Drug allergy Flashcards Preview

302: Scientific basis of medicine > Drug allergy > Flashcards

Flashcards in Drug allergy Deck (10)
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1
Q

Define type A drug reaction, include examples

A
  • 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.
2
Q

Define type B drug reaction, include examples

A

Drug hypersensitivity reaction.

  • Not directly related to pharmacology ,
  • Unpredictable
  • Often dose independent
  • High mortality
3
Q

Immediate drug hypersensitivity reaction

  • Features
  • Examples
A
  • 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.
4
Q

Immediate drug hypersensitivity reactions

- Symptoms

A

Skin: angioedema, urticaria

Respiratory: rhinitis, bronchospasms, laryngeal edema

Gut: vomiting, diarrhoea

Cardiovascular collapse

5
Q

Non Ig-E mediated Immediate drug hypersensitivity reaction

  • Definition
  • Examples
A

Non specific mast cell activation

Examples

  • opiates
  • myorelaxants
  • radiocontrast media.
  • ACEis: inhibition of bradykinin inhibitor.
  • NSAIDs: Urticaria, angioedema, aspirin sensitive asthma, rhinitis, true anaphylaxis.
6
Q

Mast cells tryptase

A

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
7
Q

Non immediate drug hypersensitivity reaction

  • Features
  • Biggest group of drugs
  • Example of reactions
A
  • 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).
8
Q

TEN (toxic epidermal necrolysis) and SJS (Stevens-johnson syndrome)

  • Gender
  • Onset
  • Common drugs
A

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.
9
Q

Local anaesthesia reaction

  • Symptoms
  • Diagnosis
A
  • Symptoms: local swelling, syncope, sensitivity to adrenaline.
  • Never reproducible
  • Skin testing Is not useful= refer to immunology for challenge test
10
Q

NSAIDs allergy

A
  • 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.