4) Prescribing in older people Flashcards
How does ageing affect drug therapy?
Ageing leads to progressive loss of organ function, altered receptor responses, and decreased homeostatic mechanisms. These changes impact drug absorption, distribution, metabolism, and excretion, increasing the risk of adverse effects and drug accumulation.
What is frailty and how does it impact medication use?
Frailty is a state of increased vulnerability due to ageing, associated with reduced physical and psychological reserves. It is linked to falls, immobility, delirium, susceptibility to drug side effects, and incontinence, all of which complicate medication management.
How does drug absorption change with age?
The extent of drug absorption remains largely unchanged, but the absorption rate may slow down. This can lead to delayed peak plasma drug concentrations, but does not usually require dose adjustments.
How does drug distribution change with age?
Older adults have reduced body water and lean body mass but increased fat stores. Water-soluble drugs (e.g., digoxin) have a reduced volume of distribution (Vd), leading to higher plasma concentrations. Lipid-soluble drugs (e.g., diazepam) have an increased Vd, leading to prolonged drug effects and half-life.
What are examples of drugs affected by changes in body composition in older people?
Diazepam (fat-soluble, increased Vd leading to prolonged sedation) and Digoxin (water-soluble, decreased Vd leading to increased plasma levels and toxicity). Tricyclic antidepressants also accumulate in fat stores, leading to prolonged effects and toxicity.
How does hepatic metabolism change with ageing?
Hepatic metabolism decreases due to reduced CYP450 enzyme activity. This can increase the risk of toxicity with drugs like diazepam, theophylline, and warfarin. Hepatic metabolism declines due to reduced liver size and blood flow. Phase I metabolism (oxidation, reduction) is particularly affected, increasing plasma concentrations of drugs with extensive first-pass metabolism (e.g., propranolol, metoclopramide, benzodiazepines).
How does renal drug excretion change with age?
Renal function declines by about 10% per decade after young adulthood. This reduces clearance of renally excreted drugs (e.g., lithium, gentamicin, digoxin, vancomycin, DOACs), which may accumulate to toxic levels. Monitoring renal function is crucial in older patients.
How do pharmacodynamic changes affect older adults?
Older adults show increased sensitivity to central nervous system depressants (e.g., benzodiazepines, opioids), reduced β1- and β2-receptor responsiveness (affecting beta-blockers), and increased susceptibility to anticholinergic side effects.
What is polypharmacy and why is it a concern?
Polypharmacy is the use of multiple medications, common in older adults due to multimorbidity. It increases the risk of drug interactions, adverse drug reactions (ADRs), prescribing cascades, and non-adherence.
What are key principles of good prescribing in older people?
- Use familiar drugs with well-established safety profiles.
- Prescribe the lowest effective dose.
- Monitor therapy for drug interactions and ADRs.
- Avoid prescribing cascades (where an ADR leads to additional medications).
- Involve caregivers and encourage patient adherence.
What is inappropriate prescribing?
Inappropriate prescribing includes:
- Misprescribing: Use of drugs that significantly increase ADR risk (e.g., benzodiazepines, anticholinergics).
- Overprescribing: Prescribing drugs without clear clinical benefit.
- Underprescribing: Failing to prescribe beneficial drugs (e.g., missing anticoagulation in atrial fibrillation).
What are common reasons for inappropriate prescribing in older adults?
Includes excessive response to symptoms, failure to recognize ADRs, patient demands, prescriber expectations, lack of individualization, and inadequate medication review. Prescribers may also be hesitant to deprescribe due to fear of worsening symptoms.
What are examples of drugs poorly tolerated by older people?
Drugs commonly causing harm include:
- Digoxin (>187.5 mcg, due to toxicity risk)
- Benzodiazepines (increased fall risk, sedation)
- Tricyclic antidepressants (strong anticholinergic effects)
- Antipsychotics (stroke risk, sedation, falls)
- Anticholinergics (cognitive impairment, urinary retention)
What are tools used to detect inappropriate prescribing?
- Medication Appropriateness Index (MAI): Evaluates ten prescribing criteria.
- Beers’ Criteria: Lists drugs to avoid in older adults.
- STOPP/START Criteria: Identifies inappropriate prescriptions (STOPP) and missing beneficial treatments (START).
What is the Medication Appropriateness Index (MAI)?
A tool assessing ten criteria for prescribing appropriateness, requiring clinical judgment. It is useful for identifying inappropriate prescribing but does not address underprescribing.
What is Beers’ Criteria?
A guideline listing drugs that should generally be avoided in older adults due to safety concerns. It includes disease-specific medication risks but does not consider drug-drug interactions or underprescribing.
What is the STOPP/START tool?
STOPP (Screening Tool of Older Persons’ potentially inappropriate Prescriptions) identifies unnecessary prescriptions.
START (Screening Tool to Alert doctors to Right Treatment) highlights missing beneficial treatments. This tool is more comprehensive than Beers’ Criteria as it also considers underprescribing.
What is deprescribing?
Deprescribing is the supervised withdrawal of inappropriate medications to reduce polypharmacy and improve patient outcomes. It requires careful monitoring to avoid withdrawal and rebound effects.
What are challenges to deprescribing?
Barriers include:
- Resistance to change (both prescribers and patients).
- Lack of evidence on how to safely withdraw some medications.
- Risk of withdrawal syndromes.
- Prescriber reluctance due to concerns about patient deterioration.
What are possible outcomes of deprescribing?
Potential outcomes include:
- Resolution of ADRs (e.g., improved cognition after stopping anticholinergics).
- Improved quality of life.
- Withdrawal syndromes (e.g., rebound hypertension after stopping beta-blockers).
- Reappearance of disease symptoms if treatment was necessary.
How can pharmacists support prescribing in older adults?
Pharmacists play a key role in:
- Identifying inappropriate medications.
- Monitoring for ADRs and interactions.
- Supporting deprescribing efforts.
- Educating healthcare providers and patients about safer alternatives.
What are key considerations for medication review in older adults?
Medication reviews should:
- Assess medication necessity.
- Monitor for ADRs and interactions.
- Simplify regimens to improve adherence.
- Avoid unnecessary polypharmacy.
- Involve multidisciplinary teams where possible.
Why is medication use in older adults challenging?
Older adults experience age-related changes in drug metabolism, increased sensitivity to drugs, polypharmacy, and higher risk of adverse drug reactions (ADRs).
How does ageing affect renal drug elimination?
Renal clearance decreases due to reduced glomerular filtration rate (GFR), renal blood flow, and tubular function, leading to accumulation of renally excreted drugs like digoxin, aminoglycosides, and lithium.
