Effect of Triethyl Citrate Vapor on Annealing of Dry Coated Formulations

Our study described a new annealing approach for dry-coated formulations, which includes heating of the dosage forms in plasticizer vapor. First, coated tablets were produced by V-shaped blending of tablets and polymer particles without any solvents. Second, these tablets were placed in a desiccator, in which triethyl citrate in liquid state was pre-charged, followed by heating at various temperatures. The resulting tablets were characterized. The polymer particles layered on the surface of tablets coalesced by heating at 80°C or more in plasticizer vapor, indicating that using plasticizer vapor could lower heating temperature required for film formation of coated polymer. The weight of polymer compacts increased by heating in plasticizer vapor as heating temperature increased. These data were correlated with vaporization rate of the plasticizer, indicating that plasticizer in gas state was absorbed in polymer particles, promoting film formation due to a decrease in glass transition temperature of the polymer.