Prescribing in special groups 2

Question 1

Why have life expectancies at birth and retirement improved?

Answer 1

reduced impact of risk factors e.g. smoking

advances in healthcare

Question 2

What are the consequences of the ageing population?

Answer 2

focus shifts to chronic diseases
shit from one time interventions correcting a single problem to… ongoing management of multiple diseases and disabilities
increasing disability => increasing need for long-term care services
need to integrate medical and long term care services

Question 3

What’s made drug treatment complicated?

Answer 3

co-morbidities - risk of drug interactions => causes polypharmacy
also increases risk of adverse drug reactions

Question 4

What are the definitions of physiological ageing and frailty?

Answer 4

physiological ageing=> time related loss of functional units within an organ system e.g. nephrons, neurones

Frailty => progressive physiological decline in multiple organ systems => loss of function, loss of physiological reserve and increased vulnerability to disease and death

Question 5

What is appropriate polypharmacy?

Answer 5

polypharmacy traditionally defined at 4 or more drugs

prescribing for complex conditions or multiple conditions where medicines use is optimised and prescribed according to best evidence - for many this will extend life expectancy and improve QoL

Question 6

What is problematic polypharmacy?

Answer 6

prescribing of multiple medications inappropriately or where intended benefit of medication is not realised
increase risk of drug interactions and adverse reactions, impair adherence to medication and reduce quality of life

Question 7

What are the pharmacokinetic changes in absorption in the elderly?

Answer 7

reduced saliva (solid oral formulations)
increased gastric pH 
decreased GI motility 
Decreased GI and regional blood supply 
however little evidence that dosage needs to be altered due to this

Question 8

What happens in terms of 1st pass metabolism in the elderly?

Answer 8

normally 1st pass metabolism can result in extensive metabolism of lipid soluble drugs (90-95%)
but in elderly reduced hepatic blood flow means reduced 1st pass metabolism and greater drug effect

even a minor reduction in 1st pass metabolism can result in significant increase in drug bioavailability

Question 9

How does the pharmacokinetics of distribution change in the elderly?

Answer 9

distribution of body fat and water is altered in the older adults

• increased proportion of fat => increasing Vd of lipid soluble drugs = therefore lipid soluble drugs accumulate
• decrease in total body water =>decrease Vd for water soluble drugs therefore lower doses of water soluble drugs

reduced plasma protein conc - increase in free drug =>increased risk of toxicity

Question 10

In terms of metabolism how does it change in the elderly?

Answer 10

hepatic metabolism of many drugs thought CYP50s decreases with age
- reduced metabolic clearance resulting in increased levels or duration of action of drugs extensively metabolised
pro drugs may be less effective

Question 11

In terms of elimination how does it change in the elderly?

Answer 11

one of the most important pharmacokinetic changes is decreased renal elimination of drugs
GFR falls with age (60-70ml/min by 80)
renal tubular function also falls
therefore renally excreted drugs need dose adjustments - digoxin, gentamicin, lithium salts, opiates

Question 12

What are the body systems affected during ageing?

Answer 12

heart

• changes in cardiac architecture, less compliance
• loss of pacemaker cells
• calcification of conduction system
• less response to catecholamines

endocrine changes
- reduction in hormone production, target sensitivity - oestrogen, testosterone, GH, IGF-1

skeletal muscle - atrophy

bones and joints- osteoporosis and osteoarthritis

CNS - vision and hearing

Question 13

What pharmacodynamic changes occur with ageing?

Answer 13

changes in receptor sensitivity
reduction in receptor numbers
=> increases sensitivity to several drugs

Question 14

What are the categories of impairment that appear in the elderly = geriatric giants?

Answer 14

immobility, instability, incontinence, and impaired intellect/memory

Question 15

What are the frailty syndromes?

Answer 15

new definitions of geriatric giants

• falls => collapse, legs gave way
• immobility => sudden change in mobility
• delirium => acute confusion, muddledness
• incontinence=> change in continence
• susceptibility to SE of medication=> confusion with codeine, hypotension with antidepressants

Question 16

What is the leading cause of mortality in older people >75?

Answer 16

falls are a major cause of disability - can lead to osteoporotic fractures

Question 17

How can fall risk be minimised?

Answer 17

identify drugs causing falls
review of medication to reduce polypharmacy
adequate nutrition, especially with calcium and vit D to reduce risk of osteoporosis
multidisciplinary falls service

Question 18

What drugs tend to cause falls?

Answer 18

anything acting on brain or circulation - usually mechanism leading to falls is:
1) sedation, with slowing of reaction times and impaired balance
2) hypotension or arrhythmias
Strong associations
- psychotropic medications (benzos, anxiolytics, hypnotics, sedatives, antidepressants, and anti-psychotic drugs)
- cardio medications

Question 19

What drugs can cause impaired intellect/memory?

Answer 19

ageing associated with marked structural and neurochemical changes in CNS
dementia characterised by gradual deterioration of higher mental functions / intellectual capacity
anticholinergics, hypnotics and antidepressants can all cause intellectual impairment, confusion
cognitive impairment can lead to poor compliance

Question 20

How can dosage forms affect compliance in the elderly?

Answer 20

simplify regimens (OD or BD)
blister packs and bottle tops 
liquids and measuring 
sublingual tablets and dry mouths 
functional capacity

Question 21

What tools are available to identify if elderly are taking appropriate medications?

Answer 21

beer’s criteria, medication appropriateness index, gerontoNet ADR risk score, STOPP/START

Question 22

What is the STOPP/START criteria?

Answer 22

screening tool of older people’s prescriptions (STOPP) and screening tool to alert right treatment (START)
START = unless status is en of life these criteria are drug therapies to be considered where omitted for no valid clinical reasons
STOPP - prescriptions which are potentially inappropriate to use in patients >65

Question 23

What needs to be done for older people with social care needs in terms of their medications?

Answer 23

need to plan collaboratively

• discuss managing medicines with each person and their carer
• note any requirements about managing medicines into the care plan

Question 24

What drugs shouldn’t be given to patients with renal impairment and why?

Answer 24

nephrotoxicity= NSAIDs cause interstitial nephritis

Some drugs are renally eliminated and shouldnt be given or given with caution - vancomycin

some drugs are BOTH nephrotoxic and eliminated by kidneys

some are just ineffective - bendroflumethiazide, nitrofurantoin

Question 25

How is renal function determined?

Answer 25

creatinine is a crude marker
can lead to incorrect categorization of patients with both “normal” and decreased GFR
MDRD formula can determine dosage adjustments in place of creatinine or creatinine clearance = mathematically modified serum creatinine with additional info from patients age, sex and ethnicity

Question 26

What are the different stages of renal impairment in terms of eGFR?

Answer 26

Stage 1 = normal - >90
Stage 2 = mild - 60-89 
Stage 3 =moderate - 30-59
Stage 4 = severe - 15-29 
Established renal failure - <15

Question 27

What drugs should be avoided in renal impairment?

Answer 27

aminoglycosides = nephrotoxic
metformin - increased risk of lactic acidosis
nitrofurantoin - not effective if eGFR <45
K supplements - risk of hyperkalaemia (ACEI and K sparing diuretics can potentiate this risk)
lithium - narrow therapeutic index
NSAIDs - avoid chronic kidney disease (exacerbate fluid overload and oedema)

Question 28

What should you do if a patient develops an AKI?

Answer 28

aim is to prevent further injury and facilitate recovery of renal function

• assess circulating vol ad fluid admin
• prevent and/or treat hyperkalaemia and metabolic acidosis
• discontinue all potentially nephrotoxic drugs
• dose adapt drugs excreted by the kidneys to the patients renal function
• other supportive manage measures (may inc diuretics for fluid management)

Question 29

What does prothrombin time reflect?

Answer 29

synthesis of clotting factors and is a useful measure of hepatic synthetic capacity, but does not reflect metabolic capacity

Question 30

What can reduced hepatic function lead to with drug metabolism?

Answer 30

hypoproteinuria = affect protein binding

reduced clotting = increased sensitivity to warfarin, NSAIDs

Question 31

What other mechanisms does hepatic insufficiency affect the actions of drugs?

Answer 31

biliary obstruction - prevents excretion of some drugs and prevent the actions of others

hypoalbuminaemia = complicate the interpretation of plasma phenytoin concentrations

reduced hepatic synthetic function will increase a patients sensitivity to drugs such as warfarin

Question 32

What does hepatic insufficiency lead to?

Answer 32

fluid overload => avoid the use of drugs that could exacerbate this = NSAIDs, corticosteroids

Question 33

What drugs can precipitate hepatic encephalopathy?

Answer 33

avoid :

• sedative drugs
• diuretics = can cause hypokalaemia
• drugs that can cause constipation

Question 34

What factors need to be considered when prescribing in hepatic impairment?

Answer 34

whether the drug is highly protein bound (phenytoin) - decreased serum albumin can increase free drug

how the drug is metabolised ?

how the drug is excreted?
whether the drug is hepatotoxic