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Pharmacology Exam 5 > 68 - Geriatric Pharmacology > Flashcards

68 - Geriatric Pharmacology Flashcards

1
Q

Describe the use of medications in the elderly

A

90% use at least 1 drug per week

  • 40% use 5 or more different drugs per week (polypharmacy)
  • 12% use 10 or more drugs per week
  • Drug use greatest among the frail elderly, hospitalized patients, and nursing home residents
  • Typical nursing home resident is taking 7 to 8 different drugs regularly
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2
Q

What is a prescribing cascade?

A
  • You give a drug
  • The patient has a side effect
  • You treat the side effect with another drug

More of a problem with older adults with multiple chronic diseases

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3
Q

What are some ways to prevent a prescribing cascade?

A

Some ways to prevent prescribing cascade

  • Avoid prescribing until test results confirm suspected diagnosis
  • Start with low dose and titrate slowly
  • When possible, avoid starting multiple medications simultaneously
  • Reach therapeutic dose before switching or adding agents
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4
Q

What is a drug interaction

A

Use of a drug results in a drug-drug, drug-food, drug-supplement, or drug-disease interaction, leading to adverse effects or decreased efficacy.

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5
Q

Describe inadequate monitoring

A

A medical problem is being treated with the correct drug, but the patient is not monitored for complications, efficacy, or both.

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6
Q

Describe inappropriate drug selection

A

A patient is taking a drug for no medically valid reason

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7
Q

Describe lack of patient adherence

A

The correct drug for a medical problem is prescribed, but the patient is not taking it

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8
Q

Describe an overdose

A

A medical problem is being treated with too much of the correct drug

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9
Q

Describe under prescribing

A

A medical problem is being treated with too little of the correct drug

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10
Q

Describe an untreated medical problem

A

A medical problem requires drug therapy, but no drug is being used to treat that problem.

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11
Q

What are the three tools you need to know for making medication decisions in older adults?

A
  • BEERS Criteria
  • STOPP
  • START
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12
Q

What is the BEERS criteria?

A
  • List of medications likely to cause adverse effects in elderly
  • Periodically updated by American Geriatric Society

3 categories:

  • Drugs problematic most older patients (high risk)
  • Problematic for certain diseases/conditions (moderate)
  • Drugs to be used with caution (some risk)
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13
Q

What is the STOPP tool?

A

Screening Tool of Older Persons’ potentially inappropriate Prescriptions

It is atool to assess use of drug with specific patient with specific conditions

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14
Q

What is the START tool?

A

Screening Tool to Alert doctors to Right Treatment

Used to identify potential underuse of beneficial medications in older adults

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15
Q

What is important when prescribing drugs in the elderly?

A

Functions need to be determined for each individual because some healthy subjects have little age-related decrease in specific functions

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16
Q

What are some of the physiological changes associated with aging?

A
  • Increase in fat content as we age
  • Weight will go down, but waist circumference increases and fat content increases
  • This has important consequences on the distribution
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17
Q

Describe the changes in body composition in geriatrics that affect drug therapy

A
  • Decreased water
  • Decreased lean body mass
  • Increased body fat
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18
Q

Describe the cardiovascular changes in geriatrics that affect drug therapy

A
  • Decreased myocardial sensitivity to beta-adrenergic stimulation
  • Decreased baroreceptor activity
  • Decreased cardiac output
  • Increased total peripheral resistance
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19
Q

Describe the liver changes seen in geriatrics that affect drug therapy

A
  • Decreased hepatic size

- Decreased hepatic blood flow

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20
Q

Describe thepulmonary changes seen in geriatrics that affect drug therapy

A
  • Decreased respiratory muscle strength
  • Decreased chest wall compliance
  • Decreased total alveolar surface
  • Decreased vital capacity
  • Decreased maximal breathing capacity
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21
Q

Describe the renal changes seen in geriatrics that affect drug therapy

A

THIS IS REALLY IMPORTANT

  • Decreased glomerular filtration rate
  • Decreased renal blood flow
  • Decreased filtration fraction
  • Decreased tubular secretory function
  • Decreased renal mass

This is important for the clearance of drugs

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22
Q

Describe the skeletal changes seen in geriatrics that affect drug therapy

A

Loss of skeletal bone mass (osteoporosis)

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23
Q

Describe the pharmacokinetics of therapeutically acitive drug concentrations

A
  • A drug is therapeutically active over a limited range of concentrations and at specific sites of action in the patient
  • If it doesn’t get there at the right concentration, if it doesn’t get there fast enough, or if it doesn’t stay there long enough, then it won’t work.
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24
Q

What is pharmakokinetics?

A

“What the body does to a drug”

  • absorption
  • distribution
  • metabolism (biotransformation)
  • clearance/elimination
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25
Q

Which of the four pharmacokinetic mechanisms is the LEAST affected by aging?

A

ABSORPTION **

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26
Q

How are the other pharmakokinetic mechanisms affected by aging?

A

First pass metabolism
- Reduced with aging (drug concentrations will be higher)

Distribution in the body
- Differences in body composition change distribution

Metabolism and clearance

  • Reduced liver function and blood flow
  • Reduced kidney function
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27
Q

What is bioavailablility?

A

Fraction of drug reaching the systemic circulation. For an iv dose, bioavailability is 1 (i.e., 100%).

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28
Q

What is first pass inactivation?

A

First pass inactivation:
- Before entering the systemic circulation, a drug can be metabolized (inactivated) in the gut wall, or more commonly in the liver.

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29
Q

What is first pass activation?

A

First pass activation:

- Prodrugs require metabolism to became activated

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30
Q

What is the effect of first pass metabolism on plasma drug concentrations? How is this different in the elderly?

A

First pass metabolism is often reduced in elderly

  • Potentially a lower dose requirement in elderly with drugs that are inactivated by first pass metabolism
  • Potentially a higher dose requirement in elderly with prodrugs that require activation by first pass liver metabolism (Codeine, propranolol, enalapril, perindopril, and simvastatin)
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31
Q

What is volume of distribution?

A

It is the volume of fluid into which the given dose of drug must be dissolved in order to achieve the plasma concentration of that drug

32
Q

How do you calculate volume of distribution?

A

Vd = (amount of drug in body)/(plasma drug concentration)

33
Q

What would a very large volume of distribution mean?

A

A very large Vd would indicate that the majority of the drug distributes to the extravascular compartment

34
Q

What would a very small volume of distribution mean?

A

A Vd that is smaller or closer to the actual blood or plasma volume would indicate that the drug is retained primarily in the vasculature

35
Q

Describe the volume of distribution in the elderly

A

Elderly individuals tend to have a higher fat mass and a lower lean body mass (i.e., more fat and less muscle)

Lipophilic drugs will have a higher volume of distribution in elderly

Hydrophilic drugs (highly water soluble) will have a decreased volume of distribution due to decreased body water

36
Q

What is the effect of the volume of distribution on half life? Use the half life equation in your explanation

A

t(1/2) = 0.693 x Vd/CL

Would a highly lipid soluble drug have an increased or decreased t1/2 in an elderly patient when compared to a younger patient? Increased half life***

37
Q

Describe how a drug being water soluble does create as big of a difference in elderly patients as a drug being lipid soluble does

A

The decreased Vd of a highly water soluble drug tends to be balanced by a reduction in clearance in elderly patients

This means there will be less of an increase in ½ life than compared to lipid soluble drugs

38
Q

Would the loading dose of a highly water soluble drug be larger or smaller in an elderly patient when compared to a young patient?

A

Smaller***

In general, loading doses for lipophilic drugs should be decreased in elderly patients

39
Q

What factors affect the volume of distribution in elderly?

A
  • How tightly a drug binds to tissues

- How lipid soluble or water soluble the drug is

40
Q

Describe the volume of distribution of drugs that tightly bind to tissues

SUMMARY

A

Drugs which are tightly bound to tissues have large Vd

When lean body mass is lowered and adipose tissue is increased in the elderly, drugs that bind to muscle (digoxin) will have a decreased volume of distribution because there is less muscle

When there is less binding of the drug to tissues, there is less volume of distribution and therefore less of a loading dose is required (more stays in the vasculature)

41
Q

Describe the volume of distribution of drugs that are lipid soluble and the effects of this

SUMMARY

A

Lipid soluble drugs can pass through lipid membranes of cells more easily and have higher Vd than water soluble drugs

There is more body fat and less body water in the elderly, meaning that for lipid soluble drugs, there is an increased volume of distribution

And for water soluble drugs, there is a decreased volume of distribution

This affects the loading dose, because if the volume of distribution is low (water soluble drugs) the loading dose can be less because less is distributed thoughout the body and a higher concentration is in the vasculature

Another effect is that fat soluble drugs have an increased half life because they stay in the fat tissues longer

42
Q

What is drug clearance?

A

Clearance: The rate of elimination of a drug from the body in relation to drug concentration

43
Q

How do you calculate drug clearance?

A

CL = Q x E

CL = clearance
Q = flow rate of the organ
E = extraction ratio
44
Q

What is total drug clearance?

A

Hepatic clearance + renal clearance + other clearance

45
Q

Describe hepatic drug clearance

A

Portal and arterial hepatic blood flow affect flow rate to the liver.

Liver metabolism affects the extraction ratio.

46
Q

What are the two types of enzymes that influence hepatic drug clearance?

A
  • Phase I enzymes

- Phase II reactions

47
Q

Describe phase I enzymes

A

Cytochrome p450 enzymes

48
Q

Describe phase II reactions

A

Large polar groups are conjugated to drug molecules forming larger highly polarized metabolites that can be more easily excreted

49
Q

What are the effects of aging on the liver?

A
  • Decrease blood flow
  • Reduced activity of Phase I enzymes (cytochrome p450 enzymes)
  • Phase II enzyme activities are NOT usually reduced
50
Q

What is a capacity limited drug

A

A capacity limited drug has a clearance rate limiting step which depends on liver enzyme function

51
Q

Describe how phase II capacity limited drug clearance is different in elderly patients

A

Trick question - it’s not!

No change in an elderly patient’s hepatic clearance of a capacity limited drug if it metabolized by phase II enzymes

52
Q

Describe how phase I capacity limited drug clearance is different in elderly patinets

A

Decreased clearance if metabolized by Phase I enzymes

53
Q

What are flow rate limited drugs in terms of hepatic clearance?

A

Flow rate limited: A drug whose rate-limiting hepatic clearance step is flow rate (e.g., how fast it can get to the liver cells).

Drugs that are flow rate limited are generally going to have reduced hepatic clearance in elderly individuals

54
Q

What is the effect of hepatic clearance on maintenance doses?

A

We use the hepatic clearance to keep the drug at a steady state concentration for maintenance drugs

For maintenance drug dosing, we administer a level equal to the rate of clearance

55
Q

If there is a reduction in hepatic clearance, how will we adjust maintenance dosing?

A

Thus, a reduction in hepatic clearance of a drug requires less frequent and lower maintenance doses.

56
Q

In an elderly person, how would you PREDICT you would need to change the maintenance dosing for a capacity limited drug which is metabolized by phase II enzymes?

A

No change in maintenance dose for capacity limited drugs that are metabolized by phase II enzymes

57
Q

In an elderly person, how would you PREDICT you would need to change the maintenance dosing for a capacity limited drug which is metabolized by phase I enzymes

A

Decrease in maintenance dose in capacity limited drugs that are metabolized by phase I enzymes

58
Q

In an elderly person, how would you PREDICT you would need to change the maintenance dosing for a capacity limited drug which is metabolized flow rate?

A

Decrease in maintenance dose in flow rate limited drugs

59
Q

Describe renal clearance in elderly

A

Renal excretion is often decreased in elderly individuals

60
Q

How much does the glomerular filtration rate decreased by in normal aging?

A

15%-40%

61
Q

What does polypharmacy do to tubular secretion

A

Polypharmacy increases risk of drugs competing for active transporters

62
Q

Describe glomerular filtration rate (GFR)?

A

The glomerular filtration rate (GFR) is an index of kidney function because it is equal to the sum of the filtration rates of all functioning nephrons

63
Q

Describe the role of creatinine

A

Plasma contains predictable amounts of creatinine which originates from the metabolism of creatine phosphate in muscle.

Creatinine is filtered and not reabsorbed

Creatinine clearance is an index of glomerular filtration rate (GFR)

64
Q

How do you measure creatinine?

A
  • Creatinine clearance can be measured directly by comparing the creatinine concentration in a 24 hour urine sample to the serum concentration.
  • Creatinine clearance can be estimated by measuring amount of serum creatinine (without 24 hour urine collection)
65
Q

What happens to creatinine when renal function decreases?

A

Concentration in blood increases and concentration in urine decreases as renal function decreases

66
Q

How does aging affect creatinine?

A
  • Elderly individuals will have less serum creatinine because of decreased muscle mass
  • Thus, even with decreased GFR, they can have the same plasma creatinine concentration as a younger individual with normal GFR.
67
Q

Describe the Cockroft and Gault equation

A

Cockcroft and Gault equation accounts for decreased muscle mass in elderly patients

Takes into account creatinine clearance, age, weight, serum creatinine

You multiply it by 0.85 for women because they have 15% less muscle mass

68
Q

What is the effect of renal and hepatic clearance on half life

A

Decreases in hepatic and renal clearance are the most significant parameters that increase t1/2 of drugs in elderly

t1/2 = 0.693 x Vd/CL

Lipophilic drugs have an even further increase in half life because Vd is increased in elderly

Remember that it takes approximately 4-5 half-lives to reach steady state plasma concentration or for a drug to be eliminated

69
Q

What is the equation for half life?

** NEED TO KNOW **

A

t1/2 = 0.693 x Vd/CL

70
Q

What homeostatic control mechanisms decrease in the elderly?

A
  • Enhanced sensitivity to postural hypotension
  • Gait disorders
  • Reduced thirst and volume regulation
  • Reduced glucose and electrolyte control
  • Reduced thermoregulation
  • Increased sensitivity to anesthetic agents
  • Decreased β-adrenergic responsiveness
71
Q

What is pharmacodynamics?

A

What the drug does in the body

72
Q

What are the pharmacodynamic changes with age?

A
  • Decreased cardiac and vascular β-adrenergic responsiveness
  • Decreased responsiveness of elderly individual to hypotensive effect of β-blockers
  • Acute blood pressure response to calcium channels blockers is exaggerated in older people
  • Reduced baroreflex activation with aging
73
Q

Describe the use of NSAIDs in geriatric patients

A
  • Elderly are very susceptible to toxicities of NSAIDs
  • NSAIDs are cleared primarily by kidneys
  • Can cause RENAL DAMAGE
  • Local renal production of prostaglandins low in healthy younger individuals
  • When renal blood flow becomes reduced with aging, increases in prostaglandins help to increase blood flow and maintain glomerular filtration rate
  • NSAIDs block increase in prostaglandins
74
Q

What are the adverse effects of NSAIDs

A
  • GI bleeding and irritation

- RENAL DAMAGE

75
Q

What are the adverse effects of anticholinergic drugs in the elderly?

A

Dry mouth, decreased gut motility, bladder hypotonia (decreased muscle tone), decreased cognition, sedation, orthostatic hypotension, blurry vision

These effects can lead to increased risk of overall functional decline from injuries from falls, and impaired cognition

76
Q

What medications have anticholinergic properties

A
  • Anticonvulsants
  • Antidepressants
  • Antihistamines
  • Antipsychotics
  • Cardiovascular
  • GI antispasmodics
  • H2 antagonists
  • Muscle relaxants
  • Parkinson disease
  • Urinary antispasmodics
  • Vertigo

Pharmacology Exam 5 (5 decks)

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