In clinical trials,  the antihyperglycemic effectiveness of acarbose and miglitol is less than 50% than that of either sulfonylureas or metformin. When used as monotherapy, acarbose primarily affects post-prandial glucose levels, which is reduced by 40-50 mg/dl after meal.  As with the other classes of agents, since the mechanism of action of a-glucosidase inhibitors is different from other oral agents, their effects on glycemic control are additive when used in combination.  This can be seen in an early study (shown to the right) where acarbose was compared with tolbutamide (Am J Med 1995;98:43) .