfarin, phenytoin, or indomethacin. There is no information on the effect of other highly plasma protein- bound drugs on doxazosin binding. Doxazosin has been administered without any evidence of an adverse drug interaction to patients receiving thiazide diuretics, beta-blocking agents, and nonsteroidal anti-inflammatory drugs. In a placebo-controlled trial in normal volunteers, the administration of a single 1 mg dose of doxazosin on day 1 of a four-day regimen of oral cimetidine (400 mg twice daily) resulted in a 10% increase in mean AUC of doxazosin (p=0.006), and a slight but not statistically significant increase in mean C max and mean half-life of doxazosin. The clinical significance of this increase in doxazosin AUC is unknown. In clinical trials, doxazosin tablets have been administered to patients on a variety of concomitant medications; while no formal interaction studies have been conducted, no interactions were observed. Doxazosin tablets have been used with the following drugs or drug classes: 1) analgesic/anti-inflammatory (e.g., acetaminophen, aspirin, codeine and codeine combinations, ibuprofen, indomethacin); 2) antibiotics (e.g., erythromycin, trimethoprim and sulfamethoxazole, amoxicillin); 3) antihistamines (e.g., chlorpheniramine); 4) cardiovascular agents (e.g., atenolol, hydrochlorothiazide, propranolol); 5) corticosteroids; 6) gastrointestinal agents (e.g., antacids); 7) hypoglycemics and endocrine drugs; 8) sedatives and tranquilizers (e.g., diazepam); 9) cold and flu remedies. Concomitant administration of doxazosin with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension (see DOSAGE AND ADMINISTRATION ).
If too much is taken
OVERDOSAGE Experience with doxazosin overdosage is limited. Two adolescents, who each intentionally ingested 40 mg doxazosin with diclofenac or acetaminophen, were treated with gastric lavage with activated charcoal and made full recoveries. A two-year-old child who accidently ingested 4 mg doxazosin was treated with gastric lavage and remained normotensive during the five-hour emergency room observation period. A six-month-old child accidentally received a crushed 1 mg tablet of doxazosin and was reported to have been drowsy. A 32-year-old female with chronic renal failure, epilepsy, and depression intentionally ingested 60 mg doxazosin (blood level = 0.9 µg/mL; normal values in hypertensives = 0.02 µg/mL); death was attributed to a grand mal seizure resulting from hypotension. A 39-year-old female who ingested 70 mg doxazosin, alcohol, and Dalmane® (flurazepam) developed hypotension which responded to fluid therapy. The oral LD 50 of doxazosin is greater than 1000 mg/kg in mice and rats. The most likely manifestation of overdosage would be hypotension, for which the usual treatment would be intravenous infusion of fluid. As doxazosin is highly protein bound, dialysis would not be indicated.
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This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 14 August 2024. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.