Mucoadhesive alginate matrices containing sodium carboxymethyl starch for buccal delivery: in vitro and in vivo studies

Alginate-based matrix tablets for drug delivery

INTRODUCTION

As a nature-derived polymer with swelling and gelling properties, alginate has found wide biopharma-relevant applications. However, there is comparatively limited attention on alginate in tablet formulations. Therefore, this review aimed to provide an overview of the applications of alginate in solid dosage form formulations.

AREAS COVERED

This review outlines the role of alginate for oral sustained release formulations. For better insights into its application in drug delivery, the mechanisms of drug release from alginate matrices are discussed alongside the alginate inherent properties and drug properties. Specifically, the influence of alginate properties and formulation components on the resultant alginate gel and subsequent drug release is reviewed. Modifications of the alginate to improve its properties in modulating drug release are also discussed.

EXPERT OPINION

Alginate-based matrix tablets is useful for sustaining drug release. As a nature-derived polymer, batch consistency and stability raise some concerns about employing alginate in formulations. Furthermore, the alginate gel properties can be affected by formulation components, pH of the dissolution environment and the tablet matrix micro-environment pH. Conscientious efforts are pivotal to addressing these formulation challenges to increase the utilization of alginate in oral solid dosage forms.

Stability, Permeability and Cytotoxicity of Buccal Films in Allergy Treatment

Oral mucoadhesive systems, such as polymer films, are among innovative pharmaceutical products. These systems can be applied in swallowing problems and can also be used in geriatrics and paediatrics. In our earlier work, we successfully formulated buccal mucoadhesive polymer films, which contained cetirizine-hydrochloride (CTZ) as the API. The present study focused on investigating the stability and permeability of the prepared films. The stability of the films was studied with an accelerated stability test. During the stability test, thickness, breaking hardness and in vitro mucoadhesivity were analysed. Furthermore, the interactions were studied with FT-IR spectroscopy, and the changes in the amount of the API were also monitored. Cytotoxicity and cell line permeability studies were carried out on TR 146 buccal cells. Compositions that can preserve more than 85% of the API after 6 months were found. Most of the compositions had a high cell viability of more than 50%. Citric acid (CA) decreased the stability and reduced every physical parameter of the films. However, cell line studies showed that the permeability of the films was enhanced. In our work, we successfully formulated CTZ-containing buccal films with adequate stability, high cell viability and appropriate absorption properties.

Biomaterials and Contraception: Promises and Pitfalls

The present state of reproductive and sexual health around the world reveals disparities in contraceptive use and effectiveness. Unintended pregnancy and sexually transmitted infection transmission rates remain high even with current prevention methods. The 20th century saw a contraceptive revolution with biomedical innovation driving the success of new contraceptive technologies with central design concepts and materials. Current modalities can be broadly categorized according to their mode of function: reversible methods such as physical/chemical barriers or hormonal delivery devices via systemic (transdermal and subcutaneous) or localized (intrauterine and intravaginal) administration, and nonreversible sterilization procedures such as tubal ligation and vasectomy. Contraceptive biomaterials are at present dominated by well-characterized elastomers such as polydimethylsiloxane and ethylene vinyl acetate due to their favorable material properties and versatility. Contraceptives alter the normal function of cellular components in the reproductive systems to impair fertility. The purpose of this review is to highlight the bioengineering design of existing methods, explore novel adaptations, and address notable shortcomings in current contraceptive technologies.

Alginate: Current Use and Future Perspectives in Pharmaceutical and Biomedical Applications

Over the last decades, alginates, natural multifunctional polymers, have increasingly drawn attention as attractive compounds in the biomedical and pharmaceutical fields due to their unique physicochemical properties and versatile biological activities. The focus of the paper is to describe biological and pharmacological activity of alginates and to discuss the present use and future possibilities of alginates as a tool in drug formulation. The recent technological advancements with using alginates, issues related to alginates suitability as matrix for three-dimensional tissue cultures, adjuvants of antibiotics, and antiviral agents in cell transplantation in diabetes or neurodegenerative diseases treatment, and an update on the antimicrobial and antiviral therapy of the alginate based drugs are also highlighted.

Buccal tablets containing cysteine and chlorhexidine for the reduction of acetaldehyde levels in the oral cavity

There is growing evidence that a large proportion of upper digestive tract tumors are ascribable to heavy alcohol drinking and tobacco consumption. The cancer-promoting action of ethanol is mediated by acetaldehyde, its first metabolite, also derived from the bacterial oxidation of alcohol by the oral microflora, classified by the International Agency for the Research on Cancer as a carcinogen. Acetaldehyde is also one of the major components of tobacco smoke. These findings suggest two different strategies to decrease the risk of alcohol-related oral cancers: the reduction of the levels of alcohol-derived acetaldehyde in saliva and the reduction of oral bacterial flora. Therefore, the aim of our study was to develop and characterize some buccal tablet formulations containing both 20 mg L-cysteine hydrochloride (able to chemically neutralize acetaldehyde) and 10 mg chlorhexidine diacetate (well-known antiseptic compound active against a large spectrum of oral microbes). One of these formulations, chosen on the basis of its favourable delivery kinetics of the active principles, was demonstrated to be able to reduce acetaldehyde concentration in an in vitro system and to lower its salivary levels in volunteers after ethanol contact. Our findings support the hypothesis that the application of buccal devices containing cysteine and chlorhexidine could reduce salivary acetaldehyde levels and thus the incidence of upper gastrointestinal cancer in drinkers and smokers.

Preparation, in vitro characterization and preliminary in vivo evaluation of buccal polymeric films containing chlorhexidine

The aim of this work was to investigate the suitability of some polymeric films as buccal systems for the delivery of the antiseptic drug chlorhexidine diacetate, considered as a valid adjunct in the treatment of oral candidiasis. Six different film formulations, mono- or double-layered, containing 5 or 10 mg of chlorhexidine diacetate, respectively, and alginate and/or hydroxypropylmethylcellulose and/or chitosan as excipients, were prepared by a casting-solvent evaporation technique and characterized in terms of drug content, morphology (scanning electron microscopy), drug release behavior, and swelling properties. Moreover, the in vivo concentrations of chlorhexidine diacetate in saliva were evaluated after application of a selected formulation on the oral mucosa of healthy volunteers. The casting-solvent evaporation proved to be a suitable technique for preparing soft, flexible, and easily handy mono- or double-layered chlorhexidine-loaded films. Some prepared formulations showed favorable in vitro drug release rates and swelling properties. The behavior of a selected formulation, chosen on the basis of its in vitro release results, was preliminarily investigated in vivo after application in the oral cavity of healthy volunteers. The films were well tolerated and the salivary chlorhexidine concentrations were maintained above the minimum inhibitory concentration for Candida albicans for almost 3 h. These preliminary results indicate that polymeric films can represent a valid vehicle for buccal delivery of antifungal/antimicrobial drugs.

EVA copolymer matrix for intra-oral delivery of antimicrobial and antiviral agents

Biocompatible ethylene vinyl acetate copolymer (EVA) was utilized to study the release of an antiviral drug (acyclovir (ACY)) and an antimicrobial drug (doxycycline hyclate (DOH)). Release of both drugs from EVA was measured individually and in combination. The effect of drug combination of DOH and ACY is presented. Additionally, the release rate of DOH after coating of the matrix with a different copolymer, in drug-loading with increasing loads of DOH, and with increases in temperature are also presented. The drugs incorporated in EVA films were prepared from the dry sheet obtained by solvent evaporation of polymer casting solutions with drugs. Drug release from the films was examined for about 12 days in distilled water at 37 degrees C. Changes in optical density were followed spectrophotometrically. The combination of ACY and DOH resulted in an increased release of ACY by about three times (P < 0.001) while DOH showed a decrease in rate of about two times compared to the individual release rates (P = 0.008). Increases in drug levels of DOH resulted in increases in drug release rates (P = 0.001). The release rate of DOH increased with temperature (P = .001; 27, 32, 37 and 42 degrees C were studied) and the energy of activation (DeltaE ( not equal) = 56.69 kJ/mol) was calculated using the Arrhenius equation for the diffusion of DOH molecules. Thus, the release rates of drugs were influenced by many factors: drug combination, coating the device, drug-loading, and temperature variation. Therefore it is proposed that controlling these variables should make it possible to obtain therapeutic levels of drugs released from drug loaded polymer, which may be beneficial in treating oral infections.

Poly(ethylene-co-vinyl acetate) copolymer matrix for delivery of chlorhexidine and acyclovir drugs for use in the oral environment: effect of drug combination, copolymer composition and coating on the drug release rate

OBJECTIVES

This study utilizes a bio-compatible ethylene vinyl acetate (EVA) copolymer to deliver drugs at therapeutic levels over extended periods of time. The release rate of an anti-fungal and an anti-microbial drug namely acyclovir (ACY) and chlorhexidine diacetate (CDA) from EVA was investigated individually and as a mixture. The effect of drug combination, the composition of the copolymer and the coating of the matrix with a different polymer on the rate of drug release are presented.

METHOD

Polymer casting solutions were prepared by homogeneously dissolving EVA copolymer and the drugs in the ratio (40:1) in dichloromethane. The drugs ACY and CDA were used individually as well as in three different weight ratios maintaining the total drug concentration in the polymer at 2.5%. Different concentrations of vinyl acetate (VA) 28, 32 and 40% in the EVA matrix were used to study the release of either ACY or CDA alone while 40% VA was used for the release study of the individual drug as well as their mixtures. Thin square films of 3cmx3cm with a thickness of 0.7mm were cut from the dry sheet obtained by solvent evaporation. Coated films were prepared by dipping ACY and CDA drug-loaded EVA films (VA 40%) into EVA copolymer of VA 32% and then dried. All of the drug-loaded samples were extracted at 37 degrees C in 10ml distilled water that was replaced daily. The rate of individual drug release was measured by UV-spectrophotometer while the mixtures of drugs were measured by high performance liquid chromatography (HPLC).

RESULTS

The release rate of ACY is higher than that of CDA both individually and in the ACY/CDA 50/50 mixture. In the other mixtures, the release of the drug is proportional to its concentration in the mixture. Total release of ACY is higher than CDA in most compositions. The effect of increasing the vinyl acetate content of the EVA matrix increased the drug release rate (p=0.02) while coating of films resulted in a decrease of the release rate of the drugs.

SIGNIFICANCE

Measurements of the in vitro rate of drug release showed that there was a sustained release of drug at an almost constant concentration over extended period of time, thus providing a basis for oral treatment modality. We show that it is possible to alter the rate of drug release in the EVA matrix to a desired value by: (1) changing the composition of the EVA copolymer, (2) altering the mixtures of drugs and (3) coating the matrix with additional polymer. The use of mixtures of drugs that can enhance or decrease the rate of drug release may prove more effective in treating persistent oral infections in immunocompromised patients.