Module 3: Pharmacokinetic changes in elderly

Question 1

What are the pharmacokinetic alterations in older adults related to absorption?

Answer 1

Decreased splanchnic blood flow (blood supply to abdominal organs)

Increased gastric pH

Drug-drug interactions

Question 2

How does altered body composition affect distribution?

Answer 2

Altered body composition:
- decreased lean body mass
- increased body fat
- water soluble drugs = decreased volume of distribution, increased serum concentration and risk for adverse effects
- fat soluble drugs = increased volume of distribution, decreased initiation response/concentration, prolonged response due to accumulation in fat

Question 3

How does decreased serum proteins affect distribution?

Answer 3

Decreased serum albumin = less to bind with drug = increased unbound drug = increased risk for adverse effects and toxicity

Exacerbated by:
- liver disease
- malnutrition
- drug-drug interactions

Question 4

How is metabolism altered in the older adult?

Answer 4

Decrease size of liver
Decreased hepatic blood flow
Decreased hepatic enzyme activity (CYP450) = decreased metabolism of drugs and increase for drug toxicity

Question 5

How is excretion altered in the older adult?

Answer 5

Renal function declines
Loss of lean muscle mass
Cockroft-Gault formula (prediction of creatinine clearance) limitations in older adult