Non-Immediate Cutaneous Hypersensitivity Drug Reactions: Are Positive Patch Tests Long-Lasting?
Introduction: Like in allergic contact dermatitis, in non-immediate (NI) cutaneous adverse drug reactions (CADR) delayed hypersensitivity to antibiotics and anticonvulsants is considered to be lifelong. Although in allergic contact dermatitis patch tests remain positive for several years, this has seldom been assessed in the setting of NI-CADR to systemic drugs.
Objective: To evaluate the long term behaviour of positive patch test reactions in NI-CADR to beta-lactams, clindamycin and carbamazepine. Methods: The drugs associated with the largest number of positive patch test reactions (beta-lactams, clindamycin and carbamazepin) were selected and 64 patients with history of NI-CADR to these drugs and relevant positive reactions were invited to repeat patch tests, at least 2 years thereafter. New patch test reactions were compared with the original ones.
Results: In the 23 patients included in the study (10 males/ 13 females, median age 51 years) there were 44 positive reactions at the first patch tests and 40 (91.1%) of these remained positive after a median interval of 6.5 years (min. 2.0 – max. 30.7 years). Concerning beta-lactams, 17/19 reactions persisted positive for aminopenicillins (amoxicillin or ampicillin), 8/8 for isoxazolyl penicillins (flucloxacillin or dicloxacillin), 3/3 for benzylpenicillin, 1/1 for cefoxitin and 1/1 with piperacillin. Reactions with clindamycin remained positive in 5/7 cases. All five patch tests repeated with carbamazepine were positive. In 62.5% of the tests the same intensity of reaction was observed and was not affected by the time interval between tests, gender or age at performing patch tests.
Conclusion: In NI-CADR to several antibiotics and carbamazepine, most of the patch test reactions remained positive after several years.
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