| Andrographolide is one of active components from Chinese herbal medicine Andrographis paniculate (Burm) Nees. which has the disadvantage of low water-soluble. Recently, it was reported that Andrographolide exhibited an extensive specturm of pharmacological activities, such as antipyretic, anti-inflammtory, anti-virus, antihypotensive, hepatic protecetant and cholagogic. It is applied widely in clinic for treating pneumonia, common cold, upper respiratory tract infection, cardiovascular diseases, bacillary dysentery and so on. However,Andrographolide is administrated only in the form of injects and tablets in clinic so far. Due to affecting by liver first pass effect which has the low bioavailbility when oral administration. Injection administration not only causes the pain, but there are many adverse actions. The clinieal use of Andrographolide is limited.Microemulsion is a new carrier of drugs with small diameter , good stability, and easy to prepare, its formation was spontaneous and no energy was required, especially increasing the solubility of drugs, it provide a novel delivery of administration for low water-soluble drugs. Microemulsion has been used in the study of many transdermal preparations such as naproxen, ketoprofen and penciclovir. According to the characteristics of microemulsion, In this study, Andrographolide microemulsion was prepared for transdermal delivery system, the drugs release sustained, maintaining the constant and active plasma concentration,it is conventinert to administration, and improving the compliance of patient.We study the properties of Andrographolide before determing the formulation. Dtermining the dissolubility of Andrographolide in different solvent, the results show that the dissolubility of Andrographolide in water is 0.68 mg·ml-1, it is difficult to effect. According to the area of microemulsion basing on the pseudo-tertiary phase diagram, the potimum formmlution were designed in initially, which is EO/Tween -80/PEG-600/H2O.Preparing the Andrographolide by titrating, meantime evaluate the quality of Andrographolide microemulsion by appearance, size distribution, morphology, stability, drug-loading and entrapment rate. The microemulsion presented as small spherieal drops under SEM, demine the size by laser particle size analyzer, with the average diameter of 34.41 nm. Preliminary stalility show that storaging two month under 4℃and 25℃, there are no obvious changes in appearance and the contents. After centrifuging, Andrographolide microemulsion didn't stratify, demulsificate and precipitate, Andrographolide microemulsion delivery system is stable, correspond to medication requirement. Andrographolide was adopted the methods of HPLC to determining the contents, which is 4.6334 mg·mL-1. The dissolubility of Andrographolide in microemulision is 6.81 times compared with water. The entrapment rate is 90.81%, it shows the loss of drugs during preparing process is less. The recovery and accuracy of determining method all accord with the relevant regulation,the method is simple, senstive, accurate and reliable for quantitative analysis of Andrographolide.According the special advantage of microemulsion, the Andrographolide microemulsion transdermal delivery were studied compared with the Andrographolide and cyclodextrin inclusion of Andrographolide withβ-cyclodextrin using the node skin in vitro.The results show that the Andrographolide microemulsion extending the active time of drugs, improving the transdermal rate of drugs, maintaining the constant and active plasma concentration,the drugs release sustained.In this study, Andrographolide microemulsion was prepared for transdermal delivery system, which has changed the original route of administration, enriching clinic dosage form, this study provides the consistence foundtion for the safe and efficient delivery system. With great theoretical value and practical signicicance,it will promote the development of Chinese medicinal new delivery.
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