Geriatric PK/PD: Absorption

Question 1

PO absorption: stomach emptying time

Answer 1

Delayed retention of indigestible solids: large EC products
Decreased rate of absorption
Acid-labile drugs

Question 2

PO absorption: INCREASED intestinal motility may result in DECREASED absorption of these drugs:

Answer 2

digoxin and phenytoin

Question 3

PO absorption: INCREASED intestinal motility may result in INCREASED absorption and why?

Answer 3

Increased absorption due to increased dissolution

Question 4

PO absorption: DECREASED intestinal motility may result in INCREASED absorption of what drug?

Answer 4

L-dopa

Question 5

Overall, what happens to intestinal blood flow with aging?

Answer 5

It decreases due to age, decreased CO, etc.

Question 6

PO absorption: gastric acid secretion

Answer 6

Decreases

Question 7

PO absorption: H. pylori may lead to what?

Answer 7

Atrophic gastritis

Question 8

PO absorption: gastric blood flow

Answer 8

Generally decreases with age and may decrease absorption of high-permeability, water-soluble drugs

Question 9

What disease state may decrease blood flow to the gut?

Answer 9

HF

Question 10

Bioavailability in elderly patients

Answer 10

REDUCED FIRST PASS EFFECT –> increases bioavailability of some drugs

Question 11

These drugs have increased bioavailability in elderly patients

Answer 11

propranolol, morphine sulfate, lidocaine, verapamil, labetalol…basically high-extraction drugs will reach the systemic circulation in higher concentrations

Question 12

Bioavailability on bowel CYP3A4 and pGp activity

Answer 12

No proven effect

Question 13

Overall net effect of absorption

Answer 13

No significant effect on rate or extent of absorption with the exception of first-pass effect

Question 14

Parenteral absorption

Answer 14

Generally, there is reduced vascularity

IM: reduced muscle mass
SQ: increased lipid

Question 15

TD absorption: dermal changes

Answer 15

Drying of the stratum corneum
Changes in sebaceous gland activity and lipid composition in the skin surface layers
Decrease in the number of dermal capillary loops

Question 16

TD absorption effects

Answer 16

Absorption of lipophilic compounds is about the same, could be delayed
Decreased absorption of hydrophilic compounds

Question 17

TD absorption: fentanyl patches

Answer 17

cachexia affects fentanyl patches → erratic absorption in patients with little to no SQ fat (generally a decrease in rate of absorption because there’s no fat), so we usually don’t use these in elderly patients due to delayed onset and overall reduction in plasma concentrations

Question 18

TD absorption: ointments, creams, etc.

Answer 18

Decreased absorption

Question 19

Mucosal absorption

Answer 19

Pretty much stays the same; may be a decrease in perfusion if there’s a decrease in capillary loops