Methods: Literature review and case description.
Results: Female patient, 37 years, from São Paulo came to our clinic for evaluation due to lombocitalgy therapy caused by a disc herniation. She reported a history of flushing, reddish plaques and itching in the body 24 hours after using diclofenac and piroxicam simultaneouly. At the Emergency Department received promethazine, methylprednisolone and dexchlorpheniramine and the lesions subsided in few hours. Another episode occurred after a hysterectomy surgery, when she received tenoxicam, dipyrone, metoclopramide and cefazolin. Next day, there were "urticaria" plaques in cervical and abdominal region. The patient was treated with antihistamine and improvement after 1 week. We performed a Patch Test with piroxicam, tenoxicam and thimerosal in the concentration of 10%. The first reading was done in 48 hours and evidenced erythema and bullous lesions for thimerosal and erythema for piroxican. The 96 hours reading showed microvesicles, erythema and pseudopods for piroxicam and erythema and microvesicles for thimerosal. The patch test was negative with tenoxicam.
Conclusions: Piroxicam may induce photoallergy through a photoproduct, wich is structurally similar to the antigenic thiosalicylic acid present in the formula of thimerosal. There is no evidence of cross-reaction between piroxicam and tenoxicam, because this photoproduct is not formed upon irradiation of tenoxicam. The diagnosis of drug photosensitivity reaction is performed by clinical history associated with photo patch test.