Excipient
From Pharmpedia
An 'excipient is a substance used as a "filling agent" in a medication. I'n general, the active substances (such as aspirin) may not be easily administered and absorbed by the human body; they need to be put in some appropriate form. The active substance is then dissolved or mixed with an excipient.
Depending on the route of administration, and medication form, various excipients may be used:
- oral route
- rectal route
- suppositories made of a greasy substance such as cocoa butter
Once the active ingredient has been purified, it cannot stay in purified form for very long. In many cases it will denature, fall out of solution, or stick to the sides of the container. To stabilize the active ingredient, excipients will be added to ensure that the active ingredient stays active, and is stable for a long period of time to ensure that the shelf-life of the product makes it competitive with other products. The formulation of these excipients in many cases is considered a trade secret.
'Tablets Excipients:'An excipient is a substance used as a "filling agent" in a medication. In general, the active substances (such as aspirin) may not be easily administered and absorbed by the human body; they need to be put in some appropriate form. The active substance is then dissolved or mixed with an excipient. Depending on the route of administration, and medication form, various excipients may be used:
Types or classification of excipeints:
They are classified according to following 2 types,
a) According to components b) According to characteristics
a) According to components:
According to componenets excipeints are of 3 types which are as follows,
• Diluent • Binders and Addhesive agents • Lubricants
1) Diluents: In order to facilitate tablet handling during manufacture and to achieve targeted content uniformity, the tablet size should be kept above 2-3 mm and weight of tablet above 50 mg. Many potent drugs have low dose (for e.g. diazepam, clonidine hydrochloride) in such cases diluents provide the required bulk of the tablet when the drug dosage itself is inadequate to produce tablets of adequate weight and size. Usually the range of diluent may vary from 5-80%. Diluents are also synonymously known as fillers. Diluents are often added to tablet formulations for secondary reasons like to provide better tablet properties such as:
i)To provide improved cohesion ii)To allow direct compression manufacturing iii)To enhance flow iv)To adjust weight of tablet as per die capacity
Examples of diluents are as follows with little description
INSOLUBLE TABLET FILLERS OR DILUENTS SOLUBLE TABLET FILLERS OR DILUENTS Starch Powdered cellulose Microcrystalline cellulose Calcium phosphates, etc. Lactose Sucrose Mannitol Sorbitol, etc.
2) Binders and addhesive agents: Binder is one of an important excipient to be added in tablet formulation. In simpler words, binders or adhesives are the substance that promotes cohesiveness. It is utilized for converting powder into granules through a process known as Granulation.
BINDER SPECIFIED CONCENTRATION Starch Paste 5-25%w/w Pregelatinized Starch (PGS) [Partially and Fully PGS] 5-10%w/w (Direct
Compression) 5-75%w/w (Wet Granulation ) Hydroxypropyl Methyl Cellulose (HPMC) 2-5%w/w Polyvinyl Pyrrolidone (PVP) 0.5-5%w/w
Polyethylene Glycol (PEG) 6000 10-15%w/w
3) Lubricants:
Lubricants are the agents that act by reducing friction by interposing an intermediate layer between the tablet constituents and the die wall during compression and ejection. Lack of adequate lubrication produces binding which can results in tablet machine strain and can lead to damage of lower punch heads, lower cam track, die seats and the tooling itself. And it may also yield tablets with scratched edges and are often fractured at the top edges.
Examples of lubricants with little description are as follows,
Stearates(Magnesium Stearate, Calcium Stearate, Sodium stearate) Talc Sterotex Waxes Stearowet Glyceryl behapate(Compritol®888) Liquid paraffin WATER SOLUBLE LUBRICANTS Boric acid Sodium benzoate Sodium oleate Sodium acetate Sodium Lauryl sulfate (SLS) Magnesium lauryl sulfate (MLS)
b) According to characteristics:
According to characteristics excipeints are as of following types,
• Disintigrating agents • Colourants • Sweetners • Flavourants
1) Disintigrating agents:
Disintegrants, an important excipient of the tablet formulation, are always added to tablet to induce breakup of tablet when it comes in contact with aqueous fluid and this process of desegregation of constituent particles before the drug dissolution occurs, is known as disintegration process and excipients which induce this process are known as disintegrants.The objectives behind addition of disintegrants are to increase surface area of the tablet fragments and to overcome cohesive forces that keep particles together in a tablet.
Examples with little discription are as follows,
Starch USP, Starch 1500, Alginic acid, Methyl cellulose, Na CMC, HPMC
2) Colourants:
Colourants neither contribute to therapeutic activity nor do they improve product bioavailability or stability but are incorporated into tablets for purposes like to facilitate identification of similar looking products with in a product line to avoid mix ups, to facilitate identification of products of similar appearance that exist in the lines of different manufacturers, to overcome colour change on aging, disguising of off-colour drugs, for brand image in the market, to enhance the aesthetic appearance of the product to have better patient acceptance. Most widely used colourants are dyes and lakes which are FD & C and D & C approved. SOME COMMONLY USED PHARMACEUTICAL COLOURANTS (SYNTHETIC) FD & C COLOUR COMMON NAME Red 3 Erythrosine Red 40 Allura red AC Yellow 5 Tartrazine Yellow 6 Sunset Yellow Blue 1 Brilliant Blue Blue 2 Indigotine Green 3 Fast Green
3) Flavourants:
Flavors are commonly used to improve the taste of chewable tablets as well as mouth dissolved tablets. Flavors are incorporated either as solids (spray dried flavors) or oils or aqueous (water soluble) flavors. Solids that is dry flavors are easier to handle and generally more stable than oils. Oil is usually added at the lubrication step because of its sensitivity to moisture and their tendency to volatilize when heated during drying.
4) Sweeteners:
Sweeteners are added primarily to chewable tablets.They are used to give tablets a pleasant taste. SOME OF THE SWEETENERS USED IN TABLET FORMULATION NATURAL SWEETENERS ARTIFICIAL SWEETENERS Mannitol Lactose Sucrose Dextrose Saccharin Cyclamate Aspartame
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