Oral mucosal drugdelivery system is widely applicable as novel site for administration of drug and controlled release action by preventing first pass metabolism and enzymatic degradation due to GI microbial flora. The oral cavity represents a challenging area to develop an effective drugdelivery modelling. This arises due to the various inherent functions of the oral cavity (eating, swallowing, speaking, chewing), as well as the presence of the fluid that is involved in all these activities, saliva. This fluid is continually secreted into and then removed from the mouth. Oral Mucosa drugdelivery system provides local and systemic action. The delivery of drugs through the buccal mucosa has attracted much research interest over the past two decades and numerous approaches, both conventional and complex, have been developed in an attempt to deliver a variety of pharmaceutical compounds via the buccal route. To outline the progress in the in vitro and in vivo modeling of Mucosal drugdelivery and provide a critical review of currently used methods. The purpose of this review is to represent the modeling of oral cavity with Mucoadhesivedrugdeliverysystems and clarify the potential alternative to conventional therapy.
The mechanism of adhesion of certain macro- molecules to the surface of a mucous tissue is not well understood yet. The mucoadhesive must spread over the substrate to initiate close contact and increase surface contact, promoting the diffusion of its chains within the mucus. Attraction and repulsion forces arise and, for a mucoadhesive to be successful, the attraction forces must dominate. Each step can be facilitated by the nature of the dosage form and how it is administered. For example, a partially hydrated polymer can be adsorbed by the substrate because of the attraction by the surface water Thus, the mechanism of mucoadhesion is generally divided in two steps, the contact stage and the consolida- tion stage (Figure 1). The first stage is characterized by the contact between the mucoadhesive and the mucous membrane, with spreading and swelling of the formulation, initiating its deep contact with the mucus layer. In some cases, such as for ocular or vaginal formulations, the delivery system is mechanically attached over the membrane. In other cases, the deposition is promoted by the aerodynamics of the organ to which the system is administered, such as for the nasal route. On the other hand, in the gastrointestinal tract direct formulation attachment over the mucous membrane is not feasible. Peristaltic motions can contribute to this contact, but there is little evidence in the literature showing appropriate adhesion. Additionally, an undesirable adhesion in the esophagus can occur. In these cases, mucoadhesion can be explained by peristalsis, the motion of organic fluids in the organ cavity, or by Brownian motion. If the particle approaches the mucous surface, it will come into contact with repulsive forces and attractive forces. Therefore, the particle must overcome this repulsive barrier.
The current article focuses on the principles of mucoadhesivedrugdeliverysystems based on adhesion to biological surfaces that are covered by mucus. Bioadhesion can be defined as the process by which a natural or a synthetic polymer can adhere to a biological substrate. When the biological substrate is a mucosal layer then the phenomena is known as mucoadhesion. Drug actions can be improved by developing new drugdeliverysystems, such as the mucoadhesive system. These systems remain in close contact with the absorption tissue, the mucous membrane, releasing the drug at the action site leading to a bioavailability increase and both local and systemic effect. Mucoadhesion is defined as the ability of material adheres to biological tissue for an extended period of time. Mucoadhesive dosage forms extend from the simple oral mucosal delivery to the nasal, vaginal, ocular and rectal drugdeliverysystems. The success and degree of mucoadhesion bonding is influenced by various polymer-based properties. Evaluation of such mucoadhesive formulations has transgressed from first-generation charged hydrophilic polymer net-works to more specific second generation systems based on lectin, Thiol and various other adhesive functional groups. Various theories are consider like Electronic theory, Wetting theory, Absorption theory, Fracture theory in mucoadhesion. Various In vitro and In vivo tests carried out for determination of mucoadhesion.
The purpose of my study was to formulate and evaluate the mucoadhesive tablet of metronidazole for the treatment and management of Amoebaisis. Metronidazoleis a nitro- imidazole antibiotic medication used particularly for anaerobicbacteria and protozoa. Metronidazole is an anti-bacterial against anaerobic organisms, amoebicide and anti-protozoa. It is the drug of choice for first episodes of mild-to-moderate Clostridium difficile infection. Mucoadhesion is a field of current interest in the design of drugdeliverysystems. Mucoadhesivedrugdelivery system prolong the residence time of the dosage form at the site of application or absorption and facilitate an intimate contact of the dosage form with the underline absorption surface and thus contribute to improved and or better therapeutic performance of the drug. In recent years many such mucoadhesivedrugdeliverysystems have been developed for oral, buccal, nasal, rectal and vaginal routes for both systemic and local effects. The mucoadhesive tablet was prepared by wet granulation. The mucoadhesive tablets were coated with Eudragit S-100 by dip coating method. The prepared mucoadhesive tablets were evaluated by hardness, friability, weight variation, wash off test, in -vitro drug release.
Mucoadhesion can be defined as a state in which two components, of which one is of biological origin are held together for extended periods of time by the help of interfacial forces mucoadhesion is the attachment of the drug along with a suitable carrier to the mucous membrane. Mucoadhesion is a complex phenomenon which involves wetting, adsorption and interpenetration of polymer chains the mucoadhesive polymers can be categorized into two broad categories, materials which undergo matrix formation or hydrogel formation by either a water swellable material or a water soluble material. Mucoadhesivedrugdeliverysystems is one of the most important novel drugdeliverysystems with its various advantages and it has a lot of potential in formulating dosage forms for various chronic diseases. The current review provides a good insight on mucoadhesive polymers, the phenomenon of mucoadhesion and the factors which have the ability to affect the mucoadhesive properties of a polymer.
Mucoadhesivedrugdeliverysystems are the systems which utilize the property of mucoadhesion of certain polymers, which become adhesive on hydration and hence can be used for targeting a drug to a particular region of the body for extended period of time.Bioadhesion is an integral phenomenon in which two materials, at least one of which is biological are held together by means of interfacial forces. In the case of polymer attached to mucin layer of a mucosal tissue, the term mucoadhesion is used. The mucosal layer lines a number of regions of the body including the nose, gastrointestinal tract, urogenital tract, the airways, the ear and eye. 
Mucoadhesion can be defined as a state in which two components, of which one is of biological origin, are held together for extended periods of time by the help of interfacial forces. Mucoadhesivedrugdeliverysystems is one of the most important novel drugdeliverysystems with its various advantages and it has a lot of potential in formulating dosage forms for various diseases and has controlled release of drugdelivery system. Drug actions can be improved by developing new drugdeliverysystems, such as the mucoadhesivedrugdelivery system. These systems remain in close contact with the absorption tissue, the mucous membrane and release the drug at the action site leading to increase the bioavailability of drug and both local and systemic effects. So, carrier technology offers a novel approach for drugdelivery by coupling the drug to a carrier particle such as microsphere, nanoparticle, liposome, etc. which modulates the release and absorption characteristics of the drug. Hence, the discussion focus on physiology of mucus, mucoadhesive dosage forms, and novel methods for mucoadhesive gel such as microemulsion, liposomal, microspheres based gel and their evaluation techniques.
Polymers Used For MucoadhesiveDrugDeliveryMucoadhesivedrugdeliverysystems are being discovered for the localization of the active component to a specific site. In the designing of such dosage form polymers played a very important role that’s increase the residence time of the active component at the target site. Mucoadhesive polymersare water-soluble and water insoluble polymers,which are swellable network, joined by cross linking agents. These polymers possess optimal polarity to make sure that they permit sufficient wetting by the mucus and optimal fluidity that permits the mutual adsorption and interpenetration of polymer and mucus to take place.
different hydrophilicity, surface charge and terminal groups. The in vivo mucoadhesive capacity in form of gastric retention time of KTN/KOS composite nanopar- ticles could be controlled by changing the ratios of KTN to KOS, as well as for controlled drug release due to the pH-sensitive feature of KTN. Besides, the drug bioavail- ability also could be regulated by controlling the gastric retention time and drug release rate of nanoparticles. Furthermore, the mechanisms of mucoadhesion of kerat- ins (KTN and KOS) were firstly investigated in present study. The binding between KTN and PGM is dominated by electrostatic attractions and hydrogen bonding at pH 4.5, and disulfide bond also plays a key role in the inter- action at pH 7.4. Unlike KTN, the main mechanism of KOS and PGM interactions is hydrogen bonding at pH 4.5, and hydrogen bonding and hydrophobic interactions s are the main mechanisms of interaction between KOS and PGM at pH 7.4. This study offers an efficient strategy to control the gastric mucoadhesion and drug release of keratin based nano drugdeliverysystems, and the revela- tion of mucoadhesive mechanisms of keratins in different pH conditions are helpful for the design and develop- ment of mucoadhesivedrugdeliverysystems.
This review explains some aspects of mucoadhesion related to the nasal drugdelivery system. On the first count, the theories of the adhesion of mucoadhesive polymers to the mucosa epithelium are described. Secondly, the characteristics and application of several widely used mucoadhesive polymers in nasal drugdelivery are presented. The nasal mucosa provides a potentially good route for systemic drugdelivery. One of the most important features of the nasal route is that it avoids first-pass hepatic metabolism, thereby reducing metabolism. The application of mucoadhesive polymers in nasal drugdeliverysystems has gained to promote dosage form residence time in the nasal cavity as well as improving intimacy of contact with absorptive membranes of the biological system. The aspiration of any drugdelivery system is to endow with a therapeutic amount of drug to the proper site in the body to achieve promptly & then uphold the desired drug concentration. That is why the drugdelivery system should deliver drug at a state dictated by the needs of the body over a specified period of treatment. This idealized objective points to the two aspects most important to drugdelivery, namely, spatial placement relates to targeting a drug to a specific organ or tissue while temporal delivery refers to the control of rate of drugdelivery to the target tissue. Over the last few decades, the relevance of mucoadhesive polymers in nasal drugdeliverysystems has gained significance among pharmaceutical scientists as a means of promoting dosage form residence time in the nasal cavity as well as for improving intimacy of contact with absorptive membranes of the biological system. In addition, the improved paracellular absorption subsequent the swelling of the mucoadhesive polymers on the nasal membranes provides an important way for the absorption of the macromolecules through the nasal cavity.
Bioadhesive Polymers 1, 4, 5, 14 : Mucoadhesive polymers are the important component in the development of buccal deliverysystems. The first step in the development of buccoadhesive dosage forms is the selection and characterization of appropriate bioadhesive polymers in the formulation. Bioadhesive polymers play a major role in buccoadhesive drugdeliverysystems of drugs. Bioadhesive polymers have properties to get adhered to the biological membrane and hence capable of prolonging the contact time of the drug with a body tissue. The use of bioadhesive polymers can significantly improve the performance of many drugs. This improvement ranges from better treatment of local pathologies to improved bioavailability and controlled release to enhance patient compliance. Mucoadhesive polymers used in the oral cavity were shown in Table 2.
1. Gastrointestinal DrugDelivery System: Mucoadhesive polymers may offer increased intimacy with the lining of the GI tract and hence bioavailability. Furthermore, ‘‘absorption windows” within the GI tract such as those making up the gastro-associated lymphatic tissue may be targeted allowing for the absorption of larger poorly soluble therapeutic agents 73 . Therefore, a primary objective of using mucoadhesivesystems orally would be achieved by obtaining a substantial increase in residence time of the drug for local drug effect and to permit once-daily dosing. A number of mucoadhesive- based dosage forms, including sustained-release tablets, semisolid forms, powders, and micro- and/or nanoparticles in the GI tract, have been widely studied. Nonetheless, successful systems that will be retained in the GI tract of humans for a desirable time have not yet been developed 74, 66 . Matharu and Sanghavi used carbopol 934P and poly (acrylic acid) cross-linked with 0.001% ethylene glycol to prepare mucoadhesive tablets for captopril 75 . Second-generation vehicles are now receiving increased attention. A thiolated chitosan tablet has recently been reported for the oral delivery of insulin. Further advances in this field have included the attachment of second- generation mucoadhesives to the surface of microspheres 76 .
the use of polymers in the aqueous phase was intended to promote sustained delivery of the plant extract because it is retained in the polymer network and exhibits a slower libera- tion and controlled manner. In systems that have polymeric network compositions, the drug may be homogenously dis- persed in the polymer matrix or adsorbed on their surface or within a reservoir. This phenomenon involves the liberation of the same physical and chemical processes, such as water penetration into the matrix, diffusion of the drug through the pores of the matrix, polymer degradation or a combination of the last two mechanisms. 13,34
L - 42 patient compliance; their compact nature, stability and low cost; and the ease of packaging, transports, and manufactures (Banker GS and Anderson NR, 1987). Administration of oral conventional dosage forms in multiple daily dosing produces wide ranging fluctuations in drug concentration in blood stream and tissues with consequent undesirable toxicity and poor performance associated with non- adherence to dosage regimen (Vyas SP and Khar RK, 2002), and also had short-term limitations due to their inability to restrain and localise the delivery system in GI tract (Khan GM. 2001); however their performance can be improved with C/E-R or targeted-delivery products (Chang RK and Robinson JR, 1982) that excellently control drug levels in plasma; minimises dosing frequency; improves patient convenience/compliance, safety margin and efficacy; reduces intensity of local or systemic side effects, health care costs, and expenses and complications involved in marketing new drug entities; and many more to list (Belgamwar V et al. 2009). The real hurdle in the development of oral C/E-R drugdeliverysystems was to control release profile over extended period of time by special technological construction (Lee TW and Robinson JR, 2000); and to improve short GI retention/residence time or GI transit time, associated with the rapid GI transit phenomenon of the GI tract, that diminishes the extent of absorption of drug associated with diminished exposure time of the delivery system at the absorption site (Helliwell M. 1993) which in turn limits the duration of action to approximately 8-12 hours. The GI retention time of solid dosage forms may be improved by the mechanisms of mucoadhesion (Arya RKK et al. 2010), flotation (Hoffman A and Stepensky D, 1999), sedimentation (Singh BN and Kim KH, 2000), or by expansion (Vasir JK et al. 2003). Due to convenience and safety oral C/E-R mucoadhesive system was widely exploited (Costa MS and Margarida Cardoso MM, 2006).
There are several pharmaceutical forms that have been developed, such as matrix tablets, patches, ointments, nano- particles, and ﬁ lms. 2,14,55 – 72 The electrospun nano ﬁ ber scaf- fold has become one of the most promising among them due to the concurrent delivery of different drugs, elevated load- ing capacity, user-friendly operation, and low-cost technique. 73 – 79 There are various possible designs for deliv- ery systems that can be formulated depending on the kind of drug to be administered, such as a fast dissolving polymer for a bidirectional drug release system, two-layer drug deliv- ery system, one water resistant polymer and one fast dissol- ving polymer for a unidirectional drug release, and ﬁ nally a three-layer mucoadhesive with a bioadhesive polymer core, a fast dissolving drug release layer, and a water- resistant layer (Figure 7). 6,54
In recent years scientific and technological advancements have been made in the research and development of oral drugdelivery system. Oral sustained drugdelivery system is complicated by limited gastric residence times (GRTs). In order to understand various physiological difficulties to achieve gastric retention, we have summarized important factors controlling gastric retention. To overcome these limitations, various approaches have been proposed to increase gastric residence of drugdeliverysystems in the upper part of the gastrointestinal tract includes floating drug dosage systems (FDDS), swelling or expanding systems , mucoadhesivesystems , magnetic systems, modified-shape systems, high density system and other delayed gastric emptying devices.
Buccal mucosa is the preferred site for both systemic and local drug action. The mucosa has a rich blood supply and it relatively permeable. The buccal region of the oral cavity is an attractive target for administration of the drug of choice, particularly in overcoming deficiencies associated with the latter mode of administration. Problems such as first-pass metabolism and drug degradation in the gastrointestinal environment can be circumvented by administering the drug via the buccal route. Moreover, rapid onset of action can be achieved relative to the oral route and the formulation can be removed if therapy is required to be discontinued. It is also possible to administer drugs to patients who unconscious and less co-operative. In buccal drugdeliverysystems mucoadhesion is the key element so various mucoadhesive polymers have been utilized in different dosages form. Mucoadhesion may be defined as the process where polymers attach to biological substrate or a synthetic or natural macromolecule, to mucus or an epithelial surface. When the biological substrate is attached to a mucosal layer then this phenomenon is known as mucoadhesion. The substrate possessing bioadhesive polymer can help in drugdelivery for a prolonged period of time at a specific delivery site. Both natural and synthetic polymers are used for the preparation of mucoadhesive buccal patches. However, this review article provides a current status of buccal drugdelivery of patches (films) along with formulation development and characterization of mucoadhesive buccal patches.
in gel formulation prepared by using Carbopol 981P was higher than that in solution and lyophilized powder formulation based on the same polymer 31 . However, because of its high viscosity the gel is difficult to administer and an accurate drug dose cannot be measured. To overcome this problem the nasal in situ gel has been developed, i.e., thermosensitive or pH-sensitive gel 65, 85, 86 . The in situ gel is fluid-like before nasal administration, which increases accuracy of drug dosing and convenient for administration. After the formulation contact with the mucosa, the special temperature or pH value of the mucus promotes the transition from liquid to gel, which prolongs drug residence times and improves drug bioavailability. Zaki et al. prepared an in situ gel of metoclopramide hydrochloride with solution-gel transition temperature of about 25–32°C by using poloxamer 407 as thermogelling moderator 65 . Results of rat experiment showed that this in situ gel prolonged the mucociliary transport time from 10 to 52 minutes (compared with sodium chloride) and maintained nasal mucosal integrity after 14 days of application 65 . The bioavailability study in rabbits revealed that the absolute bioavailability of metoclopramide hydrochloride was significantly increased from 51.7% in case of the oral drug solution to 69.1% by nasal in situ gel 65 . Ghosh et al. designed intranasal in situ gel systems of sumatriptan with a gelation temperature below 34°C using thermoreversible polymer Pluronic F127 and mucoadhesive polymer Carbopol 934P120.
Chitosan embedded liposomes incorporating clotrimazole were designed and the results showed it as a promising formulation for vaginal topical therapy. EFdA (a proprietary topical microbicide) films were formulated to treat different sexually transmitted diseases 23 . Fast dissolving films were made with PVA, HPMC E5 and propylene glycol and the produced films were applied intravaginally. The results indicated that they can be used for the effective prevention of HIV infection. Olive oil based emulsion hydrogels have been produced for the treatment of sexually contagious disorders. In this case, sorbitan mono palmitate was added as a structuring agent. The resultant films were biocompatible and showed non- Newtonian flow and can be used to prevent sexually transmitted infections. Curcumin liposomes were prepared for the inhibition of vaginal infections. In this case mucoadhesive polymers like chitosan and Carbopol have been used to prepare the liposomes. Then different physiological properties including mucoadhesion strength were checked and it was revealed that the formulated mucoadhesive liposomes were useful as novel delivery system for vaginal infections. Mucoadhesive caplets of 3′-azido-3′- deoxythimidine and polystyrene sulfonate (anti-HIV drug) were developed and characterized. Different mucoadhesive polymers like ethyl cellulose, polyacrylic acid have been used to prepare the caplet. The results proved that mucoadhesive caplets of the above drug can be used as potential drugdeliverysystems for treatment of HIV infected patients 44 . Bio adhesive mini tablets were formulated and evaluated for the vaginal delivery of hexyl amino levulinate hydrochloride. Different nonionic cellulose ethers and MCC were investigated as matrix forming agents
In the development of drugdeliverysystems, mucoadhesion of the device is a key element. The term ‘mucoadhesive’ is commonly used for materials that bind to the mucin layer of a biological membrane. Mucoadhesive polymers have been utilised in many different dosage forms in efforts to achieve systemic delivery of drugs through the different mucosa. These dosage forms include tablets, patches, tapes, films, semisolids and powders. To serve as mucoadhesive polymers, the polymers should possess some general physiochemical features such as predominantly anionic hydrophilicity with numerous hydrogen bond-forming groups, suitable surface property for wetting mucus/mucosal tissue surfaces and sufficient flexibility to penetrate the mucus network.