Patch Testing in Drug Eruptions: Practical Aspects and Literature Review of Eruptions and Culprit Drugs

Abstract

There is overwhelming evidence that many delayed cutaneous adverse drug reactions (beginning >6 hours after drug intake) are mediated by delayed-type (type IV) hypersensitivity, including maculopapular eruptions, erythroderma, symmetrical drug-related intertriginous and flexural exanthema/baboon syndrome, eczematous eruptions, fixed drug eruptions, acute generalized exanthematous pustulosis, and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome. Therefore, after resolution of the reaction, patch tests should be performed as first diagnostic method to identify the culprit drug(s). This article provides tools to perform drug patch tests properly and safely, discussing clinical history, indications, procedure, drug patch test materials, sensitivity, the meaning of negative patch tests, and safety of the procedure. In addition, a literature review of eruptions and culprit drugs is provided in tabular format.

Patch testing in drug reaction with eosinophilia and systemic symptoms (DRESS): A literature review

“…From the studies presented thus far, no evidence for the optimal patch test concentration and vehicle for any drug has emerged and, therefore, some practical recommendations are given here, which also apply to other delayed-type drug hypersensitivity reactions. 4,[255][256][257] In the authorʼs opinion, patch testing should be the first diagnostic method in the search for the drug(s) that are responsible for cutaneous adverse drug reactions, with the possible exception of cases where patients with DRESS had used only allopurinol or sulfasalazine. Preferably, the pure drugs, not the commercialized tablets, used by the patients, should be tested to obtain well-defined test materials and to avoid falsepositive results (ie, not indicating hypersensitivity to the active drug material) due to hidden additives in the drug formulations, degradation products, or impurities.…”

“…wt/wt. 4,255,256,257 When the content of the active drug is too low in the patient's drug to achieve a 10% concentration, the whole powder should be diluted in 30% pet., which is non-irritant for nearly all commercial medications. 258 When possible, the excipients of the pharmaceutical should also be patch tested.…”

“…36,40 The patch test materials should be removed after 2 days and the reactions read 30 minutes later; a second reading at day (D) 3 or D4 259 is necessary and a later reading at D7 (or D8-D10) is strongly recommended, the latter especially for corticosteroids (due to the anti-inflammatory effect of the molecule), 260 iodinated contrast media, heparins, and aminoglycoside antibiotics. 255 Test reading is usually performed according to the ESCD guidelines for conducting patch tests (at least in Europe) 256 ; the system used by the German Contact Allergy Group is virtually identical. 261 The relevance of any positive drug patch test should be carefully assessed.…”

“…Generally, performing patch tests in DRESS is considered to be a safe procedure. 2,10,11,20,21,255 Adapted from ref. 255 For oral or parenteral (intravenous, intramuscular, subcutaneous injections) administration or as enema.…”

“…2,10,11,20,21,255 Adapted from ref. 255 For oral or parenteral (intravenous, intramuscular, subcutaneous injections) administration or as enema.…”