Patch testing in the detection of cutaneous reactions caused by carbamazepine

Carbamazepine is a widely used antiepileptic drug associated with various side effects including skin eruptions. Peroral provocation test with any suspected drug is a reliable method of investigating the etiology: however, it is both laborious and potentially dangerous to the patient. Patch testing has been reported with variable success in skin drug reactions. Four cases (one male, three females) with epileptic seizures were reviewed; all had received carbamazepine therapy with appropriate dosage, then suffered from various cutaneous reactions including maculopapular exanthema, exfoliative dermatitis, erythema multiforme and Stevens-Johnson syndrome after the initial therapy for two weeks to one month. Skin patch test was done with 1% and 10% carbamazepine in petrolatum applied on the back, then read at 48 and 72 hours. All four patients had positive allergic patch test reactions to carbamazepine. One patient had extreme (+3), one had strong (+2) and another two had weak (+) reactions. There were no any skin reaction to vehicle and control cases. This limited study demonstrates that patch testing may be useful in the detection or confirmation of any type of exanthematous eruption caused by carbamazepine.