Dipeptidyl peptidase-4 inhibitors are slightly less effective than metformin in the management of type 2 diabetes, but cause fewer adverse events

In this study researchers compared the effects, and side effects, of DPP-4 inhibitors and metformin when used as first therapy for type 2 diabetes. The effects of drug treatments were reviewed when these drugs were given together (called combination therapy), or alone (called monotherapy).

Dipeptidyl peptidase-4 (DPP-4) inhibitors (i.e. januvia) and metformin (glucophage) are both effective drugs in the management of type 2 diabetes mellitus (T2DM), but have different rates of side effects. To assess the efficiency and safety of DPP-4 inhibitors versus metformin, researchers reviewed all recently published trials comparing the use of these drugs, or reviewing the use of both drugs as combination therapy. The efficiency of diabetic drugs is usually assessed by checking the levels of HgbA1c in the blood. High levels of HgbA1c indicate that the patient's blood glucose levels were abnormally high during the past 3 month, and that the patient's diabetes is not well controlled.  

The authors examined eight studies which compared DPP-4 inhibitors to metformin, or that reviewed the effect of combined therapy. All studies were published between 2007 and 2012, and included a total of 7,778 patients. Across these studies, the authors found no difference among the different types of DPP-4 inhibitors. Although DPP-4 inhibitors were shown to be effective at reducing blood glucose levels, HgbA1c and excess body weight, metformin therapy was shown to be even more effective at controlling diabetes than DPP-4 inhibitors. However, DPP-4 inhibitors caused fewer adverse side effects. When the authors compared metformin monotherapy to metformin plus DPP-4 inhibitor combined therapy, results were similar in both groups with regards to diabetic control. However, the addition of DPP-4 inhibitors in combined therapy did not reduce the frequency of side effects relative to metformin alone.

Both metformin and DPP-4 inhibitors are effective at treating T2DM. However, metformin has proven to be the most effective, and should be considered as the treatment of choice. For patients who cannot tolerate metformin, DPP-4 inhibitors are also a good treatment option, and are associated with fewer side effects.

The authors compared DPP-4 inhibitor and metformin monotherapies to one another, as well as metformin monotherapy to combined therapy. However, they did not compare DPP-4 inhibitor monotherapy to combined therapy. Furthermore, across the eight studies, different dosages of metformin (500-2000 mg) and DPP-4 inhibitors (5-100 mg) were used. The authors did not correct for these differences, which could have affected the results.

Consult with your physician about the best drug options for controlling diabetes.