An excipient is an inactive substance used as a carrier for the
active ingredients of a medication. In many cases, an "active" substance (such as aspirin) may not be easily administered and absorbed by the human body; in such cases the substance in question may be dissolved into or mixed with an excipient. Excipients are also sometimes used to bulk up formulations with very potent active ingredients, to allow for convenient and accurate dosage. In addition to their use in the single-dosage quantity, excipients can be used in the manufacturing process to aid in the handling of the active substance concerned. Depending on the route of administration, and form of medication, different excipients may be used. For oral administration tablets and capsules are used. Suppositories are used for rectal administration.
Often, once an active ingredient has been purified, it cannot stay in purified form for 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 are added, ensuring that the active ingredient stays "active", and, just as importantly, stable for a sufficiently long period of time that the shelf-life of the product makes it competitive with other products. Thus, the formulation of excipients in many cases is considered a
Pharmaceutical codes require that all ingredients in drugs, as well as their
chemical decompositionproducts are identified and guaranteed to be safe. For this reason, excipients are only used when absolutely necessary and in the smallest amounts possible.
Types of excipients
Antiadherents are used to reduce the adhesionbetween the powder ( granules) and the punch faces and thus prevent sticking to the tablet punches.
Binders hold the ingredients in a tablet together.
Binders ensure that tablets and granules can be formed with required mechanical strength. Binders are usually
starches, sugars, celluloseor modified cellulose such as hydroxypropyl cellulose, lactose, or sugar alcohols like xylitol, sorbitolor maltitol.
Binders are classified according to their application:
*Solution binders are dissolved in a solvent (for example
wateror alcohol and used in wet granulation processes. Examples include gelatin, cellulose, cellulose derivatives, polyvinylpyrrolidone, starch, sucroseand polyethylene glycol.
*Dry binders are added to the powder blend, either after a wet granulation step, or as part of a direct powder compression (DC) formula. Examples include
cellulose, methyl cellulose, polyvinylpyrrolidone, and polyethylene glycol.
Tablet coatings protect tablet ingredients from deterioration by moisture in the air and make large or unpleasant-tasting tablets easier to swallow. For most coated tablets, a cellulose (plant fiber) film coating is used which is free of sugar and potential
allergens. Occasionally, other coating materials are used, for example synthetic polymers, shellac, corn protein zeinor other polysaccharides. Capsules are coated with gelatin.
Changing the dissolution rates of active species
Enteric coatings control the rate of drug release and determines where the drug will be released in the digestive tract.
Disintegrants expand and dissolve when wet causing the tablet to break apart in the digestive tract, releasing the active ingredients for absorption. Disintegrant types include:
*Water uptake facilitators
*Tablet rupture promotersThey ensure that when the tablet is in contact with
water, it rapidly breaks down into smaller fragments, thereby facilitating dissolution.Examples of disintegrants include: starch, cellulose, crosslinked polyvinyl pyrrolidone, sodium starch glycolate, sodium carboxymethyl cellulosemethycellulose.
Fillers fill out the size of a tablet or capsule, making it practical to produce and convenient for the consumer to use. By increasing the bulk volume, the final product has the proper volume for patient handling.
A good filler must be inert, compatible with the other components of the formulation, non-hygroscopic, soluble, relatively cheap, compactible, and preferably tasteless or pleasant tasting.
cellulose(pure plant filler) is a popular filler in tablets or hard gelatin capsules. Dibasic calcium phosphateis another popular tablet filler. A range of vegetable fats and oilscan be used in soft gelatin capsules.
Other examples of fillers include:
lactose, sucrose, glucose, mannitol, sorbitol, calcium carbonate, and magnesium stearate.
Flavors and Colors
Flavors and Colors are added to improve the taste or appearance of a formulation. Color consistency is important as it allows easy identification of a medication.
Glidants are used to promote powder flow by reducing interparticle friction and cohesion. These are used in combination with lubricants as they have no ability to reduce die wall friction. Examples include colloidal silicon dioxide, talc, and etc.
Lubricants prevent ingredients from clumping together and from sticking to the tablet punches or capsule filling machine. Lubricants also ensure that tablet formation and ejection can occur with low frictionbetween the solid and die wall.
Common minerals like
talcor silica, and fats, e.g. vegetable stearin, magnesium stearateor stearic acidare the most frequently used lubricants in tablets or hard gelatin capsules.
preservativesused in pharmaceutical formulations are
antioxidantslike vitamin A, vitamin E, vitamin C, retinyl palmitate, and selenium
amino acids cysteineand methionine
citric acidand sodium citrate
* synthetic preservatives like
methyl parabenand propyl paraben.
Sorbents are used for tablet/capsule moisture-proofing by limited fluid sorbing (taking up of a liquid or a gas either by adsorptionor by absorption) in a dry state.
Sweeteners are added to make the ingredients more palatable, especially in chewable tablets such as antacidor liquids like cough syrup. Therefore, tooth decayis sometimes associated with cough syrupabuse. Sugarcan be used to disguise unpleasant tastes or smells.
Pharmacology- Placebo- Placebo effect- Quality system
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