Background The aim of the study was to compare antihypertensive effect and safety of new slow-release formula of acebutolol SR (400 mg tablets) administered once daily with the standard formula (tablets containing 200 mg) given twice a day in patients with essential hypertension, WHO grade I and II.
Material and methods Randomized, double-blind placebo controlled, cross-over study was performed in 41 female and male hypertensive patients. 7 day placebo period was followed by 8 weeks of active treatment. According to randomization in the I phase of treatment patients were treated for 4 weeks with: acebutolol SR tablet 400 mg given in the morning followed by one placebo tablet in the evening (group I) or standard tablet of acebutolol 200 mg every 12 hours (group II). After 4 weeks lasting phase I of the study the second phase was based on cross-over: previously treated group with acebutolol SR 400 mg was switched to standard acebutolol 200 mg twice a day. In the opposite group acebutolol SR 400 mg once daily was given. Antihypertensive efficacy was evaluated by 24 hour ambulatory blood pressure monitoring within the last day of placebo administration and the last day of active treatment of phase I and phase II. During physical examination resting blood pressure in the sitting and standing position were measured. Adverse effects of medication and laboratory results were analysed.
Results After 4 weeks acebutolol SR 400 mg given once daily decreased significantly systolic and diastolic blood pressure by 18,5 ± 9,1 mm Hg and 15,8 ± 6,6 mm Hg respectively (p < 0,001) in the sitting position and the effect was comparable with the antihypertensive efficacy of standard tablets of acebutolol 200 mg given twice daily (systolic and diastolic blood pressure reduction by 16,5 ± 10 mm Hg and 13,2 ± 6,7 mm Hg respectively).
Both formulas exerted comparable effect on resting heart rate: after acebutolol SR 400 mg and acebutolol 200 mg twice daily heart rate diminished by 6,9 ± 6,8/min (p < 0,001) and 4,6 ± 10,2/min (p < 0,05) as compared with baseline conditions. These results were confirmed by 24 hour ambulatory blood pressure monitoring. 24 ABPM showed prolonged effect of acebutolol SR 400 mg on blood pressure and heart rate.
Conclusions Our results indicate prolonged antihypertensive effect of acebutolol SR 400 mg lasting more than 24 hours. In the studied group of patients with essential hypertension, WHO grade I and II, acebutolol SR 400 mg given once daily and standard acebutolol 200 mg given twice a day demonstrated the comparable antihypertensive efficacy and tolerability. The study clearly showed that it was possible to maintain the equipotent antihypertensive effect when the patient receiving one formula was switched to another.