Tablet

From Free net encyclopedia

For other meanings please see Tablet (disambiguation)

Image:FlattenedRoundPills.jpg A pharmacological tablet is a medicinal or other active substance mixed with binder powders and pressed into a tablet form.

Most tablets are circular-shaped, or disk-shaped, but recent decades have seen many that are oblong or various-shaped.

When Tylenol (paracetamol/acetaminophen) capsules were laced with cyanide (an incident referred to as the Tylenol scare), many people stopped buying capsules because they are easy to contaminate, in favor of tablets, which are not. Some makers of OTC (over-the-counter) drugs responded by starting to make what they termed "caplets", which were actually just tablets made in the shape of a capsule.

1 Tabletting formulations
2 Tablet coating
3 Tablet presses
4 External links

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Tabletting formulations

In the tablet-pressing process, it is important that all ingredients be dry, powdered, and of uniform grain size as much as possible. Mixed grain sizes tend to separate out due to operational vibrations, resulting in inconsistent tableting, while any moisture in the system will tend to clog the tableting pathways. Image:OblongPills.JPG

Image:Tetralysal.jpg Some substances may be tableted as pure substances, but this is usually not the case; most formulations include excipients. Normally, an inactive ingredient termed a binder is added to help hold the tablet together and give it strength. A wide variety of binders may be used, some common ones including lactose powder, sucrose powder, tapioca starch (cassava flour) and microcrystalline cellulose.

Often, an ingredient is also needed to act as an Disintegrant. This is an ingredient that dissolves readily in water to help the tablet disperse once swallowed. Some binders, such as starch, are also excellent disintegrants.

Small amounts of lubricants are usually added, as well. The most common of these are stearic acid (stearin) and magnesium stearate. These help the tablets, once pressed, to be more easily ejected from the die. Image:VariousPills.JPG

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Tablet coating

Many tablets today are coated after being pressed. Although sugar-coating was popular in the past, the process has many drawbacks. Modern tablet coatings are polymer and polysaccharide based, with plasticizers and pigments included. Tablet coatings must be stable and strong enough to survive the handling of the tablet, must not make tablets stick together during the coating process, and must follow the fine contours of embossed characters or logos on tablets. Coatings can also facilitate printing on tablets, if required. Coatings are necessary for tablets that have an unpleasant taste, and a smoother finish makes large tablets easier to swallow. Tablet coatings are also useful to extend the shelf-life of components that are sensitive to moisture or oxidation. Opaque materials like titanium dioxide can protect light-sensitive actives from photodegradation. Special coatings (for example with pearlescent effects) can enhance brand recognition.

If the active ingredient of a tablet is sensitive to acid, or is irritant to the stomach lining, an enteric coating can be used, which is resistant to stomach acid and dissolves in the high pH of the intestines. Enteric coatings are also used for medicines that can be negatively affected by taking a long time to reach the small intestine where they are absorbed.

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Tablet presses

Tablet presses, the machines that make the tablets, range from small, inexpensive bench-top models that make one tablet at a time, no more than a few thousand an hour, and with only around a half-ton pressure, to large, computerized, industrial models that can make hundreds of thousands of tablets an hour with much greater pressure. Some tablet presses can make extremely large tablets, such as some of the toilet cleaning and deodorizing products or dishwasher soap.

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