Drugs and Polypharmacy Flashcards
how is absorption affected in the elderly and what is the outcome of it
- Rate but not extent of absorption from GI tract is reduced
- May lead to delayed onset of action
- E.g. reduced saliva production causes reduced absorption of buccally administered drugs like GTN
4 ways the elderly body has changed in composition
- Reduced muscle mass
- Increased adipose tissue
- Reduced body water
- Decreased albumin
Effect of increased adipose tissue on distribution
- Fat soluble drugs: increase in distribution and duration of action
- E.g. Diazepam
Effect of reduced body water and albumin on distribution
- Water soluble drugs: decrease in distribution and increase in serum levels (e.g. digoxin)
- Decreased albumin leads to reduced binding and there increase serum levels of acidic drugs (e.g. furosemide)
How is metabolism affected in the elderly and what’s the result of this
- Hepatic metabolism affected by decreased liver mass + blood flow
- Toxicity due to reduced metabolism/excretion
- Reduced first pass metabolism
What happens to first pass metabolism in the elderly and what the result of it
- Reduced
- Increase bioavailability of some drugs (propranolol)
- Reduced bioavailability of pro-drugs (enalapril)
Why is excretion reduced in the elderly and what’s the result of this
- Reduced GFR
- Reduces clearance by half + increases half-life of many drugs leading to toxicity
Change in pharmacodynamics of the elderly and why
-Increased sensitivity to particular drugs
Due to:
-Change in receptor binding
-Decrease in receptor no.
-Altered translation of a receptor initiated cellular response into a biochemical reaction
2 drugs that the elderly are v sensitive to
- Diazepam (increased sedation)
- Warfarin (increased anti-coagulation)
6 principles of prescribing for (older) people
- Why do you want to prescribe a drug (symptom control or prevention of incidents)
- Could the symptoms be the SE of another drug
- Is there an evidence base for the drug you’re considering in this person
- Is the person likely to benefit from the drug within their lifetime
- What are the risks of the SE
- Are there administration or compliance issues
Describe “creeping cardex syndrome”
- Drugs started for preventative reasons, but not reviewed
- Drugs started with intention of short-term symptomatic relief, but never stopped
- Drugs started to relieve side effects of other drugs
Describe prescribing cascade
Drug 1 => ADR interpreted as new medical condition => drug 2 => ADR interpreted as new medical condition => drug 3
5 drugs most associated with admission due to adverse drug reaction (ADR)
- NSAIDs (29.6%)
- Diuretics (27.3%)
- Warfarin (10.5%)
- ACE inhibitors (7.7%)
- Anti-depressants (7.1%)
2 drugs least associated with admission due to adverse drug reaction (ADR)
- Clopidogrel (2.4%)
- Prednisolone (2.5%)
SE of Tolterodine
-Risk of falls
SE of Bendroflumethiazide
- Hypo Na
- Hypotension
SE of Sertraline
- Hypo Na
- Low orthostatic BP
- Risk of falls
SE of omeprazole
- Hypo Na
- Associated with osteoporosis
What is hyponatraemia associated with
Risk of falls + fracture
3 prescribing tools and guides
- Beers’ criteria
- START-STOPP criteria
- NHS Scotland Polypharmacy Guidance
4 reasons to deprescribe
- ADR or drug-drug/drug-disease interaction
- Better alternative
- Not effective
- Not indicated/not evidence-based
Problems with prescribing benzodiazepines to elderly patients
- Falls
- Confusion
Problems with prescribing anti-psychotics to elderly patients
- Postural hypotension
- Stroke
- Confusion
- Movement disorders
Problems with prescribing opioids to elderly patients
- More sensitive to effects
- Lower doses needed
- Pethidine and tramadol may be less useful
Problems with prescribing NSAIDs to elderly patients
Increased adverse effects:
- Renal impairment
- GI bleeding
Problems with prescribing digoxin to elderly patients
- Increased toxicity
- Lower doses needed
Problems with prescribing diuretics to elderly patients
- Decreased peak effect but reduced clearance (abnormal U&Es)
- Issues around continence + mobility
- Often inappropriate indication (swollen legs)
Problems with prescribing anti-hypertensives to elderly patients
- Exaggerated effect of BP + HR
- Renal adverse effects
- More likely to be issues with postural hypotension
- ACE-I often pro-drugs which may not be metabolised to active form
Problems with prescribing anti-coagulants to elderly patients
- More sensitive to Warfarin
- Greater risk from warfarin i.e. GI bleeding, falls
Problems with prescribing antibiotics to elderly patients
Increased adverse effect
- Seizures
- Delirium (quinolones)
- Renal impairment (aminoglycosides)
- Blood dyscrasias (co-trimoxazole, trimethoprim)
- Diarrhoea + c. diff infection
