Pharmacokinetics, beta-adrenoceptor blockade and anti-hypertensive action of labetalol during chronic oral treatment.
1 beta-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 beta-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 beta-adrenoceptor blockade and the change in systolic pressure at 2 h after the oral dose. 4 Efficacy of labetalol as a beta-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-1, the mid point labetalol concentration (Cmax+Cmin) divided by 2 and the isoprenaline dose ratio-1 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-1 and the CSS labetalol ng ml-1.
D000284:Administration, Oral; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D004983:Ethanolamines / Q000378:metabolism*; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D007700:Kinetics; D007741:Labetalol / Q000378:metabolism* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013997:Time Factors
D004983:Ethanolamines; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D007741:Labetalol