Sugar coating tablets

How should multivitamin tablets be coated with a sugary coating, knowing that the tablets are very sensitive to moisture?

Sugar coating is a combination of art and science as it requires more skills to get perfect sugar-coating. Sugar-coated tablets should look like “Shining Gems”, which is the success of perfect sugar coating. Generally, there are a number of stages involved in the sugar coating of tablets as follows,

  • Seal coat (of core tablets) of hydrophobic materials such as shellac, Cellulose acetate phthalate dissolved in alcohol (suspension).
  • Drying of tablets
  • Pre-coating with inert excipients such as calcium carbonate, Talc powder, in sugar and gum syrup.
  • Coating with excipients and gums such as calcium carbonate, Talc powder, etc. in sugar syrup
  • Coating with excipients in sugar syrup with colour added in the suspension (background colour coating)
  • Drying of tablets
  • Coloured syrup coating (first coat) Only colour dissolved in sugar syrup.
  • Coloured syrup coating (second & third coats) Only colour dissolved in sugar syrup.
  • Drying of tablets
  • Polishing of coated tablets (with carnauba wax as very fine powder)
  • Holding of polished tablets in coating pan (stabilization)

After each stage of coating, there is a ‘weight gain’ of tablets which needs to be controlled properly to ensure the final average weight of tablets within specifications including its dimensions (diameter, thickness etc.)
As there are many stages the entire sugar coating cycle of a batch of tablets takes about 5 to 6 days. The process is lengthy and more operator-dependent (manual operations) as it requires skills. Hence nowadays very few companies follow the sugar coating process. Instead of sugar-coating the tablets are film-coated. The film coating process is fully automatic and can be easily standardized and less operator-dependent.

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@sunilrbudhkar nicely explained

Thank you Sir.