Geriatric PK/PD: Absorption Flashcards
PO absorption: stomach emptying time
Delayed retention of indigestible solids: large EC products
Decreased rate of absorption
Acid-labile drugs
PO absorption: INCREASED intestinal motility may result in DECREASED absorption of these drugs:
digoxin and phenytoin
PO absorption: INCREASED intestinal motility may result in INCREASED absorption and why?
Increased absorption due to increased dissolution
PO absorption: DECREASED intestinal motility may result in INCREASED absorption of what drug?
L-dopa
Overall, what happens to intestinal blood flow with aging?
It decreases due to age, decreased CO, etc.
PO absorption: gastric acid secretion
Decreases
PO absorption: H. pylori may lead to what?
Atrophic gastritis
PO absorption: gastric blood flow
Generally decreases with age and may decrease absorption of high-permeability, water-soluble drugs
What disease state may decrease blood flow to the gut?
HF
Bioavailability in elderly patients
REDUCED FIRST PASS EFFECT –> increases bioavailability of some drugs
These drugs have increased bioavailability in elderly patients
propranolol, morphine sulfate, lidocaine, verapamil, labetalol…basically high-extraction drugs will reach the systemic circulation in higher concentrations
Bioavailability on bowel CYP3A4 and pGp activity
No proven effect
Overall net effect of absorption
No significant effect on rate or extent of absorption with the exception of first-pass effect
Parenteral absorption
Generally, there is reduced vascularity
IM: reduced muscle mass
SQ: increased lipid
TD absorption: dermal changes
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
TD absorption effects
Absorption of lipophilic compounds is about the same, could be delayed
Decreased absorption of hydrophilic compounds
TD absorption: fentanyl patches
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
TD absorption: ointments, creams, etc.
Decreased absorption
Mucosal absorption
Pretty much stays the same; may be a decrease in perfusion if there’s a decrease in capillary loops
