Patient-factors associated with metformin steady-state levels in type 2 diabetes mellitus with therapeutic dosage

AIMS: This prospective study aimed to analyze metformin steady-state concentration in repeated constant dosage and the influencing patient-factors as well as to correlate them with glycemic control. METHODS: The validated HPLC-UV method was used to examine metformin steady-state concentration, while FBG and glycated albumin were used as the parameters of glycemic control during metformin administration. RESULTS: A total of 82 type-2 diabetes patients were involved with 32.1% of them having metformin Css(min) and 84.1% having Css(max) of metformin within the recommended therapeutic range. One patient had metformin Css that exceeded minimum toxic concentration despite his normal renal function and administered therapeutic dosage of metformin. Higher Css(max) was found in patients with metformin monotherapy, while patients with longer duration of metformin use had significantly higher Css(min). CONCLUSIONS: Along with initial hyperglycemia and eGFR, metformin Css(min) became the only parameter that influenced FBG level (P < 0.05). Duration of previous metformin use should be considered in the strategy of optimizing metformin dosage. The type-2 diabetes patients with obesity are more suggested to take shorter interval of metformin administration (or possibly with sustained-release formulation) to keep Css(min) within the therapeutic range.