Bioadhesion

There are various approaches for the delivery of therapeutic substance to the target site in a controlled release fashion. One such approach is using microspheres as carriers for drugs or active pharmaceutical compound. However, the success of this drug delivery system is limited due to their short residence time at the site of absorption. Mucoadhesive microspheres can be tailored to adhere to any mucosal tissue including those found in stomach, thus offering the possibilities of localized as well as systemic controlled release of drugs. This article presents the  advantages of Mucoadhesive microsphere, mechanism, theories involved in mucoadhesion, factor that affect the mucoadhesion, polymer in Mucoadhesive drug delivery system, methodology of preparation of Mucoadhesive microsphere, method of evaluation and their applications in drug delivery. Mucoadhesive drug delivery systems promises several advantages that arise from localization at a given target site, prolonged residence time at the site of drug absorption and an intensified contact with the mucosa increasing the drug concentration gradient.

Olmesartan medoxomil is an angiotensin II antagonist used as an antihypertensive drug which has poor oral bioavailability. Hence, an attempt was made to prepare and evaluate mucoadhesive buccal films containing Olmesartan medoxomil as model drug. Various mucoadhesive buccal films were prepared by employing HPMC alone, and in combination with Eudragit RL100, Carbapol 934, Ethyl cellulose were prepared by solvent casting method using ethanol , water and acetone as solvents, tween 80 as solubilising agent and glycerine as plasticizer. The prepared mucoadhesive buccal films were evaluated for their physic-chemical parameters such as thickness uniformity, weight uniformity, folding endurance, drug content , surface pH, swelling index, bioadhesion, percentage moisture loss and uptake, vapor transmission rate. The formulations exhibited good results. In – vitro drug release studies were conducted for OLM loaded films in phosphate buffer (pH 6.8) solution. The drug release was in the range of 67 to 90 % in 6hrs.. Stability studies were carried out with selected formulation. In- vivo release was evaluated in rabbits by patch test and it showed good correlation with the in-vitro release data. Drug release was found to be diffusion following zero order as per kinetic studies.

The study aim was concerned with formulation and in vitro evaluation of mucoadhesive buccal patch of carvedilol, which is extensively metabolized by liver. During last few years mucoadhesive dosage forms have promoted an area of drug delivery system that renders the treatment more effective and safe, not only for topical disorders but also for systemic problems. Therefore the present investigation is concerned with the development of the bucco-mucoadhesive patches, which were designed to prolong the buccal residence time, to increase penetration through buccal mucosa and thus increase the bioavailability. Various formulations were developed by using release rate controlling patches forming polymers like HPMC (K15, K4), HPC-L, Sodium alginate, PVP K30& Carbopol 934P in  alone & various combinations by solvent casting technique using plasticizer glycerol. For unidirectional release, backing layer prepared using ethyl cellulose 2.5%w/v dissolve in isopropyl alcohol and acetone. Glycerol used as a plasticizer was casted on the patches. The patches were evaluated for their thickness uniformity, folding endurance, weight uniformity, content uniformity, swelling behaviour, tensile strength, and surface pH, In vitro release studies, in vitro residence time, in vitro diffusion study. Patches exhibited drug release (diffusion) in the range of 75.69% to 96.53%. Kinetic models i.e. Higuchi, Korsemeyer-peppas, zero order were applied on data of diffusion release to explain release. The optimized formulation (F1) shows the zero order release.

  Mucoadhesive delivery systems were proven to be suitable for the purpose of reduction of transit time of the dosage form through the gastro-intestinal tract, and increasing bioavailability of drug. Buccal tablets of Carvedilol were prepared by direct compression method for using various compositions of combination of Starch: C934 and Starch: HPMCK15M in various ratios. The tablets were evaluated for their characteristics properties, mucoadhesion and in vitro-in-vivo study. All the physicochemical properties were acceptable within the limit. Formulation containing starch and Carbopol 934(E4) showed better bioavailability as compared to tablet containing  Starch and HPMCK15 (F5) and The bioadhesive strength of the formulations containing polymers were in the order of E4> F5. Stability studies were carried out as per ICH guidelines and formulations were found to be Stable.