Diagnosis and Assessment
ÎPossible laboratory tests might include but are not limited to a chest x-ray examination, electrocardiography, a complete blood cell count with differential, sedimentation rate or C-reactive protein, autoantibody tests, and specific immunologic tests. (C)
ÎThe most useful test for detecting IgE-mediated drug reactions caused by penicillin and many large-molecular-weight biologicals is immediate hypersensitivity skin testing. (B)
ÎSpecialized immunologic tests are sometimes able to confirm the immunologic basis of drug-induced cytotoxic reactions. (B)
ÎDrug patch testing may be useful for certain types of cutaneous drug reactions—including maculopapular exanthems, acute generalized exanthematous pustulosis, and fixed drug eruptions—but generally is not helpful for SJS or urticarial eruptions. The lack of standardization of reagent concentrations may limit the clinical usefulness of drug patch testing. (B)
ÎLymphocyte proliferation assays may have utility as retrospective indicators of cell-mediated drug reactions, but their positive and negative predictive values have not been determined and they are not available in most medical centers. (C)
ÎIn complex cases where multiple drugs are involved without a clear- cut temporal relationship, a skin biopsy may be useful in suggesting a drug-induced eruption. However, there are no absolute histologic criteria for the diagnosis of drug-induced eruptions, and a skin biopsy may not definitively exclude alternative causes. (C)
Treatment
Table 3. Classification of Induction of Drug Tolerance (Formerly Referred to as Desensitization)
Type of Drug Tolerance
Immunologic IgE (drug desensitization)
Immunologic non-IgE
Undefined 6
Time/ Duration
Hours Initial Dose
Possible Outcomes
Micrograms Antigen-specific mediator depletion, downregulation of receptors
Hours to days Milligrams Unknown
Pharmacologic Hours to days Milligrams Metabolic shiſt, internalization of receptors
Days to weeks Micrograms to milligrams
Unknown
Example Penicillin
TMP-SMX Aspirin
Allopurinol
