Principles of prescribing and deprescribing in the elderly Flashcards
Does increasing in age alter drug pharmacokinetics?
Yes
As age increases, how is absorption of drugs generally affected?
As age increases, drug absorption decreases
Why does reduced intestinal blood flow decrease drug absorption?
Less drugs can be absorbed into systemic bloodstream/circulation
Define gastrointestinal (GI) motility
Coordinated contractions and relaxations of the muscles of the GI tract necessary to move contents from the mouth to the anus
As age increases, how is GI motility affected?
Reduced GI motility
Which route of drug administration is most affected by GI motility?
Oral
What gastric mechanism is regulated by GI motility, that is the major factor as to why GI motility reduces drug absorption in elderly people?
Gastric emptying rate
Slow rate means that drug stays in stomach for longer so much less of drug will be absorbed
Give 3 reasons why having a slow gastric emptying rate reduces drug absorption?
Stomach has much smaller surface area than bowels, which is where drug absorption is high
Lower gastric pH which can decrease solubility of drugs
Stomach lining coated with thick mucus so less diffusion of drug into bloodstream occurs
How does gastric emptying rate change as age increases, and what is the general overlying reason?
As age increases, gastric emptying rate decreases
Because gastric emptying rate is regulated by GI motility, which is reduced by old age
Define drug distribution (pharmacokinetics)?
Movement of drug into body tissues
As age increases, how does the concentration of plasma proteins that can bind to drugs change, and how can this lead to drug toxicity?
Concentration decreases
So more unbound/active drugs in bloodstream, so can be distributed more easily: increased effects and drug toxicity
As age increases, why are more lipid-soluble and less water-soluble drugs distributed to body tissues?
Reduced total water volume, so less water-soluble drugs are distributed
More total body fat, so more lipid-soluble drugs are distributed
What metabolic process is reduced due to decreased hepatic blood flow as age increases, and why?
As age increases, hepatic blood flow decreases so less active drugs can be transported from GI tract to liver to allow first-pass metabolism
Other than reduced hepatic blood flow, why is first-pass metabolism decreased as age increases?
Liver enzyme function decreases as age increases
Less first-pass reactions can be catalysed
How can decreased first-pass metabolism of liver cause drug toxicity, in elderly people?
First-pass metabolism decreases, so more active drugs absorbed into circulation with high bioavailability, which can increase toxicity
Why is drug excretion decreased as age increases, and what harmful effect does this have?
Renal function decreases with age (usually after 40 yrs old)
which can lead to build up of toxic levels of drugs
After which age does renal function tend to decrease?
After 40 years old
How are drug pharmacodynamics affected by increasing age?
As age increases, drug pharmacodynamic effects are larger/smaller
Give 4 physiological causes why altered drug pharmacodynamics result from increasing age?
Drug-receptor interaction
Post receptor events
Adaptive homeostatic responses
Pathologic changes in organs (in frail patients)
Which 3 body systems most commonly have altered pharmacodynamic effects of drugs, as age increases?
CNS
GI
Cardiovascular
What problem can occur when using drug dosage for younger patients to determine the correct dosage of that drug to prescribe to an elderly patient?
Drug dosages for young patients not accurately extrapolated, so elderly patients are prescribed dosage that can be toxic
Define polypharmacy?
simultaneous use of multiple medicines by a patient
Why is polypharmacy more common in elderly patients, and what 2 interactions due to polypharmacy have increased risk in elderly patients?
Increased prevalence of co-morbidities which often results in polypharmacy
increases drug-disease and drug-drug interactions
Define drug-disease interaction, and what problem it can commonly lead to in elderly patients?
Pharmacotherapy used to treat a disease causes adverse effect of another disease in a patient
Causes prescription cascade: New drug prescribed to treat adverse effect of a disease, as the adverse effect is misinterpreted as a symptom of a new disease
