Alternative Antibiotics for Patients with Antibiotic Allergies

Assessment of Antibiotic Allergies

A detailed allergy history should always be performed and critically appraised to determine if a true allergy exists, as less than 10% of patients with an antibiotic allergy label are truly allergic 1
Key information to collect includes the date of occurrence 2, nature, intensity, onset, and duration of symptoms 1, whether the reaction was immediate or delayed 2, and the severity of the reaction 1

Cefazolin can be safely used in patients with suspected immediate-type allergy to penicillin, regardless of severity or time since reaction, as it does not share side chains with available penicillins 2
Patients with non-severe immediate-type reactions to penicillin that occurred >5 years ago can receive cephalosporins with similar side chains in a controlled setting 2
Monobactams and carbapenems can be administered to patients with immediate-type penicillin allergy without prior allergy testing 2
Erythromycin is a suitable alternative for patients with penicillin allergy, particularly for mild infections 3

Cross-reactivity between different cephalosporins is dependent on R1 side chain similarity 2
Ceftazidime, cefiderocol, and aztreonam share an identical side chain, resulting in higher cross-reactivity risk 2

For patients with allergies to multiple beta-lactam antibiotics, guidelines recommend avoiding all beta-lactam antibiotics in cases of suspected severe delayed-type allergies 4
Aminoglycosides may be an option for patients with multiple beta-lactam allergies 4

Sulfonamide allergies do not preclude the use of cephalosporins, as there is minimal cross-reactivity between these classes 5

Overestimating cross-reactivity between penicillins and cephalosporins, leading to unnecessary avoidance of effective antibiotics 1
Not considering the time elapsed since the allergic reaction, which can affect the risk of recurrence 2

Cross-reactivity only occurs within the beta-lactam family (penicillins, cephalosporins, carbapenems, and monobactams) and is primarily driven by side chain similarity, not between entirely different antibiotic classes, according to the Infectious Diseases Society of America 6, 7.
Patients with penicillin allergies are commonly prescribed non-beta-lactam alternatives, including fluoroquinolones, macrolides, and nitrofurantoin, without concern for allergic reactions, as recommended by the Clinical Infectious Diseases society 8, 9.

The primary concern with penicillin allergy is avoiding beta-lactam antibiotics when there is a documented severe reaction, not avoiding all antibiotics, as stated by the Clinical Infectious Diseases society 8, 9.
Patients labeled as penicillin-allergic are exposed to more alternative antibiotics and have increased risks of resistant infections (MRSA, VRE, C. difficile), making appropriate use of non-cross-reactive antibiotics like nitrofurantoin important, according to the Clinical Infectious Diseases society 8.

No allergy assessment or skin testing is required before prescribing nitrofurantoin to penicillin-allergic patients, unlike when considering cephalosporins or other beta-lactams, as recommended by the Clinical Infectious Diseases society 8.
Only beta-lactams cross-react with each other based on side chain similarity, and penicillin allergy does not predict reactions to unrelated classes like nitrofurantoin, according to the Clinical Microbiology and Infection society 6.