Zefei 200 mg Injection (Gemcitabine) is a prescription chemotherapy medication used in the treatment of several solid tumors such as lung, pancreatic, bladder, and breast cancers. The active ingredient, gemcitabine, works by disrupting cancer cell DNA replication, slowing tumor growth. Zefei should be administered by trained medical professionals through intravenous infusion and requires regular blood monitoring throughout treatment.