Novel concept for a mucosal adhesive ointment

Development and Evaluation of a Novel Oral Mucoadhesive Ointment Containing Pomegranate Peel Extract as an Adjuvant for Oral Hygiene of Dogs

Herbal therapies are used worldwide to treat a variety of health conditions, including dental conditions in veterinary medicine. In this context, the use of medicinal plant-based formulations as potential therapeutics and preventatives in veterinary dentistry is worth highlighting. The objective of the present study was to develop a mucoadhesive ointment formulation, named orabase, that contained pomegranate extract for use in the oral cavity of dogs, with the aim of improving their oral hygiene. The hydroalcoholic extracts of pomegranate peels was incorporated into the orabase in 3 different concentrations. The formulations were subjected to in vitro microbiological testing by a modified disc-diffusion method to study the susceptibility of microorganisms collected from the oral cavities of the dogs. The samples were taken from the buccal mucosa of dogs having the same management and diet. The most effective formulation was submitted to physicochemical tests to evaluate the functionality of the product, namely pH, swelling index, spreadability, and mechanical properties (hardness, cohesiveness, and adhesiveness). The formulation containing 25.0% w/w of the extract was considered most suitable for the intended use as it showed antiseptic activity and demonstrated a swelling index of approximately 35% in the first 20 minutes of the test, high spreadability, and suitable mechanical properties. The results suggest that the product obtained from pomegranate peel extract is a viable option for use to improve oral hygiene, helping to reduce the bacterial component of dental plaque in dogs.

The effect of triamcinolone in liposomes on oral wound healing in rats

The purpose of this study was to determine whether oral mucosa wounds in rats can be successfully treated with triamcinolone acetonide (TA), incorporated into liposomes. A round wound was inflicted on the oral mucosa of female Wistar rats divided into four groups of 12 animals. This wound was treated topically from day 1 with liposomes without the inclusion of TA and liposomes containing 0.01% or 0.05% TA. The wounds of the animals in the control group were not treated. Polymethyl metacrylate was used as an ointment for mixing in liposomes. The size of the wound was measured until day 6. The area of inflammatory infiltrate under the wound was evaluated by histopathology, the expression of iNOS (inducible nitric oxide synthase) enzyme under the wound was evaluated by immunohistochemistry until day 6. On the sixth day of experiment, the size of the wound and the area of the inflammatory infiltrate was the smallest in the group receiving empty liposomes (EL). Expression of iNOS was the most reduced in the group receiving EL. We conclude that oral mucosa wounds can be successfully treated with liposomes, although the incorporated drug triamcinolone would not be the appropriate drug for treating wounds of traumatic origin.

Vesiculo-erosive Oral Mucosal Disease—Management with Topical Corticosteroids: (1) Fundamental Principles and Specific Agents Available

Vesiculo-erosive diseases of the oral mucosa pose a major challenge in oral medicine, because they are chronic, painful, and interfere with the daily activities and quality of life of the patients, including disturbing eating, drinking, talking, and personal relationships. Many are autoimmune diseases, and corticosteroid therapy is currently central to their treatment. These diseases present with inflammation and alterations to epithelial integrity, through cell and/or humoral immunity-mediated attack on epithelial-connective tissue targets. Until recently, despite their serious adverse effects, it was necessary to prescribe systemic corticosteroids to control severe erosive oral diseases. Now, however, many of these diseases can be controlled by high-potency topical corticosteroids, which have proved to be highly efficacious and to cause fewer adverse effects compared with systemic corticosteroids. Nevertheless, although topical corticosteroids are still the most widely used drugs in the practice of oral medicine, the scientific body of evidence for their use in the oral cavity is virtually non-existent, and therefore many of the protocols followed are, of necessity, drawn from experience of their use in a dermatological setting. This review aims to set out the key aspects of the use of topical corticosteroids in oral medicine. The issues covered include the indications and basic rules for their use, the types of corticosteroids, the drug selection, and the specific formulations.

The effect of chlorhexidine dentifrice or gel versus chlorhexidine mouthwash on plaque, gingivitis, bleeding and tooth discoloration: a systematic review

OBJECTIVE

To systematically review and evaluate the available scientific evidence on the effectiveness of chlorhexidine dentifrice or gel (CHX DF/gel) compared to chlorhexidine mouthwash (CHX MW) on plaque, bleeding, gingival inflammation and tooth discoloration scores.

MATERIAL AND METHODS

PubMed-MEDLINE, Cochrane-CENTRAL and EMBASE databases were searched to identify appropriate studies.

RESULTS

Independent screening of the 2256 unique titles and abstracts resulted in five publications that met the eligibility criteria. Considerable heterogeneity was found between the studies. Three of the five studies showed a positive effect on plaque scores in favour of the CHX MW. With respect to gingival index and bleeding scores, no significant differences were found. Chlorhexidine mouthwash, however, showed a significantly more tooth discoloration than the CHX DF/gel. A meta-analysis of the effect on 'de novo' plaque formation of CHX DF/gel versus CHX MW resulted in a difference in means of 0.27 [95% CI: 0.14; 0.39] (P < 0.0001).

CONCLUSION

Chlorhexidine gel can be successfully formulated and will inhibit plaque growth to some degree, but not to the same extent, as a CHX MW. When CHX DF/gel is used in a non-brushing model, it is significantly less effective in plaque inhibition compared to CHX MW. Based on one study when CHX gel was applied with a finger after brushing, it is significantly more effective on plaque scores and the gingival index. The only brushing study also with a long follow-up showed that there is no significant difference between CHX DF and CHX MW. However, as a corollary, significantly more tooth discoloration was observed with the CHX MW. Altogether, the data show that when daily oral hygiene cannot be performed, CHX MW is the first product of choice.

Mucoadhesive buccal films of glibenclamide: Development and evaluation

Background:

Glibenclamide is an oral hypoglycemic drug completely metabolized in the liver, the principal metabolite being very weakly active, buccal delivery may be useful for the treatment of diabetes more effectively. The aim of the present study was to design formulations and systematically evaluate in vitro and ex vivo performances of buccal films of glibenclamide so that the required therapeutic plasma concentrations can possibly be achieved more rapidly using the different grades of hydroxypropyl methyl cellulose (HPMC) as the base matrix.

Materials and Methods:

Mucoadhesive buccal films of glibenclamide were prepared by solvent casting technique using different grades of HPMC with different ratios. Prepared films were evaluated for weight, thickness, surface pH, swelling index (SI), folding endurance, drug content uniformity, in vitro release, and ex vivo permeation studies.

Results:

The film thickness and weight were in the range of 0.213–0.4892mm and 22.25–39.83 mg, respectively. The films exhibited controlled release over more than 6 h. HPMC, HPMCK100, and HPMC3000 films exhibited satisfactory swelling. Surface pH of buccal films was found to be 6.4–6.8. SI observed to be highest for GF12 (275.3 ± 12.17) and lowest for GF1 (173.5 ± 5.65). The films exhibited controlled release over more than 6 h. HPMC exhibited satisfactory swelling, an optimum residence time, and promising drug release. The Higuchi plots were found to be linear with correlation coefficient values of 0.8933, 0.9138, and 0.9947 for GF4, GF8, and GF9, respectively.

Conclusions:

Among all the formulations, GF9 shows good controlled release results correlated with ex vivo permeation studies.

Rheological investigation and its correlation with permeability coefficient of drug loaded carbopol gel: influence of absorption enhancers

CONTEXT

The present study was planned to investigate the effect of absorption enhancers on the microstructure of Losartan potassium gel and hence its influence on the diffusion of Losartan potassium across nasal mucosa.

METHOD

Losartan potassium loaded carbopol gel (1% w/v) with and without absorption enhancers was prepared. Polyethylene glycol (PEG) 4000 and ethanol were used as absorption enhancers. Microstructural elucidation of prepared gels was done using shear rheology. Ex vivo drug release studies were performed on the prepared gels.

RESULTS

It was observed that the absorption enhancers PEG 4000 and ethanol altered the gel microstructure. The prepared gels were viscoelastic in nature suggesting their suitability for topical application. Permeability coefficient of Losartan potassium loaded into gels was found to be inversely proportional to the storage modulus. Thus increase in storage modulus lead to slow drug diffusion.

CONCLUSION

The current study emphasizes on the fact that selection of polymeric carrier for nasal drug delivery and/or absorption enhancer strongly influence the microstructure of the gel and hence the pharmaceutical performance of the formulation.

Formulation and evaluation of buccoadhesive quetiapine fumarate tablets

The aim of present study was to develop and evaluate buccoadhesive Quetiapine Fumarate (QF) tablets, which is extensively metabolised by liver. Buccoadhesive tablets of QF were prepared using HPMC K4M, HPMC K15M and combination of carbopol and HPC as mucoadhesive polymers by direct compression method. Sodium deoxycholate was added to formulation to improve the permeation of drug. The formulations were tested for bioadhesion strength, ex vivo residence time, swelling time and in vitro dissolution studies and ex vivo permeation studies. Optimized formulation (F3) showed 92% in vitro release in 8 h and 67% permeation of drug through porcine buccal mucosa and followed fickian release mechanism with zero order kinetics. FTIR studies of optimized formulation showed no evidence of interaction between the drug and polymers. In vivo mucoadhesive behaviour of optimized formulation was performed and subjective parameters were evaluated.

Development and characterization of mucoadhesive patches of salbutamol sulfate for unidirectional buccal drug delivery

Buccal patches of salbutamol sulfate were prepared using five different water soluble polymers in various proportions and combinations using PEG-400/PG as plasticizers. A 32 full factorial design was used to design the experiments for each polymer combination. Patches were laminated on one side with a water impermeable backing layer for unidirectional drug release. The thickness of medicated patches ranged between 0.2 and 0.4 mm and showed an increase in mass whenever PEG-400 was used as plasticizer. The surface pH of all patches approached neutral. Eight formulations which had shown high folding endurance (> 300) were selected for evaluation. Patches prepared with PEG-400 showed a high swelling index. The residence time of the tested patches ranged between 105 and 130 min. Formulations A10, A32, B10 and B32 fitted the Higuchi model best, whereas formulations A19 and B19 showed super case II transport drug release. Stability studies indicated that there was no change in the chemical and physical characteristics during the test period of 6 months.

Enhanced mucoadhesive capacity of novel co-polymers for oral protein delivery

Graft co-polymer networks have shown promise as devices for oral delivery of proteins. By increasing adhesion of these networks at the delivery site of the upper small intestine by utilizing small covalent chemical linkages caused by the addition of an aldehyde functional group we can make them more viable. These aldehydes bind covalently by way of a condensation reaction with the amines of the amino acids found in the glycoprotein network of the mucus layer of the small intestine to form imines. To investigate the effectiveness of this linkage the co-polymers are prepared in three different percentages of poly(ethylene glycol) (PEG) and aldehyde-modified PEG, and characterized through swelling, release and adhesion testing. The percentages of aldehyde-modified PEG used are 0.06, 0.6 and 3.3%. The swelling results indicate that the formulations with the aldehyde-modified PEG maintained the same pH sensitivity and transition around a pH of 5.8 as those formulations without the aldehyde moiety. Release results indicate that the release of insulin of the most promising 3.3% aldehyde formulation was successful with a release of about 80% after 3 h, which compares favorably with the similar release of the controls done in previous work. Adhesion testing was carried out through the use of a mechanical testing apparatus. Data have been gathered and plotted to give a detachment force (N) versus displacement (m) curve, of which the work of adhesion (μJ) was found by taking the area underneath the curve. Adhesion results indicate an increase to the already present adhesion of the co-polymers due to increased percentages of the aldehyde-modified PEG tethers where the 3.3% formulation showed an increase of 10-30 μJ over both control formulations.

Formulation and evaluation of bioadhesive buccal drug delivery of tizanidine hydrochloride tablets

The study aim was concerned with formulation and evaluation of bioadhesive buccal drug delivery of tizanidine hydrochloride tablets, which is extensively metabolized by liver. The tablets were prepared by direct compression using bioadhesive polymers such as hydroxylpropyl methylcellulose K4M, sodium carboxymethyl cellulose alone, and a combination of these two polymers. In order to improve the permeation of drug, different permeation enhancers like beta-cyclodextrin (beta-CD), hydroxylpropyl beta-cyclodextrin (HP-beta-CD), and sodium deoxycholate (SDC) were added to the formulations. The beta-CD and HP-beta-CD were taken in 1:1 molar ratio to drug in formulations. Bioadhesion strength, ex vivo residence time, swelling, and in vitro dissolution studies and ex vivo permeation studies were performed. In vitro release of optimized bioadhesive buccal tablet was found to be non-Fickian. SDC was taken in 1%, 2%, and 3% w/w of the total tablet weight. Stability studies in natural saliva indicated that optimized formulation has good stability in human saliva. In vivo mucoadhesive behavior of optimized formulation was performed in five healthy male human volunteers and subjective parameters were evaluated.

Engineering design and molecular dynamics of mucoadhesive drug delivery systems as targeting agents

The goal of this critical review is to provide a critical analysis of the chain dynamics responsible for the action of micro- and nanoparticles of mucoadhesive biomaterials. The objective of using bioadhesive controlled drug delivery devices is to prolong their residence at a specific site of delivery, thus enhancing the drug absorption process. These mucoadhesive devices can protect the drug during the absorption process in addition to protecting it on its route to the delivery site. The major emphasis of recent research on mucoadhesive biomaterials has been on the use of adhesion promoters, which would enhance the adhesion between synthetic polymers and mucus. The use of adhesion promoters such as linear or tethered polymer chains is a natural result of the diffusional characteristics of adhesion. Mucoadhesion depends largely on the structure of the synthetic polymer gels used in controlled release applications.

Formulation and characterization of mucoadhesive buccal films of glipizide

Mucoadhesive buccal films of glipizide were prepared by solvent casting technique using hydroxypropylmethylcellulose, sodium carboxymethylcellulose, carbopol-934P and Eudragit RL-100. Prepared films were evaluated for weight, thickness, surface pH, swelling index, in vitro residence time, folding endurance, in vitro release, permeation studies and drug content uniformity. The films exhibited controlled release over more than 6 h. From the study it was concluded that the films containing 5 mg glipizide in 4.9% w/v hydroxypropylmethylcellulose and 1.5% w/v sodium carboxymethylcellulose exhibited satisfactory swelling, an optimum residence time and promising drug release. The formulation was found to be suitable candidate for the development of buccal films for therapeutic use.

Effect of hydrophilic polymers on buccoadhesive Eudragit patches of propranolol hydrochloride using factorial design

The purpose of this study was to develop formulations and systematically evaluate in vitro performances of buccoadhesive patches of propranolol hydrochloride using the hydrophobic polymer Eudragit L-100 as the base matrix. The hydrophilic polymers Carbopol 934 and polyvinyl pyrrolidone (PVP) K30 were incorporated into the Eudragit patches, to provide the patches with bioadhesive properties and to modify the rate of drug release. The patches, which were prepared by the solvent casting method, were smooth and elegant in appearance; were uniform in thickness, weight, and drug content; showed no visible cracks; and showed good folding endurance. A 3(2) full factorial design was employed to study the effect of independent variables like hydrophilic polymers Carbopol 934 and PVP K30, which significantly influenced characteristics like swelling index, ex vivo mucoadhesive strength, in vitro drug release, and ex vivo residence time. A stability study of optimized Eudragit patches was done in natural human saliva; it was found that both drug and buccal patches were stable in human saliva. It can be concluded that the present buccal formulation can be an ideal system to improve the bioavailability of the drug by avoiding hepatic first-pass metabolism.

Formulation, evaluation, and comparison of bilayered and multilayered mucoadhesive buccal devices of propranolol hydrochloride

The purpose of this research work was to establish mucoadhesive buccal devices of propranolol hydrochloride (PRH) in the forms of bilayered and multilayered tablets. The tablets were prepared using sodium carboxymethylcellulose (SCMC) and Carbopol-934 (CP) as bioadhesive polymers to impart mucoadhesion and ethyl cellulose (EC) to act as an impermeable backing layer. Buccal devices were evaluated by different parameters such as weight uniformity, content uniformity, thickness, hardness, surface pH, swelling index, ex vivo mucoadhesive strength, ex vivo mucoadhesion time, in vitro drug release, and in vitro drug permeation. As compared with bilayered tablets, multilayered tablets showed slow release rate of drug with improved ex vivo bioadhesive strength and enhanced ex vivo mucoadhesion time. The mechanism of drug release was found to be non-Fickian diffusion (value of n between 0.5 and 1.0) for both the buccal devices. The stability of drug in both the optimized buccal devices was tested for 6 hours in natural human saliva; both the buccal devices were found to be stable in natural human saliva. The present study concludes that mucoadhesive buccal devices of PRH can be a good way to bypass the extensive hepatic first-pass metabolism and to improve the bioavailability of PRH.

In vivo study of liposomes as drug carriers to oral mucosa using EPR oximetry

The purpose of this study was to select the best types of liposomes for use as drug carriers for topical treatment of oral mucosal lesions. Electron paramagnetic resonance (EPR) oximetry, using the paramagnetic probe lithium phthalocyanine, was used in vivo to measure the effects of a hyperemic drug, benzyl nicotinate (BN) which was incorporated into liposomes of varying size and composition. The liposomes were made from either hydrogenated or non-hydrogenated soy lecithin and mixed with polymethyl methacrylate ointment for application. EPR oximetry was used to measure the partial pressure of oxygen (pO2) in the oral mucosa before and after application of liposomes. It was found that the most pronounced changes of pO2 in oral mucosa and also the longest action of the drug occurred after the topical application of BN in multi-lamellar liposomes made from hydrogenated soy lecithin (p<0.0001). When these liposomes were applied to oral mucosa over 3 successive days it was found that pO2 increased the most on the first day, the effect gradually decreased following application on the second and third days. The duration of the resulting hyperemia was the longest on the second day (p<0.01). Among the examined carriers, multi-lamellar liposomes made from hydrogenated soy lecithin appear to be the most appropriate for local drug delivery to oral mucosa.

The effect of two different dental gels and a mouthwash on plaque and gingival scores: a six-week clinical study

AIM

To evaluate the clinical efficacy of two gel formulations containing chlorhexidine gluconate and neem extract with a commercially available chlorhexidine gluconate mouthwash.

METHOD

An open labelled randomised six-week clinical study with parallel group design in 48 subjects divided into four groups. Plaque accumulation and gingival condition were recorded using plaque index and gingival index. On the basis of mean baseline plaque and gingival scores, subjects were allocated to four different groups, using their assigned products twice a day, before bed and after breakfast. Plaque and gingival scores were recorded after three and six weeks.

RESULTS

Mean plaque and gingival scores were reduced over the six-week trial period for experimental and control groups. Chlorhexidine gluconate gel reduced the plaque and gingival scores significantly more (p<0.05) than the chlorhexidine gluconate mouthwash. Neem extract gel also showed significant (p<0,05) reduction in plaque and gingival scores when compared with the control group. But there was no significant difference between the groups treated with chlorhexidine gel and neem extract gel.

CONCLUSION

The results of this clinical study indicate that better therapeutic efficacy can be achieved using gels for treating oral infections than conventional treatments using mouthwash.

In vivo study of different ointments for drug delivery into oral mucosa by EPR oximetry

The aim of the present study was to determine the rate of transport and long-term effect of a drug applied to the oral mucosa in different ointments. Three ointments with bioadhesive properties: Orabase, Carbopol 935P, and polymethyl methacrylate (PMM) and the ointment Miglyol without such properties were used. Benzyl nicotinate (BN) was used as an active ingredient that causes hyperemia. The kinetics of drug action was measured by electron paramagnetic resonance (EPR) oximetry in vivo using the paramagnetic probe (Lithium phthalocyanine) implanted beneath the epithelium of the buccal mucosa in rats. EPR spectra line-width was proportional to local changes of partial pressure of oxygen (pO(2)) in tissue and was monitored for 90 min after the application of ointments mixed with BN. The greatest increase in pO(2) and the highest efficiency of drug action was observed after the application of 2% BN in PMM (P<0.01). Additionally in PMM the drug effect increased linearly with BN concentration up to 3%, at higher concentrations (3.5 and 4% BN) no further effect was observed. The results demonstrated that the greatest and the longest effect caused by a hyperemic drug in PMM. By increasing the concentration of the drug in PMM higher pO(2) in the oral mucosa can be established but only until the saturation is reached.

Evaluation of antiplaque activity of Azadirachta indica leaf extract gel--a 6-week clinical study

Various chemical agents have been evaluated over the years with respect to their antimicrobial effects in the oral cavity; however, all are associated with side effects that prohibit regular long-term use. Therefore, the effectiveness of neem (Azadirachta indica A. Juss) leaf extract against plaque formation was assessed in males between the age group of 20-30 years over a period of 6 weeks. Present study includes formulation of mucoadhesive dental gel containing Azadirachta indica leaf extract (25 mg/g). A 6-week clinical study was conducted to evaluate the efficacy of neem extract dental gel with commercially available chlorhexidine gluconate (0.2% w/v) mouthwash as positive control. Microbial evaluation of Streptococcus mutans and Lactobacilli species was carried out to determine the total decrease in the salivary bacterial count over a period of treatment using a semi-quantitative four quadrant streaking method. The results of the study suggested that the dental gel containing neem extract has significantly (P<0.05) reduced the plaque index and bacterial count than that of the control group.

Mucoadhesive buccal patches of miconazole nitrate: in vitro/in vivo performance and effect of ageing

Mucoadhesive patches containing 10mg miconazole nitrate were evaluated. The patches were prepared with ionic polymers, sodium carboxymethyl cellulose (SCMC) and chitosan, or non-ionic polymers, polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC) and hydroxypropylmethyl cellulose (HPMC). Convenient bioadhesion, acceptable elasticity, swelling and surface pH were obtained. Patches exhibited sustained release over more than 5h and the addition of polyvinyl pyrrolidone (PVP) generally enhanced the release rate. Optimum release behaviour was shown with patches containing 10% w/v PVA and 5% w/v PVP. Study of the in vivo release from this formulation revealed uniform and effective salivary levels with adequate comfort and compliance during at least 6h. On the contrary, in vivo release of the commercial oral gel product resulted in a burst and transient release of miconazole, which diminished sharply after the first hour of application. Storage of these patches for 6 months did not affect the elastic properties, however, enhanced release rates were observed due to marked changes in the crystal habit of the drug.

Preparation and in vitro/in vivo evaluation of the buccal bioadhesive properties of slow-release tablets containing miconazole nitrate

Slow-release buccal bioadhesive tablets of miconazole nitrate were prepared by using polymer mixtures of buccoadhesive materials such as hydroxypropylmethylcellulose, sodium carboxymethylcellulose, carbopol 934p, and sodium alginate. The physicochemical properties, swelling index, microenvironment pH, in vitro drug release, in vivo buccoadhesion time, and miconazole salivary concentrations of the prepared tablets were shown to be dependent on the type and composition of the buccoadhesive materials used. The dissolution of miconazole from all the prepared tablets into phosphate buffer (pH 6.8) was controlled and followed non-Fickian release mechanisms. All the prepared tablets gave reasonable buccoadhesion time (2.45-3.65 hr). Infrared spectroscopy and differential scan calorimetry studies revealed the absence of significant interactions between miconazole nitrate and the selected buccoadhesive materials. Duration of the antifungal activity as measured by the inhibition zone of Candida albicans by extracted human saliva was significantly longer (p < 0.05), compared with commercial miconazole oral gel (Daktaren oral gel). Based on the results obtained, the prepared slow-release buccoadhesive tablets of miconazole would markedly prolong the duration of the antifungal activity with more patient convenience.

Release of triamcinolone acetonide from mucoadhesive polymer composed of chitosan and poly(acrylic acid) in vitro

Transmucosal drug delivery (TMD) system using mucoadhesive polymer has been recently interested due to the rapid onset of action, high blood level, avoidance of the first-pass effect and the exposure of the drug to the gastrointestinal tract. A novel mucoadhesive polymer complex composed of chitosan and poly(acrylic acid) (PAA) was prepared by template polymerization of acrylic acid in the presence of chitosan for the TMD system. Triamcinolone acetonide (TAA) was loaded into the chitosan/PAA polymer complex film. TAA was evenly dispersed in chitosan, PAA polymer complex film without interaction with polymer complex. Release behavior of TAA from the mucoadhesive polymer film was dependent on time, pH, loading content of drug, and chitosan PAA ratio. The analysis of the drug release from the mucoadhesive film showed that TAA might be released from the chitosan/PAA polymer complex film through non-Fickian diffusion mechanism.

Consistency of Carbopol 971-P NF gels and influence of soluble and cross-linked PVP

A study is made of the polymerization process of polyacrylic acid, commercially known as Carbopol 971 NF, assessing its consistency as a function of the degree of neutralization at pH values from 3 to 12, approximately. Percentage concentrations ranging from 0.1 to 1.4% (w/w) were studied. The gels obtained were non-Newtonian, and pseudoplastic. As concentration and pH rise, the consistency of the gels increase to a maximum, which appears between pH 6 and 8, allowing their use as vehicles in bioadhesive formulations for mucosal application. Over the increasing viscosity interval, functions were obtained to indicate the consistency of the gel as a function of pH and concentration. Since the correlation between the theoretical and experimental results is excellent, the equation found can be used to theoretically calculate the working concentration and pH required to secure the necessary consistency for a given vehicle. The addition of soluble polyvinylpyrrolidone (PVP), and cross-linked PVP (PVPP) does not substantially modify the rheological behavior of the gels, thus permitting their addition to usual vehicles.

Formulation and evaluation of controlled release Eudragit buccal patches

Controlled release buccal patches were fabricated using Eudragit NE40D and studied. Various bioadhesive polymers, namely hydroxypropylmethyl cellulose, sodium carboxymethyl cellulose and Carbopol of different grades, were incorporated into the patches, to modify their bioadhesive properties as well as the rate of drug release, using metoprolol tartrate as the model drug. The in-vitro drug release was determined using the USP 23 dissolution test apparatus 5 with slight modification, while the bioadhesive properties were evaluated using texture analyzer equipment with chicken pouch as the model tissue. The incorporation of hydrophilic polymers was found to affect the drug release as well as enhance the bioadhesiveness. Although high viscosity polymers can enhance the bioadhesiveness of the patches, they also tend to cause non-homogeneous distribution of the polymers and drug, resulting in non-predictable drug-release rates. Of the various bioadhesive polymers studied, Cekol 700 appeared to be most satisfactory in terms of modifying the drug release and enhancement of the bioadhesive properties.

Characterisation of bioadhesives for periodontal and oral mucosal drug delivery

Whilst there is keen interest in developing improved drug delivery devices to the periodontal pocket and oral mucosa, there are few reports which have examined the physical properties of gels and semi-solid formulations which favour retention and bioadhesion in situ. Hydration and rheological properties appear to be of prime importance in this context and this study aimed to correlate the measurement of these properties with observed bioadhesion, both in vitro and in vivo. Three candidate bioadhesives were selected from previous experiments which had used in vitro organ culture models. These were chitosan, xanthan gum and poly (ethylene oxide) aqueous formulations. Hydration rates with various media were determined in specially constructed cells. Rheological properties were measured using a controlled stress rheometer under carefully regulated conditions. These findings were also correlated with in vivo assessments in the periodontal pocket and oral mucosa. The results demonstrated that three formulations with differing bioadhesive properties also possessed widely different physical characteristics. Hydration experiments indicated a direct relationship between the rate of hydration and bioadhesion or retention. Rheological studies suggested that possession of a gel structure could be an important determinant of retention where shear displacing forces are present in vivo, e.g. the oral mucosa. Furthermore, these studies indicated that formulations which could demonstrate resistance to changes in rheological properties on hydration would also favour retention in situ. Physical characterisation therefore appears to have an important place in screening polymeric formulations prior to clinical testing in the periodontal pocket and oral mucosa.

Evaluation of some electrical methods for objective assessment of oral mucosal dryness

The aim of this study was to evaluate different electrical methods (resistance, capacitance and polarization resistance) for clinical and objective registration of dryness of the oral mucosa. Measurements were performed in the buccal and in the lip mucosa before and every 30 min after injection of 1.0 ml methylscopolamine nitrate submucosally in the labial sulcus in 10 healthy subjects. For comparison, a dental mirror sliding test was used. About 1 h after injection, all three methods showed statistically significant decreases of values in the buccal as well as the lip mucosa except for polarization resistance, which showed such a difference only in the buccal mucosa. The deviations from initial values in the individual subject showed no agreement between measurements with the electrical instruments and oral mucosal dryness assessed with the mirror test. Neither was there any agreement between values registered with the three electrical methods. It seems that these electrical methods are not suitable for registration of individual variations in oral mucosal dryness.

The behaviour of bioadhesive betamethasone tablets in the mouth

Disk-shaped adhesive tablets, for treatment of mouth lesions, were prepared by direct compression of a mix of high viscosity sodium carboxymethyl-cellulose and 0.061% betamethasone valerate. They were evaluated in six healthy volunteers. The tablets hydrated rapidly, increased their wet weight fourfold in 15 min and maintained contact with the oral mucosa for at least 4 h. Erosion of the tablets was variable with only minor losses in one subject at all times tested, whereas over 80% tablet weight loss occurred in two subjects after 2.5 h. These differences were not solely related to differences in salivary flow. Loss of betamethasone occurred in parallel with the loss of weight from the tablet suggesting that drug release was mainly by erosion of the gelled polymer and not by diffusion from the matrix. The tablets provided prolonged contact with the mucosa but the intersubject variability and drug loss should be addressed to improve the formulation.

Performance of a hydroxypropyl cellulose film former in normal and ulcerated oral mucosa

Although oral ulcers are commonly encountered in clinical dental and medical practice, current therapeutic options with respect to pain relief are limited. This study evaluated the mucosal binding characteristics and the pain relief and protection properties of Zilactin, a hydroxypropyl cellulose film former. In 12 healthy volunteers, the mean duration of mucosal adherence of Zilactin was 3.92 hours, which was significantly longer than that of a widely available topical preparation (1.38 hours, p = 0.0001). When evaluated in 20 subjects with recurrent aphthous ulcerations, Zilactin demonstrated the ability to significantly decrease ulcer pain over a 4-hour period when compared with the subjects' individual standardized level of initial discomfort, which was used as an internal control for all subsequent steps. Challenge with an irritating citrus beverage was made before and after application of the medication. A significant difference in premedication and postmedication sensitivity was shown (p = 0.0001), indicating that the film provides protection, as well as pain relief. As a result of its unique and tenacious film-forming characteristics, this agent is exceptionally effective in the treatment of oral mucosal ulcerations. Greater awareness on the part of physicians and dentists may lead to the development of additional applications.