Approach to penicillin allergy

* A penicillin allergy history includes the following:

• Each agent reportedly associated with a reaction and the indication for its use (to make sure that the agent matches the indication).
• The exact signs and symptoms that occurred, in as much detail as the patient and/or medical record can provide.
• When the reaction occurred (ie, how long ago) and at what point in therapy (immediately after starting or later in course).
• The dose and route of medication taken (if known).
• Other concurrent medications, especially if they were new or temporary.
• Any treatment given and response to that treatment (including the duration of reaction).

¶ Allergy can be excluded based upon history if:

• Reaction was not allergic (eg, isolated nausea or diarrhea, yeast vaginitis, other predictable adverse effect of drug) or
• Patient never took a penicillin but has family members with penicillin allergy.

Δ Immediate reactions usually begin within 1 hour of the last administered dose and may begin within minutes. Some guidelines include reactions beginning up to 6 hours after the last administered dose. Common symptoms and signs include pruritus, flushing, urticaria, angioedema, bronchospasm (wheezing, repetitive cough, difficulty breathing), laryngeal edema (throat tightness, change in voice quality), abdominal cramping, nausea, vomiting, diarrhea, and hypotension.

◊ Delayed reactions begin later than 6 hours and more typically days into a course of treatment. A maculopapular or morbilliform eruption is the most common form of delayed reaction, but more serious forms exist. The evaluation and management of delayed reactions are discussed in the UpToDate topic on delayed hypersensitivity reactions to penicillins.

§ Alternative agents include antibiotics that are unrelated to penicillin, such as sulfonamides, tetracyclines, macrolides, or fluoroquinolones. Refer to the discussion of the use of related antibiotics (ie, cephalosporins, carbapenems, and monobactams) in the UpToDate topic on choice of antibiotics in penicillin-allergic patients.