Difference between coated and uncoated tablets – When is the coating necessary?

If you’re wondering when coating a tablet is necessary, there’s not just one answer. Uncoated tablets are rougher and don’t really taste good. This makes them harder to swallow especially for children, as they also leave a bad aftertaste in the mouth. So coating is important to mask an unpleasant taste. Another reason may be that the active ingredient the tablet is made of is acid sensitive, so an enteric coating may help resist stomach acidity.

On the other way around, the enteric coating can also help protect the stomach from a more aggressive drug. Apart from that, the coating reduces also tablet friability and it can modify or control drug release. In uncoated tablets, any excipient or added substance is not specifically intended for this purpose.

Problems that can occur during uncoated tablets manufacturing

Disintegration time for uncoated tablets

Disintegration is the ability of a tablet to break down into smaller particles to allow the drug to be absorbed by the body. The disintegration test is paramount for tablets that are intended for mouth administration except for chewable tablets.

The disintegration tester consists of a basket that can hold six tablets. The basket is raised and lowered into a beaker that has water as the immersion fluid, unless there is another medium specified, having the temperature at 35 °C to 39 °C.

After running the device for the specified time, if all the tablets are disintegrated completely, they are good to go. If one or two tablets fail the test, it must be repeated on 12 additional tablets. If not less than 16 out of 18 tablets tested are disintegrated, the requirements are met.

Friability test for uncoated tablets

Which type of excipients do you have to use in uncoated tablets?

During uncoated tablet manufacturing, you cannot think to start without having your excipients. They play an important role and fulfill different functions – they can improve the taste or modify the disintegration time or the time and place of substance release. Saying that they are everything other than APIs, i.e. active pharmaceutical ingredients. When making uncoated tablets, there are some types of excipients you have to use.

For example, excipients used in orally disintegrating tablets (ODT) are sucrose, mannitol or sorbitol. Since this type of tablet disintegrates very quickly upon contact with saliva, disintegrants such as polyvinylpyrrolidone or sodium starch glycolate play a fundamental role here. In effervescent tablets instead, excipients used are citric acid, sodium citrate, fumaric acid, tartaric acid, with citric acid being one of the most important.