They work by different mechanisms to provide better control of blood sugar when single or dual therapy is not effective. Glimepiride is a sulfonylurea which works by increasing the amount of insulin released by the pancreas in order to lower the blood glucose. Metformin is a biguanide. It works by lowering glucose production in the liver, delaying glucose absorption from intestines and increasing the body's sensitivity to insulin. Pioglitazone is a thiazolidinedione which further increases insulin sensitivity.
Common side effects
Hypoglycemia (low blood glucose level), Nausea, Diarrhea, Headache, Edema (swelling), Anemia (low number of red blood cells), Upper respiratory tract infection, Dizziness, Vomiting, Flatulence, Bronchitis (inflammation of the airways)