Penicillin Allergy

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 2017)

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

Augmentin (Co-amoxiclav)

Benzylpenicillin (Penicillin G)

Flucloxacillin

Phenoxymethylpenicillin (Penicillin V)

Piperacillin/tazobactam (Tazocin)

Pivmecillinam

Temocillin

Cefaclor

Cefalexin

Meropenem

If there is no alternative to a cephalosporin, these cephalosporins* can be used with caution

*Cefotaxime

*Ceftazadime

*Ceftriaxone

*Cefuroxime