Preliminary results of the Norwegian doxazosin postmarketing surveillance study: a twelve-week experience. The study was designed to investigate the safety and efficacy of doxazosin in the control of blood pressure in general medical practice; the results presented concern the first 748 patients evaluated over a 12-week period. Blood pressure was significantly reduced after treatment with doxazosin (-13/-9 mm Hg), and heart rate was not significantly altered. In addition, doxazosin significantly reduced total cholesterol levels (-6.7%), reduced triglyceride levels (-19.8%), increased high-density lipoprotein cholesterol levels (+2.5%), and the high-density lipoprotein:total cholesterol ratio (+9.7%). The calculated risk of coronary heart disease was reduced by 20.5% over a 12-week period. Thirty-five percent of patients reported at least one side effect, and the number of patients experiencing severe adverse reactions was small. Twenty patients (2.7%) discontinued treatment because of adverse events, and 2.7% had the dose of doxazosin reduced. 