Question
What is pharmacokinetics? How does that differ in older adults versus the general population?
Answer
Pharmacokinetics is defined as how the body processes drugs. The four areas in pharmacokinetics are: absorption, distribution, storage, and elimination. The processes of pharmacokinetics changes as people age. As a result, they tend to process drugs differently.
Absorption
Older adults have decreased esophageal motility, increased gastric emptying time, decreased hydrochloric acid and decreased stomach muscle mass and blood flow. These issues lead to overally decreased peristalsis. In an older adult, drugs may not absorb as readily and may stay in the system longer.
Distribution
There is decreased albumin and alpha-1 glycoprotein levels. There is a decreased ability for drugs to be carried through the blood stream as a result. Older adults tend to have decreased total body water which can lead to drug toxicity. Finally they can have increased percentage of body fat which can increase the duration of activity for fat soluable drugs.
Metabolism
Older adults have a decreased liver size and weight with decreased hepatic blood flow. As the liver is the primary metabolizer, decreased blood flow leads to increased half life of drugs and increased drug toxicity.
Elimination
There is a slower speed at which the blood is filtered by the kidneys. Due to the decreased renal blood flow, drugs are not excreted as efficiently. There is also a reduction in elimination causing increased potential for toxicity.
