Comparison of labetalol versus enalapril as monotherapy in elderly patients with hypertension: results of 24-hour ambulatory blood pressure monitoring. PURPOSE: This study compared the safety and efficacy of labetalol and enalapril as antihypertensive therapy for elderly patients. PATIENTS AND METHODS: A randomized, open-label, parallel controlled trial was conducted. After completing a 4-week placebo phase, 79 elderly (65 years or older) patients with an average standing diastolic blood pressure (BP) 95 mm Hg or above and 114 mm Hg or less were randomized to receive a 12-week course of either labetalol or enalapril in an open-label design. The patients' BP and heart rate were evaluated biweekly by trained observers unaware of the treatment status, and drug dosage was titrated (up to 400 mg twice a day of labetalol or 40 mg daily of enalapril) to achieve a standing diastolic BP of less than 90 mm Hg and a decrease of 10 mm Hg from baseline. Patients underwent 24-hour ambulatory BP monitoring (ABPM) at the end of the placebo phase and again after 8 weeks of active treatment. RESULTS: The treatment groups were comparable in their reduction of supine diastolic BP, with no significant differences between the two treatments. Labetalol demonstrated a significantly greater reduction (p less than 0.05) in standing diastolic BP at the end of the titration period compared to enalapril, but this difference was not significant by the end of the study period. Based on 24-hour ABPM readings, labetalol reduced mean 24-hour diastolic BP (p less than 0.05) and mean heart rate (p less than 0.05) more than enalapril. The labetalol-treated patients were significantly less often above their diastolic BP goal throughout the 24-hour ABPM period (p less than 0.01). The two treatments were equally well tolerated. CONCLUSIONS: The results indicate that labetalol and enalapril are equally effective in lowering supine diastolic BP in the elderly, but labetalol is more effective in lowering ambulatory BP and heart rate throughout the day. 