Prescribing & de-prescribing in elderly Flashcards
What factors affect drug action?
- Age
- Genetic factors
- Immunological factors
- Disease (especially when they affect drug elimination or metabolism e.g. kidney or liver disease).
- Drug interactions
- Ethnicity
How does age affect drug action?
Drug elimination is less efficient in older people- means drugs produce greater & more prolonged effect
Body composition changes w/ age- fat contributes greater proportion to body mass in elderly (reduction in lead body mass) as muscle vol is decreased- results in change in volume of distribution of drug- changes in fat & lean tissue changes distribution.
- E.g. some drugs more lipid soluble or water soluble
o Renal excretion of drugs- glomerular filtration rate falls slowly from 20 y of age (25% by 50 & 50% by 75) assuming no renal disease present (i.e. half life of drugs in body increases in elderly) many drugs are cleared (excreted) by body via kidneys. I.e metabolism of drug affected by age
- Drugs excreted by urine- lithium, digoxin, gentamicin(antibiotic- IV)
- Drugs mainly metabolised- diazepam, phenytoin, sulfamethoxypridazine
- Digoxin is used for heart problems e.g. arterial fibrillation- is linked to creatine clearance- digoxin clearance decreases w/ creatine clearance in elderly which leads to build-up of digoxin which can be very toxic.
Relationship between plasma creatinine & creatinine clearance- creatinine synthesis reduced in elderly due to reduction in muscle mass- so need to take this into account when estimating glomerular filtration rate. eGFR used to estimate creatinine clearance in patients- used as plasma level of creatinine in blood does not directly correlate w/ clearance of creatinine by kidneys.
o Drug metabolism depends on range of enzymes in liver- activity of these heaptic microsomal enzymes declines w/ age.
Plasma concentration of drug can cause different effects In young & old people- benzodiazepines (e.g. diazepam) produce confusion in elderly compared to young people. Anti-hypertensive drugs- postural hypotension more common w/ older patients on anti-hypertensive- contributes to increased risk of falls in patients
What is co-morbidity? How does it affect drugs prescribed?
o Chronic diseases co-exist
o Means number of different prescribed- so greater potential for drug interactions (can be adverse)
Examples of chronic diseases?
- Alzheimer disease
- Arthritis
- Asthma
- Cancer
- COPD
- Diabetes
Co-morbidities in diabetes?
hypertension
retinopathy
nephropathy
cardiovascular disease peripheral vascular disease
Why is reviews of meds necessary?
Due to effects of age on drug metabolism, clearance, side effect- regular reviews important
Definition of de-prescribing?
De-prescribing- process of w/drawal of inappropriate medication, supervised by a healthcare professional w/ goal of managing polypharmacy & improving outcomes
Why are patients on so many drugs? Definition of polypharamcy? Why is it an issue?
Doctors less trained in stopping meds;
- Thus patients accumulate increasing range of meds during lifetime
- Polypharmacy- patient being prescribed 4 or more medications
- Risk of drug interactions & risk of confusion on how to take meds (especially if need to be taken more than once a day)
- Polypharmacy becoming more common in UK- increases w/ age & increasing no of medical conditions & if female
- Trend to prescribe for asymptomatic patients to prevent future ill ness- incentivised in primary care when payment are made under quality & outcomes framework
When to consider de-prescribing?
Medication review- essential- does patient still need med for every med on the list
Hospital admission- vital to make it clear at discharge that some meds have been stopped, otherwise may be restated in community
When we need to treat new condition- essential due to drug interaction s between existing frug & new one- as list gets longer, potential for confusion increases w/ risks of wrong dose being taken or missed
What are the factors that lead to polypharmacy in old age?
Multiple pathology/comorbidities
Poor patient education
Lack of routine review of all meds
Patient expectations of prescribing
Over-use of drug interventions by doctors
Attendance at multiple specialist clinics
Poor communication between specialists
What is diazepam? What drug family is it in? Side effects? When to avoid?
Used for muscle spasms, tetanus, anxiety & insomnia associated w/ anxiety, sedation for dental procedures & convulsions.
Drug family- benzodiazepines
Avoid injections containing benzyl alcohol in neonates- chronic
Side effects-
- Appetite abnormal
- concentration impaired
- gastrointestinal disorder
- movement disorders
- muscle spasms; palpitations
- sensory disorder
- vomiting
- Due to risk of addiction- only used for short course
Risk of using benzodiazepines w/ opioids? Other cautions when using them?
Benzodiazepines prescribed w/ opioids can produce addictive CNS depressant effects- increasing risk of sedation, respiratory depression, coma & death- only co-prescribe if no
For all benzodiazepines- avoid prolonged use, debilitated patients (reduce dose) (in adults), elderly (reduce dose) (in adults); history of alcohol dependence or abuse; history of drug dependence or abuse; myasthenia gravis; personality disorder (within the fearful group—dependent, avoidant, obsessive-compulsive) may increase risk of dependence; respiratory disease
What is a low dose of amitriptyline used for? Caution- when not to use? Contra-indications? Side effects?
Used for neuropathic pain e.g. painful diabetic neuropathy, abdominal pain, migraine prophylaxis, emotional lability in multiple sclerosis
Not recommended in major depressive disorders (w/ or w/out cardiovascular disease)- increased risk of fatality in overdose.
Contra-indications- Arrhythmias; during manic phase of bipolar disorder; heart block; immediate recovery period after myocardial infarction
Side effects- Anticholinergic syndrome; drowsiness; QT interval prolongation
What adverse reaction do NSAID have in old age?
Gastrointestinal bleeding
Peptic ulceration
Renal impairment
What adverse reaction do Dieurtics have in old age?
Renal impairment
Gout
Hypotension
Postural hypotension
