Pharmacokinetics, beta‐adrenoceptor blockade and anti‐hypertensive action of labetalol during chronic oral treatment

Abstract

1 fl-adrenoceptor blockade, plasma labetalol concentrations and anti-hypertensive actions were investigated at 2 hourly intervals during the interdose period of chronic oral therapy in six hypertensive patients.2 f,-adrenoceptor blockade varied during the inter-dose period and was maximal 2 and 4 h after the oral dose (P < 0.05). 3 Systolic pressure rose during the interdose period (P < 0.05). A significant correlation was found between the degree of fl-adrenoceptor blockade and the change in systolic pressure at 2 h after the oral dose.4 Efficacy of labetalol as a P-adrenoceptor antagonist and anti-hypertensive drug was assessed 2 h after an oral dose during chronic eight hourly dosage in sixteen hypertensive patients. Pharmacokinetics of labetalol were studied in the same patients. 5 Peak plasma labetalol concentration occurred 2 h after the oral dose and subsequently the plasma concentration declined monoexponentially.6 The steady state concentration (Css) of labetalol was correlated significantly with the daily oral dose in mg kg , the mid point labetalol concentration (Cmax + Cmin) and the isoprenaline dose ratio-I 2 at 2 h after the oral dose.7 No correlation was found between the antihypertensive effect and the Css ng ml-1 labetalol or between the isoprenaline dose ratio-I and the Css labetalol ng ml-.