Simvastatin Alcohol Plasmid Preparation Of Gel And Its In Vitro Release Studies

Objective:To prepare simvastatin ethosome gel and administer through skin to avoid first pass effect of liver, increase the bioavailability of simvastatin and reduce the burden of liver.Methods:(1) HPLC method was used to determine the content of simvastatin. Agilent1200liquid chromatograph (G1314B UV detector, G1314A pump, Rev.B.04.02[98] chromatography workstation),0.025mol/L PBS (pH4.5)-acetonitrile (65:35) as mobile phase. C18column (250mm×4.60mm,5μm), the detection wavelength is238nm.(2) Simvastatin ethosome was prepared by injection method. Dialysis method was used for the determination of encapsulation efficiency of simvastatin. Investigated the approximate level range of factors by single-factor tests. L9(34) orthogonal test was used to optimize the prescription of simvastatin ethosome. The optimal prescription was obtained by range analysis of encapsulation efficiency of simvastatin. Evaluated the quality of simvastatin ethosomes prepared by the optimal prescription.(3) Prepared gels using carbomer matrix and evaluated their physical and chemical properties. The ZTY smart transdermal diffusion instrument was used to evaluate the transdermal penetration in vitro of gels. Preparation Ⅰ (simvastatin gel) as a contrast, studied the transdermal penetration behavior in vitro of preparation Ⅱ (simvastatin gel containing1%mentha-camphor), preparations Ⅲ (simvastatin gel containing3%mentha-camphor), and preparation Ⅳ (simvastatin ethosome gel). Evaluated the four gel formulations’transdermal penetration behavior, including the cumulative permeation amount of simvastatin in perunit area and content of simvastatin retained in skin.(4) Determined the skin irritation of blank gel and simvastatin ethosomes gel. Acute skin irritation test:observed erythema and edema condition of rabbit skin and scoring in1,24,48, and72h after smear gels. Skin irritation test of multiple administration in14days:smeared gels, observed erythema and edema condition of rabbit skin and scoring every day. Cut sections of rabbits’skin after irritation tests for pathological examination.Results:(1) Peaks of simvastatin and lovastatin were separated well. The concentration of simvastatin ranged from0.5μg/ml to20μg/ml had a good linear relation, R2=1; RSD of precision tests at1.0μg·ml-1,5.0μg·ml-1, and10μg·ml-1were0.69%,0.14%, and0.11%respectively. Simvastatin solutions were stable in4days, RSD=1.75%; in three levels (1.0μg·ml-1,5.0μg·ml-1,10μg·ml-1), the average recovery rate was97.37%～101.23%and93.73%～96.00%in the empty ethosome dialysis medium and transdermal receiving media respectively.(2) The optimal prescription of simvastatin ethosome was that ethosome containing soybean lecithin0.15g, ethanol4.6ml, cholesterol2mg, polyoxyethylene hydrogenated castor oil50mg, pH7.0of PBS5.4ml in10ml ethosome suspension. The particles were nearly round observed by transmission electron microscopy, the average diameter was52.4±3.91nm, encapsulation efficiency measured by dialysis method was74.40±3.6%. Simvastatin ethosome remained stable after centrifugal, high temperature, high humidity and high bright light accelerating tests, there was no significant change of appearance of simvastatin ethosome after12months at4℃and room temperature.(3) The gels had good characterics and stability. In vitro permeability test, compared with preparation Ⅰ, cumulative permeation amount in unit area of preparation Ⅱ, increased significantly at8h (P<0.05), preparation Ⅲ and preparation Ⅳ increased significantly since4h (P<0.05); cumulative permeation amount in unit area of preparation Ⅳ was significant higher than preparation Ⅱ and preparation Ⅲ since4h (P<0.05); The cumulative permeation amount in unit area of the four preparations regression to time coincided linear equations in2-8h, and coincided the higuchi equations in8～24h. The simvastatin amount retaining in skin of preparation Ⅱ, Ⅲ and Ⅳ was significant higher than preparation Ⅰ (P<0.05).(4) The simvastatin ethosomes gel and blank gel had no acute irritations to the rabbit skin, the multiple skin irritation was also mild; erythema appeared once in process of multiple skin irritation tests, but the skin had reversible changes over time, and tended to be normal after the tests. Results of pathology slices showed that the stratum corneum of the skin were normal, hyperkeratosis or parakeratosis situation didin’t appeare, there was no thicking, liquefaction and other lesions of the basal layer; indicated that the structure of dermis layer was complete and had no obvious lesions; The dermis layer had no edema and inflammation; subcutaneous subsidiary organ such as hair follicles, hair bundles had no significant lesions.Conclusions:HPLC was used for the determination of simvastatin, the degree of dissociation, specificity, linearity, precision, stability, and recovery attained the standard for determination, HPLC was suitable for determination of simvastatin. Ethosomes prepared by the optimized formulation had good characteristic, particle size, encapsulation efficiency and stability. Cumulative penetration in unit area of simvastatin ethosome gel was significant higher than simvastatin gel, gels with1%and3%mentha-camphor (P<0.05), simvastatin retaining in the skin of simvastatin ethosome gel was significant higher than simvastain gel (P<0.05), indicated that ethosome had the quality of transdermal penetration promoting of simvastatin. Skin irritation test showed that the simvastatin ethosome gel has no irritations on the rabbit skin.