The reality of in-line tablet coating

Abstract

The possibility of continuous processing in pharmaceutical tablet manufacturing is hampered by the viscoelastic recovery of tablets post-compaction. Compacted tablets are typically aged before coating to allow complete viscoelastic recovery so as to avoid subsequent coating defects. There has been little attempt to overcome tablet recovery in order to enable continuous processing and improve manufacturing efficiency. However, with the introduction of improved or newly developed types of tablet-coating equipment, there is renewed interest in the coating of tablets in-line. In-line tablet coating is defined as the coating of tablets immediately after compaction. It is a one-step highly integrated system that circumvents the delay in processing time typically given to allow viscoelastic recovery of tablets. This review aims to summarize the requirements of an in-line tablet-coating system. The possibility of carrying out in-line tablet coating in the near future will also be discussed.

Keywords::

• In-line
• tablet coating
• tablet compaction
• stress relaxation
• viscoelastic strain recovery
• decompression
• internal stress
• coating defects