OBJECTIVES: To compare cost-effectiveness of two metformin formulations (immediate release [IR] and extended release [XR]) in the cohort of patients with diabetes mellitus type-2 (DM2) and ischemic heart disease (IHD). METHODS: Cost-effectiveness analysis of metformin IR (Siofor® 500 mg tid) and metformin XR (Glucophage® Long 750 mg bid) was performed using cohort modeling. Daily dosage of metformin was the same for both formulations, 1500 mg a day. For a model cohort of 100 patients, annual cost of metformin treatment was 359,270 RUB (11,841 USD) for metformin IR and 498,347 RUB (16,425 USD) for metformin XR. Effectiveness of the treatment was evaluated using the data of UKPDS study (1998), which demonstrated that 1% reduction of HbA1c led to 14% reduction of angina attacks rate. RESULTS: Assuming linear character of relationships between HbA1c level and angina attacks rate, and taking into account the data of Donnelly L.A. et al. (2008) that using metformin XR provides additional 0.7% reduction of HbA1c level, we suggested that administration of metformin XR  would reduce the frequency of angina attacks in DM2 patients with OHD by 9.8%. It was assumed that average frequency of angina attacks in this cohort was 1 per year per patient; therefore administration of metformin XR instead of metformin IR would annually prevent approximately 10 cases of angina in the modeled cohort of 100 patients. According to standards of IHD treatment in Russia,  angina attack treatment costs 19,970 RUB per patients (658 USD), for 10 patients it will total 199,700 RUB (6,580 USD). This sum might be saved by administration of metformin XR, and even taking into account higher cost of metformin XR, annual saving per 100 patients would be 60,600 RUB per year (1,997 USD). CONCLUSIONS: Administration of metformin XR to patients with DM2 and IHD is more cost-effective that administration of metformin IR.