6: Pharmacology Flashcards
Pharmacokinetics: body’s action on the drug - ADME
(Absorption, distribution, metabolism, excretion)
Pharmacodynamics: drug’s action on the body
A patient’s ___ has an effect on the concentration of drugs they are administered.
age
Different drugs can ___ to change their metabolism.
interact
The ___ of the environment a drug is in affects its absorption.
pH
acidic drugs require an acidic environment for absorption
basic “” for “”
The route of delivery of a drug is important when talking about older patients.
Why?
Difficulty swallowing
Nasogastric or PEG tubes - tablets need to be suitable for them
Delirious patients won’t tolerate tablets, injections etc.
Pre-op patients may be nil-by-mouth
? how much of this we need to know
Name an example of an acidic drug.
Aspirin
Penicillin
Name an example of a basic drug.
TCAs
Opioids
Benzos
revise volume of distribution
high vd means more drug is stored in fatty tissue
dangerous when cachexic - fat broken down, drug released into circulation
Older patients have greater ___ stores than younger patients.
fat stores
high Vd means drug is lipophilic and most is absorbed into fat
low Vd means drugis hydrophilic and tends to be absorbed by the plasma
biological half life is the time taken for the activity of a drug to half
t1/2 = 0.693 (or ln2) x Vd all over clearance
lipophilic drugs have a large Vd so therefore their t1/2 is greater
older patients have a lower clearance and less body water (i.e plasma), so combined with a high Vd they take ages to clear lipophilic drugs
older people have reduced liver and kidney function so excretion is impaired
serum creatinine dependent on muscle mass, so not reliable for measuring renal function - use eGFR instead obviously
therapeutic index = toxic dose / effective dose
narrow therapeutic index (i.e <2) is bad
drug dose required to produce an effect decreases as you age, so therapeutic index narrows as you age
Opioids - think constipation
Steroids - think osteoporosis
Calcium supplements and T3 need to be taken at morning/night - interact with one another
Avoid long-term NSAIDs, risk of peptic ulcers, renal impairment, gammy other drugs
Opioids and benzos (e.g lorazepam) increase risk of falls
4 Cs and C. diff
ask about OTC medication and herbal remedies
go over drug side effects
stopp-start tool
