16 - Adverse Drug Reactions Flashcards
ADR
Response to a drug that is noxious and unintended and which occurs at doses normally used. Most are mild, severe reactions are uncommon
Any unexpected, undesired, unintended, excessive response to a medicine that requires clinically significant action
How do ADRs relate to medication errors?
Medication errors are mishaps that occur during prescribing, transcribing, dispensing, administering, adherence or monitoring a drug. More common but result in harm less than 1% of the time.
Adverse drug event?
An adverse drug EVENT is an injury that results from the use of a drug (incl. OD, ADRs, dose reductions.
Adverse drug events can rseult from medication errors but MOST do not.
Allergy?
An allergy IS and adverse drug reaction. It is specifically and ADR that is mediated by an immune response.
Side effect?
A side effect is also an ADR - but it is an expected and known effect that is NOT the intended therapeutic outcome
Classification of ADRs according to DoTS (dose, timing, susceptibility)
Dose
- supratherapeutic (toxic effects)
- standard therapeutic (collateral effects)
- Subtherapeutic doses in susceptible people
Classification of ADRs according to DoTS (dose, timing, susceptibility)
Timing - Timing independent reactions - Timing dependent reactions Rapid First dose Early (i.e. opiates and nausea) Intermediate Late Delayed
Classification of ADRs according to DoTS (dose, timing, susceptibility)
Susceptibility
- reasons for hypersensitivity include genetics, age, sex, disease etc
4 reasons that ADRs are important
- Cause death and serious harm
- Hospital admission or prolonged stay
- Cost
- Many are preventable (often occur IN hospital)
Elderly on warfarin with intracerebral haemorrhage - what makes her susceptible to an ADR
age
What patients are at higher risk to ADRs
- younger children (need to tailor doses) and elderly (comorbidities, reduced physiological reserve, use more drugs)
- comorbidities (esp renal impairment - clearance/elimination)
- polypharmacy
- women (lower body weight and organ size)
- race and genetic polymorphism
Dr based strategies to prevent ADRs
- avoid and be aware of high risk drugs and conditions
- stop unnecessary drugs
- if there is a new symptom consider that it could be the drug
- avoid treating side effects with another drug
- avoid drug-drug interactions
- adjust dosing based on CLcr
Systems based strategies to prevent ADRs i.e. healthcare
- computerised order system
- electronic medication administration record
- bar coding
- smart pumps
- education programs (MODEST effect)
- accurate allergy list
2 places to find out about ADRs
- Nz Formulary
2. Medsafe (data sheets) - drug regulatory authority in NZ. Contains every approved drug in NZ
What 2 places does knowledge about ADRs come from?
- drug development and clinical studies
- surveillance (post market and prescription event monitoring and reporting of ADRs)
Phase 1
Tolerability
- note the dose at which adverse effects occur
Phase 3
Safety
- learn the adverse effects in the target population
Phase 4
Post Marketing
- confirm the common adverse effects
- learn the less common adverse effects
What 4 things for safety does Medsafe contain
- education and information
- Alerts
- recalls
- report a problem
On NZ Formulary there is also a patient information sheet for every drug. If extensive info then should be discussed with the patient
How can you tell if its an ADR
- ALWAYS consider the possibility that a drug may be associated with worsening of a condition or a new medical problem
- is the drug KNOWN to cause such a reaction
- rule out alternative explanations
- timing; is there a temporal link between onset of rx and drug administration
- probability assessment tool (naranjo probability scale)
What 4 things do you do when you suggest an ADR
- withdraw the medicine
- record the suspected ADR in the drug chart
- inform the patient, care giver, family dr
- Complete a CARM ADR form
CARM reporting?
WHAT
- ADR only has to be suspected not known
- do not need evidence of association of cause
WHO
- health professionals, pharm companies, consumers
HOW
- record patient details, medicine and event
- yellow form on ward
- return by email, post, fax
What are some strategies to avoid ADRs
- do not give a drug unless absolutely indicated
- use a familiar drug if possible
- look out for DRs when prescribing a new med
- prescribe as few as possible
- give very clear instructions on taking the medicine
- assess if taking other medications incl herbal
- have they had previous reactions
- warn the patient of side effects/potential ADRs
