OBJECTIVES: Metformin extended release (XR) has higher treatment adherence than immediate release (IR) formulation, due to lower pill burden and better gastrointestinal tolerability, leading to better glycated hemoglobin (HbA1c) levels control. This study aimed to compare metformin XR versus metformin IR monotherapy for type 2 diabetes mellitus (T2DM) considering the long-term cost-effectiveness outcomes.

METHODS: A discrete event simulation model based on a comprehensive literature review was used to estimate costs and effectiveness of a therapeutic sequence started with metformin XR versus metformin IR in T2DM patients. This model was based on UKPDS modelling framework. HbA1c profile progression was modelled monthly, the impact of adherence on effectiveness was considered and Saudi Arabia specific data was included whenever available. This study assessed quality adjusted life years (QALY), time to insulin therapy, time spent with diabetes complications and lifetime costs.

RESULTS: Metformin XR represents lifetime savings of 3,028 SAR per patient comparing with IR formulation (total lifetime costs with metformin XR: 420,356 SAR vs IR: 423,384 SAR). The delay in more expensive advanced lines of therapy in patients with metformin XR as first-line therapy (time to insulin initiation with metformin XR: 12.31 years vs IR: 12.05 years) leads to lower lifetime drug costs (drug costs with metformin XR: 234,420 SAR vs IR: 236,826 SAR). QALY are estimated to be higher with XR formulation compared to IR (12.46 QALY vs