Adverse Drug Reaction Flashcards
What is an adverse drug reaction?
Preventable or unpredictable medication event with harm to the patient
Describe the classification of ADRs based on onset.
Acute = < 1 hour Sub-acute = 1-24 hours Latent = > 2 days
Describe the classification of ADRs based on severity of the reaction.
Mild – requires no change in therapy
Moderate – requires change in therapy
Severe – disabling or life-threatening
Define Type A ADR.
Extension of pharmacological effect
This is usually predictable and dose-dependent
This is the most common type of ADR – 2/3
Example: atenolol can slow down heart rate but if you give too much you could cause heart block
Define Type B ADR.
‘Bizarre’ type of ADR
Idiosynchratic or immunologic reactions – includes allergy or pseudoallergy
This is very rare and unpredictable
Example: chloramphenicol and aplastic anaemia
Define Type C ADR.
Associated with long-term use
Involves drug accumulation
E.g. methotrexate and liver toxicity
Define Type D ADR.
Delayed effects – sometimes dose independent
E.g. carcinogenicity and teratogenicity
Define Type E ADR.
Withdrawal reactions
Rebound reactions
Adaptive reactions
Describe and explain clonidine rebound.
Clonidine is an alpha-2 agonist so it suppresses the release of noradrenaline
Long-term use of clonidine leads to an upregulation in adrenergic receptors on the post-synaptic membrane
If the dose of clonidine is missed once or twice, it will cause an increase in noradrenaline release, which then acts on an increased number of receptors so has a greater effect
This causes a large increase in blood pressure
What is the ABCDE classification of adverse drug reactions?
A – augmented pharmacological action B – bizarre C – chronic D – delayed E – end of treatment
Describe the classification of allergies.
Type 1 – immediate, anaphylaxis (IgE)
Type 2 – cytotoxic antibody (IgG + IgM) ]
Type 3 – serum sickness (IgG + IgM)
Type 4 – delayed hypersensitivity (T cell)
Give examples of pseudoallergies.
Aspirin/NSAIDs and bronchoconstriction
•This occurs because aspirin and NSAIDs inhibit the production of prostanoids, which are bronchodilators
• They promote the production of leukotrienes, which are bronchoconstrictors
ACE inhibitors and cough/angioedema
• ACE inhibitors prevent the breakdown of kinins
• Kinins accumulate in the sensory nerves in the lungs and trigger cough
What are the most common causes of ADRs
Antineoplastics
Cardiovascular drugs
NSAIDs/analgesics
CNS drugs
What is the yellow card scheme?
A voluntary scheme allowing doctors, dentists, nurses, coroners and pharmacists to report serious adverse drug reactions
Why is it difficult to determine the incidence of drug-drug interactions?
There is a lack of availability of comprehensive databases
Difficulty in assessing OTC and herbal drug therapy use
Difficulty in determining contribution of drug interaction in complicated patients