A comparison of the trough-to-peak ratio of cardio-selective beta-blockers in patients with newly diagnosed hypertension.
BACKGROUND
The drug can be administered once a day, if the trough-to-peak ratio (T/P) exceeds 50-66%. The objective of this work was to determine and compare the T/P ratio for betaxolol hydrochloride and for extended-release metoprolol tartrate.


METHODS
An open, randomized, prospective, comparative clinical study. The 24-h ambulatory blood pressure was measured with a SpaceLab 90207 automatic instrument (Redmond, Washington, USA) before and after 3 months of beta-blocker treatment. In order to determine the peak value, the individual maximum hourly mean blood pressure reduction was determined in the 3 to 6-h post-dose interval. For the determination of the trough value, the individual hourly mean blood pressure decrease in the 23-h post-dose interval, minimal 30 min after getting up in the morning was used. The T/P ratio was calculated as the mean of individual T/P ratios with statistical description of standard deviation (SD) and 95% confidence intervals (CIs).


RESULTS
Betaxolol hydrochloride reduced the mean peak systolic blood pressure value by 17.87+/-8.32 mmHg, the mean peak diastolic blood pressure value by 16.07+/-6.65 mmHg, the mean trough systolic blood pressure value by 11.83+/-5.98 mmHg and the mean trough diastolic blood pressure value by 11.33+/-6.74 mmHg. The mean T/P ratio was calculated as 72.84+/-33.32% (95% CI, 60.40-85.285%) for systolic blood pressure and as 71.57+/-29.35% (95% CI, 60.62-82.53%) for diastolic blood pressure. Metoprolol reduced the mean peak systolic blood pressure value by 16.70+/-10.54 mmHg, the mean peak diastolic blood pressure value by 14.20+/-8.67 mmHg, the mean trough systolic blood pressure value by 11.30+/-9.12 mmHg and the mean trough diastolic blood pressure value by 10.00+/-8.38 mmHg. The mean T/P ratio was calculated as 70.59+/-31.66% (95% CI, 58.76-82.41%) for systolic blood pressure and as 66.95+/-31.60% (95% CI, 55.15-78.75%) for diastolic blood pressure.


CONCLUSIONS
The T/P ratio determined for betaxolol hydrochloride and extended-release metoprolol tartrate is higher than 66%. This ratio guarantees a satisfactory 24-h effect of both the above-mentioned drugs.
Soucek
Miroslav
M
2nd Clinic of Internal Diseases, St Anna Teaching Hospital, Brno, Czech Republic.
Rihacek
Ivan
I
Frana
Petr
P
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000328:Adult; D015784:Betaxolol / Q000008:administration & dosage*; D001794:Blood Pressure / Q000187:drug effects; D018660:Blood Pressure Monitoring, Ambulatory / Q000295:instrumentation; D003692:Delayed-Action Preparations / Q000008:administration & dosage; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D008790:Metoprolol / Q000008:administration & dosage*; D011446:Prospective Studies; D013997:Time Factors
D000319:Adrenergic beta-Antagonists; D003692:Delayed-Action Preparations; D008790:Metoprolol; D015784:Betaxolol