| Background and objective:Metformin is the first-line treatment for type 2 diabetes,however,there are individual differences in the efficacy and adverse reactions when used in the patients.How do we develop an appropriate dosage regimen is a problem to be solved.Population pharmacokinetics is an important tool in individualized administration.The main purpose of this research is to establish a population pharmacokinetic model for metformin in Chinese type 2 diabetes subjects and to simulate the optimal dosing regimen for the patients.Methods:In this study,a metformin quantitative assay was first established to determine the human plasma concentration of metformin by RP-HPLC.Atenolol was used as the internal standard.The methodology was examined for specificity,linear range,lower limit of quantitation,precision,accuracy,recovery and stability.This method was then used to determine the drug concentrations in plasma in 125 T2DM patients.The SNPs of the transporters of metformin were studied.The Sanger dideoxy sequencing was used to sequence the four SNPs located in the genes encoding the transporters OCT1,OCT2 and MATE 1:rs622342,rs316019,rs2289669 and rs2252281.The different genotype frequencies in the SNP loci were determined whether they were consistent with Hardy-Weinberg equilibrium.Finally,a model of pharmacokinetics of metformin in type 2 diabetics was established by a nonlinear mixed-effects model(NONMEM)to quantitatively examine body weight,age,BMI,estimated glomerular filtration rate(eGFR),gene polymorphisms and other effects on the model.The final population pharmacokinetic model was then established for metformin.Based on the pharmacokinetic parameters estimated by the final model,the Monte Carlo simulation method was used to simulate the optimal dose according to the eGFR levels of the subjects.Results:(1)The quantitative analysis results of metformin was as the following.The linear range of the calibration curve was 0.2 μg·ml-1～5 μg·ml-1,with the equation of Y=1.153X+0.0366(R2=0.9999)and the quantitative lower limit of 0.2 μg·ml-1.The inter-and intra-day precisions were less than 9.96%and the accuracy was within ±5.58%.The extraction recoveries were 65%-76.9%.Under various stability conditions,the low(0.6 μg·ml-1)and high(4 μg·ml-1)concentrations of plasma metformin were within the range of 91.99%to 106.52%.(2)Gene polymorphism distributions of the four variants of the genes encoding the transporters OCT1,OCT2 and MATE1 were all consistent with the Hardy-Weinberg equilibrium(χ2 ＝0.37,P=0.54(rs622342);χ2= 0.67,P=0.41(rs316019);χ2=0.33,P=0.57(rs2289669);χ2= 0.23,P=0.63(rs2252281).(3)NONMEM software was used to establish the final population pharmacokinetic model.The estimated population parameters θ CL,θ V,θKA and θALAG1 were 53L/h,438L,1.4 and 0.914,respectively.OFV of the final model equals-63.206.One of the simulated doses for the type 2 diabetic patients with different eGFR levels(45-59,60-89,90-119,≥120 ml.min-1.1.73 m-2)were 750 mg,1275 mg,1500 mg and 2,550 mg per day,respectively,and with an interval of 8 hours.Another the simulated doses for the type 2 diabetic patients with different eGFR levels(45-59,60-89,90-119,≥120 ml.min-1.1.73 m-2)were 1000 mg,1700 mg,2000 mg and 3000 mg per day,respectively,and with an interval of 12 hours.Conclusions:This article has established a specific and high sensitivity,suitable for the metformin quantitative study of population pharmacokinetics for metformin in type 2 diabetic patients.The selected population has a representative group.The established pharmacokinetic model of metformin is stable and can be used to estimate population pharmacokinetic parameters.Renal function is an important factor influencing the metformin clearance rate.It can be achieved by simulating the optimal dose for different renal function patients. |
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