11 - Drugs & Polypharmacy 2 Flashcards
name a factor which may reduce the rate of absorption of a buccally administered drug - e.g. GTN?
reduction in saliva production
what is an exception to decreased absorption of a drug in elderly people and what is this because of?
levodopa - used for Parkinson’s
this is because there is less dopa-decarboxylase (enzyme) which breaks down levodopa
what are the 2 most important factors that affect drug distribution in the elderly?
changes in body composition
changes in protein binding
what is changes in body composition and protein binding also accompanied by?
decrease in total body water
how are fat soluble drugs distributed in elderly?
Vd is increased due to increased body fat - longer duration of action
2 fat soluble drugs?
diazepam
haloperidol
how are water soluble drugs distributed in the elderly?
Vd is decreased - resulting in higher serum levels
2 water soluble drugs?
theophylline
atenolol
what factor affects the pharmacological effects caused by a drug?
free drug concentrations - this is because a bound drug cannot bind to target tissues
name 4 conditions which depress albumin in elderly?
heart failure
renal disease
rheumatoid arthritis
hepatic cirrhosis
how much does serum albumin decrease by in elderly patients?
decreased by 12%
what is the binding site for basic drugs?
α1-acid glycoprotein
when does α1-acid glycoprotein change?
in acute illness, not with age
name 4 acidic drugs?
diazepam
cimetidine
furosemide
NSAIDs
how does age affect the permeability of the blood-brain barrier and what is the result of this?
it increases the permeabiity - therefore drugs are more readily available to be distributed in the CNS
name a water-soluble drug with a high Vd and explain why this is?
digoxin - due to widespread distribution into muscle and reduced muscle mass in elderly populations
what has to be altered about digoxin when given to older people?
loading dose has to be substantially reduced
how does Vd affect how widely distributed a drug is?
drugs with low Vd are not widely distributed, drugs with high Vd are
2 factors which affect hepatic metabolism?
Decreased liver mass
Decreased liver blood flow
2 consequences of decreased hepatic metabolism?
Toxicity due to reduced metabolism/excretion
Reduced first pass metabolism
how is excretion and renal function affected with age & what is the result of this?
renal function and therefore excretion decreases with age - also reduces the clearance and increases half-life of many drugs - leading to toxicity
3 reasons which account for the increased sensitivity to some medicines as we get older?
change in receptor binding
decrease in receptor number
altered translation of a receptor initiated cellular response into a biochemical reaction
in general, how are doses/ frequency of administration affected when prescribing for elderly people?
lower doses and lesser frequency of administration are recommended
describe 5 principles of prescribing for older people?
Review all prescriptions regularly and stop any medicines that are not beneficial
Try to keep regimens as simple as possible
Consider compliance issues which elderly patients in particular may experience
‘start low, go slow’
Review the new drug and check whether it is achieving its aim
what prescribing tool can be used for ruling out inappropriate drugs for older people?
Beers’ Criteria
what research tool can be used for finding medical optimisation when prescribing in older people?
START-STOPP criteria
