Hemodynamic effect of lofexidine with a diuretic in hypertension.
We measured the first dosage effect and the long-term effect of lofexidine on blood pressure, heart rate, plasma catecholamines, and their major metabolites in 16 patients with primary hypertension who were receiving 50 mg hydrochlorothiazide twice a day while they were recumbent and upright and during isometric handgrip contraction. We also measured the first dosage effect of lofexidine on forearm blood flow and its long-term effect on plasma renin activity. Lofexidine, both in a single dose and after long-term therapy, induced a substantial fall in blood pressure of patients in recumbent and upright positions, whereas it decreased heart rate in both positions only during long-term dosing. Lofexidine did not prevent or diminish the pressure and heart rate rise by isometric handgrip contractions. Single and long-term lofexidine dosing induced a fall in plasma levels of catecholamines and their metabolites. There was a positive correlation between the fall in blood pressures and the reduction in plasma norepinephrine during long-term therapy. There was a positive correlation between the decrease in blood pressure induced by single doses and by long-term dosing, which suggests that lofexidine in a single dosage at the start of therapy may facilitate identification of responders.
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002986:Clinical Trials as Topic; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D004837:Epinephrine / Q000097:blood; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006852:Hydrochlorothiazide / Q000627:therapeutic use; D006973:Hypertension / Q000188:drug therapy*; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood
D006852:Hydrochlorothiazide; D003000:Clonidine; C025655:lofexidine; D009638:Norepinephrine; D004837:Epinephrine