Drugs and Polypharmacy Flashcards
Common iatrogenic drug problems
Confusion, dry mouth, constipation, blurred vision, urinary retention and orthostatic hypotension with anticholinergics
Confusion and unsteady gait with tricyclics
Digoxin toxicity with normal serum concentrations
CNS toxicity with long-acting benzodiazepines
Confusion with narcotics
Costly medication-related problems/ADRs in older patients
Falls
Cognitive Loss /delirium
Dehydration
Incontinence
Depression
End result can be
Loss of functional capacity
Poor quality of life
Nursing home placement
Prescriptions and older adults
Older adults (age>50) get 2-3 times as many prescriptions
12% of population; > 32% of prescription drugs
Typical 85yr old older adult takes 8-9 prescriptions and 2 OTC drugs at once
Why?
More acute & chronic disease
More doctors visits
Drugs often given to counteract a side effect of another drug
Several other factors arising from prescribers, patients and the system
Adverse drug reactions look like “growing old”
Unsteadiness
Dizziness
Confusion
Nervousness
Fatigue
Insomnia
Drowsiness
Falls
Depression
Incontinence
Prescribing cascade
Medical conditions might have different presenting signs and symptoms in elderly patients
Hyperthyroidism
Young patient
Tremor
Anxiety
Weight loss
Diarrhoea
Elderly patient
Depression
Cognitive impairment
Muscle weakness
Atrial fibrillation
Heart failure
Angina
Healthcare provider factors that
contribute to polypharmacy
No med review with patient on regular basis
Presumes that patient expects meds
Prescribes without sufficiently investigating clinical situation
Evidence that a particular drug is the “best” drug for a problem
Complicated by the existence of many problems and multiple providers
Provides unclear, complex or incomplete instructions about how to take meds
No effort to simplify medication regimen
Ordering automatic refills
Lack of knowledge of geriatric clinical pharmacology
what are worst polypharmacy drugs
NSAIDs 29.6%
Diuretics 27.3%
Warfarin 10.5%
ACEI 7.7%
Antidepressants 7.1%
Beta blockers 6.8%
Opiates 6.0%
Digoxin 2.9%
Prednisolone 2.5%
Clopidogrel 2.4%
which drugs give most adverse effects from polypharmacy use
Anticholinergics
Sedatives
Absorption in the elderly
Physiological changes occur that effect the rate but generally not the extent of absorption from the GI tract
May lead to a delay in onset of action
Examples
A reduction in saliva production may result in a reduction in the rate of absorption of buccally administered drugs e.g. glyceryl trinitrate (GTN)
Distribution in the elderly
Body composition changes
Reduced muscle mass
Increased adipose tissue
Fat soluble drugs: ↑ Vd, ↑ T1/2, ↑ duration of action e.g. diazepam
Reduced body water
Water soluble drugs: ↓Vd, ↑ serum levels e.g. digoxin
Protein binding changes
Decreased albumin
↓ binding, ↑ serum levels acidic drugs e.g. furosemide
Increased permeability across the blood-brain barrier
Metabolism in the elderly
Hepatic metabolism is affected by
Decreased liver mass
Decreased liver blood flow
Consequences
Toxicity due to reduced metabolism/excretion
Reduced first pass metabolism
↑ in bioavailability with some drugs e.g. propranolol
Can cause ↓ bioavailability of pro-drugs e.g. enalapril
Excretion in the elderly
Renal function decreases with age
Reduces clearance and increases half-life of many drugs leading to toxicity
Pharmacodynamics in the elderly
Increased sensitivity to particular medicines
Due to:
change in receptor binding,
decrease in receptor number,
altered translation of a receptor initiated cellular response into a biochemical reaction.
Examples: diazepam (↑ sedation), warfarin (↑ anti-coagulation)
Principles of prescribing for older people
Where possible, be clear about the diagnosis to avoid prescribing a drug to manage an adverse effect
Consider whether drug therapy is the best therapeutic action
Lower doses (or reduced frequency of administration) are generally needed
Think about whether the drug causes particular problems in elderly patients
Check whether a lower dose is recommended in the elderly: start at the lowest dose and titrate up slowly (‘start low, go slow’)
Review the new drug and check whether it is achieving its aim
Review all prescriptions regularly and stop any medicines that are not beneficial
Try to keep regimens as simple as possible
Consider compliance issues which elderly patients in particular may experience
