Geriatrics - drugs + polypharmacy Flashcards
- Describe how pharmacokinetics and pharmacodynamics differ in elderly patients
- Explain the principles that underpin prescribing in the older individuals
- Explain what help is available to clinicians in choosing and adjusting drug dosage in elderly patients
- List some common medicines to which elderly patients are especially likely to respond differently to younger patients
- Describe polypharmacy, its prevalence and why it arises
- Highlight drugs most commonly implicated in adverse drug reactions
- Improve knowledge of deprescribing practices
.
What are some ADRs in the elderly that may just come across as symptoms of old age
Unsteadiness Dizziness Confusion Nervousness Fatigue Insomnia Drowsiness Falls Depression Incontinence
Reasons that doctors cause polypharmacy
No medication review with patient
Prescribes without sufficiently investigating clinical situation
No effort to simplify medication regimen
Drugs most commonly implicated in ADRs
NSAIDs Diuretics Warfarin ACEI Antidepressants Beta blockers
Most ADRs are due to what class of drugs
Anticholinergics
What are the common peripheral (i.e. not CNS) side effects of antimuscarinics (subtype of anticholinergics)
Dry mouth, eyes Constipation Reduced peristalsis Dilated pupils Urinary retention Tachycardia
What are the central peripheral (i.e. CNS) side effects of antimuscarinics (subtype of anticholinergics)
Impaired memory Confusion Agitation Hallucinations Delirium Falls
Classic antimuscarinic drugs
GI antispasmodics For overactive bladder Tricyclic antidepressants Sedating antihistamines Antiemetics Antipsychotics
How may pharmacokinetics differ in the elderly compared to the young
- A (1)
- D (5)
- M
- E
Absorption - reduced saliva production means reduced rate of absorption of buccal drugs
Distribution
- reduced muscle mass,
- increased fat tissue means fat soluble drugs will sit in reserve for longer
- reduced body water means reduced distribution of water soluble drugs so higher blood conc.
- REDUCED PROTEIN BINDING so increased free drug conc. in blood
- increased permeability across BBB
Metabolism
-decreased liver metabolism due to decreased mass and blood flow
Excretion
-decreased renal function so decreased drug clearance meaning increased half life –> toxicity
Principles that underpin prescribing in older individuals
Be clear about the diagnosis to avoid prescribing a drug to manage an adverse effect
Consider whether drug therapy is the best therapeutic action
Start with lowest dose possible
Consider whether that particular drug tends to cause problems in the elderly
Review the new drug after some time and check if it’s working
Review all prescriptions and stop any drugs that not beneficial
Try to keep drug regimes as simple as possible
Clinical trial drugs usually performed in younger population so the benefits don’t always translate to the elderly
What help is available to clinicians in choosing and adjusting drug dosage in elderly patients
BNF
Beers’ criteria - list of ‘inappropriate’ drugs for older people (but not that helpful)
START-STOPP criteria - advice on optimising medicine
NHS Scotland Polypharmacy Guidance
How to the elderly react differently to psychiatric drugs
- sedatives
- antipsychotics
- anti-depressants
Sedatives - benzodiazepines cause falls and confusion
Antipsychotics - postural hypotension, stroke, confusion
Antidepressants - less effective
How do the elderly react differently to analgesia
- opioids
- NSAIDs
Opioids - more sensitive, lower dose needed
NSAIDs - renal impairment, GI bleed
How do the elderly react differently to cardio drugs
- digoxin
- diuretics
Digoxin - more toxic, lower dose needed
Diuretics - decreased peak effect, reduced clearance, incontinence
How do the elderly react differently to cardio drugs
- antihypertensives
- anticoagulants
Antihypertensives - increased effects on BP + HR, postural hypotension
Anticoagulants - more sensitive to warfarin (GI bleed, falls)
