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Oncology, pharmacology, anaesthetics (IHD DEN303) > Geriatric pharmacology > Flashcards

Geriatric pharmacology Flashcards

1
Q

Challenges of geriatric pharmacology

A

Elderly most physiologically heterogenous category
-state of health varies extensively: physical strength, cardiac condition, renal and liver function for clearance of drugs
• New drugs available each year
• Changing managed-care formularies
• Advanced understanding of drug-drug interactions
• Increasing popularity of “nutriceuticals”
• Multiple co-morbid states
• Polypharmacy
• Medication compliance
• Effects of ageing physiology on drug therapy
• Medication cost

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2
Q

Effects of ageing on pharmacokinetic absorption

A

Little evidences of major absorption alteration with ageing
Rate of absorption may be delayed
Lower peak concentration
Delayed time to peak concentration

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3
Q

Factors affecting absorption

A 
Route of administration
What is taken with the drug
-divalent cation (Ca, Mg, Fe)
-food, enteral feedings
-drugs that influence gastric pH
-drugs that promote or delay GI motility
Comorbidity
> GI pH
< gastric emptying
Dysphagia
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4
Q

Distribution

A

Elderly have reduced
-lean body mass
-body water
-serum albumin (binds to many drugs)
-kidney weight
Elderly have increased fat as a percentage of body mass
Thus ratio of free drugs may be significantly altered

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5
Q

Effects of ageing on volume of distribution (VD)

A

< lean body mass - < VD for drugs that bind to muscle (digoxin)
< body water - < VD for hydrophylic drugs (ethanol and lithium)
< plasma protein (albumin) - > % of unbound or free drug (active)
-diazepam, warfarin, valproic acid
> fat store - > VD for lipophilic drugs (diazepam, trazadone)
> plasma protein (α1 - acid glycoprotein) - < % unbound or free drug (active)
-quinidine, propanolol, amitriptyline

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6
Q

Metabolism with age

A

Capacity of liver to metabolise drugs does not appear to decline consistently for all drugs
Most of changes occur in phase I reaction (P450)
For drugs with extensive first-pass metabolism, bioavailability
may increase because less drug is extracted by the liver

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7
Q

Causes of change in metabolism with age

A

< blood flow in liver
< liver mass
< liver’s ability to recover from injury malnutrition
Diseases affecting hepatic functions (i.e. heart failure)

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8
Q

Metabolism: phase I

A

Modification (oxidation, reduction, hydrolysis)
Converts drugs into metabolites to facilitate excretion
Hepatic clearance of drugs metabolized by phase I reactions is more
likely to be prolonged in the elderly

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9
Q

Metabolism: phase II

A

Conjugation
Adds charged species (i.e. glutathione, sulfate, glycine)
Medications undergoing Phase II hepatic metabolism are generally
preferred in the elderly due to inactive metabolites (no accumulation)

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10
Q

Elimination

A

Age related decrease of kidney function is crucial for drug elimination
Main result is marked PROLUNGATION of drugs’ HALF-LIFE and
possibility of ACCUMULATION to toxic level if dosage is not
modified.
Creatinine clearance decrease in about 2/3 of the population.
However this is not reflected in an equivalent rise in serum creatinine
as muscle mass decrease in elderly

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11
Q

Causes of changes in elimination

A
  • Decreased kidney size
  • Decreased renal blood flow
  • Decreased number of functional nephrons
  • Decreased tubular secretion
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12
Q

Results of changes in elimination

A

< glomerular filtration rate (GFR)

< drug clearance: (i.e. gabapentin, H2 blockers, digoxin)

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13
Q

Factors affecting drug metabolism

A

Glomerular filtration
-kidney clearance reduced
Cardiac index
-blood flow to all organs (i.e. kidney, liver) is reduced
-clearance is reduced
Maximal breathing capacity
-breathing affects clearance of inhaled anaesthetics
Drug absorption is normal in elderly
-slow GI tract gives plenty of time for absorption

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14
Q

What does the effect of ageing do to the body with benzodiazepines

A

> sensitivity to sedation and psychomotor impairment

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15
Q

What does the effect of ageing do to the body with analgesics

A

> level and duration of pain relief

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16
Q

What does the effect of ageing do to the body with beta-blockers

A

< heart rate response

17
Q

What does the effect of ageing do to the body with anti-cholinergic agents

A

Increased sensitivity

18
Q

Factors contributing to adverse drug reactions in elderly pts

A

Impaired/ altered organ function
Decreased homeostatic regulation
Altered drug concentration
Multiple disease states –> multiple drug administration –> altered compliance

19
Q

Adverse drug events (ADEs)

A

Responsible for 5 - 28% of acute geriatric hospital admissions
>95% of ADEs in the elderly are considered predictable
and approx 50% considered preventable
Most errors occur at ordering and monitoring stages

20
Q

Risk factors for ADEs

A

Polypharmacy
Co-morbidity
Low body weight or body mass index

21
Q

Drugs involved in ADEs

A

Benzodiazepines, NSAIDs, Cardiovascular agents, CNS agents,

Musculoskeletal agents, Opioid analgesics, CNS agents, Anticholinergics

22
Q

Drug-drug interactions causes

A

> or < drug’s absorption
Additive effects due to similar effects of drugs
Antagonizing effects due to opposite effects of drugs
Changes in drug metabolism (inhibition or induction)
Duplication of drug therapy
Note: Risk of drug-drug interactions increases as number of medication
taken increases

23
Q

Most common drug-drug interactions

A

Most common are seen in association with cardiovascular and psychotropic drugs

24
Q

Risk of adverse effects in CV and psychotropic drug-drug interactions

A

Confusion, Cognitive impairment, Hypotension, Acute renal failure

25
Q

Risk from benzodiazepine + antidepressant or antipsychotic

A

Sedation, confusion

26
Q

Risk from ACE inhibitor + potassium

A

Hyperkalemia

27
Q

Risk from digoxin + antiarrythmic

A

Bradycardia, arrhythmia

28
Q

CCB/ nitrate/ vasodilator/ diuretic

A

Hypotension

29
Q

Drug-disease interaction causes

A

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

30
Q

Risk from NSAIDS and CHF

A

Fluid retention; CHF exacerbation

31
Q

Risk from alpha blockers and anticholinergic

A

Urinary retention

32
Q

Risk from CCB; narcotics or anticholinergics + constipation

A

Exacerbation of conspation

33
Q

Risk from NSAIDs + gastropathy

A

> ulcer and bleeding risk

34
Q

Risk from NSAIDs + hypertension

A

Fluid retention; < effectiveness of diuretics

35
Q

Principles of prescribing in the elderly

A
  • Start with a low dose and titrate slowly
  • Avoid starting 2 agents at the 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 medication to treat 2 conditions
  • Consider drug-drug and drug-disease interactions
  • Use simplest regimen possible
  • Adjust doses for renal and hepatic impairment
  • Avoid therapeutic duplication
36
Q

Non-adherence factors

A

Rate may be as high as 50% in elderly
Financial, cognitive, or functional status
Beliefs and understanding about disease and medications

37
Q

Common errors in prescribing for elderly people

A

• Polypharmacy - a drug for every complaint
• Side effects are missed because they are misinterpreted as part of
ageing (i.e. senility, hearing loss)
• Elderly people often see different doctors
• Physicians often assume that the patients are ill because they are
not taking their medications when in fact they are taking them and
the amount prescribed for them too much

38
Q

Compliance problems for taking medications

A

• Opening containers (i.e. weak/arthritis pain/tremors/spills)
• Cognitive impairment - can’t recall a few moments ago
• Fear of choking while swallowing or concerns after reading labels and
information
• Depression - sleepy - poor concept of time for doses
• Adverse drug reactions limit benefit of medications

39
Q

Pharmacology in the elderly

A

Successful pharmacotherapy means using the correct drug at the
correct dose for the correct indication in an individual patient
• Age alters PK and PD
• ADEs are common among the elderly
• Risk of ADEs can be minimized by appropriate prescribing

Oncology, pharmacology, anaesthetics (IHD DEN303) (6 decks)

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