Drugs and polypharmacy Flashcards
What are some 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
Prescribing cascade
This is how an elderly patient can end up on multiple unnecessary drugs
- Drug 1
- Adverse drug event occurs and is interpreted as new medical condition
- Drug 2
- Adverse drug event occurs and is interpreted as new medical condition
- Drug 3
Medical conditions might have different presenting signs and symptoms in elderly patients.
Using Hyperthyroidism as an example, list the contrasting signs/symptoms in both the young and elderly patient.
Young patient
- Tremor
- Anxiety
- Weight loss
- Diarrhoea
Elderly patient
- Depression
- Cognitive impairment
- Muscle weakness
- Atrial fibrillation
- Heart failure
- Angina
Why might a doctor or healthcare provider contribute to polypharmacy?
- No med review with patient on regular basis
- Presumes that patient expects medication
- 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
How does drug absorption differ 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.
- E.g – A reduction in saliva production may result in a reduction in the rate of absorption of buccally administered drugs e.g. glyceryl trinitrate (GTN)
What are the 2 most important factors that affect drug distribution in the elderly?
- Changes in body composition
- Protein binding
Changes in body composition in the elderly
- Reduced muscle mass
- Increased adipose tissue - this occurs even in the absence of overt obesity.
- Theses changes are combined with a decrease in total body water
A drug’s vol of distribution is dependant on how it distributes into the body’s aqueous and lipid phases, these changes will have a significant effect on drug distribution. This will be particularly significant if a drug is highly lipid soluble, is distributed widely into muscle or is largely confined to body water.
- Fat soluble drugs - the Vd is increased - increase in body fat, drugs stay in adipose tissue so longer half life (increased duration of action) e.g diazepam
- Water soluble drugs - the Vd is reduced resulting in higher serum levels e.g digoxin
Protein binding changes in the elderly
- Free drug = active drug as it can bind to target tissues
- Total serum albumin decreases by approx 12% with age
- Acidic drugs such as cimetidine, furosemide, NSAIDs and sulphonylureas, diazepam, salicyic acid are bound by serum albumin and will be affected.
- Less binding, increase in serum levels of unbound acidic drug - predispose to ADRs
- Also some diseases that are common in the elderly depress albumin - including heart failure, renal disease, rheumatoid arthritis, hepatic cirrhosis and some malignancies.
- Albumin is reduced in malnutrition, or acute illness,
- Basic drugs are bound to α1-acid glycoprotein which is unaltered with age but may be increased during acute illness.
What is Hepatic metabolism affected by?
- Decreased liver mass
- Decreased liver blood flow
What are the consequences of disrupted hepatic metabolism? (2)
- 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 (it needs to be metabolised by the liver to become active so in this case it is not produced)
As you get older your renal function declines. What effect does this have on drug clearance and half life of drugs?
- Reduced clearance
- Increases the half-life of many drugs leading to toxicity
How does Pharmacodynamics (what the drug does to the body) differ in the elderly?
There is 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)
General 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
- Review any 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 i.e use blister packs etc
What is STOPP/START criteria?
Stands for: Screeening Tool to Alert doctors to Right Treatment and Screening Tool of Older Person’s presciptions
- Advice on medical optimisation
- Reduction in ADRs and LoS
What is de-prescribing?
To reduce, substitute or discontinue a drug
