Physiological Drug

Question 1

Absoprtion

Answer 1

• In general, absorption of drugs is slower in the older adult due to diminished gastric motility and reduced gastrointestinal blood flow – as a result, drugs response may be somewhat delayed
• Increased gastric pH can delay absorption of medications that require high acidity to dissolve

Question 2

What affects distribution?

Answer 2

• Reduced concentration of serum albumin
• Increased percent body fat
• Decreased percent lean body mass and total body water

Question 3

What affects metabolism

Answer 3

• Liver’s production of enzymes decreases
• Reduced hepatic blood flow
• Reduced liver size

Question 4

Excretion

Answer 4

• There is a reduction in renal blood flow, glomerular filtration rate, tubular secretion, and nephron function – this will decrease the excretion of drugs
• When excretion is reduced, the potential for toxicity is markedly increased
• Index of renal function

In the elderly, the proper index of renal function is:

Creatinine clearance

Question 5

Pharmacodynamics

Answer 5

Beta-adrenergic blocking agents (beta-blockers) are less effective

• A reduction in the number of available beta receptors
• A reduction in the affinity of beta receptors for beta-receptor blocking agents

Other drugs (some CNS depressants, oral anticoagulants) produce effects that are more intense in the elderly than in younger adults, suggesting a possible increase in receptor number (receptor affinity or both)

Question 6

Factors that influence drug regimen

Answer 6

Poly-pharmacy

• Altered pharmacokinetics (absorption, distribution, metabolism & elimination)
• Accumulation of toxic amounts of drugs secondary to impaired renal excretion
• Poor patient compliance (forgetfulness, failure to understand instructions, complex regimens, unpleasant side effects)