In Brazil pancreatic adenocarcinoma represents 2% of tumors, and 4% mortality being an uncommon disease, however very aggressive.Only 20% of cases are indicated for curative surgery, of which only 20% are alive within 5 years. For locally, advanced or metastatic disease, since 1997, single chemotherapy with gemcitabine is the standard treatment for first line, with survival around 6 months approximately.There is no standard treatment regimen for second-line, however Paclitaxel demonstrated effect on second-line phase II study. Metformin is an oral hypoglycemic drug used for treatment of diabetes mellitus. There is a growing number of preclinical studies which show antitumor effect against pancreatic adenocarcinoma, probably due to the effect of anti-insulin growth factor (IGF-1). This study will add metformin to standard treatment for second line of locally advanced or metastatic pancreatic adenocarcinoma in ICESP previously treated with gemcitabine. The objective is to evaluate whether metformin improves the efficacy of the standard treatment with paclitaxel by clinical and radiological evaluation.