title: Pharmacokinetics of bethanidine in hypertensive patients.
abstract: The pharmacolinetics of bethanidine-14C was studied in three hypertensive patients. A 25-MG DOSE OF BETHANIDINE-14 C hemisulfate was administered intravenously. Plasma levels of drug were measured over the first 6 hr. In 3 to 4 days, 89% to 94% of the dose was excreted in the urine. Thin-layer chromatography (TLC) and isotope dilution analysis of the urine samples indicated that only intact bethanidine was excreted. Plasma level and urinary excretion rate profiles had miltiphasic characteristics. Estimated half-lives of the terminal phase ranged from 7 to 11 hr. Average renal clearance over the initial 6 hr approached renal plasma flow. In 2 of the patients, renal clearance between 2 and 4 hr after administration was reduced to one-helf that observed during the initial 2-hr period. After single oral administration of a 25-mg dose of bethanidine-14C hemisulfate, 48% of 61% was excreted in urine and 15% to 48% in feces. Peak urinary excretion rates were reached 6 hr following administration. The urinary excretion kinetics of bethanidine during and after repetive oral dosing was also studied. A 25-mg dose was dividied into 12 to 16 equal doses and administered avery 6 hr. A larger fraction of the cumulative dose was recovered in the urine (72% to 74%) than after the single dose, suggesting higher availability at the lower dose. Steady-state urinary excretion rates were achieved in 4 to 7 doses. The steady-state urinary excretion levels were consistent with pharmacolinetic predictions based on single oral dose data. When 2 of the patients were given imipramine for 2 days prior to an oral 25-mg dose of bethanidine-14C hemisulfate, the terminal half-lives of the urinary excretion rate profiles were shorter than those in the same patients not given imipramine.
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001593:Benzyl Compounds / Q000008:administration & dosage / Q000378:metabolism; D003864:Depression, Chemical; D005243:Feces / Q000032:analysis; D006146:Guanidines / Q000008:administration & dosage / Q000378:metabolism*; D006207:Half-Life; D006626:Hippurates / Q000378:metabolism; D006801:Humans; D006973:Hypertension / Q000378:metabolism*; D007099:Imipramine / Q000494:pharmacology; D007275:Injections, Intravenous; D008875:Middle Aged; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D001593:Benzyl Compounds; D006146:Guanidines; D006626:Hippurates; D007099:Imipramine