title: Acute effect of labetalol on blood pressure in relation to the sympathetic nervous system and plasma renin activity.
abstract: A single oral dose of 300 mg labetalol was given to 10 subjects with uncomplicated primary hypertension; its effects on blood pressure, heart rate (HR), plasma renin activity (PRA), and plasma concentration of catecholamines and of their major metabolites, octopamine ( OTP ), and dopamine-beta hydroxylase (DbH) were investigated. Although HR did not change after dosing, both systolic and diastolic blood pressure decreased in 2 hr and remained below control up to 12 hr. There was symptomatic orthostatic hypotension in two subjects in the first 2 hr after dosing. PRA decreased in the first 2 hr and followed a gradual rise that became significant at 24 hr. Although DbH did not change, plasma concentrations of norepinephrine (NE) and its major metabolites and of OTP increased between 2 and 4 hr after dosing and remained elevated up to 12 hr. There was no correlation between change in blood pressure and control levels or changes of PRA or NE concentrations.
mesh_terms: D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood; D004983:Ethanolamines / Q000494:pharmacology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000188:drug therapy; D007741:Labetalol / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D012083:Renin / Q000097:blood*; D013564:Sympathetic Nervous System / Q000187:drug effects*
chemical_list: D002395:Catecholamines; D004983:Ethanolamines; D012083:Renin; D007741:Labetalol