Penicllin Allergy
Antimicrobial prescribing: NHS Forth Valley
TAKING A RELIABLE HISTORY IS VERY IMPORTANT
Penicillins are life-saving antimicrobials and patients should not be labelled ‘penicillin-allergic’ without careful consideration.
Please note that patients who have a vague history of symptoms or gastro-intestinal intolerance are probably not truly allergic to penicillins.
Life-threatening adverse reactions to penicillins due to immediate hypersensitivity (IgE mediated) are rare with anaphylaxis occurring in less than 0.05% of treated patients.
General hypersensitivity reactions (e.g. rashes) occur in between 1 and 10% of exposed patients
Cross-reactivity to cephalosporins is about 0.5 – 6.5%. Patients with a history of immediate hypersensitivity/anaphylaxis to penicillin should NOT receive a cephalosporin. If a cephalosporin is essential in these patients because a suitable alternative antibacterial is not available, then cefotaxime, ceftazadime, ceftriaxone or cefuroxime where indicated in the policy can be used with caution. (BNF)
Types of allergy
|
Characteristics |
Type I immediate hypersensitivity reactions |
Non-Type I reactions (Types II-IV and idiosyncratic) |
|
Timing of onset |
1 to 4 hours from exposure (up to 72 hours) |
> 72 hours from exposure |
|
Clinical signs |
Anaphylaxis Laryngeal oedema Wheezing / bronchospasm Angioedema Urticaria / pruritus Diffuse erythema |
Maculopapular rash Morbilliform rash Reduced RBC and platelets Drug fever (serum sickness) Tissue injury (immune complex) Contact dermatitis |
Contra-Indicated and cautioned drugs
Patients with a history of clinical signs of Type I immediate hypersensitivity (life threatening allergy):
|
Drugs in RED are contra-indicated |
Drugs in ORANGE are NOT for use in patients with a serious penicillin allergy Use with caution in patients with a history of minor allergic symptoms |
|
|
Amoxicillin Co-amoxiclav (Augmentin) Benzylpenicillin Flucloxacillin Phenoxymethylpenicillin (Pen V) Piperacillin/tazobactam (Tazocin) Pivmecillinam Temocillin |
Cefaclor Cefalexin
*Ceftriaxone *Cefotaxime *Cefuroxime *Ceftazadime |
Meropenem is a B-lactam antibiotic with a very small risk of cross reactivity in patients with true penicillin anaphylaxis (<1%). Usually benefit of use as recommended within these guidelines would outweigh risk of cross-reactivity.