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Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 260376
We do not publish dosing.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 Terazosin capsules are indicated for the treatment of symptomatic benign prostatic hyperplasia (BPH). There is a rapid response, with approximately 70% of patients experiencing an increase in urinary flow and improvement in symptoms of BPH when treated with terazosin capsules. The long-term effects of terazosin on the incidence of surgery, acute urinary obstruction or other complications of BPH are yet to be determined. Terazosin capsules are also indicated for the treatment of hypertension. It can be used alone or in combination with other antihypertensive agents such as diuretics or beta-adrenergic blocking agents.
About this medicine
DESCRIPTION Terazosin hydrochloride, USP an alpha-1-selective adrenoceptor blocking agent, is a quinazoline derivative represented by the following chemical name and structural formula: (RS)-Piperazine,1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-[(tetra-hydro-2-furanyl)carbonyl]-, monohydrochloride, dihydrate. Terazosin hydrochloride, USP is a white to pale yellow crystalline powder, slightly soluble in water pH 1.3 (HCl), water pH 12.6 (NaOH), ethanol 95% and chloroform, sparingly soluble in water pH 6, soluble in methanol, and practically insoluble in n-hexane. Its molecular formula is C 19 H 25 N 5 O 4 •HCl•2H 2 O and has a molecular weight of 459.93 g/mole. Each capsule, for oral administration, contains terazosin hydrochloride, USP equivalent to 1 mg, 2 mg, 5 mg, or 10 mg of terazosin. In addition, each capsule contains the following inactive ingredients: Colloidal silicon dioxide, lactose monohydrate, magnesium stearate, and pregelatinized starch. The capsule shell contains D&C yellow no. 10 (2 mg, 5 mg and 10 mg), D&C red no. 28 (5 mg), FD& C green no. 3 (10 mg), FD&C red no. 40 (5 mg), gelatin, iron oxide black (1 mg), sodium lauryl sulfate, and titanium dioxide. The capsules are printed with black ink composed of ammonia solution, black iron oxide, potassium hydroxide, propylene glycol, and shellac. FDA approved dissolution test specifications differ from USP. image description
Who should not take it
CONTRAINDICATIONS Terazosin capsules are contraindicated in patients known to be hypersensitive to terazosin hydrochloride.
Warnings
WARNINGS Syncope and "First-dose" Effect Terazosin capsules, like other alpha-adrenergic blocking agents, can cause marked lowering of blood pressure, especially postural hypotension, and syncope in association with the first dose or first few days of therapy. A similar effect can be anticipated if therapy is interrupted for several days and then restarted. Syncope has also been reported with other alpha-adrenergic blocking agents in association with rapid dosage increases or the introduction of another antihypertensive drug. Syncope is believed to be due to an excessive postural hypotensive effect, although occasionally the syncopal episode has been preceded by a bout of severe supraventricular tachycardia with heart rates of 120 beats to 160 beats per minute. Additionally, the possibility of the contribution of hemodilution to the symptoms of postural hypotension should be considered. To decrease the likelihood of syncope or excessive hypotension, treatment should always be initiated with a 1 mg dose of terazosin, given at bedtime. The 2 mg, 5 mg and 10 mg capsules are not indicated as initial therapy. Dosage should then be increased slowly, according to recommendations in the Dosage and Administration section and additional antihypertensive agents should be added with caution. The patient should be cautioned to avoid situations, such as driving or hazardous tasks, where injury could result should syncope occur during initiation of therapy. In early investigational studies, where increasing single doses up to 7.5 mg were given at 3 day intervals, tolerance to the first dose phenomenon did not necessarily develop and the "first dose" effect could be observed at all doses. Syncopal episodes occurred in 3 of the 14 subjects given terazosin at doses of 2.5 mg, 5 mg and 7.5 mg, which are higher than the recommended initial dose; in addition, severe orthostatic hypotension (blood pressure falling to 50/0 mmHg) was seen in two others and dizziness, tachycardia, and lightheadedness occurred in most subjects. These adverse effects all occurred within 90 minutes of dosing. […]
Reported side effects
ADVERSE REACTIONS Benign Prostatic Hyperplasia The incidence of treatment-emergent adverse events has been ascertained from clinical trials conducted worldwide. All adverse events reported during these trials were recorded as adverse reactions. The incidence rates presented below are based on combined data from six placebo-controlled trials involving once-a-day administration of terazosin at doses ranging from 1 mg to 20 mg. Table 1 summarizes those adverse events reported for patients in these trials when the incidence rate in the terazosin group was at least 1% and was greater than that for the placebo group, or where the reaction is of clinical interest. Asthenia, postural hypotension, dizziness, somnolence, nasal congestion/rhinitis, and impotence were the only events that were significantly (p ≤ 0.05) more common in patients receiving terazosin than in patients receiving placebo. The incidence of urinary tract infection was significantly lower in the patients receiving terazosin than in patients receiving placebo. An analysis of the incidence rate of hypotensive adverse events (see PRECAUTIONS ) adjusted for the length of drug treatment has shown that the risk of the events is greatest during the initial seven days of treatment, but continues at all time intervals. TABLE 1: ADVERSE REACTIONS DURING PLACEBO-CONTROLLED TRIALS BENIGN PROSTATIC HYPERPLASIA BODY SYSTEM TERAZOSIN (N = 636) PLACEBO (N = 360) BODY AS A WHOLE †Asthenia 7.4% * 3.3% Flu Syndrome 2.4% 1.7% Headache 4.9% 5.8% CARDIOVASCULAR SYSTEM Hypotension 0.6% 0.6% Palpitations 0.9% 1.1% Postural Hypotension 3.9% * 0.8% Syncope 0.6% 0.0% DIGESTIVE SYSTEM Nausea 1.7% 1.1% METABOLIC AND NUTRITIONAL DISORDERS Peripheral Edema 0.9% 0.3% Weight Gain 0.5% 0.0% NERVOUS SYSTEM Dizziness 9.1% * 4.2% Somnolence 3.6% * 1.9% Vertigo 1.4% 0.3% RESPIRATORY SYSTEM Dyspnea 1.7% 0.8% Nasal Congestion/Rhinitis 1.9% * 0.0% SPECIAL SENSES Blurred Vision/Amblyopia 1.3% 0.6% UROGENITAL SYSTEM Impotence 1.6% * 0.6% Urinary Tract Infection 1.3% 3.9% * † Includes weakness, tiredness, lassitude and fatigue. * p ≤ 0.05 comparison between groups. […]
Interactions with other medicines
Drug Interactions In controlled trials, terazosin has been added to diuretics, and several beta-adrenergic blockers; no unexpected interactions were observed. Terazosin has also been used in patients on a variety of concomitant therapies; while these were not formal interaction studies, no interactions were observed. Terazosin has been used concomitantly in at least 50 patients on the following drugs or drug classes: 1) analgesic/anti-inflammatory (e.g., acetaminophen, aspirin, codeine, ibuprofen, indomethacin). 2) antibiotics (e.g., erythromycin, trimethoprim and sulfamethoxazole). 3) anticholinergic/sympathomimetics (e.g., phenylephrine hydrochloride, phenylpropanolamine hydrochloride, pseudoephedrine hydrochloride). 4) antigout (e.g., allopurinol). 5) antihistamines (e.g., chlorpheniramine). 6) cardiovascular agents (e.g., atenolol, hydrochlorothiazide, methyclothiazide, propranolol). 7) corticosteroids. 8) gastrointestinal agents (e.g., antacids). 9) hypoglycemics. 10) sedatives and tranquilizers (e.g., diazepam). Use with Other Drugs In a study (n = 24) where terazosin and verapamil were administered concomitantly, terazosin's mean AUC 0-24 increased 11% after the first verapamil dose and after 3 weeks of verapamil treatment it increased by 24% with associated increases in C max (25%) and C min (32%) means. Terazosin mean T max decreased from 1.3 hours to 0.8 hours after 3 weeks of verapamil treatment. Statistically significant differences were not found in the verapamil level with and without terazosin. In a study (n = 6) where terazosin and captopril were administered concomitantly, plasma disposition of captopril was not influenced by concomitant administration of terazosin and terazosin maximum plasma concentrations increased linearly with dose at steady-state after administration of terazosin plus captopril (see DOSAGE AND ADMINISTRATION ). Carcinogenesis, Mutagenesis, Impairment of Fertility Terazosin was devoid of mutagenic potential when evaluated in vivo and in vitro (the Ames test, in vivo cytogenetics, the dominant lethal test in mice, in vivo Chinese hamster chromosome aberration test and V79 forward mutation assay). […]
If too much is taken
OVERDOSAGE Should overdosage of terazosin lead to hypotension, support of the cardiovascular system is of first importance. Restoration of blood pressure and normalization of heart rate may be accomplished by keeping the patient in the supine position. If this measure is inadequate, shock should first be treated with volume expanders. If necessary, vasopressors should then be used and renal function should be monitored and supported as needed. Laboratory data indicate that terazosin is 90% to 94% protein bound; therefore, dialysis may not be of benefit.
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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 20 December 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.