Drugs and Polypharmacy Flashcards
Define polypharmacy
Many drugs or inappropriate amount of drugs
Common Adverse Drug Reactions (ADR)
Confusion
Dry mouth
Vision
Urinary retention
DIGOXIN TOXICITY
Confusion
See paper patient
Normal serum concentrations
Complications of polypharmacy
Falls
Mortality
Over 50s 2-3x as many prescriptions
85y/o arond 8-9 + 2 OTC simultaneously
More acute and chronic illness
Increased visits to GP
Drugs to counteract side effects
Lack of continuity of care- discontinuation of prescription meds
PRESCRIBING CASCADE
Prescribed drug leads to ADE; interpreted as new medical condition –> prescription of additional drug –> ADE–> additional prescription etc
Hyperthyroidism- presenting signs and symptoms - Young patient
Tremor
Anxiety
Weight loss
Diarrhoea
Hyperthyroidism presenting signs and symptoms- Elderly
Depression Cognitive impairment Atrial fibrillation, Heart Failure, Angina Delirium Muscle weakness
Factors contributing to polypharamacy
Lack of regular med reviews
Presume patient expects medication
Prescribe without sufficient clinical investigation
Unclear/complex/incomplete instructions on how to take meds provided
No effort to simplify regimen
Ordering automatic refills
Lack of geri clinical pharmacology knowledge
Worst drugs for ADR
NSAIDS Diuretics Warfarin ACEi Antidepressants
Effect of physiological changes on Absorption
Alters rate but not extent
eg, reduced saliva production, reduced GTN absorption
Exception - levodopa in Parkinsonism - lower enzyme levels in elderly - increased absorption; higher peak plasma level, shorter time to peak
What changes affect distribution?
Body composition - muscle mass, water (digoxin), adipose tissue (fat soluble drugs- diazepam)
Protein binding changes - albumin decrease, increase serum levels
Permeability across blood-brain-barrier
Factors affecting hepatic metabolism
Reduced mass
Reduced blood flow
Leads to toxicity
Increased availability of some drugs eg propanolol
Decreased bioavailability of pro-drugs- enalapril (activated once passed through liver)
Excretion
Decreased renal function
Reduced clearance
Increased half life of drugs
–> Toxicity
Pharmacodynamics
change in receptor binding,
decrease in receptor number,
altered translation of a receptor initiated cellular response into a biochemical reaction
Beer’s Criteria
List of inappropriate drugs to prescribe elderly
START STOPP Criteria
Optimisation
Deprescribing
To reduce, substitute or discontinue a drug
Reasons for deprescribing
Adverse drug reaction Drug-drug interaction Drug-disease interaction Better alternative Not effective Not indicated Not evidence-based Minimise polypharmacy
Adverse effects Psychiatric drugs
Sedatives - benzodiazepines; falls and confusion
Anti-psychotics - Postural hypotension, stroke, confusion, movement disorders
Anti-depressants; ineffective in treating agitation –> more dangerous?
Adverse effects Anlagesia
Opioids - more sensitive to effects, lower doses needed
NSAIDs- Renal impairment, GI bleeding
Adverse effects Cardiovascular
Digoxin
Increased toxicity, lower doses needed
Narrow therapeutic index
Adverse effects Cardiovascular
Diuretics
Decreased peak effect, reduced clearance - abnormal U&Es
Incontinence and mobility need considered
Inappropriate indication - swollen legs
Adverse effects Cardiovascular
Anti Hypertensives
May have exaggerated effects on BP and HR
More likely to be issues with postural hypotension
ACE inhibitors often pro-drugs which may not be metabolised to the active form
Renal adverse effects
Adverse effects Cardiovascular
Anticoagulants
More sensitive to warfarin
Greater risk from warfarin - GI Bleeding, falls
Decreased requirements per decade of life (clotting factors)
Antibiotics Adverse Effects
Diarrhoea and c. diff infection Blood dyscrasias (trimethoprim, co-trimoxazole) Delirium (quinolones) Seizures Renal impairment (aminoglycosides)
