Research On Estradiol Vaginal Thermosensitive Gels

Vaginal atrophy and urogenital atrophy are common conditions among postmenopausal women,which is commomly associated with decreases in estrogen levels caused by menopause?spontaneous or induced?and aging.Hormone replacement therapy?estrogentherapy,ET?is an approved treatment,drug deliverys include systemic administration ET?eg,oral,trandermal?and vaginally administered local ET.Vaginally administered local low-dose estrogen is an effective and well tolerated therapy recommanded by the North American Menopause Society?NAMS?.Estradiol is spontaneous estrogen secreted by mature ovarian follicle,which can improve and adjust normal development of secondary sex characteristics and sexual organs.Estradiol vaginally administered products approved are micronized estradiol hemihydrate vaginal tablet,estradiol cream and a sustained-release silastic ring that delivers estradiol.There are some limitations such as easy leak,inconvenient administration,poor patient compliance and so on.Vaginal thermosensitive gels were developed in order to improve biological adhesion,extend residence time in vagina,and use easilier.The cold dissolving method was used to prepare estradiol thermosensitive gel?E₂-VTG?based on Poloxamer 407/188 as thermosensitive materials and polycarbophil as bioadhensive materials.Tube inversion method was used to measure the gelling temperature.The apparent viscosity was determined by viscometer.The rheological properties of estradiol vaginal thermosensitive gel was determined by rotational rheometer.Effects of ethanol,polycarbophil and poloxamer were examined through single factor experiment.Central composite design/response surface method was useded to optimize the amounts of poloxamer 407 and poloxamer 188 with gelling temperature as dependent variable.The optimized formulation was confirmed as 18%P407,2.96%P188,5%glycerin,5%ethanol and 0.2%PCP,the observed gelling temperature was 33.4?.The preparation had good temperature sensitivity.It is Newtonian fluid with low viscosity at room temperature and became pseudoplastic fluid with high viscosity at the body temperature,Which made it suitable for vaginally administration.A quality control method of estradiol was established.A quantitative HPLC method was used to determine the estradiol contents in E₂-VTG.This method had good specificity,high precision and good stability.Estradiol standard curve is linear over the range of 0.2²0.0?g·ml^-1.The labeled amount of 3 batches E₂-VTG were 97.85%,101.07%and 97.85%?n=3?,pH values were 4.64,4.64,4.66,gelling temperatures were 33.0?,33.4?and 33.4?.The dynamic membrane dialysis method and HPLC-fluorometric method were used to determine in vitro release characteristics of the estradiol vaginal thermosensitive gel.Results confirmd that the specificity,sensificity,precisiony and stability met requirements.In the concentration range of 0.02⁵?g·ml^-1,the linear relationship was good.Estradiol could be released slowly from the thermosensitive gel and the release profile was fit with Higuchi equation,and it indicated that estradiol release was through diffusion mechanism.With appearance,pH,T_GELEL and estradiol content as indexs,preliminarystability test preparation was evaluated by influencing factor experiment and long-term experiments.The results show that E₂-VTG was sensitive to high temperature and illumination.Long-term experiments results showed that the stability of E₂-VTG preserved in collapsible tube and aluminum-plastic package was good.CRi Maestro was applied to evaluated the retention of E₂-VTG in ICR mice with IR820 as fluorescent markers.NIR imaging and fluorescence quantitative analysis showed that duration of drug resided in vagina could be prolonged till24h by E₂-VTG.It was shown in the vaginal mucosa irritation test on female SD rats that E₂-VTG had no apparent irritation,compared with the saline group.To sum up,E₂-VTG descibied in this report has good temperature sensitivity,quality stability and slow-release effect.It has long residence time in vivo and has good biocompatibility.E₂-VTG would provide a better choice for the menopausal women to improve reproductive tract and urinary tract atrophy symptoms.