Mucoadhesive Drug Delivery Systems

Abstract

Pharmaceutical aspects of mucoadhesion have been the subject of great interest during recent years because mucoadhesion could be a solution for bioavailability problems that result from a too short length of stay of the pharmaceutical dosage form at the absorption site within the gastro-intestinal tract.

This paper describes some aspects of bioadhesion such as mucus structure, stages of adhesion and the theories proposed that attempt to explain the adhesion mechanism. The factors that affect the bioadhesive power of a polymer, the methods that permit the evaluation of a bioadhesive system and the methods for surface characterization of biomaterials are discussed. Finally, the various polymers used and the bioadhesive systems designed for several therapeutic purposes are presented.     

Mucoadhesive Drug Delivery Systems

Pharmaceutical aspects of mucoadhesion have been the subject of great interest during recent years because mucoadhesion could be a solution for bioavailability problems that result from a too short length of stay of the pharmaceutical dosage form at the absorption site within the gastro-intestinal tract.

This paper describes some aspects of bioadhesion such as mucus structure, stages of adhesion and the theories proposed that attempt to explain the adhesion mechanism. The factors that affect the bioadhesive power of a polymer, the methods that permit the evaluation of a bioadhesive system and the methods for surface characterization of biomaterials are discussed. Finally, the various polymers used and the bioadhesive systems designed for several therapeutic purposes are presented.     

Buccal Drug Delivery Systems

Abstract

Buccal administration offers certain unique advantages for the drugs which cannot be easily or efficiently administered by oral or intravenous route. However, transbucccal delivery receiived relatively little attention and few well-controlled studies of buccal mucosa permeability have been conducted. The oral mucosa provides a protective covering for the underlying tissue, being as a barrier for microorganisms and toxins. This article extensively reviews the histology of buccal mucosa, permeation studies (both invitro and in vivo) of buccal drug delivery system, their development and various types of techniques and devices available for the delivery of drugs through buccal mucosa.     

Mucoadhesive Drug Delivery Systems

Mucoadhesion in drug delivery systems has recently gained interest among pharmaceutical scientists as a means of promoting dosage form residence time as well as improving intimacy of contact with various absorptive membranes of the biological system. Besides acting as platforms for sustained-release dosage forms, bioadhesive polymers can themselves exert some control over the rate and amount of drug release, and thus contribute to the therapeutic advantage of such systems. This paper describes some aspects of bioadhesion such as mucus layer, mucoadhesion, and theories of bioadhesion to explain the adhesion mechanism. The factors important to mucoadhesion, the methods used to study bioadhesion, and bioadhesive polymers are described. The methods that evaluate the mucoadhesive dosage forms and finally the bioadhesive drug delivery systems designed for several therapeutic purposes are presented.     

Buccal Drug Delivery Systems

Buccal administration offers certain unique advantages for the drugs which cannot be easily or efficiently administered by oral or intravenous route. However, transbucccal delivery receiived relatively little attention and few well-controlled studies of buccal mucosa permeability have been conducted. The oral mucosa provides a protective covering for the underlying tissue, being as a barrier for microorganisms and toxins. This article extensively reviews the histology of buccal mucosa, permeation studies (both invitro and in vivo) of buccal drug delivery system, their development and various types of techniques and devices available for the delivery of drugs through buccal mucosa.     

Oral Bioadhesive Drug Delivery Systems

The oral mucosal cavity is a feasible, safe, and very attractive site for drug delivery with good acceptance by users. The mucosa is relatively permeable and robust, shows short recovery times after stress or damage, is tolerant to potential allergens, and has a rich blood supply. Moreover, oral mucosal drug delivery bypasses the first-pass effect and avoids presystemic elimination in the gastrointestinal tract. Bioadhesive systems provide intimate contact between a dosage form and the absorbing tissue, which may result in high concentration in a local area and hence high drug flux through the absorbing tissue. The efficacy of oral bioadhesive drug delivery systems is affected by the biological environment and the properties of the polymer and the drug. In the present paper, we review systematically some relevant citations regarding the environment, strategies for oral drug delivery and evaluation, and utilization of the main polymers.     

New Ophthalmic Drug Delivery Systems

One of the ways to optimize ocular drug delivery is to prolonge precorneal drug residence time. This review focusses on recent findings on the formulation effects in ocular drug bioavailability, employing polymers for the preparation of hydrogels, bioadhesive dosage forms, in situ gelling systems and colloidal systems including liposomes and nanoparticles. The results observed suggested that mucoadhesion or bioadhesion played a role in the sustained action of drugs more significantly compared to non-mucoadhesive polymers. Encapsulation of drugs in liposomes and nanoparticles was correlated to an increase of the drug concentration in the ocular tissues. However, all the results described suggest that the physico-chemical properties of the encapsulated drug have a significant influence on the effect with the carrier. The results suggest also that the superficial charge, the binding type of the drug onto the nanoparticles and the nature of the polymer were the most important factors regarding the improvement of the therapeutic response of the drug.     

Implantable Controlled Release Drug Delivery Systems: A Review

Abstract

Origins of rate controlled implantable drug delivery dates back to 1964 when silicone implants were used to prolong a drug effect. Despite much activity in the years since 1964, the progress to a safe, effective and acceptable implant system(s) has been slow. The critical factors in implant research which need to be addressed include: erodibility, reproducibility, lack of irritation and carcinogenicity, lack of dose dumping, duration and pulses. While it is possible to surgically implant and remove drug-containing devices or polymeric matrices, the requirement for such intervention could have a significant negative impact on the acceptability of a product candidate. In recent years, two implant systems have been approved for human use; (a) a silicone-based device (Norplant^R), and (b) a system based on lactide/glycolide copolymers to release a luteinizing hormone - releasing hormone (LHRH) agonist for treatment of male reproductive tract tumours. This approach to drug delivery is very appealing for a number of classes of drugs, particularly those that cannot be given via the oral route, and drug candidates whose therapeutic index is relatively large. This article reviews the background to implantable drug delivery systems, the rationale behind using implantable drug delivery systems, the types of systems being currently researched, and the various methods available for their evaluation.     

Development of Anticandidal Delivery Systems: (II) Mucoadhesive Devices for Prolonged Drug Delivery in the Oral Cavity

Conventional dosage forms designed for drug delivery in the oral cavity suffer from the disadvantage of an initial burst of activity followed by a rapid decrease in concentration to subtherapeutic levels. To counter this effect, two prolonged-release dosage forms were devised for the treatment of oral candidiasis. These devices were to contain the antifungals, chlorhexidine and clotrimazole, for therapy against Candida albicans, and also benzocaine and hydrocortisone to combat the pain and inflammation secondaly to a candidal infection. Release studies demonstrated that only chlorhexidine and clotrimazole could be delivered in a controlled manner from the mucoadhesive patches. On the other hand, release of all four drugs could be controlled from the mucoadhesive tablets, with optimum release of the drugs in 24 hr achieved using sodium carboxymethylcellulose and polyethylene oxide (85:15) combination tablets.