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Heart disease: pharmaceutics

Watch Ian explain how inactive ingredients, called excipients, are used to give a tablet the physical properties it needs.
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SPEAKER 1: In this video you’re going to learn about tablets– by far, the most common type of medicine. Being so common, it is important to know what makes a good tablet, and why. Atorvastatin, the medicine Steve is taking for his heart, comes in the form of tablets. As a type of medicine, tablets offer us and pharmaceutical companies many advantages. People understand how to use them, and they’re easy to measure. It is simple to count one, two, or even half a tablet. And compared to liquid medicines, by and large, we can easily carry them around with us if we need to. From a pharmaceutical company point of view, their packaging can keep the drug dry and in the dark.
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Moisture and light can cause a drug to degrade and change its chemical structure. Tablets can also be manufactured at high speeds relatively efficiently. For a medicine to act quickly, tablets must disintegrate and the drug must dissolve quickly. To understand how this happens, we first need to know what tablets are made of. Along with the drug, tablets contain a number of other ingredients. These inert ingredients, technically known as excipients, are normally added as powders, as is the drug. So there’s at least one mixing, or blending, step involved in making a tablet. And as some of these powders are sticky and are hard to handle, sometimes these powder mixtures are combined together to form granules. This process is called granulation.
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These granules are then squeezed together, compacted, to form tablets.
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Excipients commonly used are fillers, or diluents, disintegrants, binders, and lubricants. Many drugs are quite potent, meaning that we only need to take small amounts of them. Fillers are used to add bulk to a tablet, so that it is physically bigger and easier to handle. Lactose, the sugar in milk, is the most common filler. A binder holds the granules together and makes the tablet hard. We will learn about tablet hardness shortly.
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Disintegrants do as their name suggests. Upon becoming wet, the disintegrant expands and makes the tablet disintegrate into its constituent granules. A balance of binder and disintegrant is necessary to have a hard tablet that will still disintegrate quickly. Tablets are formed in a dye, squeezed together by an upper and lower punch. To help the tablets be ejected from the dye, a lubricant is added to the powder mix. Lubricants are usually a kind of wax. When we swallow a tablet, it disintegrates into its constituent granules. Disintegrating into granules increases the amount of contact between water and the drug, and so increases the speed at which the drug dissolves. The drug must be dissolved to be absorbed into our body.
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Most tablets are designed to disintegrate and dissolve as quickly as possible after swallowing. While the tablet must disintegrate quickly and dissolve fast, if we want the medicine to act quickly, there are other physical properties a tablet must have. If tablets are too soft, they might break into small pieces when you try to get them out of their packaging, or try to break them in half. You might lose some of these small pieces, which means you wouldn’t be taking the full dose. On the other hand, if they’re too hard, they might not disintegrate quickly enough. So there’s a balance between being too soft and too hard. Tablet hardness is, therefore, another important property of the tablet.
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During manufacturing and packaging, tablets collide with one another and with machinery at high speed. It is important that no fragments are broken off a tablet because of these collisions. Otherwise, the package tablet wouldn’t contain all the drug it needs to. Friability tests the ability of a tablet to survive these impacts, without edges or chips being broken off. Excipients are used to control these properties of disintegration, dissolution, hardness, and friability. To learn more about tablet design, please visit our virtual tablet formulation laboratory, where you’ll be challenged with making a tablet yourself.

Watch Ian explain how inactive ingredients, called excipients, are used to give a tablet the physical properties it needs.

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The Science of Medicines

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