Pharmacokinetics in the Elderly

Pharmacokinetics - is the way that the body absorbs, distributes, metabolizes, and excretes medication. Age-related physiological changes affect body systems, altering pharmacokinetics and increasing or altering a drug’s effect.

	Physiological Change	Effect on Pharmacokinetics
Absorption	■ Decreased intestinal motility ■ Diminished blood flow to the gut	■ Delayed peak effect ■ Delayed signs and symptoms of toxicity
Distribution	■↓fluid volume ■↑body fat percentage ■↓plasma proteins ■↓lean body mass	■↑serum concentration of water-soluble drugs ■↑half-life of fat-soluble drugs ■↑amount of active drug ■↑drug concentration
Metabolism	■↓blood flow to liver ■↓liver function	■↓rate of drug clearance by the liver ■↑accumulation of some drugs
Excretion	■↓kidney function ■↓creatinine clearance	■↑ accumulation of drugs that are normally excreted by the kidneys