Principles Of Drug Use In The Elderly Flashcards
Why is drug use in older people important?
Co-morbidities Polypharmacy (=/>4) Susceptibility to ADRs Hospital admissions increasing Compliance/adherence High cost
What is a drug interaction?
A situation in which a substance (usually another drug) affects the activity of a drug when both are administered together
What is an adverse drug reaction (ADR)?
Undesirable effect (i.e. injury) of a drug beyond its anticipated therapeutic effects occurring during clinical use (serious and growing public health problem in the elderly)
What are the risk factors for adverse drug reactions (ADRs)?
Polypharmacy
IP
Physiological affects of ageing
Comorbidities
What are adverse drug reactions (ADRs) related to?
DoTS classification:
- Dose
- Time-course
- Susceptibility
How can a dose of a drug ABOVE the therapeutic range cause adverse drug reactions (ADRs)?
Above therapeutic range = toxic reaction e.g. bleeding following too high dose of Warfarin
Treatment:
- Reduce dose
- Prevent by using min. effective dose
How can a dose of a drug WITHIN the therapeutic range cause adverse drug reactions (ADRs)?
Within therapeutic range = collateral reaction e.g. drowsiness with antihistamines
Treatment:
- May be unavoidable
- Try reducing dose w/o reducing desired therapeutic effect
- If this does not work change medicine
How can a dose of a drug BELOW the therapeutic range cause adverse drug reactions (ADRs)?
Below therapeutic range = hypersusceptibility reaction e.g. penicillin allergy
Treatment:
- Avoid by using foreknowledge of patient allergies - ask in history what allergies and what there reaction is
- Permanently avoid said drug
How can the time-course of a drug cause adverse drug reactions (ADRs)?
- 1st dose reaction
- Early reactions
- Intermediate reactions
- Late reactions
- Withdrawal reactions
- Delayed reactions
How can the dose of a drug cause adverse drug reactions (ADRs)?
- Above therapeutic range
- Within therapeutic range
- Below therapeutic range
Therapeutic range = specific to patient
What is a first dose reaction?
When a patient reacts after the first dose of a drug e.g. hypotension after 1st dose of ACEi so advise/special precautions are needed e.g. advice to take 1st dose at night when lying down so they do not fall over
What is a early reaction?
When a patient gets a side effect after being on the drug for a short amount of time but the patient becomes tolerant so the reaction wears off so the patient can continue with the treatment as the ADR should wear off e.g. nitrate-induced headache
What is an intermediate reaction?
When a reaction to a drug occurs within a specific time frame but vigilance can be relaxed if no reaction occurs after this time e.g. neutropenia due to carbimazole which may make patients have a sore throat short-term
What is a late reaction?
A longer term affect of a drug that persists so increases risk of ADR with continued/repeated exposure and implies the need for long-term monitoring +/- prevention e.g. bruising, weight gain and bone loss as a result of corticosteroids
What is a withdrawal reaction?
When patients get negative affects as a result of stopping a drug (SSRIs, corticosteroids, opioids)abruptly after being on them for a while so it is important to slowly withdraw or reduce the dose of some drugs to prevent ADRs e.g. SSRI AD discontinuation syndrome can cause flu-like symptoms, shock-like sensations, dizziness, anxiety, irritability, insomnia, vivid dreams etc.
What is a delayed reaction?
When a patient gets a long-term illness or disease e.g. carcinogenesis or teratogenesis as a result of long-term use of a drug so the drug should be avoided in patients with known susceptibility to these problems e.g. HRT, chemotherapy, radiotherapy and methotrexate (not as important in elderly but more so in younger patients)
What drug in the elderly shows an important delayed reaction?
Nitrofurantoin is used as a prophylactic for UTIs but can cause irreversible progressive pulmonary fibrosis
What factors make patients susceptible to adverse drug reactions (ADRs)?
- Genetics
- Age
- Sex
- Specific physiological states e.g. pregnancy
- Diseases e.g. hepatic/renal impairment
- Exogenous factors e.g. other drugs (interactions), diet etc.
If there is a suspected adverse drug reaction (ADR), where should it be reported?
Yellow Card Scheme using the electronic form online
What is ageing?
Gradual loss of function of cells and organs with the eventual outcome of death
What factors influence ageing?
Genetics Psychology Lifestyle Socio-economic factors Environment
Why is ageing important for doctors?
- Doctors care for lots of older people
- We want to improve QoL and longevity
- Resource issues for NHS
What are the main sources of cost impact of the older population?
Benefit expenditure
NHS spending
Hospital and community health services
What are the 3 different stages of old age?
- 65-75yrs: entering old age, careers finished but still active and independent so aim to promote healthy active life but also prevent disease
- 75-84yrs: transitional phase where we aim to identify/manage on-going and emerging problems
- 85+yrs: frail old age population that show vulnerability as a result of health/social problems
What are the cardiovascular effects of ageing?
- Cardiac enlargement/LVH
- Decreased CO = reduced exercise capacity
- Decreased response of HR to exercise
- Systolic HPN
- LVF
What are the respiratory effects of ageing?
- Decreased FEV1/FVC and increased residual volume
- Increased susceptibility to infection
- Increased susceptibility to aspiration
What are the endocrine affects of ageing?
- Decreased insulin sensitivity
2. Decreased thyroid hormone production
What are the gastrointestinal affects of ageing?
- Increased gastric acid production
2. Constipation
What are the affects on skin and hair with ageing?
- Dry skin
- Wrinkles
- Increased bruising
- Slower healing = ulcers/sores
- Greying hair
What are the genito-urinary affects of ageing?
- Decreased GFR
- Benign prostatic enlargement (prostatism)
- Decreased sexual function and erectile dysfunction
- Vaginal dryness so increases UTI susceptibility
What are the musculoskeletal affects of ageing?
- Sarcopenia decreasing muscle strength/power
- Decreased mobility
- Increased likelihood of falls
- Increased susceptibility to fractures due to osteoporosis
What are the effects of ageing on the nervous system?
- Slower thought processes/reactions
- Vision deterioration inc. presbyopia and cataracts
- High-frequency hearing loss (presbyacusis)
- Inner ear dysfunction and balance problems
What are the effects of ageing on the immune system?
- Atrophy of thymus
- Decreased immune function so increased risk of infections and cancer
- Reactivation of latent infections e.g. TB and shingles
What impact will ageing and disease have on a person’s life?
- Care needs
- Mobility
- Functional capacity
- QoL
- Independence
- Wellbeing
Why do older people have higher drug sensitivity and so are more susceptible to adverse drug reactions (ADRs)?
- Receptor responses (e.g. decreased ß-adrenoceptor sensitivity)
- Altered coagulation factor synthesis
- CNS becomes more sensitive to psychotropics/hypnotics
- Baroceptor response less sensitive
- Renal clearance reduced
- Thirst response blunted
- Thermoregulation blunted
- Altered immune response
- Slower gastric emptying
- Reduced plasma albumin
- Increased ratio of adipose to lean tissue
- Altered liver metabolism
What affects the absorption stage of pharmacokinetics in the elderly?
- Swallowing
- Gastric emptying
- Intestinal motility
- Blood flow
- SA
What affects the distribution stage of pharmacokinetics in the elderly?
- Tissue perfusion and blood flow
- Reduced plasma protein binding so free fraction of drug increases
- Volume of distribution: older people have a higher fat:water ratio so fat-soluble drugs will have a longer duration of action but water-soluble drugs will have an initially high concentration that declines
What affects the metabolism stage of pharmacokinetics in the elderly?
- Hepatic mass decreased
- Hepatic blood flow decreased
- Thyroid function decreased
- Genetics
What affects the excretion stage of pharmacokinetics in the elderly?
- Renal drug excretion is decreased due to reduced renal blood flow and GFR so patients with poor renal function (exacerbated by dehydration, UTI + sepsis) take longer to eliminate renally excreted drugs
= ALWAYS assume elderly have at least mild renal impairment as this is the most important and predictable change
What are the pharmacodynamic changes in the elderly?
- Changes in receptor sensitivity e.g. ß-adrenoceptor sensitivity decreases with age
- Change in receptor no. (never static)
- Changes in hormone levels e.g. menopause
- Actions of medicines affecting CNS/CVS are frequently altered e.g. hypnotics and psychotropics
What are the common drugs that need dose adjustment in the elderly?
- ACEi
- Diazepam
- Digoxin
- NSAIDs
- Opiates
- Oral hypoglycaemics
- Warfarin
What is the J-shaped curve of diabetes treatment?
Mortality improves with tighter control of blood glucose and the less control there is, the higher the mortality HOWEVER, as patients get older they have a decreased awareness of hypoglycaemia so if you have very tight control of blood glucose, more mortality may occur as they cannot sense slight hypoglycaemic changes so the blood glucose are purposefully left less controlled so patients can notice hypoglycaemic affects decreasing acute mortality due to hypoglycaemia (longer term effects do not matter as much)
What are the changes of homeostasis in ageing?
- Decreased baroreceptor reflex with blunting of reflex tachycardia causing orthostatic hypotension
- Decreased postural control
- Decreased thermoregulation
- Decreased reserve of cognitive function
- Decreased immune response so prone to infection
What effects will multi-morbidity in the elderly cause?
- More drugs needed so higher risk of drug-drug interactions
- More change of drug-disease interactions e.g:
- Anticholinergics for prostatic hypertrophy precipitate urinary retention
- BZDs may precipitate delirium in patients with dementia
Why can polypharmacy be a problem?
- Loss of patient compliance or adherence to prescription instructions
- Prescription errors (increased risk with extra medicines prescribed)
- Increased interactions + ADRs
- IP
- Cost
What is deprescribing?
The practice of reducing or discontinuing medications that may no longer be of benefit or may cause adverse effects with the goal of reducing medication burden and potential for harm - one way of addressing the problem of IP and polypharmacy in the older population
What is associated with inappropriate prescribing (IP) in older people?
- Increased fall risk
- ADRs
- Hospitalisations
- Death
Why might elderly patients have concordance and compliance issues with medications?
- Cognitive impairment
- Visual impairment
- OTC or other medicines taken
- Communication between care providers
- Prescribing cascade
What is the prescribing cascade?
When a drug causes an adverse effect and its misinterpreted as a new medical condition so a new drug is prescribed and then this cascade continues on…
For example:
NSAIDs can cause HPN so then antihypertensives are given as well
If given an NSAID to an elderly patient is absolutely necessary, what must you do?
- Use ibuprofen not diclofenac as this has fewer upper GI side effects
- Co-prescribe a PPI
- Only give short-term
What strategies can improve concordance with medication?
- Simplify; 1 daily dose, prescribe medicines that can be taken at same time of day, use medicines with dual indications (e.g. ß-blockers) and consider daily dose reminder system (e.g. Dosette box)
- Educate: explain reasons for taking medicine and how to take it, warn of side effects and enlist support of family/carers in monitoring
- Monitor: check tablet boxes and use of medicines, monitor request for prescriptions and if indicated, serum monitoring
Who should medication reviews be carried out regularly for?
Annually: all patients over 75 years on repeat medication
6 monthly: those taking =/> 4 medicines
What can we minimize adverse drug reactions (ADRs)?
- Take good drug history inc. OTC and others
- Prescribe sensibly i.e. do the need it? can they take it? do they want it?
- Consider drug-drug and drug-disease interactions
- Minimize use of high-risk drugs e.g. warfarin and macrolides
- For every new problem, consider whether medicine could be cause
- Start low and go slow due to impaired renal/liver function
- Extreme caution when care is transferred to avoid slipping
- Record allergies/intolerances
What does the NICE guidance of prescribing in the elderly say?
- Follow guidelines for indication
- Limit range of drugs used to ones you are thoroughly familiar with
- Reduce dose
- Review regularly
- Simplify regimens
- Explain clearly
- Advise on repeats and disposal
Why should you avoid NSAIDs in the elderly?
They are nephrotoxic and this population often have lowered kidney function - also cause GI ulceration (why you prescribe with PPI) and coronary vascular disease as a result of long-term use
