Step-by-step explanation:
Pharmacotherapy in the elderly requires an understanding of the age-dependent changes in function and composition of the body. Aging is characterised by a progressive loss of functional capacities of most if not all organs, a reduction in response to receptor stimulation and homeostatic mechanisms, and a loss of water content and an increase of fat content in the body. The most important pharmacokinetic change in old age is a decrease in the excretory capacity of the kidney; in this regard, the elderly should be considered as renally insufficient patients. The decline in the rate of drug metabolism with advancing age is less marked. In addition, the volume of distribution and the oral bioavailability of drugs may be changed in the elderly compared with younger individuals. Average dosage adjustments for the aged can be derived from simple equations and mean pharmacokinetic parameters from older and younger adults. However, these average dose adjustment factors neglect the large variation in the decline in organ functions among the elderly. Individual dose adjustment factors can be obtained from the drug clearance in a particular patient, where clearance/fractional bioavailability (CL/f) may be calculated from the area under the plasma concentration-time curve (AUC) of the drug in question. Using pharmacokinetic guidelines for dose adjustments,