The purpose of this study was to determine the effects on blood pressure and selected biochemical measures of reducing the dosage of chlorthalidone from 100 mg to 50 mg. Within the larger study (Multiple Risk Factor Intervention Trial), 140 Special Intervention hypertensive men, taking 100 mg of chlorthalidone daily, were randomly assigned to either a continuation of 100 mg or a dosage reduction to 50 mg daily. Men were followed monthly for 4 months. Measures were made of blood pressure, serum potassium, serum uric acid, serum glucose, serum cholesterol, and triglycerides. Blood pressure change from baseline to 4 months revealed a significantly higher diastolic blood pressure in the group continued on the 100 mg dose compared to the dose reduction group. However, analysis of covariance, which took into account baseline differences in blood pressure, resulted in a nonsignificant difference in follow-up blood pressure (systolic and diastolic) between groups. Serum potassium increased significantly in the dose reduction group, especially in those participants taking supplemental potassium chloride. The results of this study demonstrate that a reduced dose of 50 mg chlorthalidone over the 4-month period was as effective as the 100 mg dose in long-term, well-controlled hypertensive men. Careful study of other antihypertensive agents is warranted to determine the drug dose that is maximally effective for blood pressure lowering and that also minimized toxic and adverse effects.
Bibliographical noteFunding Information:
From the Multiple Risk Fawn Intervention Trial Research Group sponsored by the National Heart, Lung and Blood Institute, National Institutes of Health, the Division of Epidemiology, School of Public Health, University of Minnesota, the Division of Biometry, School of Public Health, University of Minnesota, Wright State University, School of Medicine, Cox Heart Institute, the Department of Preventive Medicine, Rush-Presbyterian St. Luke’s Medical Center, the University of Alabama Medical Center. Health Services Research Center. Kaiser Foundation Hospitals, Harvard University, the Department of Environmental Rutgers Medical School. and the Department national Health, University of California. Received for publication accepted Nov. 20, 19X4. Reprint requests: Richard H. Grimm. Jr., Epidemiology, School of Public Health, University Gate 27, 611 Beacon St. SE, Minneapolis. MN