Effect of plasma metformin concentrations on serum lipid levels in type II diabetic patients.

In this study we evaluated the relationships between plasma metformin levels, measured by reverse-phase high-performance liquid chromatography, and serum lipid levels in 20 metformin-treated, type II diabetic patients. Mean fasting plasma metformin concentration was 490 +/- 188 ng/ml. No correlation was found between daily dose of drug and lipid parameters. A significant correlation emerged between circulating metformin concentration and serum triglycerides (r = -0.574, p less than 0.01), HDL-cholesterol (r = 0.583, p less than 0.01) and HDL2-cholesterol (r = 0.670, p less than 0.05). Multiple linear regression analysis showed that the correlation between plasma metformin concentration and serum triglycerides still remained significant after correction for other clinical and metabolic parameters. Total cholesterol and HDL3-cholesterol were not correlated with metformin concentrations. These results demonstrate the clinical usefulness of measuring plasma metformin concentrations and indicate that some effects of metformin on lipid metabolism depend on the drug plasma levels.