Whitening on deeply colored, sugar-coated tablets

Among sugar coating technicians it is well known that partial whitening is often observed on the surface of colored, sugar-coated tablets packed in glass bottles during use in the user's home. This detracts from the appearance and incurs complaints from consumers. The sucrose of the tablet surface partially dissolves on exposure to relative humidity above the critical level. Microscopic examination revealed that recrystallization under rapid drying conditions of dissolved sucrose occurred disturbing a wax layer and generated the crystal texture enough to cause the defused light reflection. These were considered to result in the whitening. Tablets taken out of a glass bottle with wet fingers and then returned showed similar whitening. We took into consideration the factors likely to influence these wetting and drying processes and evaluated countermeasures that seem effective to prevent the whitening, that is, addition of four kinds of pharmaceutical excipients (additives), use of water-insoluble aluminum lake, and alteration of package forms. The only solution we found is the use of press-through packaging and strip packaging from which we can take out a tablet without touching it with fingers.