Exam - Elderly

Question 1

Overview of prescribing in the elderly

Answer 1

BNF

Question 2

Inappropriate prescribing is common. The main reasons for this are:

Answer 2

• over prescribing for every symptom/problem
• pt or carer demanding or refusing drug
• inappropriate response to non-medical problem
• a lack of review (use if START/STOPP)
• Failure to recognise a drug reaction, which in turn leads to prescribing more drugs

Question 3

Impact of age in pharmacodynamics:

Answer 3

Changes in homeostatic mechanisms:
- cognitive function
- thermoregulation
- thirst/hydration (reduced anti diuretic hormone)
- Orthostatic regulatory response (reduced dopamine receptors)

(Increased sensitivity to drugs and increased risk of ADR, especially in women)

Question 4

Impact of age on pharmacokinetics:

(Absorption)

Answer 4

• reduced gastric acid so increased gastric PH
• decreased gastric emptying
• decrease in GI motility
• reduced surface area - significant increase in levodopa absorption

(Decreased absorption but not usually clinically significant)

Question 5

Distribution

Answer 5

• Diseases that cause low albumin are more common - change in free vs bound drug
• Reduction in lean body mass
• increase in total body fat (increased half life for lipid soluble drugs - eg diazepam)
  Reduction in total body water (decreased Vd for water soluble drugs - eg digoxin)

Question 6

Metabolism

Answer 6

• reduced liver size and blood flow (hepatotoxic drugs may cause more severe injury - eg valproate)
• impairment of phase 1 (P450) oxidation pathways - phase 2 generally not effected
• Increased bioavailability of drugs extensively metabolised in the liver
• Drug metabolism can be significantly impaired in the elderly

Question 7

Excretion

Answer 7

• decreased renal blood flow (GFR and renal tubular function)
• Serum creatinine is an unrealistic marker in elderly
• after the age of 30 GFR reduces by 8ml/min every 10 years in 2/3 of the population
• generally slower clearance, increasing half life so longer to get to steady state
• Greater risk of nephrotoxic drugs such as ACEI, NSAIDs and some antibiotics such as gentamicin
• caution with renal excreted drugs with a narrow therapeutic window
• urinary excretion of nitrofurantoin reduced (sub therapeutic effect)

Question 8

The geriatric giants (Issacs 1992) summarise common illnesses under the headings:

Answer 8

• immobility
• instability
• incontinence
• intellectual impairment

These geriatric giants are common causes of hospital admissions and are often caused by or exacerbated by poor prescribing

Question 9

START/STOPP

Answer 9

BNF

Question 10

Summery of good prescribing

Answer 10

BNF