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Like lubricants, glidants are fine powders that enhance the movement of powders or granules within the hopper and into the die cavity prior to compaction, compression, or encapsulation. By enhacing flow rates of powders or granules, there is less weight variability of the tablets manufactured, resulting in more consistent dosing of the drug substance(s). It has been suggested that the ability of glidants to enhance the movement of the powder or granules within the hopper and into the tablet die in the tablet press is due to the ability of particles of the glidants to locate within the spaces between the powder particles/ granules.
Glidants are typically hydrophobic and therefore care should be taken to ensure that the concentration of glidants used in the formulation does not (in a similar fashion to lubricants) adversely affect tablet disintegration and drug dissolution. Examples of glidants used in tablet manufacture include colloidal silicon dioxide, talc, corn starch etc.
In addition to the drug substance(s), compressed tablets also contain adsorbents. They are used whenever there is need to include a liquid or semisolid drug substance(s) or excipients (e.g., flavour) within the tablet formulation. Adsorbents adsorb moisture that may attack tablets or cause cohesiveness of tablet powder/ granules from these liquid or semi-solid components thus, allowing proper tablet compression during tablet formulation.
As the production of tablets requires solid components, the liquid/semisolid constituent is adsorbed on to a solid component which, in many cases, may be one of the other components in the tablet formulation (e.g. diluent) during mixing. If this approach is not possible, an adsorbent is specifically included in the formulation. Examples of adsorbents used in the manufacture of tablets include magnesium oxide/carbonate, kaolin/bentonite etc.
Sweeteners are incorporated in tablets to impart sweetness to the product and hence the acceptability of tablets. The excipient is of particular importance if the conventional tablet contains a bitter drug substance(s) or, more importantly, if the tablet is a chewable tablet. Sucrose is the standard against which all sweeteners, both natural and artificial, are measured.
In addition to being many more times sweeter than sucrose, artificial sweeteners have the advantage of not impacting blood sugars of diabetic or pre-diabetic patients, and they are considered non-cariogenic. Examples of sweeteners that have found use in tablet manufacture include acesulfame potassium, aspartame, confectioner’s sugar, dextrates, dextrose, fructose, mannitol, saccharin, sorbitol, sucralose, sucrose, xylitol etc.
Read Also: Preformulation Studies: Drug-Excipient Compatibility Studies
Flavourants also referred to as falvours, or flavouring agents are pharmaceutical excipients used to impart a pleasant flavour and often odour to pharmaceutical formulations. They may be derived from natural sources (e.g., fruit components) or prepared artificially. Their selected use in pharmaceutical dosage forms is based on the desired flavour, their solubility characteristics, and their physicochemical compatibility with the drug substance/ active pharmaceutical ingredient and other excipients in the formulation.
Some favouring materials are more effective than others in masking or disguising the undesirable taste of drug substances. Although individuals’ tastes and flavour preferences differ, cocoa-flavoured vehicles are considered effective for masking the taste of bitter drugs. Fruit or citrus flavours are frequently used to combat sour or acid-tasting drugs, and cinnamon, orange, raspberry, and other flavours have been successfully used to make preparations of salty drugs more palatable.
The age of the intended patient should be considered in the selection of the favouring agent because certain age groups seem to prefer certain flavours. Children for instant prefer sweet candy-like preparations with fruity flavours, but adults seem to prefer less sweet preparations with a tart rather than a fruit flavour.
Flavourants can degrade as a result of exposure to light, temperature, headspace oxygen, water, enzymes, contaminants, and other product components, so they must be carefully selected and checked for stability.
Colourants are generally employed in tablet manufacture either for aesthetics or to uniquely identify finished tablets. A distinction should be made between substances that have inherent colour and those that are used as colourants.
Colourants can be divided into water-soluble dyes and water-insoluble pigments. Concerns over the safety of these agents in pharmaceutical formulations generally arise from their adverse effects in food substances. Each country has its own list of approved colourants that may be used in medicinal products, and formulation scientists must consider this in designing pharmaceutical dosage forms for the international market.
Any of the approved, certified, water soluble FD&C dyes, mixtures of the same, or their corresponding lakes may be used to colour tablets. It is important that the colour is uniformly distributed throughout the tablet. Examples of colourants used in the manufacture of tablets include iron oxides, titanium dioxide, and aluminium lakes.
Surfactants are excipients that are added into tablet formula to improve the wetting properties of hydrophobic tablets and hence increase the rate of tablet disintegration. They may also increase the aqueous solubility of poorly soluble drug substance in the gastrointestinal tract and, as a result, the rate of dissolution of the active agent will increase. It should be noted that the surfactants should not interact with the drug substance as this may affect the dissolution rate of the drug substance.
Examples of surfactants used in the manufacture of tablets include sodium lauryl sulphate (one of the most popular surface-active agent that improves the wetting properties of hydrophobic tablets), Cetylpyridine chloride, glyceryl monooleate etc.
Excipients are essential in the formulation of tablets as it ensures successful manufacturing process and quality of the resultant formulation. Proper selection of excipients and their relative concentrations in the formulation is important in the development of a successful pharmaceutical formulation. Although excipients are often categorized as inert, preformulation studies can help determine how these excipient influence the stability, bioavailability, and processability of the dosage forms.
The need for acquiring more information and use standards for excipients has been recognized in a joint venture of the Academy of Pharmaceutical Sciences and the Council of the Pharmaceutical Society of Great Britain. The result is called the Handbook of Pharmaceutical Excipients. This reference work is now distributed widely throughout the world.
The title of this article is Excipients Used In the Manufacture of Tablets. By reading this article you will get an overview of all the excipients used In the manufacture of tablets.
