Approximately 10% of the general population claim to have a penicillin allergy, which is often reported as a skin rash that occurred during a course of penicillin in childhood. Fewer than 10% of people who think they are allergic to penicillin are truly allergic. Studies have shown that people with a label of penicillin allergy are more likely to be treated with broad‑spectrum, non‑penicillin antibiotics, such as quinolones, vancomycin and third‑generation cephalosporins. However, use of these antibiotics in people with an unsubstantiated label of penicillin allergy may lead to antibiotic resistance and, in some cases, sub‑optimal therapy1.
It is therefore essential to determine what reaction the patient experienced and ensure that this is dcumented on the allergy section of the EPMA record. In some cases it is simply an adverse drug reaction that is reported (e.g. diarrhoea, nausea), rather than allergic in nature.
The widely cited rate of 10% cross-sensitivity to cephalosporins among penicillin allergic patients appears to be based on data collected in the 1960s and 1970s and results of in vitro (immunological) tests that were not supported by clinical skin tests in penicillin-sensitive patients2. More recent data suggests that 0.5-6.5% of penicillin-sensitive patients will also be allergic to the
Carbapenems share a common beta-lactam ring with penicillins and therefore have the potential for allergic cross-sensitivity. Extensive evidence has suggested that less than 1% of penicillin-allergic patients react to carbapenems4.
Aztreonam is a monobactam and has a monocyclic beta-lactam structure. In vitro and skin testing studies have demonstrated no immunologic cross-reactivity between penicillin and aztreonam4. Based on this evidence, patients with a history of penicillin allergy may safely receive aztreonam. However, cross-reactivity between aztreonam and ceftazidime does exist, as the two drugs have identical side chains. Therefore aztreonam should be avoided in patients with confirmed allergy to ceftazidime.
- It is important to find out the
exact nature of penicillin allergy when deciding on the antibiotic regimen
(what is the allergy, is it a true allergy or a sensitivity/intolerance/side
- It is important to check what
previous antibiotics the patient has received by asking the patient,
reviewing the medication history (GP records, e- exchange, previous
patients can be recorded as allergic to antibiotics, for non-allergic reactions
e.g. nausea, vomiting, diarrhoea
- In patients with serious allergies to penicillins (i.e. previous anaphylaxis, angioedema, wheeze, urticarial rash), cephalosporins and carbapenems should be avoided where possible, and alternative agents administered.
- In patients with non-serious allergies to penicillins (i.e. mild rash alone, with no anaphylactic symptoms, angiodema or immediate-onset urticarial rash), cephalosporins and carbapenems may still be used and the patient closely monitored.
Contra-indicated in patients with true penicillin allergy
Other beta-lactam antibiotics
Cross-over allergy possible: approximately 10%, but less than 5% for carbapenems
Avoid if undefined or serious penicillin allergy
Use with caution in non-severe penicillin allergy and no alternative therapy
E.g. cefuroxime, ceftriaxone, cefalexin, ceftazidime
E.g. meropenem, ertapenem, imipenem/cilastin
Avoid in patients with confirmed allergy to ceftazidime due to identical side chains (see notes above)
Considered safe in penicillin allergy
1. National Institute for Health and Care Excellence (2014) Drug allergy: diagnosis and management of drug allergy in adults, children and young people. NICE guideline (CG183)
2. Smith, K. & Cheeseman, M. (2014) Is there a 10% cross-sensitivity between penicillins and cephalosporins? Medicines Q&A 181.4. UK Medicines Information. Available from http://www.evidence.nhs.uk
3. Baxter, K, director. British National Formulary No71. London: British Medical Association and The Royal Pharmaceutical Society of Great Britain; March-September 2016. Accessed 28/7/16 via www.bnf.org.uk.
4. Solensky, R et al. (2015) Penicillin-allergic patients: Use of cephalosporins, carbapenems, and monobactams. [Online] Available from http://www.uptodate.com [accessed 28/7/16]