Long-term efficacy of steady-dose metformin in type 2 diabetes mellitus: a retrospective study.

BACKGROUND: Few data are available on the long-term efficacy of metformin, one of the main drugs in the treatment of type 2 diabetes mellitus. MATERIAL/METHODS: This was a retrospective study of 195 type 2 diabetic patients (109 female, 86 male; mean age 50.4+/-10.1 years, diabetes duration 5.4+/-1.4 years, mean BMI 28.6+/-6.5 kg/m2 at baseline). The inclusion criterion was at least one-year treatment with metformin alone or metformin and one other antidiabetic drug in unchanged doses. The analysis included duration of metformin treatment, mode of therapy, changes in metabolic parameters (fasting blood glucose, HbA1c), body weight, and insulin dosage. RESULTS: Mean duration of metformin use was 970+/-578 (range 373-2916) days, mostly 500 mg tid. 42 patients (22%) were treated with metformin only, 82 (42%) with metformin and sulfonylurea, 61 (31 %) with metformin and insulin and 10 (5%) with metformin and acarbose. In the whole group mean fasting blood glucose decreased during the treatment significantly, from 212+/-57 to 167+/-54 mgldl (p<0.00001), HbA1c from 9.3+/-1.3 to 8.5+/-1.1% (p<0.05), body weight from 92.6+/-17.9 to 88.4+/-14.9 (by 4.5%; p<0.001). A significant positive correlation was noted between baseline body weight and body weight change (r=0.39; p<0.05). Insulin requirement was reduced by a mean of 21 IU/day in the third year of treatment. CONCLUSIONS: Metformin is an efficacious long-term use drug in poorly controlled type 2 diabetes patients, either in monotherapy or in combination.