A Prospective Comparison of Four Study Designs Used in Assessing Safety and Effectiveness of Drug Therapy in Hypertension Management
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abstract
The objective of the study was to compare prospectively the impact of study design on drug therapy safety and effectiveness data obtained in hypertension management. The main study was a randomized controlled clinical trial of four different prospective study designs used in postmarketing assessment involving 1008 primary care practices in nine Canadian provinces. Two thousand nine hundred sixty-four patients with mild to moderate hypertension received an angiotensin converting enzyme (ACE) inhibitor daily for 14 weeks in one of four postmarketing studies--a randomized double-blind clinical trial (RCT) (10 to 40 mg fosinopril daily v 5 to 20 mg enalapril daily), two structured open label trials of 10 to 40 mg fosinopril daily (one with free drugs), or an unstructured open label trial of 10 to 40 mg fosinopril daily. Patient demographic and baseline characteristics, systolic and diastolic blood pressures, adverse events reported, and data quality were recorded as the outcome measures. The results showed that the RCT patients were titrated to higher doses of ACE inhibitor than patients in the open studies, P < .008; patients in the open studies were more likely to receive adjuvant diuretic therapy, P < .008. The decrease in blood pressure was similar for patients in all four studies, mean decrease in systolic BP was between 18 and 20 mm Hg, mean decrease in diastolic BP was between 11 and 13 mm Hg. Fewer patients in the unstructured open trial reported adverse events than patients in the RCT; a 55% relative reduction in reported adverse events (P < .008) was associated with the unstructured trial. There were also fewer drug-related adverse events per patient reported in the unstructured study (17 per 100 patients) than in the other studies (27 to 41 per 100 patients), P < .008. Physician preference for rounding off blood pressure measurements to 0 or 5 occurred most often in the unstructured open trial (P < .008). In conclusion, despite differences in dose titration and in the use of adjuvant therapy, antihypertensive drug therapy effectiveness observed in an RCT may be similar to uncontrolled postmarketing studies. Open trials with scheduled follow-up visits are as effective in detecting severe adverse events as RCT, but postmarketing studies with unstructured schedules of follow-up are insufficient in identifying drug-related adverse events and have poorer quality data.
