Effects of aging

 

Effects of aging

Drug-receptor interaction

  • Brain receptors become more sensitive, making psychoactive drugs very potent.

Metabolism

  • Liver mass shrinks.
  • Hepatic blood flow and enzyme activity decline.
  • Metabolism drops to 1/2 to 2/3 the rate of young adults.
  • Enzymes lose ability to process some drugs, thus prolonging drug half-life.

Absorption

  • Gastric emptying rate and gastrointestinal motility slow.
  • Absorption capacity of cells and active transport mechanism decline

Circulation

  • Vascular nerve control is less stable.
  • Anti-hypertensives, for example, may overshoot, dropping BP too low.
  • Digoxin, for example, may slow the heart rate too much.

Excretion

  • In kidneys, renal blood flow, glomerular filtration rate, renal tubular secretion and reabsorption, and number of functional nephrons decline.
  • Age-related changes increase half-life for renally excreted drugs.
  • Oral antidiabetic drugs, among others, stay in the body longer.

Distribution

  • Lean body mass falls.
  • Adipose stores increase.
  • Total body water declines, raising the concentration of water-soluble drugs, such as digoxin, which can cause heart dysfunction.
  • Plasma protein levels decrease, reducing sites available for protein-bound drugs and raising blood levels of free drug.
    • Safety
      • Older adults are at higher risk for accidents
        • Most occur in or around the home
      • Declining thermoregulation accounts for the higher rate of deaths during severe cold spells and heat waves
      • Carefully orient older adults on admission
    • Depression
      • Not a normal part of aging
      • Second highest rate of suicide occurs in those over 75
      • Occurs together with medical conditions
    • Adequacy of sleep is a common concern
  • Evaluation
    • Is there an identifiable change in ADLs, IADLs, mental status, or signs and symptoms of the disease?
    • Does the individual consider his or her health state to be improved?
    • Does the individual think the plan is helpful?
    • Do the individual and caregiver think the care is worth the time and cost?
    • Can you document positive changes that support the interventions?

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