polypharmacy: adverse drug effects in the elderly
TRANSCRIPT
Polypharmacy: Adverse Drug Effects in the
Elderly
Centre on Aging Spring SymposiumMay 4, 2009
Acknowledgements
• Dr. Pat Montgomery• American Geriatrics Society
• Disclaimer – I have no financial conflict of interest related to the topic, and I buy my own lunch.
Outline
• Definitions• Prevalence and Harm• Causes and contributing factors• Measuring• Interventions
Definitions
• Polypharmacy - many drugs– How many is too many? 3? 6? 9? Depends
what drugs?• Adverse Drug Effects - any unintended
drug effect causing harm– To a degree unavoidable: nothing
ventured, nothing gained– Avoidable ADEs ~ inappropriate
prescribing
Definitions
• Inappropriate prescribing - any Rx where potential harms outweigh potential benefits– Underprescribing and overprescribing– Beers, IPET criteria
Dave’s Drug Dichotomies
Useful Useless
Harmless Good, but rare Snake Oil
Harmful Most Rx Bad, too common
THE BURDEN OF INJURIES FROM MEDICATIONS
ADEs are responsible for 5% to 28% of acute geriatric hospital
admissions
THE BURDEN OF INJURIES FROM MEDICATIONS
ADEs occur in 35% of
community- dwelling elderly
persons
Incidence of ADEs: 26/1000 hospital beds
(2.6%)
THE BURDEN OF INJURIES FROM MEDICATIONS
In nursing homes, $1.33 is spent on ADEs for every $1.00 spent on
medications
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Burden of ADEs
• Polypharmacy is a risk factor and/or cause of most ‘geriatric syndromes’:– Falls– Cognitive impairment– Incontinence– Functional impairment
Causes of ADEs in the Elderly
• High prevalence of Rx– Drug-drug interactions
• Multiple chronic illnesses– Drug-disease interactions– Prescribing cascade
• Frailty, decreased ‘homeostasis’• Altered pharmacokinetics
Ballantine. CCNQ 2008; 31(1):40-45
Prevalence of Rx in US
0102030405060708090
100
Present 2040
People 65+ 65+ share of prescriptionsPeople <65 <65 share of presciptions
Now, people age 65+ are 13% of US population, buy 33% of prescription drugs
By 2040, will be 25% of population, will buy 50% of prescription drugs
Guidelines and polypharmacy
• Boyd et al JAMA 2004• Hypothetical 78 y.o. woman with COPD,
DM2, OA, hypertension, osteoporosis• Reviewed relevant Clinical practise
Guidelines (CPGs) on each problem (from national clearinghouse)
Poly-Guidelinism
• If followed, would result in a complex 12-med regime with 19 doses at 5 times, potential interactions, $406/month, 14 non-medication recommendations, complex monitoring and medical follow-up
Boyd et al
• Also rated 9 CPGs on common illnesses
• 7 of 9 discussed age and/or comorbidities but only 4 considered age with comorbidity
• Only 1 (diabetes) considered life expectancy vs the time needed to achieve treatment benefit
Guidelines
• Few discussed quality of life, burden of treatments on patients and family, or financial impact
• “CPGs provide little guidance for clinicians about caring for older patients with multiple chronic diseases”
• Concern about ‘Pay-for-Performance’ forcing blind compliance to guidelines
Prescribing Cascade
• Prescription of successive medications to treat side effects or drug-disease interactions or other prescriptions– Increased use of urinary anticholinergics
after donepezil started– NSAIDs and ‘gastro-protection’ but also
antihypertensives and diuretics
Frailty and Homeostasis
• Frail elderly have decreased ‘physiologic reserve’ to tolerate drug effects
• Increased heterogeneity in old vs young, so response to medication less predictable
Markers of Frailty
• nutrition: low BMI, low albumin/cholesterol• cardiovascular: CHF, postural hypotension• cognitive impairment, immobility,
incontinence, multiple co-morbidity• functional dependence, ADL/IADL• social isolation, need for home care• institutionalization
Pharmacologic Effects of Frailty
• few studies, not synonymous with aging• altered renal clearance, serum
creatinine underestimates kidney function
• reduced hepatic volume & drug clearance
• exaggerated drug effect due to impaired homeostasis
Therapeutic Consequences of Frailty
• subjects are not included in clinical trials, beneficial effects of treatment not studied
• multiple pathology and polypharmacy• limited life expectancy, loss of association
with traditional outcome predictors eg BP• quality of life as primary end-point for therapy,
?? value of preventive treatments
PHARMACOKINETICS
Absorption
Distribution
Metabolism
Elimination
Assessing Polypharmacy
• Various number cut-offs, arbitrary and not useful with individual patients
• Inappropriate prescribing:– Beers criteria, successive updates– Medication Appropriateness Index– Inappropriate Prescribing in the Elderly
Tool
The Medication Appropriateness Index
Holmes et al Arch Intern Med. 2006;166:605-609
Assessing Polypharmacy
• All rely on judgement of experts, therefore depend on credibility of the judge
• Problems with generalisibility over time, other countries
Approaches to Reducing ADEs in the Elderly
• Primary prevention/Point-of-prescribing– Start low, go slow– Academic detailing– Consideration of frail elderly in guidelines– Computerised drug interaction software– Regulatory/formulary restriction
Approaches
• Secondary/tertiary prevention– Medication review– Pharmacist structured review
“pharmacologic debridement”– Beers criteria– Academic Detailing
Approaches
• Some studies with evidence of benefit in reducing numbers of drugs
• Effects tend to wear off, tachyphylaxis develops
• Little evidence of actual changes in patient outcomes to date
Stopping Drugs in Elderly Patients “Starting Rules”
• Vast majority of medical education and CME is directed at “starting rules”
• most studies concerned with initiating drugs, rarely deal with when/why to stop
• drug company pressure• poly-pathology, proliferation of
interventions in chronic disease
Barriers to Stopping Drugs
• limited evidence base in literature• possible liability; errors of commission
versus omission• need for careful balancing of risks
versus benefits; under-recognition of frailty
• lack of clear guidelines when to stop
Therapeutic Humility
• The awareness that many (most?) available treatments are unproven for our patients
• Benefits and risks are uncertain• Competing and interacting morbidity
and mortality
Therapeutic Humility
• There is no good evidence for most interventions in the frail elderly
• One should be less confident that any given treatment will do what one expects for your patient
• …especially when you consider or encounter adverse effects, polypharmacy, costs