AGE AND CYTOCHROME P450-LINKED DRUG-METABOLISM IN HUMANS - AN ANALYSIS OF 226 SUBJECTS WITH EQUAL HISTOPATHOLOGIC CONDITIONS

Objectives: The effect of aging on drug metabolism in humans has not y et been completely described. Methods: Two hundred twenty-six patients with equal histopathologic conditions were investigated. The cytochro me P450 contents in the liver biopsy samples, the plasma antipyrine cl earance rates after oral administration and, as an independent control of vitality, serum testosterone levels were determined. Results: Cyto chrome P450 content in subjects from 20 to 29 years of age was 7.2 +/- 2.6 nmol . gm(-1), increased during the fourth decade (+7.2%, p = NS) , declined after 40 years (-16%, P < 0.01) to a level that remained un altered up to 69 years, and declined further after 70 years (-32%, p < 0.001). The antipyrine (phenazone) clearance rate in young subjects w as 46.4 +/- 18.5 ml . min(-1), remained unaltered during the fourth de cade, and declined after 40 years by a rate of 0.34 ml . min(-1) per y ear toward old age (-29%, p < 0.001). The half-life in young subjects was 9.5 +/- 2.0 hours and increased after 30 years toward old age (+26 %, p < 0.001). The volume of antipyrine distribution, 0.46 +/- 0.12 L . kg(-1) in young subjects, decreased after 30 years (-11%). In line w ith the testosterone content, the decrease in drug metabolism was equa l in both sexes. Conclusion: This study shows a reduction of in vitro and in vivo drug metabolism with age in humans. The data suggest that at least three age groups-young, middle-aged, and elderly-should be in cluded in the evaluation of the pharmacokinetics of a new drug. The re duction of drug metabolism (-30%) after 70 years of age indicates that care is needed in the prescription of drugs for elderly subjects.