| Transdermal drug delivery system (TDDS) is drug-loaded adhesivepatches which, when applied to the skin, deliver the therapeutic agent, ata controlled rate, through the skin to the systemic circulation and to thetarget organs. The performance requirements of pressure sensitiveadhesives (PSA) are demanding as they must be able toadhere well to varying skin types (both dry and moist), beremovable without leaving adhesive residue or causing skindamage, and should not irritate the skin. In accordance with the fact oftransdermal drug delivery system currently, in this paper, preparedhot-melt pressure-sensitive adhesives based on ESIS for TDDS. The mainwork was carried out as follow:The epoxidation of SIS with formic acid and hydrogen peroxide was studied. The microscopic structure of epoxidised SIS (ESIS) wascharacterized by Fourier Transform Infrared(FT-IR),1H nucleal magneticresonance (1HNMR), Gel Permeation Chromatography (GPC) andDynamic Thermomechanical Analysis (DMA). The aging properties andreaction kinetics were also discussed. The experimental results showedthat: the epoxidation reaetion mainly occurred in l,4-isoprene units, andthe molecular weight, the moisture permeability of ESIS and Tg of PIsegment were increased gradually with the increase of the epoxy degree.At the early stage of aging process, the aging reaction occurs mainly onthe epoxy groups, whereas at the later stage, the aging reaction occursmainly on the carbon–carbon double bonds. The epoxy reaction pocesswas the second order reaction, and the reaction activation energy was22.7kJ/mol, however the reaction of process between carbon-carbondouble bond and hydrogen peroxide was the first order reaction.A kind of hot-melt pressure-sensitive adhesive(HMPSA) was developedwith the synthesized ESIS employed as matric resin, and epoxy soybeanoil as the plasticizer and high-hydrogenation rosin as the tackifier. Theadhesive performance and rheology behaviors of HMPSA were studied.The results indicated that the storage modulus was proportion to thetack(initial adhesion) under the frequency(0.01Hz) condition, the storagemodulus was inverserly proportion to the holding power，and those withgreat values of viscosity, storage modulus give long holding power under the frequency(100Hz) condition. The peel strengths increased firstly andthen decreased with the increase of peel rate in the test. The tack andpeelstrngth of the PSA patch also first increased and then decreased withthe increase of the content of azoe and dimethyl sulfoxide employed astransdermal enhancers. The drug loading is the significant target of PSApatch, which can lower down the adhesion properties.The transdermal permeation property of the drug in the PSA wasresearched by using aconitine and ephedrine hydrochloride that were themain effective ingridents in Shangshiqutong cataplasm. The vitro testresults showed that the hydrophilicity of ESIS-PSA matrix could improvegreatly the drug-permeation amount in contrast to the traditional rubber.The relationship between cumulative penetration content (Q)and squareroot of release time (t1/2) satisfied with Higuchi equations, which wereQ=6.22t1/2-7.41and Q=6.49t1/2-8.98in48hours, for ESIS and traditionalsystem respectively. After48hours, Q and t1/2equations wereQ=44.2t0.6+1.67and Q=25.7t0.6+3.54respectively, which could beclassified to the non-Fick diffusion process.The quality standards of Shangshiqutong cataplasm based on ESISHMPSA matrix were studied. This method can effectively control thequality of Shangshiqutong cataplasm. |
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