Pharmacokinetics Of Oxymatrine In Rats Based On Microdialysis

Oxymatrine exists widely in sophoraflavescens, sophoraalopecuroide and sophoratonkinensis as the major active ingredients, which have a clear effect of anti-hepatic fibrosis. The clinical use of oxymatrine injection and tablet have showed satisfactory curative effects. However, injection always shows the deficiencies such as the obviously short half life,inconvenient drug administration, and the proneness to local muscle soreness. Recently, the research interest is focused on the transdermal drug delivery system of oxymatrine.In this study, microdialysis sampling was used to study the pharmacokinetics of oxymatrine gel in three parts of rats including jugular vein, liver and subcutaneous tissue, which were compared with that of plasma which collected through the caudal vein. Meanwhile, the pharmacokinetics of transdermal administration also was compared with that of intravenous administration. The major contents of the thesis were divided into the following sections: 1. the method to determine of oxymatrine; 2. the recovery of microdialysis probes; 3. multi-site pharmacokinetics after intravenous administration in rat; 4. oxymatrine gel prescription screening; 5. pharmacokinetics after transdermal administration in rat.The determination of oxymatrine and its metabolite matrine was in a linear mode, The samples were analyzed on a Diamonsil C18 column（4.6 mm × 150 mm, 5 μm） with a mobile phase consisting of acetonitrile-0.1% phosphoric acid（adjusted p H to 7.6-7.7 with triethylamine） in a linear gradient mode. The flow rate was 1.0 ml·min-1 and the detection wavelength was 220 nm. The column temperature was 35 ℃. The injection volume was 20 μL.The assay showed good linear correlation of oxymatrine and matrine over the range of 0.20 ⁵0.30 μg·m L-1, 0.20 50.10 μg·m L-1 in microdialysate and 3.17 406.00 μg m L-1,0.32 40.90μg·m L-1 in plasma, respectively. The intra- and inter-day precision of oxymatrine and matrine in microdialysate over these ranges were not more than 7.7 %, and the average accuracy was in the range of 95.9 101.3 % and 96.3 107.8 %, respectively. The intra- and inter-day precision of oxymatrine and matrine in plasma over these ranges were not more than 10.7 %, and theaverage accuracy was in the range of 97.3 102.2 % and 97.2 105.0 %, respectively. The method is accurate, simple and specific for detection of oxymatrine and matrine simultaneously in rat microdialysate and plasma.The result of probe recovery of oxymatrine showed that recovery was uncorrelated with drug concentration（5.0, 20.0, 40.0 μg·m L-1） and inversely proportional to perfusion velocity（1.0,2.0, 3.0 μL·min-1）. At the same flow velocity, in vitro, the positive dialysis recoveries were similar to the retrodialysis recoveries. While the in vitro recoveries were greater than those in vivo. Under the same conditions, the recovery of concentric cannula probe was greater than that of linear probe（P< 0.01）. For the pharmacokinetics of oxymatrine, a more accurate result was able to be achieved by means of the in-vitro positive dialysis in more convenient way, the positive dialysis recoveries of concentric cannula probe and linear probe in vitro were（61.71±1.62） % ^91.94±0.92 % and（38.13±2.73） % ^81.14±2.68 %, respectively, therefore,their recoveries could be applied to the pharmacokinetic study as drug’s probe recovery.The pharmacokinetics after intravenous administrations showed that oxymatrine could be absorbed and spread more rapidly in rat and the half life was short. The in vivo pharmacokinetics of oxymatrine and matrine in every part of rat were accorded with 2-compartment open model,which AUC and Cmax basically showed a trend as follows: plasma > blood microdialysis >liver microdialysis. The reason was that drug permeated into blood firstly and then entered liver for metabolism, and the drug concentration from blood microdialysis obtained was free drug concentration while the plasma concentration was total drug concentration which include free and protein-binding. After intravenous administration, at low（40 mg·kg-1）, medium（60 mg·kg-1）and high dosage（80 mg·kg-1）, the AUC and Cmax of oxymatrine and its metabolitematrine in every part of rat showed a rising trend. The AUC ratio of oxymatrine in every part was not significantly different（P> 0.05）. And so was its metabolite matrine.It showed good linear correlation between oxymatrine 7.93 and 1015.00 μg·m L-1 in saline solution, the standard curve is Y = 8942.323 X + 2782.106（r = 1.000, n = 5）. The optimal formulation of gel was composed with 14 % oxymatrin, 8 % azone, 5 % propanediol, 5 %peppermint oil and 7 % sodium carboxymethycellulose. The accumulative permeation amount of the gel was（18.094±1.253） mg·cm-2 in 12 h, and the permeation rate was（1.418±0.122）mg·cm-2·h-1. The pharmacokinetic resultsafter transdermal administration, showed that the AUC of oxymatrine had a trend as follows: subcutaneous microdialysis > plasma > blood microdialysis> liver microdialysis. The AUC and Cmax were increased with drug delivery areaexcept skin metabolite matrine. After transdermal administration at the low（2 cm2, 0.5 g） and high dosage groups（4 cm2, 1.0 g）, the AUC of oxymatrine’s blood microdialysis was significantly higher than that of liver microdialysis, while the AUCs of liver and blood microdialysis of metabolite matrine were similar. The AUC of low dosage transdermal administration was similar to that of 80 mg·kg-1 intravenous administrations. As demonstrated by skin microdialysis, oxymatrine can be metabolized into matrine partly in skin after transdermal absorption.Microdialysis technology can be applied well in revealing oxymatrin distribution in three parts of rats including jugular vein, liver and subcutaneous tissue, which can further reveal the distribution and metabolism of oxymatrin in vital organs, therefore provide theoretical basis for new drug research and development.