RESUMEN
INTRODUCTION: Response to different antimicrobial agents supports the infection hypothesis for lichen planus (LP). There are individual case reports describing the improvement of LP with oral metronidazole treatment in patients with concomitant intestinal amebiasis or giardiasis. There are two small studies that reported metronidazole might be effective in some patients with idiopathic LP who did not have concomitant protozoal infections of the intestinal or genital tracts. The authors performed an open trial to evaluate the effectiveness of metronidazole, as a single treatment, on different forms of LP. PATIENTS AND METHODS: A total of 49 patients, 24 male and 25 female, were selected from the dermatology outpatient clinic with a diagnosis of LP in one of its forms. Metronidazole was administered at 250 mg every eight hours daily without any concomitant therapy. Patients were examined at baseline and at days 21, 42, 63, 84 of treatment, and the follow-up period was three months. The authors used SPSS software (Version 15) for data analysis. RESULTS: A total of 20 (40.82%) skin lesions had complete response (CR) to treatment by metronidazole, 16 (32.65%) had relative healing (PR) and 13 (26.53%) did not improve (NR). The overall treatment response (CR + PR) of LP skin lesions was 73.47 percent in this study. In mucosal involvement, the overall treatment response was 66.6 percent, and finally the overall treatment response for itching was obtained in 75 percent of the cases. CONCLUSION: Based on the authors' findings, metronidazole can be an alternative therapy in treatment of LP, and is a safe agent to be considered.