Anti-hypertensive action of labetalol: a detailed profile.
Continuous, ambulatory blood pressure (BP) and self measured home recordings were used to study the response of ten mild to moderate hypertensives taking a twice daily labetalol dosage. Testing of cardiovascular reflexes was carried out 12 hours after a dose of drug. The mean 24 hour BP was reduced from 145/80 +/- 14/7 (SD) mmHg to 130/71 +/- 11/6 (p less than 0.001) and home BP from 147/96 +/- 15/9 to 134/84 +/- 10/9 (p less than 0.01). The predominant effect of labetalol was evident during the waking hours. A residual 9.5% BP reduction was seen 12 hours after a dose compared to an 11% lowering effect over the entire 24 hours (NS). No symptomatic hypotensive episodes were noted. Significant inhibition of heart rate and BP rise during dynamic exercise (p less than 0.01) and reduction of post-release BP "overshoot" (p less than 0.01) in Valsalva's manoeuvre indicated a beta adrenoceptor blocking effect. There was however a reduction in the rate of rise of BP during static handgrip (p less than 0.01) indicating a small alpha adrenoceptor blocking component. This study has demonstrated the efficacy of a twice daily regimen of labetalol in continuously lowering BP. The mode of action of the drug during exercise (static and dynamic) and Valsalva's manoeuvre would indicate a predominant beta adrenoceptor blocking action.
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D001795:Blood Pressure Determination; D002940:Circadian Rhythm; D002986:Clinical Trials as Topic; D004983:Ethanolamines / Q000627:therapeutic use*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D007741:Labetalol / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D011897:Random Allocation; D012648:Self Care; D013997:Time Factors; D014636:Valsalva Maneuver
D004983:Ethanolamines; D007741:Labetalol