Abstract
Atenolol and metoprolol succinate, dosed once daily, have different pharmacokinetic profiles. This study tests the hypothesis that differences that are especially noted in the early morning period, when cardiovascular risk is highest, in 24-hour blood pressure (BP) control exist between these 2 beta-blockers. This was a small, randomized open-label study with blinded end point evaluation in 36 hypertensive patients. All participants received hydrochlorothiazide 12.5 mg for 2 weeks before randomization to either 50 mg atenolol or metoprolol succinate given every morning; both treatments were force-titrated to 100 mg/d at 4 weeks. The primary end point was the change in early morning ambulatory systolic BP. Early morning (12 AM-6 AM) systolic BP differences were 3+/-14 mm Hg with atenolol vs -7+/-8 mm Hg with metoprolol succinate (P=.03). The overall 24-hour changes in systolic BP were 1+/-15 mm Hg with atenolol vs -9+/-11 mm Hg with metoprolol (P=.03). In conclusion, metoprolol succinate was more effective in sustaining 24-hour and early morning BP reductions compared with atenolol in a small group of hypertensive patients also treated with once-daily low-dose hydrochlorothiazide. It is possible that differences in outcome between atenolol-based and other therapies may be the result of inadequate dosing of atenolol, a medication that may not be effective for the entire 24-hour period.