Geriatric Medicine - Geriatric Pharmacology Flashcards
What is pharmacokinetics?
It describes what the body does to the drug
What are the four basic pharmacokinetic processes?
Absorption
Distribution
Metabolism
Excretion
How is drug absorption affected by the process of ageing?
The absorption rate of drugs, via all routes, is reduced
This may lead to a delayed onset of drug action
How is drug distribution affected by the process of ageing? Why?
The fat-soluble drugs have an increased distribution. The water soluble drugs have a decreased distribution
In older individuals, there is a reduction in muscle mass, increase in adipose tissue and a decrease in total body water
How is protein-binding affected by the process of ageing? How does this affect the way in which we administer drugs?
The liver produces decreased levels of albumin, which means that there is less protein-binding of drugs and therefore there’s an increased concentration of bioavailable drugs
This leads to a reduced dose requirement of protein-bound drugs in geriatric patients
How does ageing affect drugs which undergo hepatic activation? Why?
Their bioavailability decreases
This is due to decreased liver mass and blood flow
How does ageing affect drugs which undergo activation via albumin unbinding? Why? What are the effects of this?
Their bioavailability increases
This is due to decreased liver mass and blood flow, increasing plasma volume of drugs
Consequently, this can lead to drug toxicity
How is drug excretion affected by the ageing process? Why? What are the effects of this?
The drug excretion is decreased.
This is due to reduced renal function, and therefore clearance of waste materials.
Resultingly, the half-life of drugs increases, which can lead to toxicity.
What is pharmacodynamics?
It describes what the drug does to the body
How does ageing change pharmodynamics?
It affects the site of drug action and the receptor response to drugs
This may impose an increased efficacy to certain medicines
What general prescribing principle can be applied to geriatrics?
We administer lower doses and/or reduced frequency of doses of drugs to geriatric patients
These drugs require frequent review, and in cases where drug efficacy is insufficient, we titrate the dose up slowly
What is polypharmacy?
It is the prescribing of multiple drugs, typically greater than five, to one individual
This leads to an increased risk of adverse drug reactions
What are the three causes of polypharmacy in geriatrics?
There is increased susceptibility to acute and chronic disease
There is an increase in misdiagnosis due to their presentation of ‘decompensated frailty syndromes’, rather than the typical features of an illness
Prescribing cascades
What is a prescribing cascade?
When a drug administered causes adverse side effects, that are misinterpreted as a new condition, resulting in a secondary drug being prescribed
What is deprescribing?
The process of reducing, substituting or discontinuing inappropriate medications, with the goal of managing polypharmacy and improving outcomes
