Chitosan-Based Gels for the Drug Delivery System - Chitosan Based Hydrogels: Functions and Applications - page 295

and oral cavity cancers. A major difficulty of achieving success in delivering drugs to these
sites is the dilution and rapid elimination of topically applied medicines as a result of the
flushing action of saliva that is abundant in the oral cavity. Therefore, long-term adhesion
of the DDS as well as prolonging the retention of the loaded drug is required in order to
achieve this local drug delivery.
Because of its excellent bioadhesive property, chitosan is widely used as carrier material
for oral drug delivery. Initial studies showed that chitosan provides an extended retention
time on the oral mucosa and has the ability to inhibit the adhesion of Candida albicans cells
to human buccal cells, preventing the development of mycosis [153]. TPP-cross-linked chi-
tosan gel and film were prepared for local delivery of chlorhexidine gluconate, an antifun-
gal agent, to the oral cavity. An in vitro study indicated that a prolonged release of
chlorhexidine gluconate of up to 4 h was achieved with the film. Also, an increase in anti-
fungal activity of the drug was observed with the chitosan gel [153]. Chitosan is, moreover,
an excellent candidate for the development of DDSs aiming to treat oral mucositis, which
is a frequent severe complication of cancer chemotherapy and increases the risk of infec-
tion trigger by Candida . The hitosan gel prepared as above was also used to deliver a pro-
phylactic agent for oral mucositis (nystatin) to the oral cavity [154]. This chitosan gel
formulation significantly reduced the severity and incidence of oral mucositis, reduced
weight loss and increased survival, and provided significant healing.
Chitosan microspheres were utilized for the controlled release of triclosan in oral-care
formulations [155]. Triclosan was encapsulated into chitosan microspheres using a dou-
ble-emulsion solvent evaporation technique, and the release profiles were established
under simulated “in use” conditions. The controlled release of the drug over extended
time periods was obtained, and the kinetics study showed that the release was a
diffusion-controlled one.
In addition, buccal bilayered tablets composed of a drug-containing mucoadhesive layer
of chitosan with polycarbophil and a backing layer of ethylcellulose were obtained by
direct compression [156]. The double-layered structure provided unidirectional drug
delivery toward the mucosa, and avoided a loss of drug resulting from wash-out with
saliva flow. A striking feature of this device was the utilization of an in situ cross-linking
reaction between cationic chitosan and anionic polycarbophil, which progressed upon
penetration of the aqueous medium into the tablet. As a result of the cross-linking effect,
the tablets showed controlled swelling and prolonged drug release, and an adequate
adhesiveness could be obtained.
6.7.2 Nasal Drug Delivery
The nasal route for drug delivery has received a great deal of attention as a convenient and
reliable method for the systemic administration of drugs, especially for those that are dif-
ficult to deliver via routes other than injection. The nasal route could be important for
drugs that are used in crisis treatments, such as for pain and for centrally acting drugs
where the putative pathway from nose to brain might provide a faster and more specific
therapeutic effect [157].
In the case of patients affected by schizophrenia or other psychotic disorders, nasal
delivery administration can provide more acceptable forms of medication and simultane-
ously enhance drugs' pharmacological profiles. Recently, Barbara Luppi et al. [158] devel-
oped freeze-dried chitosan/pectin nasal inserts for antipsychotic drug delivery. Chitosan/
pectin PECs were prepared at pH 5.0 with different polycation/polyanion molar ratios and
lyophilized in small inserts in the presence of chlorpromazine hydrochloride. Upon water