FORMULATION DESIGN, MANUFACTURE CRITERIA AND REQUIREMENT OF VARIOUS TYPES OF TABLET

About Authors:
1Sahu Deepak*, 2Ketawat Santosh
1Ass.Professor, Geetanjali Institute of Pharmacy,
2Lecturer, Geetanjali Institute of Pharmacy,
Dabok, Udaipur [Rajasthan] – 313022
*deepak.sahu.bhl@gmail.com

Abstract
Tablet is the most preferred oral dosage form, due to many advantages it offers to formulators as well as physicians and patients. However, the process of manufacturing tablets is complex. Hence, careful consideration has to be given to select right process, and right excipients to ultimately give a robust, high productivity and regulatory compliant product of good quality.

Reference Id: PHARMATUTOR-ART-1436

Introduction:
Tablets may be defined as solid pharmaceutical dosage forms containing drug substances with or without suitable diluents and prepared either by compression or molding methods. They have been in widespread use since the latter part of the 19th century and their popularity continues. The term compressed tablet is believed to have been first used by 'John Wyeth and Brother of Philadelphinn’ During the same period molded tablets were introduced to be used as Hypodermic tablets for injections. Tablets remain popular as a dosage form because of the advantages, afforded both to the manufacturer [e.g.: simplicity & economy of preparation, stability and convenience in packing, shipping, and dispensing] and the patient [e.g.: accuracy of dosage, compactness, post ability, blandness of taste and ease of administration. Although tablets are more frequently discoid in shape, they also may be round, oval, oblong, cylindrical or triangular. They may differ greatly in size and weight depending on the amount of drug substance present and the intended method of administration.

The objective of this article is to provide a comprehensive overview of the tablet core manufacturing process with emphasis on oral immediate release formulations, along with common excipients used.

Properties of Tablets :
The attributes of an acceptable tablet are as follows:
1)             The tablet must be sufficiently strong and resistance to shock and abrasion and to with stand handling during manufacturing, packing, shipping, and use. Hardness and friability tests measure this property.
2)             Tablet must be uniform in weight and in drug content of the individual tablet. This is me assured by the weight variation and content uniformity tests.
3)             The drug content of the tablet must be bioavailable. This property is measured by the dissolution test. Accurate bioavailability can be obtained from the drug levels of the drug after its administration.
4)             Tablets must be elegant in appearance and must have characteristic shape, color, and other markings necessary to identify the product.
5)             Tablets must retain all these functional attributes, which include drug stability and efficacy.

Advantages of Tablet :
1)             It is easy to be administered.
2)             It is a unit dosage form, and they offer the greater capabilities of all oral dosage forms for    the greatest dose precision and the least content variability.
3)             Cost is lowest of all oral dosage forms.
4)             It is the lightest and most compact of all oral dosage forms.
5)             Product identification is potentially the simplest and cheapest, requiring no additional processing steps when employing an embossed or monogrammed punch face.

Disadvantages of Tablets:
1)             Some drugs resist compression into dense compacts, owing to their amorphous nature or flocculent, low-density character.
2)             Drugs with poor wetting, slow dissolution properties, intermediate to large dosages, optimum absorption high in the gastrointestinal tract, or any combination of these features may be difficult or impossible to formulate and manufacture as a tablet that will still provide adequate or full drug bioavailability.
3)             Bitter drugs, drugs with objectionable odor or drugs that are sensitive to oxygen or atmosphere moisture may require encapsulation or a special type of coating which may increase the stability of the finished tablets.

Types of Tablets:2-3
Tablets are classified according to their route of administration or function. The following are the 5 main classification groups.
1. Tablets ingested orally

1.1. Compressed tablets
1.2. Multiple compressed tablets

i) Multilayered tablets

ii) Inlay tablets
1.3. Sustained action tablets
1.4. Enteric coated tablets
1.5. Sugar coated tablets
1.6. Film coated tablets
1.7. Chewable tablets

2. Tablets used in the oral cavity
2.1. Buccal tablets
2.2. Sublingual tablets
2.3. Lozenge tablets and torches
2.4. Dental cones

3. Tablets administered by other routes
3.1. Implantation tablets
3.2. Vaginal tablets

4. Tablets used to prepare solutions
4.1. Effervescent tablets

5. Molded tablets or tablet triturates (TT)
5.1. Dispensing tablets (DT)
5.2. Hypodermic tablets (HT)

*    Compressed tablets1,2,3:
These tablets are uncoated and made by compression of granules. These tablets are usually intended to provide rapid disintegration and drug release. These tablets after swallowing get disintegrated in the stomach, and its drug contents are absorbed in the gastrointestinal tract and distribute in the whole body.

*    Multiple compressed tablets2,3:
These tablets are prepared to separate physically or chemically incompatible ingredients or to produce repeat action prolonged action products. To avoid incompatibility, the ingredients of the formulation except the incompatible materials are compressed into a tablet then incompatible substances along with necessary excipients are compressed tablet.

*    Multilayered tablets3:
These tablets consist of two or more layer of materials compressed successively in the same tablets. The color of each layer may be the same or different. The tablets having layers of different colors are known as "multicolored tablets".

*    Inlay Tablet3,4:
A type of layered tablet in which instead the core tablet being completely surrounded by coating, top surface is completely exposed. While preparation, only the bottom of the die cavity is filled with coating material and core is placed upon it. When compression force is applied, some coating material is displaced to form the sides and compress the whole tablet. It has some advantages over compression coated tablets:
i) Less coating material is required.
ii) Core is visible, so coreless tablets can be easily detected.
iii) Reduction in coating forms a thinner tablet and thus freedom from capping of top coating.

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