Effects of doxazosin in the gastrointestinal therapeutic system formulation versus doxazosin standard and placebo in mild-to-moderate hypertension. Doxazosin Investigators' Study Group

The alpha 1-blocker doxazosin is a well-established therapy for hypertension and benign prostatic hyperplasia; however, in its standard form, a multiple-step titration regimen is usually required. The new gastrointestinal therapeutic system (GITS) formulation of doxazosin greatly minimizes the need for titration by changing drug-delivery rate and the pharmaco-kinetic profile. To demonstrate this in hypertensive patients, we assessed the effects of doxazosin GITS 4 or 8 mg once daily versus doxazosin standard 1-8 mg once daily, and placebo, in an integrated analysis of two multicenter, double-blind, randomized, parallel-group trials. Each trial included a 2-week washout period and 12 weeks of therapy. One study compared doxazosin GITS, doxazosin standard, and placebo in 392 patients with mild hypertension [blood pressure (BP) 95-105/ < or = 180 mm Hg]; the other study compared doxazosin GITS with doxazosin standard in 315 patients with mild-to-moderate hypertension (BP 95-115/ < or = 220 mm Hg). The primary outcome measure was the proportion of responders (sitting diastolic BP < 90 mm Hg or 10-mm Hg decrease from baseline 24 h after the dose) at the final visit for the per-protocol population. Mean baseline BP and heart rate were well matched in each group. Approximately 64% of patients with doxazosin GITS (198 of 309 patients) and 68% with doxazosin standard (207 of 304 patients) achieved goal BP response at the final visit versus 36% with placebo (25 of 70 patients; p < 0.05). The majority with doxazosin GITS (60%) remained at the initial 4-mg starting dose. Doxazosin GITS was as effective as doxazosin standard, and both were more effective than placebo in controlling BP in mild-to-moderate hypertension. Doxazosin GITS was well tolerated, and fewer patients with the GITS formulation discontinued therapy because of side effects compared with doxazosin standard or placebo. Syncope was not reported with doxazosin GITS. Whereas the efficacy of doxazosin GITS at 4 or 8 mg is equivalent to that of the standard regimen in this combined analysis, the GITS formulation appears to eliminate the need for titration in most patients.