Mucoadhesion is commonly defined as the adhesion between two materials, at least one of which is a mucosal surface. Over the past few decades, mucosal drug delivery has received a great deal of attention. Mucoadhesive dosage forms may be designed to enable prolonged retention at the site of application, providing a controlled rate of drug release for improved therapeutic outcome. Application of dosage forms to mucosal surfaces may be of benefit to drug molecules not amenable to the oral route, such as those that undergo acid degradation or extensive first-pass metabolism. The mucoadhesive ability of a dosage form is dependent upon a variety of factors, including the nature of the mucosal tissue and the physicochemical properties of the polymeric formulation. This review article aims to provide an overview of the various aspects of mucoadhesion, mucoadhesive materials, factors affecting mucoadhesion, evaluating methods, and finally various mucoadhesive drug delivery systems (buccal, nasal, ocular, gastro, vaginal, and rectal).

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A new 1:1 drug-drug cocrystal of theophylline (THP) and aspirin (ASP) was successfully prepared by liquid assisted grinding, evaporative crystallization, and slurry conversion crystallization. The obtained cocrystal was comprehensively characterized by single crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared analysis. Ternary phase diagrams were constructed for the obtained cocrystal in isopropyl alcohol at two different temperatures, i.e., 20 and 40 °C. A narrow stability region was found for the pure THP-ASP cocrystal in the phase diagram at both temperatures. By proper selection of the ratios between THP, ASP, and IPA from the stability region, THP-ASP cocrystals could be purely produced by isothermal slurry conversion in IPA. In addition, molecular modeling was deployed to provide mechanistic insights into the formation of this THP-ASP cocrystal system.

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