Disclosed is a use of a pharmaceutical composition comprising or made from a DPP-4 inhibitor which is 1-[(4-methyl-quinazolin-2-yl)methyl]-3-methyl-7-(2-butyn-1-yl)-8-(3-(R)-amino-piperidin-1-yl)-xanthine, and metformin； a stabilizer which is a nucleophilc and/or basic agent, a buffering agent or a pH modifying agent which is L-arginine, and one or more pharmaceutical excipients； for preparing a medicament for use in treating and/or preventing (including slowing the progression and/or delaying the onset) of metabolic diseases, especially type 2 diabetes mellitus and conditions related thereto (e.g. diabetic complications), either in type 2 diabetes patients who have not been previously treated with an antihyperglycemic agent, or in type 2 diabetes patients with insufficient glycemic control despite therapy with one or two conventional antihyperglycemic agents selected from metformin, sulphonylureas, thiazolidinediones (e.g. pioglitazone), glinides, alpha-glucosidase blockers, GLP-1 or GLP-1 analogues, and insulin or insulin analogues； optionally in combination with one or more other active substances； wherein the patients are in need of reduced dose metformin therapy due to reduced tolerability, intolerability or contraindication against metformin or due to impaired/reduced renal function.
