5. Geriatric Pharmacology

Question 1

Describe this parameter of age-associated pharmacokinetics: Absorption

• Age Effect
• Implications

Answer 1

• Age Effect:
  
  • Increased gastric pH
  • Decreased splanchnic blood flow, GI absorptive surface and dermal vascularity; delayed gastric emptying
• Implications: Drug-drug and drug-food interactions are more likely to affect absorption

Question 2

Describe this parameter of age-associated pharmacokinetics: Distribution

• Age Effect
• Implications

Answer 2

• Age Effect:
  
  • Increased total body fat
  • Increased α1-glycoprotein
  • Decreased lean body mass and total body water
  • Decreased albumin
• Implications:
  
  • Lipophilic drugs have a larger volume of distribution
  • Increased binding of basic drugs
  • Decreased volume of distribution of hydrophilic drugs
  • Decreased binding of acidic drugs

Question 3

Describe this parameter of age-associated pharmacokinetics: Metabolism

• Age Effect
• Implications

Answer 3

• Age Effect: Decreased hepatic mass and hepatic blood flow; impaired phase I reactions (oxidative system)
• Implications: Lower doses may be therapeutic

Question 4

Describe this parameter of age-associated pharmacokinetics: Elimination

• Age Effect
• Implications

Answer 4

• Age Effect:
  
  • Decreased renal blood flow, glomerular filtration rate, tubular secretion
  • Overall reduction in renal function by 30-50%
• Implications: Lower doses may be therapeutic

Question 5

Describe: Drug Sensitivity (3)

Answer 5

• changes in pharmacokinetics as well as intrinsic sensitivity lead to altered drug responses
• increased sensitivity to warfarin, sedatives, antipsychotics, anticholinergics, digoxin, and narcotics
• decreased sensitivity to β-blockers and β-adrenergic stimulants, though may have increased sensitivity

Question 6

Describe: Decreased Homeostasis (1)

Answer 6

• poorer compensatory mechanisms leading to more adverse reactions (e.g. bleeding with NSAIDs/ anticoagulants, altered mental status with anticholinergic/sympathomimetic/anti-Parkinsonian drugs)

Question 7

Adverse drug reactions in the elderly may present as what? (5)

Answer 7

• as delirium
• falls
• fractures
• urinary incontinence/retention
• fecal incontinence/impaction

Question 8

Define: Polypharmacy (1)

Answer 8

• prescription, administration or use of more medications than are clinically indicated

Question 9

Describe epidemiology: Polypharmacy (2)

Answer 9

• in Canada, >60% of elderly individuals reported using ≥5 medications
• hospitalized elderly are given an average of 10 medications during admission

Question 10

Name risk factors for non-compliance in polypharmacy ()

Answer 10

• greater number of medications (compliance with 1 medication is 80%, but drops to 25% with ≥6 medications)
• increased dosing frequency, complicated container design, financial constraints, and cognitive impairment

Question 11

Describe: Adverse Drug Reactions (ADRs) (1)

Answer 11

• any noxious or unintended response to a drug that occurs at doses used for prophylaxis or therapy

Question 12

Name risk factors in the elderly of: Adverse Drug Reactions (ADRs) (9)

Answer 12

• intrinsic:
  
  • comorbidities (>5)
  • age >85
  • low BMI
  • age-related changes in pharmacokinetics
  • pharmacodynamics, CrCl <50 mL/min
• extrinsic:
  
  • number of medications, (>9 medications, >12 doses/d),
  • multiple prescribers
  • unreliable drug history
  • prior ADR

Question 13

Describe: Prescribing cascade (4)

Answer 13

• process whereby an ADR is misinterpreted as a new medical condition, and a subsequent drug is prescribed to treat the initial drug-induced event. Providers should ask themselves:
  
  • is the new drug being prescribed to address an adverse event from a previously prescribed drug therapy?
  • is the initial drug therapy potentially leading to a prescribing cascade really needed?
  • what are the harms and benefits of continuing the initial drug therapy?

Question 14

Describe: Preventing Polypharmacy (5)

Answer 14

• consider drug: safer side effect profiles, convenient dosing schedules, convenient route, efficacy
• consider patient: other medications, clinical indications, medical comorbidities
• consider patient-drug interaction risk factors for ADRs
• review drug list regularly to eliminate medications with no clinical indication or with evidence of toxicity
• avoid treating an ADR with another medication

Question 15

Describe epidemiology: Inappropriate Prescribing in the Elderly (1)

Answer 15

the estimated prevalence of potentially inappropriate prescribing ranges from 12-40%

Question 16

Describe: Beers Criteria (4)

Answer 16

• a list of medications to avoid in adults ≥65 yr due to safety concerns
• 2015 update lists drugs that should be avoided or dose-adjusted based on kidney function, as well as drug-drug interactions associated with harms in older adults
• examples include long-acting benzodiazepines, strong anticholinergics, high-dose sedatives
• the elderly are often under-treated (ACEI, ASA, β-blockers, thrombolytics, oral anticoagulants)

Question 17

Describe: STOPP/START Criteria (2)

Answer 17

• another screening tool for potentially inappropriate prescribing in the elderly
  
  • STOPP: Screening Tool of Older Person’s Prescriptions
    
    • systems-based list of medications contraindicated in adults ≥65 in the context of their diagnoses
  • START: Screening Tool to Alert doctors to Right Treatment
    
    • systems-based list of medications indicated in adults ≥65 in the context of their diagnoses

Question 18

Describe: Principles for Prescribing in the Elderly (5)

Answer 18

CARED

• Caution/Compliance
• Age (adjust dosage for age)
• Review regimen regularly
• Educate
• Discontinue unnecessary medications