Prescribing in Special Circumstances

Question 1

What changes, relating to absorption of oral medications, occur as people are?

Answer 1

• Increase in gastric pH due to reduced gastric secretions
• Delayed gastric emptying
• Reduced splanchnic blood flow
• Decreased surface area for absorption odd medications in the GI tract
• Decreased GI motility

Question 2

How does age affect VoD of water-soluble medicines?

Answer 2

Reduction in total body water leads to a smaller VoD resulting in higher serum concentrations

Question 3

How does age affect VoD of lipid-soluble medicines?

Answer 3

Reduced body fat leads to increased VoD resulting in prolonged half-life

Question 4

How does the liver change with age?

Answer 4

Volume decreases (20-40%)
Decline in activity of Cytochrome P450
Hepatic blood flow reduction (~35%)

Question 5

What is the major pharmacokinetic determinant of toxicity due to medication in older people?

Answer 5

Age-related decline in renal function

Question 6

Examples of medicines excreted by the kidney?

Answer 6

Aminoglycosides (e.g. gentamicin)
Digoxin
Lithium salts
Metformin
Thiazide diuretics

Question 7

Medicines likely to cause postural hypotension

Answer 7

Alpha-blockers
Antihypertensives
Antidepressants
Beta-blockers
Diuretics
Hypnotics
Nitrates