Purpose: This multicenter, double-blind, parallel group study assessed the usefulness of the ambulatory blood pressure monitoring (ABPM) technique in differentiating between the oncedaily administration of the β blockers bisoprolol (10 to 20 mg) and atenolol (50 to 100 mg) in terms of efficacy and duration of action. Patients and methods: The study population consisted of 659 patients with essential hypertension and an average office diastolic blood pressure (BP) between 95 and 115 mm Hg after 4 weeks of placebo treatment. Office BPs were recorded at the end of the 24-hour dosing interval (trough). ABPM was performed in 11 of the 28 institutions participating in this study in a total of 203 patients. These procedures were performed at the end of the placebo phase and again after 8 weeks of active treatment. Results: With the use of conventionally measured office BPs, the two drugs significantly (p < 0.001) decreased trough systolic and diastolic BPs to a similar extent. By 24-hour monitoring, bisoprolol demonstrated a 33% greater reduction in whole-day average diastolic BP than did atenolol (11.6 ± 0.7 mm Hg versus 8.7 ± 0.8 mm Hg, p < 0.01). Significant treatment differences in systolic (p < 0.05) and diastolic (p < 0.01) BPs were also noted for bisoprolol compared with atenolol during the final 4 hours of the dosing interval (-13.2 ± 1.5/-10.9 ± 1.0 mm Hg versus -8.9 ± 1.6/-7.3 ± 1.1 mm Hg, respectively), and over the time period 6:00 AM to noon (-14.2 ± 1.3/-11.5 ± 0.9 mm Hg versus -9.9 ± 1.4/-7.7 ± 0.9 mm Hg). Conclusion: Whereas conventional BP measurements did not detect differences in the antihypertensive effects of the β blockers bisoprolol and atenolol, ABPM revealed significant treatment differences in both the efficacy and duration of action of these two agents. These findings indicate the power of this technique to discriminate potentially important differences between apparently similar antihypertensive drugs.
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