drugs and polypharmacy Flashcards
what is polypharmacy
many drugs (>5)
even one unecessary medication can place an older person at risk of an avoidable toxic reaction
there is a difference between appropriate and inappropriate polypharmacy
how common are ADRs
> 2mln serious ADRs p/a
100 000 deaths p/s
4th leading cause of death
nursing home pts ADR rate - 350 000p/a
at least 15% of hospitalised people will have some sort of ADR during their stay
relationship between ADRs and polypharmacy
6-8/9 drugs - 50% chance of ADR
9-10 drugs - ~100% chance of ADR, almost everyone has at least one symptom that can reasonably be attributed to the drug
how preventable are ADRs
nearly 1/3 of ADRs in ambulatory settings are preventable
1/2 of ADRs in nursing facilities are preventable
common iatrogenic drug problems
anticholinergics - confusion, dry mouth, constipation, blurred vision, urinary retention and orthostatic hypotension
tricyclics - confusion, unsteady gait
digoxin toxicity w/ normal serum concentrations
long acting benzodiazepines - CNS toxicity
narcotics - confusion
important drug related problems/ADRs in the elderly
falls
cognitive loss/deririum
dehydration
incontinence
depression
end result - loss of functional capacity, poor QOL, nursing home placement
prescriptions in older adults
> 50y/o - 2-3x as many prescriptions
- 12% of pop, >32% of prescription drugs
typical 85y/o - 8-9 prescriptions and 2 OTC at once
why do older adults have more prescriptions
more acute and chronic disease
more doctors visits
drugs often given to counteract a side effect of another drug - prescribing cascade
several other factors arising from prescribers, patients and the system
co-morbidity in increasing age
most people by the age of 85 have ~3 co-morbid conditions
a significant proportion will have 6 or more
what can ADRs also look like
similar presentations to ageing
unsteadiness dizziness confusion nervousness fatigue insomnia drowsiness falls depression incontinence
presentation of hyperthyroidism in young vs old patient
young: tremor anxiety weight loss diarrhoea
elderly: depression cognitive impairment muscle weakness AF heart failure angina
common conditions present differently
misdiagnosis is another key cause of polypharmacy
healthcare provider factors that contribute to polypharmacy
no medication review w/ pt regularly
presumes that patient expects meds
prescribes w/o sufficiently investigating clinical situation
evidence that a particular drug is the best drug for given issue
unclear, complex or incomplete instructions about how to take meds
no effort to simplify medication regimen
ordering automatic refills
lack of knowledge of geriatric clinical pharmacology
change in drug absorption in old age
extent is generally unaffected by age but rate slows significantly - may lead to delay in onset of action
example of change in absorption in older people
reduction in saliva production
reduction in rate of absorption of buccally administered drugs
e.g. GTN
can lead to over administration of GTN when effect isn’t seen –> GTN syncope
change in drug distribution in older people
change in body composition:
- reduced muscle mass
- increased adipose tissue - increased volume of distribution, increased 1/2 life, increased duration of action e.g. diazepam
- reduced body water - reduced Vd, increased serum levels e.g. digoxin
protein binding changes:
- decreased albumin - reduced binding, increased serum levels and increased active drug e.g. furosemide
increased permeability across the blood-brain barrier
what alters hepatic metabolism in older age
decreased liver mass
decreased liver blood flow
consequences of change in hepatic metabolism in older people
toxicity - reduced metabolism/excretion
reduced 1st pass metabolism
- increase in bioavailability w/ some drugs (propanolol)
- or decreased bioavailability of pro-drugs (enalapril) - less effective and take longer to work
changes in excretion in older age
renal function decreases with age
reduces clearance and increases 1/2 life of many drugs - toxicity
changes in pharmacodynamics in older age
increased sensitivity to particular medicines
due to:
- change in receptor binding
- decrease in receptor number
- altered translation of a receptor initiated cellular response into a biochemical reaction
e.g. increased sedation with diazepam, increased anti-coagulation w/ warfarin
principles of prescribing in older people
be clear about the diagnosis to avoid prescribing a drug to manage an adverse effect
consider whether drug therapy is the best therapeutic action
lower doses/reduced frequency of administration
think about whether the drug causes particular problems in elderly
check whether a lower dose is required in the elderly - start low and titrate up slowly
review and check whether aim is being achieved w/ new drug
review all prescriptions regularly and stop any non-beneficial meds
keep regimens as simple as possible
consider compliance issues
what is deprescribing
to reduce, substitute or discontinue a drug
why? ADR drug-drug interaction drug-disease interaction better alternative not effective not indicated not evidence based minimised polypharmacy
pro-active deprescribing
main aim is to counter polypharmacy and the associated issues
systematic review of medication withdrawal trials in >65y/o:
- diuretics - 51-100% withdrawn w/ v few problems
- anti-HT - 20-85% normotensive after 6mths-5yrs, no XS deaths
- psychotropics - reduction in falls and increased cognition
safe and/or beneficial to stop anti-HT, benzodiazepines and antipsychotics (and maybe also diuretics)
what are the drugs most asssociated w/ admission due to ADRs
NSAIDs diuretics warfarin ACEI antidepressants beta blockers opiates digoxin prednisolone clopidogrel
where do most of the negative effects of polypharmacy come from
anticholinergics and sedatives
