Vagina is a fibro muscular pipe that stretches 6-12 cm from cervix of the uterus. The top of vagina is composed of numerous folds, often called rugae. These folds keep distensability, support and provide an increased surface area of the vaginal wall. The genital wall is comprised of three layers: the epithelial layer, tunica adventia and the muscular layer. The epithelial layer creates the superficial level, which is about 200 m thick. The simple muscular fibres of the muscular coat are running along in both circular and longitudinal directions. This gives the vagina a fantastic elastic figure. Further, the connective tissues of the tunica adventia also increases the versatility of the vagina .
Fig1: Feminine reproductive system displaying vagina.
Blood Flow in Vagina
The vaginal wall membrane compromises of the dense network of arteries and expands from inside iliac artery, uterine, middle rectal and inside pudental arteries. The bloodstream enters systemic blood circulation via rich venous plexus which empties generally into internal iliac vein. The vagina lacks the direct release of mucus because it does not contain any goblet cells. But still it discharges a sizable amount of smooth. The substance has its origins from transudates through the epithelium, cervical mucus, exfoliating skin cells, and leukocytes, endometrial and tubal fluids. The vaginas nerve resource comes from two resources. The peripheral, which primarily supplies the low quarter of the vagina, makes it a highly hypersensitive area: the autonomic mostly supplies top three quarters. Autonomic fibers respond to stretch out and aren't very very sensitive to pain or temps. The upper vagina is an extremely insensitive area because of few sensory materials. That is why women almost never feel localized sensations or any irritation when using vaginal rings, and tend to be unacquainted with the existence of such items in vagina .
The physiological changes in vagina would impact the absorption of drugs and must be taken into consideration in the development of formulations. The width of epithelial level could have an effect on the permeability, where thinner epithelium triggers increased absorption. Amount of smooth is important because drugs must maintain solution before absorption. For bio adhesive systems, wetting of the tablet is vital for bio adhesion and increasing the property time. Viscosity may present as a barrier for medication absorption and constant secretion can bring about removal of the dose form .
Micro flora of Vagina
The express of a standard healthy vagina is basically a function of the bacterial community which can be an important first line of defence for your body. Lactobacillus kinds, mainly L. crispatus, L. gasseri, L. iners and L. jensenii are dominant constituents in most women's vagina worldwide and defends the vagina by e. g. producing several materials with antimicrobial activity and in doing so creating an inhospitable environment against pathogens. Despite several vaginal defence mechanisms the genital microbiota may also be disturbed and there's a change in the standard balance leading to symptoms like irregular or increased genital discharge, redness and itching. Irritability of vagina triggered by inflammation or infection is named vaginitis. Vaginitis is an extremely common disease for girls of reproductive age group around the globe but children and postmenopausal women may be influenced [4, 5].
The major and common factors behind vaginitis are bacterial vaginosis, trichomonas and Candida vaginitis. Genital candidiasis occurs about in 75% of most women once in their life time. Bacterial vaginosis is caused by a loss of lactobacilli concurrent with overgrowth of several fastidious bacterial kinds which normally could be there in low concentrations in the vagina. Candida vaginitis is a vaginal yeast infection where Candidiasis is commonly the reason for the disorder. Bacterial vaginosis and Candida vaginitis are extremely common microbe infections in women whose epidemiology and pathogenesis aren't clarified .
The symptoms of vaginitis differ with physiological conditions of women and bacterial vaginosis and Candida vaginitis are diagnosed based on each patient and it is determined by the reliability and knowledge of the clinician managing the individual. Women should not assume that a new infection is equivalent to prior and use e. g. over the counter treatment, but rather reconsider the identification and execute a thorough examination . Generally genital infection and its own symptoms greatly have an effect on women's health issues leading to serious health disorders it is therefore necessary to treat this condition efficiently .
The micro biota of normal healthy vagina comprises of certain bacterias which forms a critical defense layer against damaging pathogen. The normal micro biota of vagina consists of bacteria namely lactobacillus mainly in the lower genital tract. The bacterial vaginosis (BV) occurs most commonly among pregnant women and women who are sexually active. Bacterial Vaginosis is the condition wherein the standard lactobacillus types are replaced with harmful anaerobic microorganisms such as Gardnerella vaginalis and Bacteroides varieties. Incidence of Bacterial Vaginosis makes the feminine vagina highly susceptible to infection such HIV .
The most Symptoms and signs or symptoms can be commonly diagnosed by the vaginal discharge which is highly homogenous and appears to be white gray with a distressing scent (especially after sexual intercourse), though the gray discharge coats the walls of the vagina, it does not lead to any kind of irritation. Itching, pain and redness around the vagina vulva and vagina becomes more alkaline pH [10, 11].
Trichomoniasis is brought on by protozoan specifically Trichomonas vaginalis which brings about vaginitis in feminine. T. vaginalis is known as to be the most typical reason behind sexually transmitted contamination. In male Trichomonas are recognized in prostatic tissues in benign prostatic hyperplasia, prostatitis, and in men having prostate tumor. Trichomoniasis could also increase the transmission of human being immunodeficiency computer virus (HIV) by two- to three folds both in male and female [12, 13]. Trichomonas infects both male and female however only feminine shows symptoms male continue to be asymptomatic. Growth of Trichomonas on vaginal membrane could lead to vaginal release that smells fishy, and is apparently frothy and yellow colored. The severe nature of this condition is observed when blood starts to ooze out from vagina and post coital .
Vaginal candidiasis is brought on by Candida microorganisms and it is responsible for creating yeast vaginitis in woman. Of all species of candida, Candidiasis tends to cause major vaginal disorders. Candida glabrata is another species that could be a reason behind vaginal disorders. The condition condition can be cured either with topical ointment azoles or systemic azole (fluconazole or ketoconazole). The major problem in dealing with patients with Candida vaginitis is that organism develops resistance to topical and systemic azoles .
Diagnosis of Vaginitis
Generally patients affected by vaginitis can be diagnosed by Amsel's criterion  which really is a highly significant. Relating to Amsel's standards, the vaginal discharge is homogenous (color and amount varied from normal release). Addition of potassium hydroxide to genital secretion produces amine odor (WHIFF TEST). Microscopic study of vaginal fluid unveils clue cells. Certainly, there is a Significant change in pH of vagina greater than 4. 5 .
Vaginal Dosage Forms
The most commercially available vaginal delivery systems are usually targeting topical supervision. Pessaries (tablets or suppositories) are being among the most trusted systems. The basic principle of these action is the fact that they provide suffered release of the medication as they gradually dissolve or melt. However, this mechanism has a disadvantage and can cause low bioavailability if the formulation melted faster than planned, thereby providing shorter residence time in the vagina. Regular oral tablets intended for vaginal treatment comprises of disintegrants, binders and other excipients. Formulating very hydrophobic drugs as genital tablets may well not be an ideal methodology. However, it was advised that by adding penetration enhancing providers such as surfactants can significantly improve the drug absorption. Moreover, makes an attempt have been carried out to work with mucoadhesive polymers in genital tablet formulations in order to boost the residence time. Polyacrylic acid (PAA) is one of the bioadhesive polymers which have been implemented for vaginal formulations because of its high bioadhesive durability which allows a longer contact time with genital surface [16, 17].
Creams and gels are a different type of delivery systems frequently used. Creams are normally emulsions whereas gels are usually hydrophilic polymers that utilize covalent bonds to set-up cross-linked three-dimensional buildings .
Some formulations such as antifungal emulsion-based formulations seem to be to have better edge over many suppository formulations. A good example of gel product is the progesterone gel formulation that is dependant on a loosely cross-linked poly acrylic acid (Noveon AA1). This formulation was found to remain on vaginal tissues for 3-4 days, thus allowing dosing intervals of double a week. However, a disadvantage that may be from the use of creams and gels is that they might not exactly offer an exact dose, thus reducing the effectiveness of the medicine therapy. Ideally, genital drug delivery system that is suitable for local result should distribute uniformly throughout the website of action. However, the syndication and coverage of formulation within the genital cavity varies with the properties of the delivery system. It had been reported that disintegrating tablet show low coverage whereas solution, suspension system and emulsions display greater distribution profile .
In-situ Gelling System
Over days gone by 30 years greater attention has been centered on development of controlled and sustained drug delivery systems, which development and design of polymeric drug delivery systems has been centered a great deal and major research has been completed in this field. There is a major attention in the region of design and development of in-situ gelling systems in recent times; this is noticeable from the upsurge in quantity of studies being carried out in in-situ gel forming systems for various applications. That is widely due to the advantages that polymeric system can develop in-situ gel that can be implemented easily and regular dosing can be averted, also the improved upon patient compliance and comfort makes it a useful medicine delivery system.
In-situ gel creating medicine delivery is a type of mucoadhesive medication delivery system. In-situ gel forming medicine delivery systems are a revolution in topical medication delivery. These in-situ gelling systems are usually in the form of sol but forms gel at the required site anticipated to various factors such as pH, temps and other external stimuli .
Method of planning of in-situ gelling system
There are three broadly described mechanisms involved in creation of in-situ gel: Physiological stimuli (e. g. , temperature and pH), physical changes in biomaterials (e. g. , solvent exchange and bloating), and chemical type reactions (e. g. , enzymatic, chemical type and photo-initiated polymerization) .
IN-SITU GEL Development BASED ON PHYSIOLOGICAL STIMULI
Thermally activated system
Temperature sensitive in-situ gel is another school of polymeric delivery system and regarded as the most commonly studied class in medication delivery research. The usage of polymer solution having capacity to create gel with changes in temperature can be an attractive strategy in drug delivery system. Such system undergoes change at ambient at physiologic temperature such that professional medical manipulation is facilitated and no external way to obtain heat besides that of body is required for triggering gelation . A good system should be able to account for small differences in local temperatures, which might be came across in appendages at the top of skin area or in the mouth. You can find three main strategies used in formulation of thermo reactive sol gel polymeric system they are really classified as negatively thermo sensitive, positively thermo hypersensitive and thermally reversible gel .
pH triggered system
Sol to gel changeover predicated on change in physiological pH is another way in insitu gel formation. There are many polymers used to do this process. Cellulose acetate phthalate latex is a polymer that is trusted for sustained ophthalmic medication delivery because the latex remains as solution at pH of 4. 4 and undergoes gelation when the pH is increases to 7. 4 by the tear fluid but the lower pH of the arrangements can lead to discomfort in some patients .
The most powerful mucoadhesive property is exhibited by the commercial kinds of lightly cross-linked poly acrylic acid (Polycarbophil and Carbopol), Carbomer a cross-linked poly acrylic acid polymer (PAA) also undergoes phase transition as the pH is increased above its pKa around 5. 32. Various grades of Carbopol can be found commercially in the market. The property of tightness of gel creation depends upon crosslinking density. The mix linking density of Carbopol 934 is very low, while Carbopol 981 has intermediate combination linking capacity and highest being Carbopol 940 [25, 26].
IN-SITU GEL FORMATION PREDICATED ON PHYSICAL MECHANISM
In-situ gel development may also arise when material will absorbs drinking water from exterior environment and develop. Former mate: - Myverol 18-99 which is polar lipid that swells in water to form lyotropic liquid crystalline phase structures. It has some bioadhesive properties and can be degraded in-vivo by enzymatic action .
This method includes formation of gel by the diffusion of solvent from the top of polymer solution into exterior surface of structure either by precipitation or by solidification of polymer matrix. N-methyl Pyrrolidone (NMP) has been shown to be useful solvent for such system.
IN-SITU GEL FORMATION BASED ON Substance REACTION
Chemical reactions that results in-situ gelation may require precipitation of inorganic solids from supersaturated ionic solutions, enzymatic processes, and photo-initiated techniques.
Ionic combination linking
Polymers may experience phase transition because of the occurrence of cations and anions. The presence of mono and divalent cations such as Ca2+, Mg2+, K+ and Na+ hinders the formation of gel in case of anionic polymers such as gellan gum, In the same way, alginic acid goes through gelation in presence of Ca2+ and the relationship with guluronic acid block in alginate chains .
Natural enzymes have many advantages over substance approaches in in-situ gel development, For instance an enzymatic process does not require any monomers and initiators and it performs proficiently under normal physiological conditions. Intelligent stimuli-responsive delivery systems using in-situ gels that can release insulin have been investigated. Cationic pH-sensitive polymers filled with immobilized insulin and sugar oxidase can swell in response to blood sugar level launching the entrapped insulin in a pulsatile fashion. Adjusting the amount of enzyme also offers a convenient device for handling the rate of gel development, that allows easier administration of the mixtures prior to gelation .
Structure of Foam
Foams are thermodynamically and mechanically unpredictable systems; they are simply characterized by an extremely large interface which has a tendency to reduce itself. Foams are "elastic systems" and the entrapped gas stage can be compressed . Successful foam requires the development, progress and stabilization of the gas bubbles in the reacting medium. The bubbles in a foam can become more or less homogeneous and vary in proportions and shape which range from almost spherical to abnormal polyhedral, depending on how the foam was generated and the incorporated excipients. Other parameters include the characteristics and attentiveness of the foaming agent, viscosity of the liquid stage, temperature and pH of the machine: all these can affect the foam composition .
Preparation of Foams
Foams are made by supersaturating a liquid stage with gas. The sort of surfactant and bubble surface flexibility greatly affects the foam rheological properties . An average foaming process consists of dissolution of the foaming agent, bubble nucleation, bubble expansion, and stabilization. Methods to accomplish that include whipping, shaking, bubbling, pressurized aerosols and air spray foam pumps. Whipping, also called beating, is accomplished with different devices that agitate a liquid in order to create an user interface with a gas period. The quantity of air contained usually increases with a rise in the conquering depth. High viscosity fluids do not produce stable foams . During whipping, each air bubble undergoes severe mechanical stress and a more rapid coalescence happens during foam generation than in located foam.
Pressurized aerosols include both two-phase and three-phase aerosol foams. Inside the two-phase system, the liquefied propellant is dissolved in the solution of the foaming agent under great pressure. In the three-phase system, the propellant is dissolved in a lipid period, which is emulsified with a water period using an emulsifier. The foaming agent can also become an emulsifier . The third phase is the vapor period of the propellant above the emulsion. Both two and three-phase systems should be shaken prior to utilize. In these systems, the propellants with low boiling points evaporate rapidly resulting in immediate foam generation. Water is most commonly used as a solvent in foam aerosols, as well as ethanol and isopropanol . The most frequent propellants include n-butane, isobutene, n-propane or mixtures of these. Their concentration is typically in the range of 3-12%. Fluorinated hydrocarbon gases may be liquefied by cooling down below their boiling point or by compressing the gas at room temperature. Both of these features are being used in the filling up of aerosol pots with propellant .