This document discusses pharmacologic considerations for geriatric patients. It covers how physiological changes in aging can impact drug absorption, distribution, metabolism and elimination. Specifically, it notes decreased gastric acidity, gastrointestinal blood flow and renal function in elderly patients. This can affect the bioavailability and clearance of various drugs. It emphasizes that age-related changes in pharmacokinetics require monitoring major drug classes like sedatives, cardiovascular drugs and antimicrobials in geriatric patients. Noncompliance is also a challenge due to factors like forgetfulness and prior experiences. Simplifying drug regimens can help improve medication adherence in the elderly.

1. Slide 1 © 2001 By Default!
Pharmacologic
Considerations
Geriatrics

2. Slide 2 © 2001 By Default!
Introduction
 In the US, the elderly (>65y/o) constitute ~12% of
the total population, but account for almost 30% of
total drug expenditure
 Age-related physiologic changes make the elderly
susceptible to adverse effects
 Understanding the influence these changes have
on the pharmacokinetics and pharmacodynamics of
the elderly is essential to prevent harm

3. Slide 3 © 2001 By Default!
Physiologic Changes of Aging
Affecting Absorption
 Physiologic change
– Decreased gastric acidity
– Decreased gastrointestinal blood flow
– Delayed grastric emptying
– Slowed intestinal transit time
 General clinical effect
– None on passive diffusion or bioavailability for most drugs
– Decreased active transport: Decreased bioavailability for
some drugs
– Decreased first-pass effect: Increased bioavailability for
some drugs
 Special considerations
– Antacids decrease absorption of acidic drugs: digitalis,
phenytoin, tetracycline
– Anticholinergics: Slow GI motility and absorption rate

4. Slide 4 © 2001 By Default!
Physiologic Changes of Aging
Affecting Distribution
 Decreased Total body water
– Decreased Volume Distribution
– Increased Plasma Conc. of water soluble drugs
– Lower doses are required: Lithium, digoxin, ethanol, etc
 Decreased Lean body mass and Increased body fat
– Increased Volume Distribution, Longer (t½) of water
soluble drugs
– Accumulation into fat of lipid soluble drugs: Benzos, etc
 Decreased Serum Albumin
– Increased unbound fraction of highly protein bound drugs
– Binds acidic drugs: warfarin, phenytoin, digitalis, etc
 Decreased Alpha1 Acid glycoprotein
– Increased unbound fraction of highly protein bound drugs
– -Binds basic drugs: lidocaine and propranolol, etc

5. Slide 5 © 2001 By Default!
Metabolism
 Determined
– Primarily by hepatic function and blood flow
– Capacity of the liver to metabolize drugs does not appear
to decline consistently with age for all drugs

6. Slide 6 © 2001 By Default!
Elimination
 Determined
– Primarily by renal function
– Declines with age and is worsened by co-morbidities
– Decline is not reflected in an equivalent rise in serum
creatinine since creatinine production is reduced due to
lower muscle mass

7. Slide 7 © 2001 By Default!
Physiologic Changes of Aging
Affecting Elimination
 Physiologic change
– Decreased GFR
– Decreased renal blood flow
– Decreased renal mass
 General clinical effect
– Decreased clearance, Increased (t½) of renally eliminated
drugs

8. Slide 8 © 2001 By Default!
Pharmacodynamics
 Pharmacodynamic changes in the elderly have
been less extensively studied
 Evidence of enhanced end-organ responsiveness
or “sensitivity” to medications with aging
 Enhanced “sensitivity” may be due
– Changes in receptor affinity
– Changes in receptor number
– Post-receptor alteration
– Age-related impairment of homeostatic mechanisms
Example: decreased baroreceptor reflexes

9. Slide 9 © 2001 By Default!
Major Drug Groups Requiring
Monitoring
 CNS drugs
– Sedative-hypnotics: Benzodiazepines and barbiturates
– Analgesics: Opioids
– Antipsychotic, antidepressants: Haloperidol, lithium, TCAs
 Cardiovascular drugs
– Antihypertensives: Thiazides, beta-blockers
 Antiarrhythmic drugs
– Quinidine and procainamide: ↓ clearance and ↑ (t½)
 Antimicrobial drugs
– Beta-lactams and aminoglycosides: ↓ clearance
 Anti-inflammatory drugs
– NSAIDs: GI bleed and irritation

10. Slide 10 © 2001 By Default!
Major Reasons for Adverse Drug
Reactions in the Elderly
 Positive relationship between number of drugs taken
and incidence
 Overall incidence is estimated to be at least twice
that in the younger population
 Prescribing errors
– Polypharmacy
– Drug interactions with other prescriptions
– Unawareness of age related physiologic changes
 Drug usage errors
– “Hidden ingredients”: OTCs

11. Slide 11 © 2001 By Default!
Compliance
 There are several practical obstacles to compliance
that the prescriber must recognize
– Forgetfulness
– Prior experience
– Physical disabilities
 Recommendations to improve compliance
– Take careful drug history
– Prescribe only for a specific and rational indication
– Define goal of drug therapy
– High index of suspicion regarding drug reactions and
interactions
– Simplify drug regimen