ABSTRACT
Film coating of pharmaceutical dosage forms has evolved from its rudimentary origins
to become a sophisticated science that has contributed immeasurably to the advance-
ment of drug delivery. The earliest application of pharmaceutical coating has been
attributed to Rhazes (850-932 AD) who coated pills with the mucilage of psyllium
seeds to mask unpleasant taste (1). Other early coating systems involved the application
of gold and silver, talc, waxes, and gelatin to pills and tablets (2-4). These early coatings
were typically applied to substrates individually by supporting them with forceps or
mounting them on a needle and repeatedly dipping the articles into the coating fluid. The
origin of large scale film-coating of pharmaceuticals began with the adoption of sugar
coating from the candy industry which utilized the batch pan coating process. The first
sugar-coated pills were made available in the United States in 1842 (5) and shortly
thereafter were being manufactured in the United States in 1856 (6). Film coating with
polymers emerged in the 1950s as a more efficient alternative to sugar coating due to a
substantial reduction in drying time by the utilization of volatile organic solvents as the
dispersion media. In addition, film coating offered the benefit of less rigid coats which
reduced cracking and other coat defects and allowed for the successful coating of sub-
strates other than tablets, i.e., powders, granules, pellets, and capsules. Although film
coating with polymeric materials from organic solution offered many initial benefits,
ultimately these coating systems lost their favor due to flammability, toxicity, environ-
mental, and cost related issues. These problems regarding organic solvent-based film
coating led pharmaceutical manufacturers to re-evaluate aqueous-based coating systems.
By this time, coating equipment had substantially improved beyond the early pan coating
systems, and thus drying efficiency with aqueous coating systems was no longer a pro-
hibitive problem.
