[Epicutaneous patch testing in delayed drug hypersensitivity reactions induced by antiepileptic drugs]

Antiepileptic drugs are widely used and are associated with numerous side effects including skin eruptions. Epicutaneous tests have been used with variable success in skin drug reactions. The purpose of this study was to evaluate the profitability of epicutaneous tests in delayed hypersensitivity reactions induced by antiepileptic drugs.

We analyzed all cases of allergic skin reactions to antiepileptic drugs notified in regional pharmacovigilance center of Sfax (Tunisia) between June 1, 2014 and April 30, 2016. The imputation score, determined using the French imputation method, should be at least doubtful. Patch-tests were performed in accordance with the general Europen network on Drug Allergy/European Academy of Allergy and Clinical Immunology (ENDA/EAACI) guidelines. Patch-tests were read according to the generally accepted criteria of the International contact dermatitis research group (ICDRG).

In our study, 20 patients were included, among which 23 events were observed. The drug involved in delayed hypersensitivity reactions was carbamazepine in 11 cases, phenobarbital in 10 cases and valproic acid in 4 cases. The clinical reactions caused by the drug were classified as maculopapular exanthema (11 cases), DRESS syndrome (6 cases), Stevens-Johnson syndrome (2 cases), fixed drug eruption (2 cases) and erythroderma (2 cases). Patch-tests were positive in 19 patients (95 %). Cross-reactivity between antiepileptic drugs was observed in 4 cases: between valproic acid and carbamazepine in 2 cases between valproic acid and phenobarbital in 1 case and between phenobarbital and carbamazepine in 1 case.

In this study, patch testing was a safe and useful method in confirming the culprit drug in delayed hypersensitivity reactions induced by antiepileptic drugs.