Health and economic impact of combining metformin with nateglinide to achieve glycemic control: Comparison of the lifetime costs of complications in the U.K

BACKGROUND: To reduce the likelihood of complications in persons with type 2 diabetes, it is critical to control hyperglycaemia. Monotherapy with metformin or insulin secretagogues may fail to sustain control after an initial reduction in glycemic levels. Thus, combining metformin with other agents is frequently necessary. These analyses model the potential long-term economic and health impact of using combination therapy to improve glycemic control. METHODS: An existing model that simulates the long-term course of type 2 diabetes in relation to glycosylated haemoglobin (HbA(1c)) and post-prandial glucose (PPG) was used to compare the combination of nateglinide with metformin to monotherapy with metformin. Complication rates were estimated for major diabetes-related complications (macrovascular and microvascular) based on existing epidemiologic studies and clinical trial data. Utilities and costs were estimated using data collected in the United Kingdom Prospective Diabetes Study (UKPDS). Survival, life years gained (LYG), quality-adjusted life years (QALY), complication rates and associated costs were estimated. Costs were discounted at 6% and benefits at 1.5% per year. RESULTS: Combination therapy was predicted to reduce complication rates and associated costs compared with metformin. Survival increased by 0.39 (0.32 discounted) and QALY by 0.46 years (0.37 discounted) implying costs of £6,772 per discounted LYG and £5,609 per discounted QALY. Sensitivity analyses showed the results to be consistent over broad ranges. CONCLUSION: Although drug treatment costs are increased by combination therapy, this cost is expected to be partially offset by a reduction in the costs of treating long-term diabetes complications.