Anti-hypertensive action of labetalol: a detailed profile


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Anti-hypertensive action of labetalol: a detailed profile. G. R. Bellamy, S. N. Hunyor, D. Roffe and J. Massang. Aust. N.Z. J. Med., 1982, 12, pp. 467–472. 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<0001) and home BP from 147196 ± 1519 to 134/84±10/9 (p<001). 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<001) and reduction of post-release BP “overshoot” (P<001) 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 <001) 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.
Original languageEnglish
Pages (from-to)467-472
Number of pages6
JournalAustralian and New Zealand Journal of Medicine
Issue number5
Publication statusPublished - 1982
Externally publishedYes


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