Pharmacokinetics And Relative Bioavailability Of Metformin Hydrochloride Sustained-release Tablets

Background and objective: Metformin hydrochloride is the unique anti-diabetes drug of biguanides applicated by foreign and approved by FDA.It has the functions such as lowering the blood glucose level, lowering the blood lipid level,losing weight, preventing and managing the vessel complications of diabets, protecting the heart and having less side effect.Now metformin hydrochloride general tablet is used in clinic of inner hospitals in common. For it has the shorter half-time and needs frequent administration , and the compliance of medication is bad,it is limitied to be used extensively. To decrease the times of medication and increase the compliance of patients,we consulted Metformin hydrochloride produced by Yongkang Medicine Limited Company of Beijing City and studied pharmacokinetics and relative bioavalability of metformin hydrochloride sustained-release tablets among healthy Chinese persons.It is expected that it could provide reference for the use of medicine in clinic.Method : 18 volunteers were randomly divided into 2 groups. Metformin hydrochloride general tablets (1.0g) and sustained-release tablets(1.0g) were given to 18 healthy male volunteers in crossover .The intervening time is 2 weeks.Volunteers were given medicine with tepid water of 200mL in the morning after an overnight fast and were free to drink water at 2h and were given standard food of low fat and low protein at 4h after medication.Blood samples (3.0mL)were collected into heparinized tubes immediately before medication and at 0.5,1,1-5,2,2.5,3,4,5,7,9,11 and 15h(group of general tablets) and at 0.5,1,2,3,4,5,6,7,9, 11,15 and 24h(group of sustained-release tablets) aftermedication .Blood samples were immediately centrifuged at 3000 rpm for 10 min to separate the plasma .Blood samples were kept frozen at -30℃ until analysis.Volunteers in this trail are the same as in the last trail in a randomized crossover study.Test group were given metfonnin hydrochloride sustained-release tablets (l.Og) with tepid water of 200mL after an empty stomach at 7:30 every morning lasting 6 days .Reference group were given metfonnin hydrochloride general tablets (0.5g) with tepid water of 200mL after an empty stomach at 7:30 every morning and 19:30 every evening lasting 5 days and were given metformin hydrochloride general tablets (0.5g) one time in the morning of the 6th day .Blood samples (3.0mL)were collected into heparinized tubes immediately before medication every morning from 4th day and were measured the though-concentration (C_min).Pharmacokinetics of multiple oral doses of metformin were studied after medication in the 6th morning.Blood samples (3mL)were collected into heparinized tubes immediately before medication and at 0.5,14-5,2,2.5,3,4,5,7,9 and 12h(group of general tablets) and at 0.5,1,2,3,4,5,6,7,9,11,15 and 24h(group of sustained-release tablets) after medication. Blood samples were immediately centrifuged at 3000 rpm for 10 min to separate the plasma .Blood samples were kept frozen at -30"C until analysis. Volunteers were free to drink water at 2h and were given standard food of low fat and low protein at 4h after medication.Drug plasma concentration was examed by high-performance liquid chromatography (HPLC) assay. The chromatogram pillanthe pillar of YMC-Pack ODS-A.( 5/on,4.6 X 250 mm); Flowing phrase: methyl alcohol .' acetonitrile .' 3mM phosphate buffer liquid ( pH3.35, contain 0.2%18% SDS)=20 : 29 I 51(v/v) ; Speed: 1.3mL/min ; The wavelength:233nm; The amount of sample:2QuL.The sample processing: The heparinized blood samples were centrifuged at 3000rpm for 10 min , and 0.5mL plasma was extracted accurately, then 3mL acetonitrile was added into the plasma.Let it mix volutionly for 3 min, centrifuged at 3500rpm for 15 min. The 2.5mL organic up-layer was extracted, blowed dry with nitrogen around the 50℃ water, then dissolved with 20QuL liquor (methyl alcohol .' water=l .' 1) .At last, 20|mL sample was analysed.The plasma concentration-time data were calculated and analysed by 3p97 programwith a statistic analysis of ANOVA, two-one-side t-test and confidence zone of(l a -2a )%.The peak concentration (Cmax) and the peak time (Tmax) of metformin were determinedfrom the respective observed concentration-time data, the area under the curve (AUC) were calculated by the linear trapezoidal method. The data are expressed as mean valueslSEM throughout the paper.Result: Sensitivity of this method is 78.125/ag-L'1.The linear range is 78.125⁵000 //g-L"1. Difference inter-day and intra-day all meet with the examination of living creature sample.Movements of reference and test formulation of a single oral dose in the body matched one compartment.The pharmacokinetic paratmeters of reference and test formulation of a single oral dose were: Tmax: (2.28±0.65) h, (3.72±0.57) h; CW (1816+363) yUg-L1,(1188±259) jugh1; Ti/2ka: (0.49+0.26) h, (0.70±0.27) h; Tmke: (3.07±0.41) h, (5.40+1.00) h; MRT: (5.78+1.01) h, (11.32±2.02) h ; AUC'Q: (9884±1491) jig-h-L'1, (8637+2322)//g-h-L"1; AUCï¿¡: (10642+1556) ^g-h-L"1, (9987+2518) ^gh-L'1.Compared with standard reference formulation,the relative bioavailability of test formulation were (86.98±15.55) %(F0')and (93.74+16.71) %{F^).AUC'0,AUC; ,Cmax and Tmax between the two formulation were analysed with a statistic analysis of ANOVA and two one-side,the results show that AUC'O and AUCï¿¡ of the two formulution are biequivalent. Compared with standard reference formulation, Cmax of the test formulation reduced greatly, Tmax ,Ti/2ka and MRT of the test formulation extended obviously.The mean Cmin of reference and test formulation of multiple oral doses at the 4th,5th and 6th days were (139±41) , (137±37) , (131±41) //g-L^and (109±23) , (107+20) ,(103±14) jug-L'1, the result was no significance (P>0.05) .It indicated that the drug plasma concentration of metfoemin had averaged out steady-state until the 6th morning.Movements of reference and test formulation of multiple oral doses in the body matched one compartment.the pharmacokinetic paratmeters of reference and test formulation of multiple oral doses were: Cmin: (122±38) jugh'1, (111+27) ^g-L(13051290) /ig-L"1, (14401209) ^g-L1;^: (1.94+0.48) , (3.72+0.46) hj(0.49+0.23)h,(1.17+0.32)h;T1/2ke:(2.88+0.39)h,(5.99+1.70)h; ^t7CK:(5977 ^g-h-L"1, (10154H520 Vg-h-L"1; Cav: (498+91 Vg-L1, (423+63)^g-L"1;DF: (2.3810.45),(3.16i0.35 ) . A UCSS ,Cmax and Cav between the two formulation were were analysed with a statistic analysis of ANOVA and two one-side after the dosage of AUCSS were adjusted.The results show that AUCSS ,Cmax and Cav of the two formulution are biequivalent and the relative bioavailability of test formulation was (86.54±14.83) %. Compared with reference formulation, Tmax of the test formulation extended obviously, but DF of the test formulation increased significance Conclusion:1. The HPLC assay is shown to be sensitive,accurate and simple and the results are reliable.2. Compared with the general tablets, 0,? of the sustained-release tablets reduced greatly, Tmax ,Ti/2ka and MRT of the sustained-release tablets extended obviously. Test formulation has sustained-release characteristics.3. The two different forms of metformin hydrochlorlde are bioequivalent.