avoid ceftazidime in aztreoname allergies
- related: Pharmacology
- tags: #literature #pharm
Cephalosporins are β-lactam antibiotics first identified from a Cephalosporium mold found in a Sardinian sewer. The R1 side chain can be modified and is a locus of cross-reactivity. Cephalosporins are now divided into as many as six “generations” on the basis of the timing of introduction to clinical practice and associated activity. Although conventional teachings about the specific spectrum of activity for each generation are not entirely accurate, later-generation cephalosporins are in general used for resistant organisms (some add coverage of methicillin-resistant Staphylococcus aureus as well as extended-spectrum gram-negative coverage). For patients with severe gram-negative infections, a variety of other antibiotics, including, for example, monobactams or colistin, may be used. Many of these antibiotics have side effect profiles, including the elicitation of an array of allergies from simple drug eruption to anaphylaxis. Associations between adverse reactions to one antibiotic and another candidate antibiotic are important to know and understand. Although monobactams (eg, aztreonam) have little cross-reactivity with β-lactam antibiotics and are thus generally safe to use, ceftazidime has a side chain that appears, on the basis of in vitro and some in vivo data, to manifest cross-reactivity with aztreonam. Thus, for a patient with aztreonam-induced anaphylaxis, ceftazidime would generally be considered to be contraindicated (choice A is correct; choices B and C are incorrect).
While meropenem is another broad-spectrum antibiotic that covers Pseudomonas, it is a carbapenem and not a monobactam. Cross-reactivity between carbapenems and monobactams is rare, so the patient is likely to tolerate meropenem.123