Compression forces and amount of outer coating layer affecting the time‐controlled disintegration of the compression‐coated tablets prepared by direct compression with micronized ethylcellulose

The influence of compression force to inner core tablet or to outer coating layer of the compression‐coated tablet on the function of time‐controlled disintegration was investigated. The inner core tablet was directly compacted by sodium diclofenac (model drug) and ethylcellulose (EC) with 4.6‐μm particle size was used as an outer coating layer. The immersion time of the compression‐coated tablet previously soaked in pH 1.2 solution to simulate the residence time of the tablet in the GI tract affecting the dissolution behavior of the compression‐coated tablet was also investigated. The effect of the amount of the outer coating layer used on the drug release was examined. The results indicate that sodium diclofenac released from these compression‐coated tablets exhibited a longer lag of a period about 16.3 h in both distilled water and pH 6.8 buffer solution, followed by a different drug release behavior. The lag time was independent of the pH of dissolution medium, and the immersion time in pH 1.2 solution. After that lag time, the outer shell of the compression‐coated tablets broke into two halves to make a rapid drug release. However, the drug release behavior of the soaked tablet in pH 6.8 buffer solution was dependent on the immersion time. The compression force < 200 kg/cm2 to the inner core tablet influenced the release behavior of drug less, but > 200 kg/cm2 might delay the lag time. The lag time of the compression‐coated tablets was linearly correlated with the compression force to the outer coating layer (r = 0.9896). We also found that the more the amount of outer coating layer added, the longer the lag time obtained. The study demonstrates that the time‐controlled disintegration of the compression‐coated tablet was effectively controlled by the compression force applied and the amount of outer coating layer added. © 2001 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:2005-2009, 2001