1 Hepatic metabolism of long-acting drugs markedly declines, increasing the risk for toxicity. Kidney perfusion and the number of functional kidney cells decline, resulting in decreased excretion of waste products, such as creatinine. Drugs or their metabolites with long half-lives are toxicity risks because of the accumulation that occurs more rapidly with renal impairment. In the gastrointestinal tract, the colon and esophageal transit times slow in the elderly. There is atrophy of the gastric glands and decreased secretion of acid and trypsin, a digestive enzyme.
Active transport is slowed, decreasing the absorption of nutrients such as sugar, calcium, and iron.
In some elderly people, these changes cause constipation, which is exacerbated by most analgesics. 1 Passive diffusion, the process of absorption for most drugs, is not affected by age. Elderly people have a decreased immune response and are slow to develop fevers associated with appendicitis, decubiti, and viral or bacterial infections. Contrary to popular belief, the elderly are not less sensitive to pain. They perceive it differently, with more acceptance and resignation than younger adults.