Study On Scopolamine Hydrobromide Microemulsion Transdermal Delivery System

IntroductionMotion sickness(MS) is one of the most important problems in the field of space medicine.The response,in terms of gastrointestinal and other peripheral changes,is characteristic of a general autonomic nervous disorder during MS, including headache,dizziness,nausea,vomiting,etc.Nowadys,anticholine drugs,antihistamine drugs,calcium ion antagon and the traditional chinese medicines are used to treat and prevent MS.But,Most of them are oral administrations,which are inconvenient,slow to take effect and have several side effects.These side effects may lower physical fitness,reduce the efficiency of military operations and influence military combat capabilities seriously.Therefore,developing a new praeparatum which is effective,convenient and have fewer side effects is significant for soliders.As the first patch,since scopolamine hydrobromide transdermal delivery is developed in 1981 by Alza,because of their merits over other administrations, tansdermal praeparatum have received increased attention.It has many advantages over oral administrations:it avoids the first-pass effect of liver and gastrointestinal tract,administration is easier more convenient for the patient,it also increase patient compliance,and there is the possibility of immediate withdrawal of the treatment if necessary.But most medicin con not meet the demands of treatments owing to the barrier function of stratum corneum,so we must choose suitable vehicles,e.g.β-cyclodextrin inclusion compound,microballoons,lipisomes,microemulsions. Especially microemuision has been extensively studied by many pharmaceutical scientists during the last decades.As a novel drug vehicle,microemulsion is applied to pharmacy in 1990s.A microemulsion is defined as a system of surfactant,cosurfactant,oil and water,which is a transparent,single optically isotropic and thermodynamic stable liquid solution, with a droplet diameter usually within the range of 10～100nm.The increased absorption of drugs in topical applications is attributed to enhancement of penetration through the skin by the carrier.Therefore,a transdermal therapeutic system for scopolamine hydrobromide was formulated using microemulsion(O/W).Methods1.To investigate the physico-chemical properties of blank microemulsion1.1 The pseudo-ternary phase diagrams were constructed by the dilution method at room temperature.Cremophor EL-35,Cremophor RH-40 as the surfactant,ethanol,1,2-isopropyl alcohol,n-butyl alcohol as the cosurfactant,aceti cether,isopropyl myristate(IPM),oleic acid and Labrafil M 1944 CS as the oil phase.These elements were mixed on a magnetic stirrer.Based on the pseudo-ternary phase diagrams,we investigated the effects of microemulsion components and Km(the ratio of surfactant to cosurfactant weight)on the formation and the areas of the microemulison.1.2 Appropriate quantities of surfactant,cosurfactant,oil and water were constructed in the microemulsion region of the pseudo-ternary phase diagrams.The mean diameter and apparent viscosity were measured.Meanwhile,we studied the influence of microemulsion elements on the diameters and apparent viscosities and chose a good microemulsion system,which has larger microemulsion area and suitable diameter viscosity.2.To investigate the physico-chemical properties of scopolamine hydrobromide microemulsionWe prepared some scopolamine hydrobromide O/W microemulsions with the variety of Km,different contents of water and oil in the microemulsion system we have choosen in the first chapter and determined the values of droplet diameter and viscosity.We investigated the effects of different Km,contents of water,oil,scopolamine hydrobromide on droplet diameter and viscosity.3.In vitro skin permeation study of scopolamine hydrobromide microemulsion3.1 HPLC(high-performance liquid chromatography)analysis of scopolamine hydrobromideThe amount of scopolamine hydrobromide in receptor phase was quantitated with the HPLC method.The HPLC column used was a C₁₈ column(Diamonsil,450×4.6mm, 5μm particle size).The mobile phase consisted of 0.005mol/L potassium dihydrogen phosphate solution(pH3.2 adjusted by phosphoric acid),methanol and acetonitrile (V/V/V,75:15:10),at the flow rate and injection volume of 1.0ml/min and 20μL, respectively.The detection wavelength was 215nm.All operations were carried out at room temperature.The calibration curve of scopolamine hydrobromide was constructed.The precision,reproduction and percent recovery of the method were analyzed.3.2 In vitro skin permeation studyThe extent and rate of skin permeation of scopolamine hydrobromide from several different microemulsions used in the last chapter were determined using Franz diffusion cells fitted with excised rat skins.Skins were obtained from male Sprague-Dawley(SD)rats weighing 180～200g.After hair was removed carefully with a clipper,the subcutaneous fat and other extraneous tissues were trimmed.The excised skins were stored at -20℃and used within one week after the skin harvest. The receptor phase was 0.9%sodium chloride and 4ml was injected to the receptor phase.The effective diffusion area was 0.75cm².After 4ml of each microemulsion was applied on the skin surface,0.5mL of receptor medium were withdrawn at 0.5,1,1.5,2,3,4,6,8 and 12h.Concentrations of scopolamine hydrobromide in each sample was quanfitated through the calibration curve of scopolamine hydrobromide using HPLC,and the cumulative amount of scopolamine hydrobromide over a 12 period(Q)and the skin permeation rate(Jss)were calculated.The results combinated with the indices of droplet size and apparent viscosity helped us choose the optimum microemulsion composition.The effects of different Km,contents of oil and water on the skin permeation rate of scopolamine hydrobromide were also investigated.All skin permeation experiments were repeated three times. 2.To evaluate the effects of scopolamine hydrobromide microemulsion transdermal delivery system on MSIn this study,we used a score based on symptoms seen frequently in rats during MS,such as piloerection,tremble,urinal and fecal incontinence,as an index for the severity of MS in rodents to evaluate the effects of anti-MS drugs.32 male SD rats,weighing 180～200g,were randomly divided into four groups with 8 rats each according to the MS index after rotation,i.e.,control group(groupâ… ), oral administration group(groupâ…¡),positive control group(groupâ…¢) and microemulsion transdermal delivery group(groupâ…£).After a week,rats were given stimulus for three days,one hour per day.Corresponding medicines were given only at the first day.And record the MS index and compared the effects between groups.Results1.To investigate the physico-chemical properties of blank microemulsionThe experimental results indicated that HLB value and the number of EO base of surfactant,hydrocarbon length of co-surfactant,the ratio of the surfactant to co-surfactant(Km)and the structure of oil are important in the microemulsion formation system.The microemulsiion system with the largest area has the smallest diameter,and the viscosity is relevant to the character itself.Through drawing the pseudo-ternary phase diagrams and determining the mean diameter and viscosity,we chose the microemulsion system:surfactant was Cremophor RH-40;co-surfactant was ethanol;oil phase was Labrafil M 1944 CS.2.To investigate the phsico-chemical properties of scopolamine hydrobromide microemulsionsThe results indicated that diameter and viscosity changed with the Km,the contents of water and oil.When Km decreased and the contents of oil,water increased, the diameter would increase.When Km decreased and the content of oil increased,the viscosity would decrease.The content of drug has no effect on the diameter and viscosity of microemulsion loaded drugs.3.In vitro skin permeation study of scopolamine hydrobromide microemulsion3.1 The retention time for scopolamine hydrobromide was observed to be 6.295min, and the elements of microemulsion did not have any effect on the determination of scopolamine hydrobromide.The calibration curve of scopolamine hydrobromide was A=15866C + 28150(r=0.9997)using an HPLC method,A was the peak area and C was the concentration of scopolamine hydrobromide standard solution.The standard curve was linear in the range of 10～120μg/ml.The RSD of precision experiment of three different concentration was 1.2%,0.6%,0.4%respectively;the reproducibility RSD was 0.21%;the average recovery rate was 99.93±0.24%,RSD was 0.24%. These results confirmed the accuracy of this method as described above.3.2 The results indicated that the permeation rate was influenced by the Km value and the contents of oil,water.As the S/CoS(Km)was decreased,the skin permeation rate of scopolamine hydrobromide was increased.As the contents of water and Labrafil were increased,the skin permeation was also increased.The highest percutaneous scopolamine hydrobromide absorption was obtained with microemulsion with suitable diameter and viscosity containing 30%Cremophor RH-40+ethanol,10%Labrafil M 1944 CS,1.5%scopolamine hydrobromide and 58.5%water,Km=2:1.4.To evaluate the effects of scopolamine hydrobromide microemulsion transdermai delivery system on MSAccording to the MS index after medicines were given,it was found that the index of microemuision transdermal delivery was statistically lower than those of control group and oral administration group(P<0.01),and the index of the microemulsion transdermal delivery group was a little bit lower than the positive control group with no statistic significance(P>0.05).But the MS indices at the second and third day after medicines were given of the microemulsion transdermal delivery group were statistically lower than the positive control group(P<0.05).These results indicated that the effects of scopolamine hydrobromide microemulsion transdermal delivery last longer compared to the traditional scopolamine hydrobromide transdermal delivery..