Prescribing For the Older Person

Question 1

What are the main reasons for in appropriate prescribing for the older person? (5)

Answer 1

• Over prescribing (prescribing drugs for all problems/symptoms)
• The pt or carer demanding or refusing a drug
• Inappropriate response to non-medical problems
• Lack of regular medication review
• Failure to recognise an adverse drug reaction, which in turn may lead to prescribing more drugs

iatrogenic = a problem caused by treatment

Question 2

What are the pharmacodynamic changes in the older person?

Answer 2

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

• general increased sensitivity to drugs and increased risk of adverse drug reaction, especially woman

Question 3

What are the physiological changes in the older person effecting absorption? (4)

Answer 3

• gastric PH is higher due to reduced acid secretions
• Decrease in gastric emptying
• Decrease in gastrointestinal motility
• Reduced gut surface area - significant increase in levodopa absorption

(Decreased absorption but not usually clinically significant)

Question 4

What are the physiological changes in the older person effecting distribution? (4)

Answer 4

• Diseases that cause low albumin are more common - changes in free vs bound proportion of 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 5

What are the physiological changes in the older person effecting metabolism? (4)

Answer 5

• Reduced liver size and blood flow - hepatotoxic drugs may cause more severe injury in older people (eg valproate)
• Impairment of phase 1 (P450) oxidation pathways (phase 2 generally unaffected) - preference for prescribing drugs metabolised by phase 2 (more predictable)
• Increased bioavailability of drugs extensively metabolised in the liver
• Drug metabolism can be significantly impaired in the elderly

Question 6

What are the physiological changes in the older person effecting excretion? (7)

Answer 6

• Decreased renal blood flow (renal tubular function and glomerular filtration rate)
• Serum creatinine is an unrealistic marker in elderly
• After the age of 30 - GFR reduces by 8ml/min per decade in 2/3 of the population
• generally slower clearance and excretion of drugs, increasing half life so longer to get to steady state
• Greater risk of nephrotoxic effects of drugs such as ACEI, NSAIDs and some antibiotics
• Caution with renal excreted drugs with a narrow therapeutic window
• urinary excretion of nitrofurantoin reduced (sub therapeutic effect)

Question 7

Summarise good prescribing practice in the older person (7)

Answer 7

• Is it needed? STOPP/START
• Be familiar with the drugs you prescribe
• Is the dose correct (start low go slow)
• Consider risks of drug interactions and contraindications
• Is the treatment regime as simple as possible
• Make it clear
• Review regularly (STOPP/START)

Question 8

a) What is the acronym STOPP?

b) What is the acronym START?

Answer 8

a) STOPP - Screening tool of older person’ potentially inappropriate prescriptions (included in BNF drug monographs)

b) START - Screening tool to alert the right treatment (this tool is used to prevent omission of indicated appropriate medicines in older people with specific conditions

Question 9

What is Geriatric Giant (Isaacs 1992)? (3)

Answer 9

• Highlights illnesses associated with ageing under the headings:
• immobility
• instability
• incontinence
• intellectual impairment
• Common causes of hospital admissions
• Many of the geriatric giants can be caused by or exacerbated by poor prescribing