[1] Polypharmacy Flashcards
What is polypharmacy defined as?
Being prescribed more than 4 medications
What proportion of older patients are affected by polypharmacy?
Over 1/3
What can polypharmacy result in?
- Increased risk of side effects
- Increased risk of drug-drug interactions
- Therapeutic cascade
- Increased risk of medications not being reviewed thoroughly
What is meant by the therapeutic cascade?
A drug is prescribed and causes an adverse effect. This adverse effect is misinterpreted as a new medical condition, causing the prescription of another drug, and the cycle continues
What things are considered to be ‘inappropriate prescribing’?
- Prescribing drugs that are contraindicated
- Prescribing a drug with an inappropriate dose or duration
- Prescribing a drug that is likely to adversely affect prognosis
- Failure to use a drug that could improve patient outcomes
Why is inappropriate prescribing more common in older adults?
- Higher prevalence of chronic disease
- Higher levels of polypharmacy leading to an increased risk of drug-drug and drug-disease interaction
- Age related physiological changes
In what things are there age-related physical changes that affect drugs?
- Distribution
- Hepatic metabolism
- Renal elimination
Are age-related changes in the GI tract clinically significant in relation to drugs?
No, because they do not affect the absorption of most drugs
What age-related changes cause changes in the distribution of drugs?
- Total body fat increases
- Total body water decreases
- Serum albumin decreases
What is the effect of the increase in total body fat with ageing on drugs?
Increases the volume of distribution for fat soluble drugs
What is the effect of the decrease in total body water with ageing on drugs?
Decreases the volume of distribution of water soluble drugs
What is the effect of the decrease in serum albumin with ageing on drugs?
Increases the effects of albumin-bound drugs as levels of unbound drugs increase as a consequence
What happens to hepatic metabolism with age?
Reduces
Why does hepatic metabolism of many drugs reduce with age?
Because of reduced liver volume and enzymes activity
What is the potential result in the reduction of hepatic metabolism with age?
Can cause toxic accumulation
What should be done to prevent toxic accumulation of drugs due to reduction in hepatic metabolism with age?
Reduce dose or increase dosing interval
What drugs are effected by a reduction in the glomerular filtration rate?
Drugs that are excreted by the kidneys
What effect do reductions in the GFR have on drugs that are excreted from the kidneys?
Reduces excretion
Give an example of a renally excreted drug with a narrow therapeutic index?
Digoxin
What is the result of digoxin being renally excreted and having a narrow therapeutic index?
It often requires dose reduction in later life to prevent drug toxicity
How should toxic accumulation caused by reduced renal elimination with ageing be reduced?
Reduce dose or increase dosing interval
What proportion of hospital admissions are drug related and preventable?
1 in 15
Why are the risks of prescribing greater in older adults?
- Changes in pharmacokinetics
- Changes in pharmacodynamics
- Polypharmacy
- Frailty
- Communication problems
- Lack of evidence base
- Guidelines being based on singe-organ disease processes
What is pharmacodynamics?
Refers to how the drug interacts with the body to produce a response
What is pharmacokinetics?
What the body does to the drug
What concepts does pharmacokinetics include?
- Absorption
- Distribution across body compartments
- Metabolism
- Excretion
What happens to the metabolism and excretion of many drugs with ageing?
It decreases
What is the result of the decrease in metabolism and excretion of many drugs with ageing?
The doses need to be adjusted
When is the adjustment of drugs due to ageing especially important?
For drugs with narrow therapeutic indexes
Why is it important to adjust the doses of drugs with a narrow therapeutic index?
Because even a small increase in bioavailability can lead to toxic effects
What are the consequences of inappropriate prescribing?
- Increased morbidity and mortality
- Increased hospital length of stay
- Reduced compliance
- Increased risk of adverse drug reactions
What considerations should be made whilst prescribing?
- The benefits of a drug should outweigh the risks
- The drug should be cost-effective
- The individual patient characteristics should be taken into account to aid prescribing
- The drug should be safe
What steps can be taken to ensure you are prescribing right?
- Ensure you have gained accurate medication history
- Map medication last to PMH to ensure known medical conditions are being treated appropriately
- Prescribe in current clinical context
- Ensure essential medications are not omitted
- Review administration route if necessary
- Use monitoring to determine effect of drug and help detect adverse effects
- Remember to review if any medications are missing that should be prescribed
Give an exampling of prescribing in the clinical context
Someone being treated for dehydration is unlikely to need their diuretic therapy
Give some examples of essential medication that should not be omitted
- Antibiotics
- Anti-epileptics
- Diabetic drugs
- Parkinson’s drugs
When might the administration route need to be reviewed?
If the patient is NBM, alternative route may need to be used, especially for essential drugs
What monitoring can be done to ensure drugs are effective?
- Symptoms and signs
- Investigation results
What is meant by the prescribing paradox in frailty?
Frail adults often need drugs to treat their long-term conditions, however polypharmacy is implicated in frailty
Why is polypharmacy bad in frailty?
- A new drug is a challenge to the system, and a frail system is more likely to decompensate
- Decompensation is more likely then there is polypharmacy
- Polypharmacy is a risk factor for decline in the face of a non-pharmacological precipitant
What is the problem with evidence-based prescribing in older people?
Evidence is often extrapolated from trials involving younger adults who often do not have multi-morbidity or polypharmacy
