The aging process. Physiologic changes and pharmacologic implications.

Age-related physiologic changes are important to consider when making diagnostic and therapeutic decisions. Such changes begin in the fifth decade and continue at varying rates depending on the organ system involved. Physicians need to be aware of the ramifications of the aging process, especially with regard to decreased functional reserve and changes in drug actions. The concept of homeostenosis implies that a functional elderly person may maintain health into old age but become increasingly vulnerable to stress and illness because of a lack of physiologic reserve. Thoughtful clinical application of this concept improves purely medical outcomes and surely enhances patients' quality of life in their later years.