Review Question - QID 102795

A female with a history of atopy being treated with penicillin who develops a rash is likely suffering from urticaria as an adverse reaction. The drug should be discontinued switched to another antibiotic with little cross reactivity, but adequate coverage.

Drug hypersensitivity is an immune-mediated reaction typically involving IgE associated mast cell degranulation. It can vary from uncomplicated cases such as a drug rash to possibly fatal reactions such as anaphylaxis. Patients with a history of atopic diseases (such as other allergies, asthma, and eczema) along with a family history of atopy are more likely to suffer from effects of drug hypersensitivity. Treatment is largely supportive and involves discontinuation of offending medication along with symptomatic treatment with antihistamines, corticosteroids, and adrenergic agonists.

Riedl et al. discuss drug reactions and their treatments. They state the larger drugs with greater structural complexity along with drugs that are coupled with foreign proteins are more likely to be immunogenic. They also state that patients who are allergic to penicillin should not be provided with carbapenems due to the beta-lactam ring. They note that though the cross-allergy between penicillin and cephalosporins has been found to be only 5 percent, in cases of anaphylaxis or other fatal reactions, patients should also not receive cephalosporins unless they have been formally tested (via skin tested).

Albin et al. report the prevalence and characteristics of penicillin allergies in an urban adult population. They report that penicillin allergy is prevalent in approximately 10% of the United States. In their study, they found that 37% of the allergic reactions were rashes while 30% developed angioedema and hives. 7% of those allergic reactions were anaphylaxis. They also found that female patients were more likely to have a penicillin allergy than males (odds ratio=1.8, P<0.01) and that Asians were less likely to have the allergy and Caucasians (odds ratio=0.5, P<0.01).

Figure A shows areas of erythema and superficial swelling with papules and plaques that can be characterized as urticaria.

Incorrect Answers:
Answer 1: Continuing the current regimen will make the urticaria worse and will likely cause more distress to the patient.
Answer 2 and 3: Corticosteroids and antihistamines would be good additions to this patient's therapy if necessary, but the next best step is to stop the offending agent so this does not recur.
Answer 4: Beta agonists like epinephrine are used for serious adverse allergic reactions like anaphylaxis, and this patient's exam was benign other than the rash.