Geri: PK Flashcards
Gastric pH
What happens to acidic drug absorption
Increases pH
Decreases Acidic drug absorption
Gastric emptying rate?
In OR De
Decreased rate
Max concentration reached later
Splanchnic blood flow
In OR de
Decrease
Decreaes absorption
GI motility
De OR in
Decrease
Absorption SA
In OR de
Decreases
Body fat
In OR de
Increases
INCREASES Vd and t1/2 of
lipophilic drugs
Total body water
DECREASES
Increases plasma concentration of hydrophilic drug
Ie. For water soluble drugs = decrease Vd, increase blood concentrations (as water component decreases)
Eg. Gentamicin, dioxin, ethanol, theophylline, cimetidine
Serum albumin (protein binding)
Decreaes
Increases free fraction of protein bound acidic drug
A1 glycoprotein
Increase or stays same =
Increaes binding of basic drugs
Hepatic blood flow
Decrease
Decrease first pass metabolism
Decrease conversion of prodrug
Ie. Changes rate of phase 1 metabolism
Hepatic mass
Decreases
Enzyme activity
Decreases
Renal blood flow and GFR
Decreases
Decrease renal clearance
Best predictor of response to meds?
Measures of FRAILTY
NOT AGE
Body fat
Increases
Most systems are more affected by disease than age alone
TRUE
diseases = comorbidities
Gastric secretions
Intestinal motility
Both Decreased
Absorption rate?
Slowed down (but extent not)
IM dosing?
Decrease tissue perfusion = delay dissolution
Topical- transdermal
Reduced skin hydration = delayed release
Blood concentrations are higher
True or false
True
Hepatic extraction (HE)
Reduced liver perfusion = decrease in clearance of high HE drugs
(Ie. Verapamil, propranolol, lignocaine)
= blood flow limited metabolism
Drugs with low HE (capacity limited) will not be affected)
How much % does hepatic blood flow decline by per year
1% every year after 30
Pharmacodynamic EFFECT?
Elderly have pharmacodynamic differences due to reduced resistance to external stressors
PD.
RECEPTOR PROPERTIES
EXAMPLR
Reduced Beta- adrenoceptor fucntion =
- Reduced myocardial sensitivity to catecholamines
- Reduced response to salbutamol and propranolol
What are 1/3 of ADR related to?
Impaired renal function
PD. Homeoststic mechanism changes
Counter regulatory measures are reduced
Eg. Orthostatic hypotension through decreased baroreceptor responsiveness
AND
DRUG INDUCED ORTHOSTATIC HYPOTENSION
PD. Hypoglycaemia
Drug induced: long acting sulfonyureas
PD. CNS effects of drugs
Vulnerable to side effects…
Delirium, EPSE, arrhythmias, postural hypotension
B/w 20-80 yo. Brain weight reduces by 20%
PD. BENZOS
Greater sensitivity to actions of benzo
Dose adjustment due to PD not PK.
PD in wafarin
INR not effective marker in elderly.
Also,
-organ function (liver)
-dietary influences (vit k)
-concomitant medicines (polypharmacy)
