Pharmacodynamics describes the course of action of a drugs and aging at the effector organ level, in terms of duration and magnitude of action, and amplitude of and time to reach the peak action, for both therapeutic and adverse actions. Alterations in the number and affinity of drug receptors, postreceptor signaling processes, biochemical responses, homeostatic mechanisms, and body composition, in addition to higher likelihood of polypharmacy and concurrent pathological processes in older age, make elders more susceptible to adverse drug reactions, drug–drug interactions, or decreased/ increased sensitivity to some drug action. (more…)

We do not realize the mechanisms of biological aging or the reasons for aging are the limits of the estimated averages life expectancy of people are very empirical. The forces of natural selection with age, as in natural populations, few people survive beyond the age of reproduction. In recognition of these ideas, some would suggest an antagonistic pleiotropy hypothesis that the genes of a disadvantage in a population is not necessary to the reproductive phase, after which take place occur at the population can get. The environment is hostile, and individuals compete for resources. (more…)