Formulation study of PLGA in situ films for topical delivery of salicylates.

A film-forming system (FFS) represents a convenient topical dosage form for drug delivery. In this study, a non-commercial poly(lactic-co-glycolic acid) (PLGA) was chosen to formulate an FFS containing salicylic acid (SA) and methyl salicylate (MS). This unique combination is advantageous from a therapeutic point of view, as it enabled modified salicylate release. It is beneficial from a technological perspective too, because it improved thermal, rheological, and adhesive properties of the in situ film. DSC revealed complete dissolution of SA and good miscibility of MS with the polymer. MS also ensures optimal viscoelastic and adhesive properties of the film, leading to prolonged and sustained drug release. The hydrolysis of MS to active SA was very slow at skin pH 5.5, but it apparently occurred at physiological pH 7.4. The film structure is homogeneous without cracks, unlike some commercial preparations. The dissolution study of salicylates revealed different courses in their release and the influence of MS concentration in the film. The formulated PLGA-based FFS containing 5 % SA and 10 % MS is promising for sustained and prolonged local delivery of salicylates, used mainly for keratolytic and anti-inflammatory actions and pain relief.

A Study of Compressibility, Compactability and Mucoadhesivity of Tableting Materials for Matrix Systems Based on Chitosan.

The objective of the present research is to evaluate directly compressible chitosan-based tableting materials for the formulation of mucoadhesive matrix tablets intended for targeted drug release to distal segments of the GIT. The influence of sodium alginate, hypromellose, and silicified microcrystalline cellulose (P90) on compressibility, compactability and lubricant sensitivity ratio was tested. Furthermore, the rheological properties of the hydrated surface layer of the matrix tablets and the mucoadhesion to a mucin substrate were analysed. Compressibility was evaluated using the energy profile of the compression process, compactability by means of the tensile strength of tablets, and lubricant sensitivity ratio was calculated to assess the sensitivity to lubricant. Addition of P90 to chitosan improved compressibility, which is demonstrated by the increase in the energy of plastic deformation and the higher tensile strength of tablets. P90 also significantly reduced the high lubricant sensitivity of chitosan. Presence of retarding components led to a decrease in Emax. All tested matrix tablets revealed a good mucoadhesion without a negative effect of P90 content. The viscosity of a gel layer on the surface of matrix tablets containing hypromellose was higher compared to those with sodium alginate. This was not reflected in the adhesive strength of the tablets. The formulated tableting materials combining chitosan and P90 are a suitable matrix for incorporation of an active ingredient, whose delayed release in the intestine can be achieved by the functionality of the chitosan-sodium alginate complex.