Adverse drug reactions Flashcards
What is an adverse drug reaction?
Any undesirable reaction that results in a detriment to the wellbeing of a patient in any way in the absence of another plausible explanation that can be proven
What is a side effect?
An undesirable secondary reaction that results when using a medication within its normal dose
How does digoxin toxicity present?
Nausea & vomiting Visual disturbance (including colour vision) Bradycardia Sweats Convulsions Death
Adverse drug reactions are more common in which groups of people?
Elderly
Multi-morbidity (reduced renal or hepatic clearance)
Polypharmacy
What is the therapeutic index?
50% of lethal dose / 50% of effective dose
What is the problem with drugs with a low therapeutic index?
The become toxic very quickly
List some drugs with low therapeutic indexes?
Theophylline Warfarin Vancomycin Lithium Digoxin Gentamicin
When might acute drug reactions be detected?
Drug development phase
Clinical trial phase
Post-marketing
Describe the two phases of drug metabolism
Phase 1 - cytochrome P450 system oxidises/reduces/hydrolysis
Phase 2 - conjugation allowing for excretion in bile/urine
What are the classifications of adverse drug reactions?
Type A - dose dependent and predictable
Type B - bizzare effects (dose independent and unpredictable)
Type C - chronic effects
Type D - delayed effects
Type E - end of treatment effects
Type F - treatment failure (inappropriate prescription)
Which type of drug reaction is the most dangerous?
Type B because they are unpredictable
Which drugs can cause type A drug reactions resulting in pre-renal failure?
Diuretics - if taken when dehydrated
ACE/ARBs - if taken during episodes of diarrhoea and vomiting
Which drugs can cause type A drug reactions resulting in renal failure (AIN/ATN)?
Gentamicin - given to treat sepsis
Sulphonamides - given to treat rheumatoid
Aspirin - given in certain CVS diseases
Which drugs can cause type A drug reactions resulting in post-renal failure?
Methysergide - given to treat cluster headaches
Chemotherapy - given to treat acute leukaemia
When should a patient not take their ACE/ARBs?
If they have diarrhoea and vomiting
Give three examples of type B drug reactions
Drug rashes
Bone marrow aplasia
Hepatic necrosis
Type A drug reactions have a high mortality. T/F
False - type B drug reactions
When do type C drug reactions occur?
When the patient has been on drug therapy for a long time
Which drugs can cause type C drug reactions?
Steroids - cause Cushing’s
Beta-blockers - cause diabetes
NSAIDs - cause hypertension
Can type C drug reactions be anticipated? What is it important to do?
Yes
Warn patient of possible side effects
When do type D drug reactions occur?
Often many months/years after stopping drug treatment
Give two examples of type D drug reactions
Carcinogenic - post chemotherapy
Teratogenic - isotretinoin
What is isotretinoin used for? What can it cause?
Acne
Craniofacial abnormalities
How do type E drug reactions occur?
Abrupt withdrawal causing rebound effects
Give three examples of type E drug reactions
Beta-blocker withdrawal - angina
Steroid withdrawal - addisionian crisis
Anti-convulsant withdrawal - increased frequency of seizures
Type A drug reactions can result from three types of interactions, name these
Drug to drug interactions
Drug to disease interactions
Drug to food interactions
The majority of adverse drug reactions are of which type?
Type A
Give some examples of drug to drug type A interactions
Statins and macrolide antibiotics or fibrates increase risk of rhabdomyolysis
ACEi and sulphonylureas increase risk of hypoglycaemia
Which drugs can exacerbate chronic heart failure?
NSAIDs
Which drugs can increase risk of urinary retention in patients with BPH?
Decongestants
Anticholinergics
Which drugs worsen calcium?
Calcium
Anticholinergics
Calcium channel blockers
Which drugs lower seizure thresholds in patients with epilepsy?
Tramadol
Quinolone antibiotics
Which drugs can worsen asthma?
Beta blockers
A high sodium diet can interfere with the effectiveness of which drugs?
ACE/ARB
Diuretics (potassium sparing)
