![]() ![]() Gastrointestinal symptoms (nausea, vomiting, diarrhoea) Unlikely to be immune-mediated (non-severe, low-risk)ꝉ Hepatic enzyme derangement (does not meet criteria for liver failure or severe injury) Recommendation and resultant allergy typeĭetails of rash timing unknown and no severe features or hospitalisationĭiffuse rash or localised rash with no other symptoms developing >24 hours after starting antibiotic, over 10 years agoĭelayed hypersensitivity (non-severe, low-risk)* ![]() ![]() Table 2 - Extract from the Antibiotic Allergy Assessment Tool Recommendations for prescribing based on the phenotypes appear in the Therapeutic Guidelines: Antibiotic ( Fig. This is helpful in stratifying the risk of using alternative beta- lactam antibiotics. The assessment of penicillin allergy enables classification of phenotypes as either severe versus non-severe and immediate versus delayed. Being able to tolerate a specific antibiotic before the reaction does not predict tolerance following the reaction. Antibiotics that have been tolerated following the reaction should be considered first. The patient should be questioned about antibiotics that they have tolerated since the reaction, particularly oral penicillins or cephalosporins. In patients with true immediate penicillin allergies, the response wanes over time, with 80% of patients becoming tolerant to penicillins after 10 years. This is important for assessing the likelihood that the penicillin allergy has persisted. A delayed reaction usually occurs after ‘days’ of taking the antibiotic and the reaction can be accelerated if the antibiotic is given again.Īsk how many years ago the reaction occurred. Immediate reactions typically occur within a ‘few hours’ of the first or second dose of the antibiotic. T-cell mediated reaction) or immediate (e.g. The timing of the reaction is important to determine if it was delayed (e.g. adrenaline (epinephrine), antihistamine, systemic steroids or no therapy)? Simply asking the patient if the reaction was ‘severe’ is unlikely to gather accurate information. Information can be obtained by asking about how the reaction was managed, for example, was the patient hospitalised? What treatments were given for the reaction (e.g. For these severe delayed reactions, information regarding cross-reactivity is not a reliable guide for empirical prescribing.Īn understanding of the severity of an allergy includes obtaining a description of its ‘type’. 29, 30 There are limited data regarding cross-reactivity in severe delayed reactions, such as Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms, and acute generalised exanthematous pustulosis. While the data regarding cross-reactivity have primarily been about immediate hypersensitivities, similar patterns have been reported in non-severe delayed penicillin allergies. 23, 25-27 At the antibiotic allergy testing centres of Austin Health and the Peter MacCallum Cancer Centre in Melbourne, out of 15 patients reporting a severe-immediate cefalexin hypersensitivity, intradermal tests determined that six (40%) would not be able to tolerate ampicillin. 24 The rate of cross-reactivity between aminopenicillins and aminocephalosporins has been reported to be as high as 30–40% in predominately European studies. Manage the reaction, either by slowing the infusion or premedication (with antihistamines or corticosteroids)Ĭross-reactivity is particularly seen with aminopenicillins (amoxicillin, ampicillin) and aminocephalosporins (cefalexin, cefaclor, cefadroxil, ceprozil). Maculopapular exanthema, drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalised exanthematous pustulosisīeta-lactams, glycopeptides, sulfonamidesĪvoid implicated drug, drugs in the same class and structurally related drugsĪnaphylactoid reactions – non-immune-mediatedĭirect mast-cell stimulation or basophil activation Haemolytic anaemia, thrombocytopenia, vasculitis Caution with drugs in the same class and structurally related drugsĪntibody (usually IgG)-mediated cell destruction Urticaria, angioedema, bronchospasm, anaphylaxisĪvoid implicated drug. Type B adverse drug reactions – immune-mediated Nausea, vomiting, diarrhoea, pruritis (without rash), headacheĮncephalitis, renal impairment, tendinopathyĬefepime, aminoglycosides, fluoroquinolones Type A adverse drug reactions – non-immune-mediated Table 1 - Antibiotic allergy classifications ![]()
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