Pharmacology for Older Adults Flashcards
(9 cards)
How does drug absorption change in elderly people? Give some examples of physiological changes that cause this
- Drug absorption slows down
- ↓ GI surface area/motility, more alkaline stomach due to ↓ acid secretion, ↓ active transport
Changes to drug distribution w/ age (incl. body composition considerations)
- Increased fat, decreased water leads to higher volume of distribution of lipid-soluble drugs, and lower Vd for water-soluble ones
- Reduced protein binding, too (less protein in old people)
Which kind of dose does a change in volume of distribution affect vs not affect?
- Vd changes affect loading dose (achieving plasma conc)
- Whereas maintenance doses are more dependent on rate of clearance (hence less dependent)
How does concentration of hepatically cleared drug, on average, differ from older to younger adults
- ↓ hepatic metabolism
- Concentration ~double in older people
Mechanisms of reduced hepatic clearance in older people? Which functions/agents are maintained?
- Reduced liver size/blood flow
- Sinusoidal fibrosis may limit exposure of drugs/oxygen to hepatocytes, decreasing oxygenation rate
- Cytochrome P450 (WIT) and conjugation appears to be preserved
What do we expect to happen to renal drug clearance with age? How, exactly, do we measure this reduction?
- We expect it to decrease
- Measured through calculate creatinine clearance (e.g. 60mL/min = half normal clearance rate)
Reason out, from first principles, why it takes longer for a drug to get to a new steady state in older people
- Half life is proportional to Vd over clearance
- Since clearance (both hepatic and renal) decrease in old age, half life decreases
- Since steady state is ~5 half lives, a longer half life means longer to get to steady state
Summarise dosage changes in old person concisely
Start low. Go slow.
Older people are ____ sensitive to the same dosage of drug compared to young people, and are at a ______ risk of adverse events, even at same conc
- More sensitive to same dosage (why might this be?)
- Higher sensitivity/risk to adverse effects, even at same drug concentration
