PIROXICAM INDUCED PHOTODERMATITIS DIAGNOSED BY PATCH-TEST WITH THIOSALICYLIC ACID Jessika Arévalos Prette, Verónica Pacheco Coronel, Noelia Colomer Hernández, Miguel Díaz Palacios, Ana Giner Valero Department of Allergy, IIS Hospital La Fe. Valencia, Spain. BACKGROUND: Oxicams are nonsteroidal anti-inflammatory drugs (NSAID) widely used in osteoarticular disease. Skin eruptions, occurring in 1-3% of patients, are the second most frequent adverse events after gastrointestinal problems. Photosensitivity to piroxicam is associated to contact sensitivity to thiosalicylate. This phenomenon is due to a photoproduct of piroxicam that bounds to L-cys producing a compound with similar chemical structure than thiosalicylic acid. We present 2 cases of photodermatitis induced by piroxicam showing positive patch tests with thiosalicylic acid. METHODS: PATCH TEST NSAID Case 1 Case 2 1. IBUPROFEN 5% - - 2. NAPROXEN 5% - - A 23 years old female developed pruritus with a burning sensation 3. BUFEXAMAC 5% - - and small wheals over the right hand while she was under 4. BENZIDAMINA 5% - - treatment with oral dexketoprofen, methocarbamol and topical 5. BENZIDAMINA 3% - - piroxicam spread over the left shoulder with the same hand. 6. SALICYLIC ACID 5% - - 7. SALICYLIC ACID 1% - - 8. ACETAMINOPHEN 10% - - 9. ACETAMINOPHEN 5% - - A 67 years old male presented a skin rash, with intense redness and 10. ACETAMINOPHEN 1% - - pruritus, over the hands, neck and scalp during treatment with oral 11. INDOMETACIN 10% - - 12. INDOMETACIN 5% - - piroxicam. The skin rash lasted for several days. 13. INDOMETACIN 1% - - 14. KETOPROFEN 1% - - 15. PHENYLBUTAZONE 1% - - 16. THIOSALICYLIC ACID 0,1% +++ ++ 17. DICLOFENAC 1% - - 18. DICLOFENAC 5% - - 19. DICLOFENAC 10% - - 20. PIROXICAM 1% - - 21. THIOMERSAL +++ ++ 22. PIROXICAM GEL - RESULTS: Occlusive patch tests performed to both patients with a series of NSAID including ibuprofen, salicylic acid, acetaminophen, thiosalicylic acid, diclofenac, piroxicam and thimerosal, were positive with thiosalicylic acid and thimerosal, and negative with other drugs including piroxicam. Tolerance to alternative NSAID was confirmed by the safe use by patients or by challenge tests. Patients, instructed to avoid all oxicams, remain free of lesions. CONCLUSION: Patch test with thiosalicylic acid is an alternative diagnostic procedure in cases of photodermatitis due to piroxicam when photopatch test is not available. The use of alternative NSAID is safe in these cases. In relation to this presentation, the authors declare no conflicts of interest .