Summary

Due to their appearance, pharmacists distinguish 3 types of tablets: uncoated tablets, dragées and coated tablets. The sugar coating and coating process is carried out in special devices called drums or fluid coater. The coating process is aimed at masking the unpleasant taste or smell of the tablet ingredients, facilitating swallowing, modifying the place and time of the release of the active substance, protecting the drug substance against atmospheric factors (oxygen, carbon dioxide, light, moisture) and thus increasing its durability, preventing mistakes in using drugs by marking them in color or inscription, giving them color and aesthetic appearance Probably you have often wondered why some tablets are coated and some are not.

First, some theory. Generally speaking, pharmacists distinguish between 3 types of tablets according to their appearance:

  1. Uncoated tablets

After the tabletting process (perform on tablet press) is completed, they are not further processed in any way and are directly packaged in blisters, jars and the like. It is the cheapest and very frequently used solution.

  1. Dragees

It is a tablet coated with a sugar coating, constituting from 30% to 80% of its weight.

Dragee is the first form of a coated tablet introduced into medicine – it was in 1891.

As a result of the tableting process, the so-called tablet core is formed, which undergoes further processes in special devices:

  • priming – increasing the mechanical strength of the core, protection against moisture penetration during the coating process. Most often it consists of covering the core with a layer of a suitable protective substance bound with a mixture of syrup and gelatin gruel
  • real coating – covering the core with an essential sugar coating to which a dye is often added
  • smoothing and further dyeing – smoothing out unevenness caused by the application of solid substances to the surface of the core.
  • polishing – coating the dragee with a thin layer of wax, which protects the coating from moisture and gives it an appropriate gloss.

The coating process is laborious, time-consuming (and therefore costly!) and requires experienced staff. For these reasons, it is now used less and less.

  1. Coated tablets

Today, tablet coating is most often carried out in a fluidized bed (Würster method). It consists in applying a polymer shell to the cores by spraying the coating mixture, often called a varnish. This is done in fluid bed coater, in which the tablets fly freely in a strong stream of air fed from below. In addition to the polymer, such a coating mixture contains a number of auxiliary substances, such as, for example, talc, titanium dioxide or dyes.

The polymer shell has a thickness of about 50 to 200 ?m, so it is several dozen times thinner than the sugar shell. This process is much faster and cheaper than sugar coating and is currently the most used.

 

 

Okay, but why are we doing all this? There are several reasons.

  • Masking the unpleasant taste or smell of the tablet ingredients

some medicinal substances have a very unpleasant, often very bitter taste which is felt immediately after taking such a tablet in the mouth. Sometimes it can cause a strong gag reflex. Examples of such substances are some antibiotics, for example roxithromycin and clarithromycin, and also cefuroxime. The coating masks this unpleasant taste and makes it easier to swallow. This is especially important in the case of children who are difficult to convince to swallow something that has an unpleasant, bitter taste.

  • Make it easier to swallow

Tablets often have a rough surface and, especially if they are in addition large, are difficult to swallow. After coating, their surface becomes smooth, which is definitely easy to swallow.

  • Modifying the site and time of release of the active ingredient.

It is sometimes necessary for the tablet to pass intact through the stomach and the active ingredient not to be released until the intestine. It is necessary mainly in two situations:

– when the active substance may be irritating to the gastric mucosa (e.g. acetylsalicylic acid, a popular aspirin)

– when the active substance decomposes at the acidic pH of the stomach (e.g. omeprazole)

This effect is achieved through the use of a coating with an appropriate composition.

  • Securing the drug substance against atmospheric factors (oxygen, carbon dioxide, light, moisture) and thus increasing its durability
  • Preventing medication errors by colour coding or writing on medicines

Confusing medication can have serious consequences for the patient. It can happen to a patient who prepares drug doses for a day or even a week or in a pharmaceutical factory as a result of human error. Tablets in different colours, often marked with additional inscriptions, are much more difficult to confuse.

  • Giving color and aesthetic appearance

This is mainly a marketing argument, but it is very important in a competitive market.

As you can see, there are many reasons for coating, which is why we often come across such nice, colourful tablets.

AUTHOR: Dr n. farm. Andrzej Tarasiuk