Prescribing in Old Age Flashcards
Do acidic drugs require an acidic or basic environment in order to be absorbed?
Acidic
Do basic drugs require an acidic or basic environment in order to be absorbed?
Basic
What protein binds to acidic drugs?
Albumin
What protein binds to basic drugs?
Alpha - 1 Acid Glycoproetin
What group of antibiotics does theophylline interact with?
Macrolide
What drug should be prescribed prophylactically with an opiod?
Lactulose or Senna
What does polypharmacy generally mean?
On more than 4 medications
List some drugs which are very badly tolerated in older people?
Benzodiazepines - increase falls, decrease cognition (especially in dementia)
Since benzodiazepines are a fat soluable drugs they have an increased action in older people.
NSAIDs - renal function declines with age and these are nephrotoxic as well as being a gastric irritant
Anti cholinergics - Profound effects on cognition
Alpha blockers - Orthostatic hypotension (falls)
As we get older what happens to our % of body fat compared to our % of body water?
Increased body fat compared to body water
Why does the action of benzodiazepines increase in older people?
They are fat soluable drugs - more body fat means that they are absorbed more readily and they have a longer duration of action in older people
Why does renal function decline with age?
Reduced renal mass
Reduced renal blood flow
What happens to first pass metabolism in older age?
Reduces; probably due to a reduction in liver mass . This means that the bioavailability of drugs which undergo first pass metabolism such as opiods and metclopramide will be hugely increased. In contrast the first pass activation of pro drugs may be significantly reduced.
What substance do acidic drugs mainly bind do?
Albumin
What is an example of an acidic drug?
Phenytoin, warfarin
What is an example of basic drugs?
Lidnocaine
Propanolol
Diazepam
What is meant by pharmacodynamics?
The effect of the drug on the body
What is meant by pharmacokinetics?
The effect of the body on the drug
What is meant by bioavailability of a drug?
Proportion of the drugs reaching the systemic circulation. If drug is given IV bioavailability = 100%
What is meant by clearance of a drug?
The volume of blood or plasma cleared in unit time
What substance binds basic drugs?
Alpha 1 Acid Glycoprotein
What does a decreased body water level mean is in terms of drug prescribing?
Lower volume of distribution of hydrophillic drugs such as lithium (risky because they already have a small theraputic window!)
What are the five classes of adverse drug reactions?
- Drug drug interactions
- Drug disease interactions
- Drug food interactions
- Drug side effects
- Drug toxicity
You want start a diabetic women on an ACE inhibitor; what drug drug interaction should you consider?
ACE inhibitors increase the hypoglycaemia effect of sulfonlyureas
Give three drugs that can reduce seizure threshold?
Antipsychotics
Tramadol
Quinolones
What is meant by number needed to treat?
How many people need to take treatment for a given amount of time to prevent one event. So if the NNT is 30 then 30 people need to take the drug for 1 year to prevent 1 event
What is the average life expectancy of someone who is a nursing home with dementia?
18 - 24 months
What is the average life expectancy of someone who has heart failure with breathlessness at rest?
12 months
Which antibiotic from the following list will increase the INR of a patient who is on warfarin:
a) Amoxiciilin
b) Trimethoprim
c) Clarithromycin
d) Nitrofurantoin
e) Rifampicin
Clarithromycin is an inhibitor of the Cytochrome p450 system
Rifampicin is an inducer of the cytochrome p450 system so will reduce INR
