| Aconitium plants have been used as important ingredients in Chinese medical preparations for their excellent effects against rheumatic diseases, such as joint pain and the pain of sciatic nerve. Modern pharmacological researches demonstrate that they have a good application in cardiac, analgesic, anti-tumor and immune foundation. At present, alkali Aconitine transdermal drug delivery agents was unique used for treating Nerve root type of cervical spondylopaphy and alleviating joint pains and ischiodynia, which have strong analgesic effect and less tolerance for contimuous medication. However, those medicine including highly toxic alkaloids such as aconitine, and clinical poisoning have accurred frequently, which were winding the rational and safety application of this kind traditional Chinese medicine for a long time. Aconitine is the main active ingredient, also a major component of toxicity. Thus, a comprehensive understanding of aconitine in vivo pharmacokinetics and set up a safety evaluation system for rational use of aconitine is very important. This paper using aconitine as study subject, studied the pharmacokinetics of aconitine in rat plasma and local skin after oral and transdermal drug delivery. QT interval, QRS interval and heart rate are monitored as pharmacodynamic targets. Through the pharmacokinetic and pharmacodynamic study model analysis, the pharmacokinetics and safety evaluation of two ways of drug delivery were compared. The main research has the following aspects:1. Established a method used for the determination of aconitine in rat plasma and microdialysis by HPLC-MS/MS. The results show that the method of HPLC-MS/MS was sensitive and reliable, the linearity correlation was good and the sample handling was quickly and simply, which was suitable for determination of aconitine in plasma and microdialysis sample.2. Study of the relative recovery of aconitine microdialysis system and its influential factor. The perfusate was selected both from stability and recovery aspects and pH 5.77 isotonic phosphate buffer solution was chosed as the best condition for microdialysis's perfusate. Comparable in vitro recoveries were obtained by different established approaches including recovery estimation by gain and loss method. Recovery by loss was used to study the in vivo recovery of aconitine from rat subcutaneous tissue. The in vitro experiment results showed that in vitro recovery of aconitine from the microdialysis probe determined by gain and by loss was comparable at each flow rate studies; recovery decreased as the flow rate increased; aconitine recovery was independent of concentration over the concentration range investigated. In the present study, in vivo recovery of aconitine was 34.48±3.05% and was stable over the 6-h study period. In vitro and in vivo performance of the microdialysis technique was established for the study of aconitine. And it would prove to be a useful and reliable tool to study the pharmacokinetics of aconitine.3. Pharmacokinetic studies of aconitine after oral and transdermal administration. Following a single oral administration of aconitine to rats (0.3mg/kg) and topical transdermal administration to rats (25mg/kg), the blood samples were collected at different time after dosing. The microdialysate samples were collected by skin microdialysis method. The concentration of aconitine in plasma and microdialysate were determined by HPLC-MS/MS method described as above. Pharmacokinetics parameter calculations were carried out using non-compartmental analysis method. It was shown by the plasma concentration-time data that the concentration of aconitine in rat plasma was reduced quickly after oral administration and the difference of the rats was evident. The tmax was 0.25h; Cmax was 215.86±79.29ng/ml; the estimated elimination half-life was 6.47±4.00h; the AUC0-∞of oral dose was 202.07±99.51 ng/ml*h. the concentration of aconitine in plasma was stability after transdermal administration. The tmax was 13h; Cmax was 20.92±3.15ng/ml; the estimated elimination half-life was 4.23±2.26h; the AUC0-∞ of oral dose was 161.02±54.22 ng/ml*h. the Cmax in skin after oral administration was 1.51±0.53ng/ml, and which was 2723.8±848.8ng/ml after transdermal administration.4. Metabolism of aconitine in rat plasma and skin homogenate sample by high-performance liquid chromatography with tandem mass spectrometric method. Samples were prepared by protein precipitation, and then were analyzed using multiple reaction monitoring. Two metabolites were identified as benzolyaconine and 16-O-demethylaconitine in plasma. But there wasn't any metabolism was found in skin homogenate samples.5. Pharmacokinetic and pharmacodynamic model analysis for oral and transdermal administration of aconitine in SD rats. The pharmacokinetic and pharmacodynamic profiles of aconitine for oral and transdermal administration were analyzed by combined pharmacokinetic and pharmacodynamic model in SD rats. The plasma concentration-time profiles of the two administration ways can be described by a one-compartment open model, and the relationship between effect and effect compartment concentration of aconitine can be represented by the sigmoid Emax model. After oral administration, the pharmacodynamic parameters Emax,EC50,H,Keo,K1e of aconitine were 4.19±4.26,233.98±54.25 ng/ml,4.59±0.35,1.42±1.60 h-1,1.08±0.12 h-1. Followed transdermal administration, the pharmacodynamic parameters Emax,EC50,H,Keo,K1e of aconitine were2.48±0.04,78.18±35.22 ng/ml,0.77±0.85,0.30±0.51 h-1,0.27±0.03 h-1. Differences of pharmacokinetic and pharmacodynamic parameters between oral and transdermal administration of aconitine were found.Our studies developed a sensitive and accurate HPLC-MS/MS method and microdialysis method for the determination of aconitine in local and system pharmacokinetics. A safety evaluation system was developed using an integrated PK/PD model for characterizing the pharmacological effects and plasma concentration of aconitine after oral and transdermal administration.
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