14 CLINICAL STUDIES
14.1 Benign Prostatic Hyperplasia (BPH)
The efficacy of Doxazosin tablet was evaluated extensively in over 900 patients with BPH in double-blind, placebo-controlled trials. Doxazosin tablet treatment was superior to placebo in improving patient symptoms and urinary flow rate. Significant relief with Doxazosin tablet was seen as early as one week into the treatment regimen, with Doxazosin tablet -treated patients (N=173) showing a significant (p<0.01) increase in maximum flow rate of 0.8 mL/sec compared to a decrease of 0.5 mL/sec in the placebo group (N=41). In long-term studies, improvement was maintained for up to 2 years of treatment. In 66–71% of patients, improvements above baseline were seen in both symptoms and maximum urinary flow rate.
In three placebo-controlled studies of 14–16 weeks' duration, obstructive symptoms (hesitation, intermittency, dribbling, weak urinary stream, incomplete emptying of the bladder) and irritative symptoms (nocturia, daytime frequency, urgency, burning) of BPH were evaluated at each visit by patient-assessed symptom questionnaires. The bothersomeness of symptoms was measured with a modified Boyarsky questionnaire. Symptom severity/frequency was assessed using a modified Boyarsky questionnaire or an AUA-based questionnaire. Uroflowmetric evaluations were performed at times of peak (2–6 hours post-dose) and/or trough (24 hours post-dose) plasma concentrations of Doxazosin tablet.
The results from the three placebo-controlled studies (N=609) showing significant efficacy with 4 mg and 8 mg doxazosin are summarized in Table 3. In all three studies, Doxazosin tablet resulted in statistically significant relief of obstructive and irritative symptoms compared to placebo. Statistically significant improvements of 2.3–3.3 mL/sec in maximum flow rate were seen with Doxazosin tablet in Studies 1 and 2, compared to 0.1–0.7 mL/sec with placebo.
In one fixed-dose study (Study 2), Doxazosin tablet therapy (4 to 8 mg, once daily) resulted in a significant and sustained improvement in maximum urinary flow rate of 2.3–3.3 mL/sec (Table 3) compared to placebo (0.1 mL/sec). In this study, the only study in which weekly evaluations were made, significant improvement with Doxazosin tablet vs. placebo was seen after one week. The proportion of patients who responded with a maximum flow rate improvement of ≥3 mL/sec was significantly larger with Doxazosin tablet (34–42%) than placebo (13–17%). A significantly greater improvement was also seen in average flow rate with Doxazosin tablet (1.6 mL/sec) than with placebo (0.2 mL/sec). The onset and time course of symptom relief and increased urinary flow from Study 1 are illustrated in Figure 1.
|Figure 1 – Study 1|
In a pooled analysis of placebo-controlled hypertension studies with about 300 hypertensive patients per treatment group, doxazosin, at doses of 1 to 16 mg given once daily, lowered blood pressure at 24 hours by about 10/8 mmHg compared to placebo in the standing position and about 9/5 mmHg in the supine position. Peak blood pressure effects (1–6 hours) were larger by about 50–75% (i.e., trough values were about 55–70% of peak effect), with the larger peak-trough differences seen in systolic pressures. There was no apparent difference in the blood pressure response of Caucasians and blacks or of patients above and below age 65. In the same patient population, patients receiving Doxazosin gained a mean of 0.6 kg compared to a mean loss of 0.1 kg for placebo patients.
|PLACEBO (N=85)||Doxazosin (N=183)|
|Sitting BP (mmHg)||Baseline||Change||Baseline||Change|
|Standing BP (mmHg)||Baseline||Change||Baseline||Change|