THE EFFECTS OF VITAMIN-C ON THE PHARMACOKINETICS OF CAFFEINE IN ELDERLY MALES

Persistent Link:
http://hdl.handle.net/10150/281992
Title:
THE EFFECTS OF VITAMIN-C ON THE PHARMACOKINETICS OF CAFFEINE IN ELDERLY MALES
Author:
Trang, John Milton
Issue Date:
1981
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The influence of vitamin C on the pharmacokinetics of caffeine was investigated in ten elderly males, age 66 to 86 years. Caffeine (4 mg kg⁻¹) was administered intravenously on three different occasions over a seven-week period: before vitamin C restriction, after approximately four weeks of vitamin C restriction (15 mg dietary intake per day), and after two weeks of vitamin C supplementation (500 mg orally, twice daily). Blood and urine samples were collected over a 48-hour period following each caffeine administration. The plasma half-life (t₁/₂), rate constant of elimination (K), apparent volume of distribution (V), total body clearance (TBC), renal clearance (RC), and metabolic clearance (MC) of caffeine were determined. Simultaneous plasma (PVC), whole blood (WBVC), and leukocyte (WBCVC) vitamin C concentrations were obtained. All of the mean vitamin C values determined at the first kinetic trial (KT-1) were within the normal ranges for the respective biologic fluid or tissue. All of the mean vitamin C values changed significantly during the study; decreasing to below the normal ranges by the second kinetic trial (KT-2) following dietary vitamin C restriction, and increasing to the normal ranges by the third kinetic trial (KT-3) following vitamin C supplementation. All of the decreases and increases in the individual and average vitamin C concentrations paralleled the observed decreases and increases in the daily vitamin C intake. None of the caffeine pharmacokinetic parameters evaluated changed significantly during the study. The mean rate constant of elimination was approximately 0.15 hr⁻¹, the average plasma half-life was approximately 4.5 hours, and the mean apparent volume of distribution was approximately 500 ml kg⁻¹ for all three kinetic trials. The average total body, renal, and metabolic clearances were approximately 76.9, 1.3, and 76.0 (ml hr⁻¹)kg⁻¹, respectively, for all three kinetic trials. With the exception of V and TBC, the various pharmacokinetic characteristics investigated were in general agreement with data reported for younger subjects. The average apparent volume of distribution determined at any of the kinetic trials was about 16% lower than the value reported for young, healthy subjects. Similarly, the mean total body clearance observed was about 21% lower than that observed in young, healthy subjects. Since the average elimination rate constant observed in these elderly subjects is similar to the values observed in younger subjects and since TBC is equal to the product of V times K, the reduced TBC observed in this study appears to be due to the reduction in V, rather than to a decrease in the intrinsic metabolic capacity of the liver with aging. No relationship between vitamin C intake and/or body levels and the pharmacokinetics of caffeine was observed. These results indicate that the elimination of caffeine in the elderly is not affected significantly by the concentrations of vitamin C achieved during the study.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Vitamin C -- Physiological effect.; Caffeine -- Physiological effect.; Older men.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Pharmaceutical Sciences
Degree Grantor:
University of Arizona
Advisor:
Blanchard, James

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleTHE EFFECTS OF VITAMIN-C ON THE PHARMACOKINETICS OF CAFFEINE IN ELDERLY MALESen_US
dc.creatorTrang, John Miltonen_US
dc.contributor.authorTrang, John Miltonen_US
dc.date.issued1981en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe influence of vitamin C on the pharmacokinetics of caffeine was investigated in ten elderly males, age 66 to 86 years. Caffeine (4 mg kg⁻¹) was administered intravenously on three different occasions over a seven-week period: before vitamin C restriction, after approximately four weeks of vitamin C restriction (15 mg dietary intake per day), and after two weeks of vitamin C supplementation (500 mg orally, twice daily). Blood and urine samples were collected over a 48-hour period following each caffeine administration. The plasma half-life (t₁/₂), rate constant of elimination (K), apparent volume of distribution (V), total body clearance (TBC), renal clearance (RC), and metabolic clearance (MC) of caffeine were determined. Simultaneous plasma (PVC), whole blood (WBVC), and leukocyte (WBCVC) vitamin C concentrations were obtained. All of the mean vitamin C values determined at the first kinetic trial (KT-1) were within the normal ranges for the respective biologic fluid or tissue. All of the mean vitamin C values changed significantly during the study; decreasing to below the normal ranges by the second kinetic trial (KT-2) following dietary vitamin C restriction, and increasing to the normal ranges by the third kinetic trial (KT-3) following vitamin C supplementation. All of the decreases and increases in the individual and average vitamin C concentrations paralleled the observed decreases and increases in the daily vitamin C intake. None of the caffeine pharmacokinetic parameters evaluated changed significantly during the study. The mean rate constant of elimination was approximately 0.15 hr⁻¹, the average plasma half-life was approximately 4.5 hours, and the mean apparent volume of distribution was approximately 500 ml kg⁻¹ for all three kinetic trials. The average total body, renal, and metabolic clearances were approximately 76.9, 1.3, and 76.0 (ml hr⁻¹)kg⁻¹, respectively, for all three kinetic trials. With the exception of V and TBC, the various pharmacokinetic characteristics investigated were in general agreement with data reported for younger subjects. The average apparent volume of distribution determined at any of the kinetic trials was about 16% lower than the value reported for young, healthy subjects. Similarly, the mean total body clearance observed was about 21% lower than that observed in young, healthy subjects. Since the average elimination rate constant observed in these elderly subjects is similar to the values observed in younger subjects and since TBC is equal to the product of V times K, the reduced TBC observed in this study appears to be due to the reduction in V, rather than to a decrease in the intrinsic metabolic capacity of the liver with aging. No relationship between vitamin C intake and/or body levels and the pharmacokinetics of caffeine was observed. These results indicate that the elimination of caffeine in the elderly is not affected significantly by the concentrations of vitamin C achieved during the study.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectVitamin C -- Physiological effect.en_US
dc.subjectCaffeine -- Physiological effect.en_US
dc.subjectOlder men.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePharmaceutical Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBlanchard, Jamesen_US
dc.identifier.proquest8121923en_US
dc.identifier.oclc8618222en_US
dc.identifier.bibrecord.b13877379en_US
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