title: The effect of vitamin C on the pharmacokinetics of caffeine in elderly men.
abstract: The influence of vitamin C on the pharmacokinetics of caffeine was investigated in 10 elderly males, age 66 to 86 yr. Caffeine was administered intravenously on three different occasions over a 7-wk period: before vitamin C restriction, after approximately 4 wk of vitamin C restriction (15 mg dietary intake per day), and after 2 wk of vitamin C supplementation (500 mg orally, twice daily). Blood and urine samples were collected over a 48-h period after each caffeine administration. The plasma half-life, rate constant of elimination, apparent volume of distribution, total body clearance, renal clearance, and metabolic clearance of caffeine were determined. Simultaneous plasma, whole blood and leukocyte vitamin C concentrations were obtained. All of the average vitamin C concentrations monitored (plasma, whole blood, and leukocyte) changed significantly during the study, corresponding to the alterations in dietary vitamin C intake. Conversely, none of the caffeine pharmacokinetic parameters evaluated changed significantly during the study. The average metabolic clearance was approximately 77 (ml hr-1) kg-1 and the average half-life was approximately 4.6 h for all caffeine administrations. These results indicate that the elimination of caffeine in the elderly is not affected significantly by the concentrations of vitamin C achieved during this study.
mesh_terms: D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D002110:Caffeine / Q000097:blood / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007700:Kinetics; D008297:Male; D013997:Time Factors
chemical_list: D002110:Caffeine; D001205:Ascorbic Acid