Study On Pharmacokinetics And Bioequivalence Of Compound Metformin In Healthy Volunteers

This study introduced analytical methods to measure plasma concentration of metformin and glibenclamide, and put the methods into application for the pharmacokinetic research of compound metformin in healthy volunteers, meanwhile, the bioequivalence between formulations were investigated.1. HPLC-UV method for measurement metformin concentration in plasmaA reversed phase ion-pair HPLC-UV method was used to analyze metformin concentration. The mobile phase was composed of 3mmol.L-1 SDS ( containing 5% triethylamine, adjusted pH to 4.0 with phosphate acid) :acetonitrile (65: 35, v/v), the detection wavelength was set 232nm. The plasma sample was precipitated protein before injection into chromatography. The plasma drug concentration kept a good linear relationship with response in the range of 0.03 - 1.50@g.mL-1.The recovery was 80 - 120%, and the variance coefficient was 2.59~ 14.14%. The method was proved rapid, sensitive and accurate enough for metformin pharmacokinetic research.2. HPLC-MS for determination glibenclamide concentration in plasmaA highly sensitive, specific and reproducible high performance liquid chromatography combined with mass spectrometry has been developed for the quantitative analysis of glibenclamide hi plasma. Plasma was processed with liquid-solid extraction. The mobile phase consists of acetonitrile: 0.2% formic acid (60:40,v/v) with a flow rate of 0.2mL.min-1. The separation procedure was performed on chromatographic column of Waters Xterra MS C18 ( 150mmX 2.1mm, 3.5@m) . A Waters high performance liquid chromatography joint with mass spectrometer equipped with electrospray ionization source was used for glibenclamide concentration determination. Selected ion monitoring (SIM) using fragment ion m/z 369 was applied to quantify glibenclamide. The linear for glibenclamide was 2.5-160ng,mL-1, (γ =0.9997), and the LOD was 0.5ng.mL-1. It was suitablefor glibenclamide pharmacokinetic research.3. Pharmacokinetic study of compound metformin18 male healthy volunteers were given an orally single dose of test formulation or reference formulation. And the described methods were employed to measure plasma concentration of metformin and glibenclamide, respectively. Three formulations had similar pharmacokinetic characteristics. As to glibenclamide (tablet, capsule, reference): tmax (2.50±0.69)h, (2.89±0.83)h, and (2.67 ± 0.75)h; Cmax (75.05 ±19.67)ng.mL-1, (69.85± 17.89)ng.mL-1,and (68.96 ±18.36)ng.mL-1; t1/2 (2.73±0.83)h, (3.21 ± 1.20)h, and (3.36±1.33)h; AUC0-tn (300.54± 86.47)h.ng.mL-1, (280.93 ± 84.26)h.ng.mL-1, and (297.50±93.50)h.ng.mL-1; AUC0-~ (308.02 ± 90. 10)h.ng.mL-1, (290.18 ±87.41)h.ng.mL-1, and(311.40±101.65)h.ng.mL-1, respectively. As to metformin (tablet, capsule, reference): tmax (1.83±0.93)h, (1.94±0.76)h, and (1.77 ± 0.85)h; Cmax (0.89 ± 0.22) μg.mL-1 , (0.82 ± 0.14) μg.mL-1, and (0.89±0.22)μ g.mL-1; t1/2 (6.25±2.19)h, (6.05±2.63)h, and (5.88±2.68)h; AUC0-tn (5.66± 1.31)h.μg.mL-1, (5.40±1.20)h.μg-mL-1, and (5.30±1.10)h.μg-mL-1; AUC0-∞ (6.17± 1.77)h.P g.mL-1, (5.89± 1.73)h. μ g-mL-1 and (5.75±1.63)h.μg.mL-1; respectively. The main pharmacokinetic parameters such as tmax, Cmaxm, AUCo-tn, AUC0-∞ had no significant differences in three formulations(p>0.05), and the same condition occurred on metformin. However, there had significantly statistic differences between individuals on both glibenclamide and metformin (p<0.01). 4. Bioequivalent analysesCalculated by AUCo-tn the relative bioavailability of tablet and capsule were( 102.36± 13.48) %, (95.31±12.09)% for glibenclamide, and (107.55±16.18) %, (102.90±16.69) % for metformin, respectively. The resultsultimately showed the two test preparations were both bioequivalent with referencepreparation based on two one-sided t tests and 90% confidence interval.