Adverse drug reactions Flashcards
(40 cards)
Adverse drug reactions - what are they
An unwanted or unpleasant reaction to a drug which is unintended at the therapeutic dose
What is the difference between a side effect and an adverse drug reaction
An adverse drug reaction is unpleasant unwanted but a side effect may beneficial
Adverse drug reaction or adverse drug event
Adverse drug event is unpredictable (may not be related to the dose!)
ADRS ARE ADVERSE EVENTS BUT NOT ALL ADVERSE EVENTS ARE ADRS
Why are ADRs important, so what can they affect and reduce?
Adversely affect patient compliance
Reduce available choice of drug treatment
Reduce potential efficacy of drug treatment
Reduce quality of life
Cause diagnostic confusion – mimic disease
The burden of ADRs
Health and financial implications
6-7% of hospital admissions in the UK are due to ADRs
10 to 20% of patients will experience an ADR during their stay in hospital
Approximately 7% will be serious
0.1 – 0.3% will be fatal
What are the different types of ADR’s
TYPE A, B, C, D, E, F
Types and examples of ADRsType A
Most Common ADRs- Type A account for more than 80% of all ADRs
Type A (‘Augmented’ or ‘pharmacological)
They are Predictable, dose related
(eg) Constipation with opioids
Readily reversible on reducing the dose
Usually not severe (ADRs) example below
Peptic ulceration following NSAID use
Type A are Predictable ADRs what do they result from
Result from an exaggeration of drug’s normal pharmacological action
Drug activity is generally non-specific; drugs will block or stimulate receptors in the target system and at every other binding site
Less selective drugs will cause the most ADRs
Patient experience varies as does individual patient response
Type B
Less common but often well recognised ADRs
Type B (‘Bizarre’ or idiosyncratic)
Cannot be predicted from the known pharmacology of the drug
Not dose related
May be very severe / fatal
Achilles tendonitis caused by quinolone antibiotics
Stevens-Johnson syndrome following lamotrigine therapy
With new drugs ADRs not well recognised
What do the other types mean adverse drug reactions (C, D, E AND F)
C = chronic treatment effects
D = delayed effects
E = end of treatment effects
F = unexpected failure of therapy
Factors that affect ADR’s:
Increase in elderly population (4 times more likely to have ADR)
Increase in polypharmacy
Increase in availability of Over The Counter medicines
Increase in use of herbal/traditional medicines
Increase in medicines available via the internet
Who is most at risk from ADRs?
The elderly
Co-existing diseases
Children
Females
Atopic individuals
Polypharmacy
50% of patients on 5 drugs or more
Are ADRs avoidable? - 70% are so how do we avoid these?
Rational Prescribing
Dose optimisation
Avoid / reduce drug interactions
Consider prophylactic therapy where appropriate
Avoid new / black triangle drugs
Avoid prescribing contra-indicated drugs
Drug use in an inappropriate clinical indication
ADRs - criteria for diagnosis
Consider the timing of the ADR in relation to drug treatment
Consider any abnormal clinical measurements while on drug therapy e.g renal function, B.P, temp, pulse, blood glucose and weight – do these look like disease or ADR?
Is the presented response known to be related to medicines taken?
Patient risk factors – age, polypharmacy
Listen to patients own concerns.
Assessing the causality
Nature of the reaction
Timing
Relationship to dose
Other possible causes for the symptoms
Improvement when drug(s) stopped
Has reaction been reported before
Re-challenge?
Who might get an ADR?
Anyone who takes a medicine!
Healthcare professionals should always
consider drugs as a possible cause if the
patient is taking any form of medication
and is reporting a problem
Advance Warning - what should we tell patients or what should prescribers tell patients
Prescribers should be aware of the risk of such ADRs and warn patients of what they might experience and what to report
Don’t expect patients to know what is ‘normal’ or what is ‘acceptable’
Some may occur on stopping medicines due to ‘rebound’ physiological responses and so these drugs are withdrawn slowly
Post marketing surveillance is necessary because:
The scale of clinical trials are too small to reveal every possible problem & ADR
ADR’s with an incidence of <1 in 10,000 may be thought coincidental in trials
The length of clinical trials (typically months) may be too short to reveal long term ADR’s e.g.oral contraceptives, aspirin and Reyes Syndrome
Approved drugs may be used in patient groups for which they are not tested
Approved drugs may be used outside their licensed indication
Dose adjustment may be required when clinical experience is gained
Where do we report ADR’s
The Medicines Act (1968) was enacted as a direct result of an ADR (thalidomide)
The Yellow Card System is the main independent post marketing surveillance method
The Yellow Card System was first introduced in May 1964
The UK scheme is the oldest and largest in Europe
The yellow card scheme was initially for who and who did it get extended to?
Initially just for Doctors
Extended to Pharmacists, Nurses, Midwives and Health Visitors in October 2002. By December 2004 4,790 reports received from these groups
From January 2005 extended to patients, parents and carers
What happens to the report?
report made
data entry
signal detection
signal evaluation
risk/benefit evaluation
regulatory action
ADR signals
A signal is NOT a confirmed ADR
A signal is a reported link between an adverse event and a drug
Not previously known / incompletely documented
> 1 report = a signal
Signals are identified by statistical analysis of ADR reports – called ‘data mining’
New drugs and vaccines - what is the symbol
black triangle symbol: ▼)
What to report on a Yellow Card
Medicines
Black Triangle Scheme
Medical Devices
E-cigarettes and e-liquids
