SBM: Pharmacology & therapeutics - Elderly Flashcards
(45 cards)
What is Pharmacodynamics?
effect of drug on the body?
what is pharmacokinetics?
Way the body affects the drug/
What is involved in pharmacokinetics?
Absorption
Distribution
Metabolism
Excretion
Why does absorption reduce in the elderly?
reduced saliva, reduced gastric acid, reduced GI motility, reduced SA for absorption. REDUCED SPLANCHNIC blood flow
Describe what happens to absoption in the elder?
Decrease rate of absoption and increased time to steady state
Describe volume of distribution with an equation
Vd = [drug] in body /[plasma]
What is the Vd?
Hypothetical volume obtained if ALL the drug was in the blood
What is the importnace of Vd? (What does it affect)
Affect half lfie and duration of effect
What is the relationship between muscle in the elderly and Vd?
Elderly - Decreased muscle, therefore volume of drug that distribute into muscles reduces –> Vd decreases. Thus the plasma conc increases.
E.g. Digoxin
What is the relationship between Body Fat in the elderly and Vd?
Elderly - Increase fat, therefore volume of distribiton for fat soluble drugs increases. Vd INcreases. Thus the plasma conc decreases.
E.g. Benzodiazepine
What happens to the half life in drugs that are fat solube in the elderly?
Increases
What is the relationship between water in the elderly and Vd?
Elderly - Decreased water, therefore volume of distribiton for water soluble drugs decreases -> Vd decreases. Thus the plasma conc increases.
E.g. Digoxin
What is the consequence of lower Vd in water soluble drugs?
Lower loading doses
What is the consequence of getting old on albumin
decrease by 12-25%.
Lower albumin means what on drug vd?
Therefore drug binding reduces by 12-25%. This increases the amount of free drug
what is the process of metabolism?
Drug goes through phase 1. This is mostly inactivation of the drug. some are activated, some have no change. This leads to oxidation/reduction/hydrolysis products. This then goes onto Phase 2 - which INACTIVATES all drugs. leaving synthetic or conjuate products.
What happens to metabolism in the elderly?
decreased liver volume (30%), decreased liver blood flow (12-40%). This then decreases first pass metabolism due to decreased blood flow. The enzyme CYP450 is reduced.
this therefore reduces clearance of the drug.
increases half life. E.g. CCB
What happens to excretion in the elderly?
decreases renal blood flow, mass, fucntion (all by 20-30%). GFR declines by 1% every year after 40
What happens to the half life in drug with a reduced renal excretion?
Increased Half life
Example of drug excreted by the kidney
Digoxin, atenolol, sotalol, Li
What are the therapeutic implication ofreduced renal function?
Reduced doses in once daily preps. Increase dose intervals to give more time to excrete.
What is the relevance of absorption in the elderly?
L-Dopa- competes with nutrients. Therefore plan dosing to avoid meal times.
Describe Digoxin toxity?
cardiac - heart block, bradycardia, junctional tachycardia, Pschiatric - Delirium, fatigue, malaise, confusion.
Visual - blurred, double vision, yellow-green vision, photophobia
GI - nausea vomiting, anoxeria, diarrhoea, abdo pain
Describe increase benzo in the blood stream
drowsiness, confusion, ataxia, dependance.
