With age, there are certain physiological changes that can affect the way drugs act in the body. Normal aging changes the way drugs are absorbed, metabolized, distributed, and removed from the body. At age 75, our bodies react differently to many medications than they did at age 25. As a person ages, the ratio of lean body mass to body fat tissue changes, even though total weight may remain the same. The percentage of body fat increases.
Drugs distributed in fat have a wider distribution.
This may result in a less intense, but prolonged effect in an older person. Sleeping medications, tranquilizers. The percentage of body weight comprised of water decreases with age. The emptying of the stomach is delayed and intestinal motility slows. Drug action may be decreased or delayed.