Ampicillin and Amoxicillin
ÎSome patients with immediate-type reactions to amoxicillin and ampicillin have IgE antibodies directed at the R-group side chain (rather than the core penicillin determinants) and are able to tolerate other penicillin class compounds. (C)
ÎAmoxicillin and ampicillin are associated with the development of a delayed maculopapular rash in approximately 5% to 10% of patients. (C) These reactions are not related to IgE-mediated allergy, and they are postulated in many cases to require the presence of a concurrent viral infection or another underlying illness. (D)
Cephalosporins
ÎThe overall reaction rate to cephalosporins is approximately 10-fold lower than it is for penicillin. (C)
ÎMost hypersensitivity reactions to cephalosporins are probably
directed at the R-group side chains rather than the core β-lactam portion of the molecule. (D)
ÎSkin testing with native cephalosporins is not standardized, but a positive skin test result using a nonirritating concentration suggests the presence of drug-specific IgE antibodies. (D) A negative skin test result does not rule out an allergy because the negative predictive value is unknown. (D)
ÎEnsure patients with a history of an immediate-type reaction to one cephalosporin avoid cephalosporins with similar R-group side chains. (D) Treatment with cephalosporins with dissimilar side chains may be considered, but give the first dose via graded challenge or induction of drug tolerance, depending on the severity of the previous reaction. (D)
ÎCephalosporins and penicillins share a common β-lactam ring structure, and moderate cross-reactivity has been documented in vitro. (B)
Cephalosporin Administration to Patients With a History of Penicillin Allergy
ÎSince 1980, studies show that approximately 2% of penicillin skin test-positive patients react to treatment with cephalosporins, but some of these reactions may be anaphylactic reactions. (C)
ÎCephalosporin treatment of patients with a history of penicillin allergy (without previous penicillin skin testing and not including those with severe reaction histories) showed a reaction rate of 0.1%, based on recent studies. (C)
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