Antimicrobial adverse drug reaction form
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Penicillins are some of the most frequently prescribed antibiotics in clinical practice. The following list includes the penicillins available in Australia, and the common brand names:
A history of penicillin allergy should not rule out the use of cephalosporins. The prevalence of cross-reactivity between beta-lactams is lower than originally thought. An estimated 1-2% of patients with a penicillin allergy react to cephalosporins. 1
Antibiotics with shared structural similarities, such as those with the same or similar R1-group side-chains are more likely to cross-react:
In patients with a history of delayed severe penicillin hypersensitivity [e.g. drug rash with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome/Toxic epidermal necrolysis (SJS/TEN), Acute generalised exanthematous pustulosis (AGEP)], avoid all penicillins and cephalosporins – Do not use cross-reactivity to guide treatment as further drug exposure can be fatal.
An algorithm for the suggested management of patients reporting a hypersensitivity to penicillins in whom a beta-lactam is the preferred drug is available in the Therapeutic Guidelines:Antibiotic2:
Many patients who believe they have a ‘penicillin allergy’ are not allergic when tested. Testing involves initial risk stratification based on history and available information, with subsequent either direct de-labelling, oral challenge testing (in low risk cases), or skin testing followed by oral challenge if negative (in higher risk cases). 7 Some patients are confirmed to be allergic either by available information, or after testing.
In patients with a confirmed beta-lactam allergy, or those who have a high-risk history when there is no opportunity for testing, desensitisation can be attempted under specialist care, which will allow temporary tolerance of the antibiotic.
Prioritisation for testing and potential de-labelling will take into account the likely antibiotic requirements of the patient including factors such as:
History of bacterial infection and antibiotic requirement in the recent past
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