[The combination of insulin and metformin in obese patients with type-2 diabetes mellitus]

Abstract

Objectives: Principal: to show that the addition of metformin to insulin treatment in type-2 DM obese patients with poor metabolic control (HbA1c > 7.5%) causes a 50% increase after one year in the number of patients with acceptable (HbA1c < or = 7.5%) or good (HbA1c < 6.5%) control, and to determine how many patients reduced their HbA1c by a point. Secondary: to determine the relationship between the BMI at the start of treatment and the difference between HbA1c values before and after treatment.

Design: Quasi-experimental before-and-after intervention study.

Setting: Diabetes clinic at the San Carlos Hospital, consisting of patients referred from primary care.

Patients: 31 obese people with type-2 DM and with poor metabolic control (HbA1c > 7.5%) in spite of insulin treatment were chosen by consecutive sampling as they attended for consultation. Three people left due to their intolerance of metformin.

Interventions: Metformin was added progressively over a year in total doses of 1.7 mg. All those parameters considered in diabetes control were measured, the main criterion of evaluation being the HbA1c figures.

Measurements and results: Patients with poor metabolic control changed from 100% at the start of the study to 42.9% after a year (p = 0.0000). There was a 1.75% mean reduction of HbA1c. 78.57% of patients reduced their HbA1c by a point. The relationship between the BMI before the start of treatment and the HbA1c difference at the start and end gave a Pearson's correlation coefficient of r = -0.39 (p = 0.04).

Conclusions: Adding metformin to the treatment of obese type-2 DM patients with poor metabolic control and on insulin treatment improved their control.