The present invention relates to a physicochemically stable pharmaceutical composition, in a unit dose characterized in that it comprises effective amounts of 5 the active ingredients thiamine (Vitamin B1), pyridoxine (Vitamin B6), a flavonoid such as quercetin and a polyphenol such as curcumin, or their pharmaceutically acceptable salts in combination with pharmaceutically acceptable excipients, for the prevention of the formation and/or trapping of advanced glycation end products (glyoxal, methylglyoxal, Ni-carboxymethyl-iysine, N-carboxyethyl-lysine, pyrraline, pentosidine, lysine dimer, etc.), which can be used in the treatment and/or prevention of complications of diabetes mellitus (diabetic neuropathy, nephropathy and retinopathy). The pharmaceutical composition of the invention is presented orally, preferably in capsule, pill or sachet for oral administration.