Flashcards in EXAM #5: GERIATRIC PHARMACOLOGY Deck (33):
What are four methods to achieve successful pharmacotherapy in the geriatric population/ prevent the prescribing cascade.
1) Avoid prescribing new drugs until tests confirm diagnosis
2) Start low and titrate up
3) Avoid starting or changing multiple medications at once
4) Reach TD before switching or adding new agents
What are the tools used to evaluate appropriate medication use in the elderly?
1) Beers List
- STOPP= Screening Tool of Older Persons' potentially inappropriate Prescriptions
- START= Screening Tool to Alter doctors to Right Treatment
What body composition changes in the elderly can result in altered pharmacokinetics?
1) Decreased TBW
2) Decreased lean body mass
3) Increased body fat
What cardiovascular changes in the elderly can result in altered pharmacokinetics?
1) Decreased sensitivity to B-adrenergic stimulation
2) Decreased baroreceptor activity
3) Decreased CO
4) Increased TPR
What liver changes in the elderly can result in altered pharmacokinetics?
1) Decreased hepatic size
2) Decreased hepatic blood flow
What renal changes in the elderly can result in altered pharmacokinetics?
1) Decreased GFR
2) Decreased RBF
3) Decreased filtration fraction
4) Decreased tubular secretory function
5) Decreased renal mass
What happens to first pass metabolism with aging?
Less first pass metabolism
What happens to drug distribution with aging?
Differences in body composition lead to altered distribution
What happens to drug metabolism and clearance with aging?
Reduced liver and kidney function/ blood flow impairs metabolism and clearance
What are the implications of less first pass metabolism in the geriatric population?
1) LOWER dose requirements for drugs INACTIVATED by first pass metabolism
2) HIGHER dose requirements for PRODRUGS that require first pass metabolism for activation
What does a large Vd indicate?
Most of the drugs DISTRUBUTES to the extravascular compartment
How is Vd altered in the elderly? What will happen with the adminstration of a lipophilic drug?
High fat mass and low lean body mass INCREASE the Vd
Thus, there is an increased Vd in the elderly--especially with lipophillic drugs
What is the effect of lower TBW in the elderly in regards to water soluble drugs?
Less TBW= lower Vd (more drug stays intravascular)
How does a large Vd affect the half-life of a lipid-soluble drug? Give an example of a drug that follows this pattern.
A large Vd INCREASES the half-life
How does a low Vd of a water soluble drug alter the loading dose? Give an example of a drug that follows this pattern.
Loading dose would be DECREASED to prevent toxicity
What is drug clearance? What is the equations for clearance?
Rate of elimination of a drug
CL= Q (flow) x E(extraction)
What are the two major organs are involved in drug clearance?
How is hepatic clearance altered in elderly patients?
1) Decreased flow to liver
2) Decreased liver metabolism/ extraction
- Phase I enzymes have REDUCED activity (CYP p450)
Thus, reduced drug clearance
Which phase of liver metabolism is most affected by aging?
Phase I i.e. CYP p450
What is a capacity-limited drug? What are the implications in the elderly?
Rate-limiting step in clearance is liver enzymes (vs. flow)
*There will be decreased clearance of a capacity-limited drug if metabolized by Phase I enzymes*
What is a flow-rate limited drug? What are the implications in the elderly?
Rate-limiting step in clearance is hepatic blood flow
*All drugs that are flow limited will have decreased clearance in the elderly*
What are the implications of less drug clearance on maintenance dosing the the elderly?
Generally, less maintenance doses are needed to maintain a steady state drug concentration
What is the exception to changes in maintenance doses seen in the elderly?
No change seen in capacity-limited, phase II metabolized drugs
Why is renal excretion decreased in the elderly?
1) Decreased GFR
2) Polypharmacy causes competition at tubular transporters
Generally, what is the marker used to determine GFR?
What is creatinine directly proportional to?
Lean muscle mass
How does creatinine change in elderly patients?
Less lean body mass= less creatinine
What is the Cockcroft and Gault equation?
Equation that accounts for decreased muscle mass in elderly when calculating GFR based on creatinine
How do decreased hepatic and renal drug clearance in elderly patients alter the T1/2? What type of drug will see the largest change?
- Decreased clearance INCREASES half-life
- Lipophilic drugs have further increases in half-life b/c of increased Vd
What do you need to keep in mind about NSAIDs in the elderly?
Elderly patients are highly susceptible to toxicity of NSAIDs
Explain how NSAIDs can lead to renal damage in the elderly.
- RBF is reduced in elderly
- PGs are secreted to maintain blood flow/GFR
- NSAIDs BLOCK PGs
What can the effects of anticholinergic drugs lead to in the elderly?
Overall functional decline from:
2) Impaired congnition