Processing considerations for an EC latex coating system: influence of curing time and temperature.

The influence of curing time and curing temperature for a commercially available ethylcellulose latex coating dispersion (Aquacoat) were evaluated using response surface methodology. Levels for the factor curing time ranged from 30 to 300 minutes while levels for curing temperature ranged from 45 degrees to 75 degrees C. Responses, A, kappa, and gamma, were derived from regression analysis of the dissolution profiles and correspond to the maximum amount of drug released over the 12 hour sampling period, the rate of release, and the inflection point of the dissolution profile, respectively. The nature of the response surface was dramatically influenced by the plasticizer incorporated into the coating formula. When dibutyl sebacate was employed as the plasticizer, faster release resulted (higher A and kappa values, lower gamma values) when samples were exposed to higher curing temperatures or were stored for longer periods of time. Paradoxically, when tributyl citrate was used as the plasticizer, slower release resulted when samples were exposed to more rigorous conditions. Overall, curing temperature had a more dramatic effect than curing time.