A combined analysis of double‐blind trials of the efficacy and tolerability of doxazosin‐gastrointestinal therapeutic system, doxazosin standard and placebo in patients with benign prostatic hyperplasia
Authors: Kirby R.S. , Andersen M. , Gratzke P. , Dahlstrand C. , Høye K. 
Published: March 2003

Objective To report an integrated analysis of two previous studies fully characterizing the clinical utility of the controlled‐release gastrointestinal therapeutic system (GITS) formulation of doxazosin in the treatment of benign prostatic hyperplasia (BPH).

Patients and methods Two pivotal randomized, double‐blind studies of doxazosin GITS for BPH were assessed by an integrated analysis. Both studies included a 2‐week washout period, a 2‐week single‐blind placebo run‐in phase, and a 13‐week double‐blind treatment phase. One study compared doxazosin GITS, doxazosin standard (‐S) and placebo in 795 men; the other compared doxazosin GITS and doxazosin‐S in 680 men. Doxazosin GITS was initiated at 4 mg once daily and titrated to 8 mg once daily after 7 weeks, and doxazosin‐S was initiated at 1 mg once daily and titrated to a maximum of 8 mg once daily over 7 weeks as needed to achieve optimal symptom control. The primary outcome measures were mean changes from baseline to the final visit for the International Prostate Symptom Score (IPSS) and maximum urinary flow rate (Qmax) in the per‐protocol population. Numerous symptom‐ and urinary‐related secondary outcomes were assessed, as were effects of therapy on male erectile dysfunction measured using the International Index of Erectile Function (IIEF) in one study.

Results Both doxazosin GITS and doxazosin‐S significantly improved the symptoms of BPH, as shown by a 45% reduction for each in total IPSS from baseline to final visit, compared with a 34% reduction in patients on placebo. Doxazosin GITS and doxazosin‐S produced comparable improvements in Qmax that were significantly greater than with placebo, with a greater improvement sooner after treatment with doxazosin GITS than with doxazosin‐S. Nearly half of the patients on doxazosin GITS had symptom relief at the 4‐mg starting dose. A similar number of patients in both doxazosin groups were titrated to the maximum dose. Secondary outcomes were consistent with the primary effects. Both doxazosin GITS and doxazosin‐S produced significant improvements in sexual function according to IIEF scores among those with dysfunction at baseline. The overall incidence of adverse events was similar among patients treated with doxazosin GITS and placebo, and slightly lower than those on doxazosin‐S. There was no apparent difference in the type of adverse events reported for the two formulations of doxazosin, although most adverse events were reported at a lower frequency with doxazosin GITS.

Conclusion Doxazosin GITS is significantly more effective than placebo in reducing the clinical symptoms of BPH and improving Qmax, and as effective as doxazosin‐S. Both doxazosin formulations improved sexual function in patients with BPH and sexual dysfunction at baseline. Doxazosin GITS produced a therapeutic effect equivalent to that of doxazosin‐S, but with fewer titration steps and a slightly lower overall incidence of adverse events.