The aim of this in vitro study was assessment the cytotoxic level 6-O-desmethylnaproxen. A mouse connective tissue fibroblast cell line, L929 exposed to naproxen and 6-O-desmethylnaproxen different concentrations for 24- 48- hours. Cell viability tested by MTT, while apoptosis determined AO/PI double staining method. control group free from any agent (DMEM only) accepted as 100% viability. IC50...