Novel assay of metformin levels in patients with type 2 diabetes and varying levels of renal function: clinical recommendations

Anders Frid, Gunnar N Sterner, Magnus Löndahl, Clara Wiklander, Anne Cato, Ellen Vinge, Anders Andersson, Anders Frid, Gunnar N Sterner, Magnus Löndahl, Clara Wiklander, Anne Cato, Ellen Vinge, Anders Andersson

Abstract

Objective: To study trough levels of metformin in serum and its intra-individual variation in patients using a newly developed assay.

Research design and methods: Trough serum levels of metformin were measured once using liquid chromatography-tandem mass spectrometry (LCMSMS) in 137 type 2 diabetic patients with varying renal function (99 men) and followed repeatedly during 2 months in 20 patients (16 men) with estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) body surface.

Results: Patients with eGFR >60, 30-60, and <30 ml/min/1.73 m(2) had median trough metformin concentrations of 4.5 micromol/l (range 0.1-20.7, n = 107), 7.71 micromol/l (0.12-15.15, n = 21), and 8.88 micromol/l (5.99-18.60, n = 9), respectively. The median intra-individual overall coefficient of variation was 29.4% (range 9.8-74.2).

Conclusions: Determination of serum metformin with the LCMSMS technique is useful in patients on metformin treatment. Few patients had values >20 micromol/l. Metformin measurement is less suitable for dose titration.

Trial registration: ClinicalTrials.gov NCT00767351.

Figures

Figure 1
Figure 1
Box-plot of trough metformin levels in 137 patients grouped in patients with eGFR 2 (n = 9), 30–60 ml/min/1.73 m2, and >60 ml/min/1.73 m2 (n = 107). The outliers marked in the group with eGFR >60 ml/min/1.73 m2 are most likely due to patients accidentally taking their medication before the blood test.

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