Terazosin 2 mg Capsule, 1,000-count

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. In three placebo-controlled BPH studies 1, 2, and 3 (see CLINICAL PHARMACOLOGY ), the incidence of postural hypotension in the terazosin treated patients was 5.1%, 5.2%, and 3.7% respectively. In multiple dose clinical trials involving nearly 2,000 hypertensive patients treated with terazosin, syncope was reported in about 1% of patients.

Syncope was not necessarily associated only with the first dose. If syncope occurs, the patient should be placed in a recumbent position and treated supportively as necessary. There is evidence that the orthostatic effect of terazosin is greater, even in chronic use, shortly after dosing.

The risk of the events is greatest during the initial seven days of treatment, but continues at all time intervals. Priapism Rarely, (probably less than once in every several thousand patients) terazosin and other α 1 -antagonists have been associated with priapism (painful penile erection, sustained for hours and unrelieved by sexual intercourse or masturbation). Two or three dozen cases have been reported.

Because this condition can lead to permanent impotence if not promptly treated, patients must be advised about the seriousness of the condition (see PRECAUTIONS : Information for Patients ).

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.

Additional adverse events have been reported, but these are, in general, not distinguishable from symptoms that might have occurred in the absence of exposure to terazosin. The safety profile of patients treated in the long-term open-label study was similar to that observed in the controlled studies. The adverse events were usually transient and mild or moderate in intensity, but sometimes were serious enough to interrupt treatment.

In the placebo-controlled clinical trials, the rates of premature termination due to adverse events were not statistically different between the placebo and terazosin groups. The adverse events that were bothersome, as judged by their being reported as reasons for discontinuation of therapy by at least 0.5% of the terazosin group and being reported more often than in the placebo group, are shown in Table 2. TABLE 2: DISCONTINUATION DURING PLACEBO-CONTROLLED TRIALS BENIGN PROSTATIC HYPERPLASIA BODY SYSTEM TERAZOSIN (N = 636) PLACEBO (N = 360) BODY AS A WHOLE Fever 0.5% 0.0% Headache 1.1% 0.8% CARDIOVASCULAR SYSTEM Postural Hypotension 0.5% 0.0% Syncope 0.5% 0.0% DIGESTIVE SYSTEM Nausea 0.5% 0.3% NERVOUS SYSTEM Dizziness 2.0% 1.1% Vertigo 0.5% 0.0% RESPIRATORY SYSTEM Dyspnea 0.5% 0.3% SPECIAL SENSES Blurred Vision/Amblyopia 0.6% 0.0% UROGENITAL SYSTEM Urinary Tract Infection 0.5% 0.3% Hypertension The prevalence of adverse reactions has been ascertained from clinical trials conducted primarily in the United States.

All adverse experiences (events) reported during these trials were recorded as adverse reactions. The prevalence rates presented below are based on combined data from fourteen placebo-controlled trials involving once-a-day administration of terazosin, as monotherapy or in combination with other antihypertensive agents, at doses ranging from 1 mg to 40 mg. Table 3 summarizes those adverse experiences reported for…

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).

Terazosin, administered in the feed to rats at doses of 8 mg/kg/day, 40 mg/kg/day, and 250 mg/kg/day (70 mg/m 2 /day, 350 mg/m 2 /day, and 2,100 mg/m 2 /day), for two years, was associated with a statistically significant increase in benign adrenal medullary tumors of male rats exposed to the 250 mg/kg dose. This dose is 175 times the maximum recommended human dose of 20 mg (12 mg/m 2 ). Female rats were unaffected.

Terazosin was not oncogenic in mice when administered in feed for 2 years at a maximum tolerated dose of 32 mg/kg/day (110 mg/m 2 ; 9 times the maximum recommended human dose). The absence of mutagenicity in a battery of tests, of tumorigenicity of any cell type in the mouse carcinogenicity assay, of increased total tumor incidence in either species, and of proliferative adrenal lesions in female rats, suggests a male rat species-specific event. Numerous other diverse pharmaceutical and chemical compounds have also been associated with benign adrenal medullary tumors in male rats without supporting evidence for carcinogenicity in man.

The effect of terazosin on fertility was assessed in a standard fertility/reproductive performance study in which male and female rats were administered oral doses of 8 mg/kg/day, 30 mg/kg/day and 120 mg/kg/day. Four of 20 male rats given 30 mg/kg (240 mg/m 2 ; 20 times the maximum recommended human dose) and five of 19 male rats given 120 mg/kg (960 mg/m 2 ; 80 times the maximum recommended human dose) failed to sire a litter. Testicular weights and morphology were unaffected by treatment.

Vaginal smears at 30 mg/kg/day and 120 mg/kg/day, however, appeared to contain less sperm than smears from control matings and good correlation was reported between sperm count and subsequent pregnancy. Oral administration of terazosin for one or two years elicited a s…