Transcript Dr. Arlene Bierman

Patterns of Prescription Drug Use
among Older Adults
Arlene S. Bierman, MD, MS
Ontario Women’s Health Council Chair in Women’s Health
Centre for Research in Inner City Health
St. Michael’s Hospital
June 15, 2005
Patterns of Prescription Drug Use
among Older Adults
 Prescription Drug Use in the Elderly
– Pharmacoepidemiology
 Medication-Related Problems and Adverse Events
– Why the elderly are especially at risk
 Suboptimal Prescribing
– Scope of the Problem
 Inappropriate Prescribing
– Drugs to Avoid
 Summary and Questions
Prescription Drug Use
in the Elderly:
Pharmacoepidemiology
Drug Use in the Elderly
Benefits
 Major advances in pharmacotherapeutics.
 Effective and appropriate use of medications
can
– reduce the risk of premature mortality,functional
decline, and disability.
– improve quality of life.
Drug Use in the Elderly-Benefits
Examples
 Antihypertensives
– Reduce risk of heart failure and stroke
 ß-blockers and aspirin
– Reduce risk of mortality and recurrent heart attack
after a myocardial infarction
 Angiotensin Converting Enzyme (ACE) Inhibitors
– Reduce mortality and risk of hospitalization in heart failure
 Biphosphonates
– Reduce risk of hip and vertebral fractures in osteoporosis
Prescription Drug Use
 Persons age 65 and older 15% US population
but use 33% of all prescription drugs.
 Community-dwelling elders take an average of
3-4 prescriptions concurrently.
 Nursing home residents commonly receive an
average of 6 concurrent medications and 20%
receive 10 or more.
Use of Medications During the Preceding Week
100
90
94
91
81
80
Use, %
70
57
60
Any Use
≥ 5 Drugs
44
50
≥ 10 Drugs
40
30
25
20
12
12
5
10
0
Total
Men (≥ 65 yrs old)
Women (≥ 65 yrs old)
Kaufman, JAMA 2002
Use of Prescription Drugs During the Preceding Week
100
90
81
71
80
Use, %
70
60
50
Any Use
50
≥5 Drugs
40
30
19
20
23
7
10
0
Total
Men (≥ 65 yrs old)
Women (≥ 65 yrs old)
Kaufman, JAMA 2002
Vitamins/Minerals & Herbals/Supplements Use:
1-Week Prevalence*
≥ 65 years old
Men
(n=243)
Women
(n=351)
Total
(N=2590)
Any
vitamin/mineral
use
47%
59%
40%
Any
herbal/supplement
use
11%
14%
14%
Type
* Percentages weighted according to household size
Kaufman, JAMA 2002
Drug Use in Community Dwelling Elderly*
58.8
Cardiovascular Agents
33.9
Anti-infective Agents
Analgesics
28.3
23.9
Hormones
Psychotherapeutic Agents
18
Respiratory Agents
18
13.1
Central Nervous System Agents
Coagulation Modifiers
9.9
Anti-hyperlipidemic Agents
9.4
Diabetic Agents
8.6
0
10
20
30
Percentage (%)
40
50
60
*1996: N=27,285,988
Moxey, Health Care Financing Review 2003
Prescription Drug Use: Harms
 Medications have the potential for harm as well as
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benefit and adverse drug events (ADE) are common.
An ADE is an injury from a medication.
Annually 35% of community-dwelling elders
experienced an ADE, 29% required health care
services.
Adverse drug events responsible for 5-28% of acute
hospitalizations among geriatric patients.
In nursing home residents, 51% of ADEs were found
to be preventable.
Medication-Related Problems
Why the elderly are at risk
Why the elderly are at risk
 Patient-level factors
–
–
–
–
–
–
Age-associated changes in pharmacokinetics
Age-associated changes in pharmacodynamics
Comorbidity: drug-disease interactions
Polypharmacy: drug-drug interactions
Less physiologic reserve
Frailty
 System level factors
– Fragmentation of care (Poly-doctoring)
– Inadequate training in principles of geriatric practice
Changes in Pharmacokinetics
 Age-associated changes in physiology and organ
function result in changes in pharmacokinetics
 Pharmacokinetics is the time course of a drug
and its metabolites through the body
– Absorption
– Distribution
– Clearance: elimination (renal), metabolism (liver)
2004: Cusack, Amer. J of Geriatric Pharmacotherapy
Volume of Distribution (Vd)
 Vd is the extent of distribution in the plasma relative to
the amount in the body.
 The elderly have an increased proportion body fat and
decreased muscle mass that changes the Vd
 Increased volume of distribution for fat soluble drugs
increases longer half life-e.g., diazepam
 Decreased volume of distribution for water soluble
drugs increases drug plasma concentration-e.g.,
ethanol
Protein Binding
 Decreased albumin associated with chronic
disease: e.g.,malnutrition, liver or kidney
conditions.
 Drugs that bind to plasma proteins will have
increased bioavailability due to a higher
proportion of unbound (active) agent.
 Drugs that bind to albumin include
ceftriaxone,diazepam, phenytoin, warfarin.
Elimination: Heterogeneity of
Physiology and Organ Function
 Decreased renal function results in decreased
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elimination of drugs excreted by the kidney.
Even in the absence of kidney disease renal
clearance may be reduced 35-50%.
Reduced renal clearance of active metabolites may
enhance therapeutic effect or increase risk of toxicity.
Need to reduce dose and/or increase dosing intervals.
However, Baltimore Longitudinal Study of Aging 1/3 of
healthy elderly had no decline in renal function, and
small number actually improved-risk of subtherapeutic
dosing
Hepatic Metabolism
 Decreased liver size and hepatic blood flow.
 Regional blood flow to the liver at age 65 is reduce by
40-45% compared to a 25 year old.
 Metabolic clearance of drugs by the liver may be
reduced.
 Disease effects: liver congestion from heart failure
decreases warfarin metabolism and an increased
pharmacologic response.
 Environmental effects: smoking stimulates
monoxygenase enzymes and increases clearance of
theophylline.
Changes in Pharmacodynamics
 Age-associated changes in pharmacodynamics (the
time course and intensity of pharmacolgic effect) place
elderly at increased risk for adverse drug events.
 Older patients may have more sedation and impaired
function after a single dose of benzodiazepines than
younger persons.
 After single dose of nitrazepam older patients made
more mistakes on psychomotor testing compared to
placebo while younger patients had no impairment .
Suboptimal Prescribing
in the Elderly
Suboptimal Prescribing
 Polypharmacy
 Underuse of Effective Medications
 Drug-Drug Interactions
 Drug-Disease Interactions
 Inadequate Monitoring
 Inappropriate Dosing
 Inappropriate Duration
 Drugs to Avoid
Suboptimal Quality
 Typology of Quality Problems
– Overuse (Polypharmacy)
– Underuse
– Misuse (Inappropriate Prescribing )
– Errors
The Prescribing Cascade
1997: Rochon, BMJ
Drug-Drug Interactions
 Drug-Drug Interaction (DDI) is the pharmacologic or
clinical response to a drug combination that differs
from the effect of the two agents when given alone.
 DDIs increase with the number of drugs used and are
associated with an increased risk of adverse drug
events.
 Most common effects neuropsychologic (confusion) or
cognitive impairment, hypotension, renal failure.
 Metabolism through the hepatic cytochrome P 450
system is an important cause of DDIs.
Polypharmacy
 Polypharmacy is the administration of more
medications than are clinically indicated.
 Lipton found 59%of elderly outpatients taking drugs
that had no indication or were less than optimal.
 Schmader found 55% of outpatients to be taking
drugs with no indication, 32.7% were taking ineffective
drugs, and 16.8% were taking drugs with therapeutic
duplication.
2001: Hanlon, JAGS
Underuse
 Among patients elderly patients with cardiovascular disease
and diabetes, only 19.1% of patients were prescribed statins. In
patients 66 to 74 years old, the adjusted probabilities of statin
prescription were 37.7%, 26.7%, and 23.4% in the categories
of low, intermediate, and high baseline risk, respectively.
 The likelihood of statin prescription was 6.4% lower (adjusted
odds ratio, 0.94; 95% confidence interval, 0.93-0.95) for each
year of increase in age and each 1% increase in predicted 3year mortality risk.
2004: Ko, JAMA
Inappropriate Prescribing
in the Elderly
Inappropriate Prescribing in the Elderly
 Inappropriate prescribing is a major patient
safety concern in the aged population.
 Studies consistently find that 20-27% of older
Americans receive drugs identified as
inappropriate.
 Inappropriate prescribing increases risk for
falls, hip fractures, cognitive impairment,
diminished independence, and death.
Anticholinergics
 Many potentially inappropriate drugs have
anticholinergic properties.
 Acetylcholine neurotransmitter with key role in
both sympathetic and parasympathetic nervous
systems.
 Side effects include dry mouth, constipation,
urinary retention, blurred vision, confusion.
Summary: Drugs in the Elderly
A Double-Edged Sword
Questions
 How do age-related changes in physiology
mediate the health effects effect of
environmental exposures in the elderly?
 What do we need to know about potential
interactions between environmental exposures
and medications and/or specific diseases?
 Which elders are at higher risk and how can
these risks be mitigated?