Essay On Hydcellulose

CHAPTER-6

POLYMER PROFILE

SELECTION OF POLYMERS AS CONTROL RELEASER AND IOADHESIVE The polymers, CONTROL RELEASER and Bio-adhesive polymer controlled release of drug is important for development of a Mucoadhesive microsphere drug delivery system are selected on the basis of the following criteria32,33

1. The ingredients used in formulation should be non/minimally irritant and nontoxic to the body of the host.

2. The polymers used should be sufficiently retardant i.e. it should be able to retard the release of the drug from the dosage form.

3. The polymer and other excipients should allow incorporation of appropriate amount of active ingredients without excessively deteriorating its mechanical properties.

4. Ingredients used in formulation

The compound forms colloids when dissolved in water. Although non-toxic, it is combustible and can react vigorously with oxidising agents.[4] Hypromellose in an aqueous solution, unlike methylcellulose, it does not exhibit thermal gelation property. That is, when the solution heats up to a critical temperature, the solution congeals into a non-flowable but semi-flexible mass. Typically, this critical (congealing) temperature is inversely related to both the solution concentration of HPMC and the concentration of the methoxy group within the HPMC molecule (which in turn depends on both the degree of substitution of the methoxy group and the molar substitution. That is, the higher the concentration of the methoxy group, the lower the critical temperature. The inflexibility/viscosity of the resulting mass, however, is directly related to the concentration of the methoxy group (the higher is the concentration, the more viscous or less flexible is the resulting

Its molecular structure is predicated upon a base celluloid compound that is highly water soluble. Post-application, celluloid attributes of good water solubility reportedly aids in visual clarity. When applied, a hypromellose solution acts to swell and absorb water, thereby expanding the thickness of the tear-film. Hypromellose augmentation therefore results in extended lubricant time presence on the cornea, which theoretically results in decreased eye irritation, especially in dry climates, home, or work environments. On a molecular level, this polymer contains beta-linked D-glucose units that remain metabolically intact for days to weeks. On a manufacturing note, since hypromellose is a vegetarian substitute for gelatin, it is slightly more expensive to produce due to semisynthetic manufacturing processes. Aside from its widespread commercial and retail availability over the counter in a variety of products, Hypromellose 2% solution has been documented to be used during surgery to aid in corneal protection and during orbital