The aging liver: consequences for drug treatment in old age

Numerous age-related changes in hepatic structure and function have been described although liver function seems to be quite well maintained in old age. Few consistent and reproducible observations and a lack of correlation between structural and functional data characterize the present state of our knowledge. However, a decline in liver volume and blood flow has been shown in older subjects, which is the physiologic basis of reduced hepatic drug clearance in this age group. In contrast to renal clearance, no reliable method exists to estimate hepatic drug clearance. The contribution of age to altered drug clearance in the elderly is difficult to assess as drug interactions, numbers and types of drugs taken at a time, underlying disease and increased interindividual variability are superimposed to the aging process. Therefore, after decades of research into the matter, the old and well known aphorism ‘start lower — go slower’ is valid more than ever in the field of geriatric prescribing. Not only renally excreted drugs but also substances metabolized and excreted by the liver should be used in a starting dose which is 30–40% smaller than the average dose used in middle aged adults.