![]() ![]() Patients with a history of penicillin allergy are four times more likely to have a reaction to cephalosporins than patients without a penicillin allergy, especially if the patient is penicillin skin prick test positive. Whether a penicillin-allergic patient can safely take cephalosporins remains a difficult question to answer - many people labelled penicillin-allergic can actually take penicillin. 2It is difficult to obtain reliable data about the frequency of cephalosporin anaphylaxis, but published figures are 0.0001-0.1%. While penicillin-induced anaphylaxis is rare (0.01-0.05% of courses), it may be fatal in 10% of cases. 1In addition to anaphylaxis, less common but serious adverse reactions to cephalosporins include serum sickness-like reactions, acute interstitial nephritis and cytopenias. The most common clinical manifestation of both penicillin and cephalosporin allergy is skin reactions, occurring with a frequency of 1-3% of courses given. Non-immediate reactions such as maculopapular or morbilliform rashes are probably T-cell mediated. Immediate reactions are IgE mediated and classically manifest as anaphylaxis, urticaria, angioedema, bronchospasm and allergic rhinoconjunctivitis. Reactions to beta-lactam antibiotics can be classified into immediate and non-immediate. Over the last six months, the authors know of four cases from western Sydney including two deaths. However, reports of adverse outcomes, including fatalities, appear to be increasing. 1In clinical practice it is not uncommon for cephalosporins to be given to penicillin-allergic patients, particularly if the history of penicillin reaction was not life-threatening. ![]() Penicillins and cephalosporins exhibit partial and incomplete cross-reactivity of up to 7% that may be related to the 'generation' of cephalosporin. He remained stable on oral antihistamines and was discharged after three days. Hydrocortisone and antihistamines were given and he was admitted to hospital.Īs he was taking propranolol it was ceased, as beta blockers can potentiate further anaphylactic reactions. A diagnosis of anaphylaxis to cephalexin was made. Wheeze and tongue swelling were absent and intra-abdominal pathology was excluded. On examination he had a generalised erythematous rash that was pruritic. ![]() Oxygen and intravenous fluids were given and in the emergency department his blood pressure was 140/70. The man had a documented history of amoxycillin allergy with pruritis. He was prescribed cephalexin and had taken the first dose 10 minutes before collapsing. The man had seen his family doctor earlier that day complaining of sore throat, cough and haemoptysis. Ambulance officers noted impalpable blood pressure, shortness of breath and complaints of right-sided chest and epigastric pains. Thus, our data indicate that cephalosporins can be considered for patients with penicillin allergy.A 73-year-old man collapsed at home. Cross-reactivity is not an adequate explanation for this increased risk, and the risk of anaphylaxis is very low. Patients with allergic-like events after penicillin had a markedly increased risk of events after either subsequent cephalosporins or sulfonamide antibiotics. The unadjusted risk ratio for sulfonamide antibiotic, rather than cephalosporin after penicillin allergic-like events was 7.2 (confidence interval 3.8-13.5). The absolute risk of anaphylaxis after a cephalosporin was less than 0.001%. Among patients receiving a penicillin followed by a cephalosporin, the unadjusted risk ratio of an allergic-like event for those who had a prior event, compared with those who had no such prior event, narrowly defined, was 10.1 (confidence interval 7.4-13.8). Comparison was made with a population of patients receiving a prescription for a penicillin followed by a prescription for a sulfonamide antibiotic.Ī total of 3,375,162 patients received a penicillin 506,679 (15%) received a subsequent cephalosporin. ![]() Allergic events were defined by 2 sets of codes: 1 more restrictive, 1 more inclusive. We selected all patients receiving a prescription for penicillin followed by a prescription for a cephalosporin and identified allergic-like events within 30 days after each prescription. We conducted a retrospective cohort study using the United Kingdom General Practice Research Database. We sought to determine the risk of an allergic reaction to a cephalosporin exposure in those with prior penicillin reactions. ![]()
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