Drug allergy Flashcards
Define type A drug reaction, include examples
- Related to the pharmacology of the drug
- Predictable
- Dose dependent
- High mobility, low mortality.
Examples
- Drowsiness with first generation antihistamines
- Liver failure with paracetamol overdose
- Nausea and Constipation with opiates
- Dry mouth tricyclic antidepressants.
Define type B drug reaction, include examples
Drug hypersensitivity reaction.
- Not directly related to pharmacology ,
- Unpredictable
- Often dose independent
- High mortality
Immediate drug hypersensitivity reaction
- Features
- Examples
- Occurs within an hour of last dose
- Clinical features of mast cell degranulation
- Recedes rapidly after drug is stopped
Due to mast cell activation, can be IgE mediated.
Examples
- Antimicrobial
- Myorelaxants
- Taxene based chemo.
Immediate drug hypersensitivity reactions
- Symptoms
Skin: angioedema, urticaria
Respiratory: rhinitis, bronchospasms, laryngeal edema
Gut: vomiting, diarrhoea
Cardiovascular collapse
Non Ig-E mediated Immediate drug hypersensitivity reaction
- Definition
- Examples
Non specific mast cell activation
Examples
- opiates
- myorelaxants
- radiocontrast media.
- ACEis: inhibition of bradykinin inhibitor.
- NSAIDs: Urticaria, angioedema, aspirin sensitive asthma, rhinitis, true anaphylaxis.
Mast cells tryptase
Used as diagnostic tool
- Realeased from mast cell during anaphylaxis.
Serum tryptase levels confirm acute anaphylaxis
- Blood taken one or two hours after onset of symptoms then 24 hours after
- 70% sensitivity
Non immediate drug hypersensitivity reaction
- Features
- Biggest group of drugs
- Example of reactions
- Not directly related to drug dose
- Onset: 3-5 days if treated before or 5 to 8 days if first sensitisation
- Symptoms continue after drugs is stopped
Biggest group= antimicrobials
Examples
- Delayed: urticaria , maculopapular eruptions, fixed drug eruptions.
- Systemic: vasculitis, TEN (toxic epidermal necrolysis), SJS (Stevens-johnson syndrome), DRESS (drug reaction with eosiniophilia and systemic symptoms).
TEN (toxic epidermal necrolysis) and SJS (Stevens-johnson syndrome)
- Gender
- Onset
- Common drugs
Severe Non-immediate
- Affects men>women, especially 30 years old or younger
- Typically occurs 3 to 8 days after dose
Most common drugs: antibiotics, anticonvulsants
- Could be infection induced
- High mortality and gets worse with each exposure.
Local anaesthesia reaction
- Symptoms
- Diagnosis
- Symptoms: local swelling, syncope, sensitivity to adrenaline.
- Never reproducible
- Skin testing Is not useful= refer to immunology for challenge test
NSAIDs allergy
- Wide spectrum of symptoms: cutaneous only, true anaphylaxis, aspirin sensitive asthma, rhinitis.
- 10% react to paracetamol as well
- Avoid NSAIDs and refer in specific cases.
