Drug related involvement of specific sites in fixed eruptions: a statistical evaluation

Different drugs produce fixed eruptions over different parts of the body. However, the significance of preferential site involvement in fixed eruptions due to specific drugs has not been statistically evaluated. One hundred and twenty five patients of fixed drug eruption (FDE) were studied to examine this question. Different sites affected by individual drugs were classified as lips alone, genitalia alone, lips and genitalia together, trunk alone, trunk and limbs together, and generalized. Statistical analysis was carried out for 7 common drugs causing FDE in 5 or more patients. Cotrimoxazole, a combination of sulfamethoxazole and trimethoprim, was the most common offender for FDE (32.8%), followed by analgin (12%), tetracycline (8%), pyrazolones (8%), metronidazole (6.4%), ciprofloxacin (5.6%), and phenytoin sodium (4%). Major sites involved by FDE were trunk and limbs (24%), lips alone (20.8%), genitalia alone (20%), generalised (14.4%), lips and genitalia together (11.2%), and trunk alone (8.8%). Seventy-two (57.6%) patients had multiple lesions; 33 (42.4%) had single lesions. Involvement of mucocutaneous junctions of lips and genitalia by FDE was frequently caused by cotrimoxazole and tetracycline; trunk and limbs, by analgin and pyrazolones. Generalised eruptions were commonly caused by cotrimoxazole and phenytoin. The present statistical analysis confirms the clinical impression that genitalia alone are frequently involved in FDE due to tetracyclines (p < 0.001). FDE over trunk and limbs was significantly associated with analgin (p < 0.001), and generalised eruptions, with phenytoin sodium (p < 0.001). The association of FDE over lips with cotrimoxazole was statistically not significant.