The role of water sorption and swelling by an insoluble tablet containing cellulose, starch, or their derivative as a disintegrant during aqueous coating simulation
Abstract
Surface morphology and porosity, moisture sorption, thermal property changes due to water interaction, particle swelling, and hydration capacity of excipients including four disintegrants, i.e., microcrystalline cellulose (Avicel PH102), croscarmellose sodium (Ac-di-sol), corn starch, and sodium starch glycolate (Primojel), as well as unmilled dicalcium phosphate dihydrate (Di-Tab) were studied in order to understand the roles of water sorption and swelling of the tablets made with these excipients. All sorption isotherms of the disintegrants were type II which could be treated by G.A.B. equation. The remaining sorbed moisture was found in desorption studies due to the liquid condensation and polymer structural changes during sorption. The monomolecular sorption of water was substantially higher than that of nitrogen. The fact that water molecules interact with some specific sites on the amorphous portions of a disintegrant polymer produces a high monomolecular sorption. Water eases the segmental mobility of glassy amorphous portions which, in turn, lower glass transition temperature. This could reflect the sorption capacity owing to the loss of some water sorption sites by changing from amorphous glass to rubber. Sorbed water seemed to be tightly bound on the surface of a disintegrant. This water phase was not separately seen by exothemic differential calorimetry. However, ice present in the case of Ac-di-sol and Primojel equilibrated with 95-100% relative humidity because of the water that solvated the polymer sodium salts. Ac-di-sol, corn starch, and Primojel particles significantly swelled in the medium containing water. The superdisintegrants exhibited high values of hydration capacity compared to those of conventional ones. However, the hydration capacity of Di-Tab is extremely low. The kinetics study of moisture and liquid water uptakes for Di-Tab tablets with or without a disintegrant at 15% w/w level as well as the hydration capacity study revealed that water uptake may be governed by hydrophilicity of the tablet capillary rather than the tablet porosity. The extent of swelling and water penetration of formulated tablets during simulated aqueous coating could be described by a simple linear model. It was found that Di-Tab tablets with 15% Ac-di-sol significantly swelled during aqueous coating simulation.
Degree
Ph.D.
Advisors
Peck, Purdue University.
Subject Area
Pharmaceuticals|Pharmacology
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