Efficacy and safety of metformin for treatment of type 2 diabetes in elderly Japanese patients

Aim: The maximum dosage of metformin allowed for clinical use in Japan is much less than half that in Western countries, making it difficult to apply the results of clinical trials in Western countries to Japanese patients. In particular, the efficacy and safety of metformin in elderly patients are largely unknown. Methods: Among 1508 patients who were newly prescribed metformin at our hospital from 2000–2006, patients with sufficient clinical data were retrospectively studied for the safety (n = 1132) and efficacy (n = 568) of the drug. Of 568 patients in whom the efficacy of metformin was analyzed, 180 patients (31.7%) were elderly, aged 65 years or over. Results: Metformin was effective for the treatment of type 2 diabetes in Japanese patients, with significant improvement in HbA1c level at all time‐points after 1 month, with the largest decrease by approximately 0.9% in patients treated with 750 mg/day and approximately 0.7% in those treated with 500 mg/day, at 4 months. Metformin improved glycemic control in elderly patients as well as non‐elderly patients. The efficacy was independent of age, sex, degree of obesity and concomitant use of other drugs. No significant difference was observed in elevated lactic acid levels between elderly and non‐elderly patients. No case of lactic acidosis was observed. Conclusions: These results suggest that the efficacy of metformin in Japanese elderly patients with type 2 diabetes is not different from that in non‐elderly patients, and that its safety might be linked to specific and well‐documented contraindications rather than age itself. Geriatr Gerontol Int 2011; 11: 55–62.