Geriatric Pharmacology

Question 1

What are the challenges of geriatric pharmacology?

Answer 1

New drugs
Changing managed-care formularies
Understanding of drug-drug interactions
Co-morbid states
Polypharmacy
Medication compliance
Effects of ageing physiology on drug therapy 
Medication cost

Question 2

What are the effects of ageing on absorption of drugs?

Answer 2

• Rate delayed
• Lower peak concentration
• Delayed time to peak concentration

BUT slow GI tract gives time for absorption

Question 3

What factors affect absorption?

Answer 3

Route of administration 
What is taken with the drug: food, drugs that influence gastric pH and drugs that promote or delay GI motility 
Comorbidity
Increased GI pH
Decreased gastric emptying
Dysphagia

Question 4

What reduces with age?

Answer 4

Lean body mass
Body water
Serum albumin (binds to many drugs)
Kidney weight

Question 5

What increases with age?

Answer 5

Fat as a percentage of body mass

Question 6

How does a reduced lean body mass effect VD (volume distribution)?

Answer 6

Reduced VD for drugs that bind to muscle (digoxin)

Question 7

How does a reduced body water effect VD?

Answer 7

Reduced VD for hydrophilic drugs (ethanol and lithium)

Question 8

How does reduced plasma protein (albumin) effect VD?

Answer 8

Increased percentage of unbound or free drug (active) (diazepam, warfarin)

Question 9

How does an increased fat store effect VD?

Answer 9

Increased VD for lipophilic drugs (diazepam, trazadone)

Question 10

How does an increased plasma protein effect volume of distribution (VD)?

Answer 10

Reduced % unbound or free drug (active) (propanolol)

Question 11

When does capacity of the liver to metabolise drugs change?

Answer 11

Most changes occur in phase 1 reaction (P450)

Question 12

What causes a change in liver capacity to metabolise drugs?

Answer 12

Decreased bloodflow in liver
Decreased liver mass
Decline of liver’s ability to recover from injury malnutrition
Diseases affecting hepatic functions (e..g heart failure)

Question 13

What are the phases of drug metabolism?

Answer 13

Phase 1: modification (oxidation, reduction, hydrolysis)

• Converts drugs into metabolites to facilitate excretion
• Hepatic clearance of drugs metabolised by phase 1 rxns is more likely to be prolonged in the elderly

Phase II: Conjugation:

• Adds charged species (Sulphate, glycine)
• Meds undergoing phase II hepatic metabolisms are generally preferred in the elderly due to inactive metabolites (no accumulation)

Question 14

What impacts drugs ability to be eliminated?

Answer 14

Age related decrease of kidney function

Question 15

Impacts of reduced drug elimination?

Answer 15

More drug stays in system = takes more time for drug to be eliminated (drug prolongation)
= Accumulation to toxic level if dosage is not modified

Question 16

What else reduces drug elimination?

Answer 16

Decreased kidney size
Decreased renal bloodflow
Decreased number of functional nephrons
Decreased tubular secretion

Question 17

Results of reduced drug elimination?

Answer 17

Decreased glomerular filtration rate

Decreased drug clearance

Question 18

What impact does a reduced cardiac index have on the body?

Answer 18

Bloodflow to organs decreased = clearance reduced

Question 19

What impact does a reduced maximal breathing capacity have on drugs?

Answer 19

Affects clearance of inhaled anaesthetics

Question 20

Impacts on benzodiazepine?

Answer 20

Increase sensitivity to sedation and psychomotor impairment

Question 21

Impacts on analgesics?

Answer 21

Increased level and duration of pain relief

Question 22

Impacts on beta-blockers?

Answer 22

Decreases HR response

Question 23

Impacts on anti-cholinergic agents?

Answer 23

Increased sensitivity

Question 24

What causes adverse drug rxns in elderly pts?

Answer 24

Impaired organ func = multiple disease states = multiple drug administration = altered compliance = adverse drug rxn

Impaired organ func = Altered organ func = adverse drug rxn

Altered drug concentration or decreased homeostatic regulation = adverse drug rxn

Question 25

When do most adverse drug events occur?

Answer 25

At the ordering and monitoring stages | 50% are considered preventable

Question 26

Risk factors of adverse drug events?

Answer 26

Polypharmacy Co-morbidity Low body weight or body mass index

Question 27

What causes drug-drug interactions?

Answer 27

Increased or decreased drug's absorption Additive effects due to similar effects of drugs Antagonising effects due to opposite effects of drugs Changes in drug metabolism Duplication of drug therapy

Question 28

Where are most drug-drug interactions seen?

Answer 28

CV and psychotic drugs

Question 29

What can adverse effects cause?

Answer 29

Confusion Cognitive impairment Hypotension Acute renal failure

Question 30

What is the risk of the combination: benzodiazepine + antidepressant + antipsychotic?

Answer 30

Sedation, confusion

Question 31

Causes of drug-disease interactions?

Answer 31

Obesity alters volume of distribution of lipophilic drugs Ascites alters VD of hydrophilic drugs Dementia can increase sensitivity to drugs with CNS or anticholinergic activity Renal or hepatic dysfunction may impair metabolism and excretions of drugs

Question 32

Risks of combining NSAIDs and hypertension?

Answer 32

Fluid retention - decreased effectiveness of diuretics

Question 33

Principles of prescribing in the elderly?

Answer 33

Non-adherence Start with a low dose and titrate slowly Avoid starting 2 agents at same time Reach therapeutic dose before switching or adding agents Determine therapeutic endpoints and plan for assessment Avoid prescribing to treat side effect of another drug Use 1 med to treat 2 conditions Consider drug-drug and drug-disease interactions Adjust doses for renal and hepatic impairment

Question 34

What factors to consider regarding prescribing drugs to the elderly?

Answer 34

Financial Cognitive Functional status Beliefs and understanding about disease and medications

Question 35

Common errors in prescribing for the elderly?

Answer 35

Polypharmacy - a drug for every complaint Side effects missed as thought to be part of ageing Elderly see different doctors Physicians often think pts are ill as not taking meds but they're taking them too much

Question 36

Why is compliance a problem for taking medications?

Answer 36

Opening containers (weak, arthritis, tremors) Cognitive impairment Fear of choking or concerns after reading info Depression - tired = poor time concept for doses Adverse drug rxns limit benefit of meds