Pharmaceutical tablets may be defined as the solid unit dosage form of one or more medicaments with or without suitable excipients and prepared either by moulding or by compression. A tablet comprises a mixture of active substances and excipients, usually in powder form, pressed or compacted from the powder into a solid dose. The compressed tablet is the most popular dosage form in use today. About two-thirds of all drugs currently prescribed are in solid form in half and of these are as compressed tablets.
Major Categories of Tablets:
· Uncoated – a single layer or more than one layer of formulation that consists of active ingredients and excipients compressed together without any additional coat or cover
· Coated – tablets that have additional coating layer added. Examples of coatings include gums, sugar, plasticizers and waxes.
· Dispersible – tablets that have film coats or uncoated tablets that form a uniform dispersion when it is suspended in water
· Effervescent – tablets that are uncoated and are intended to dissolve and disperse when mixed with organic acid or bicarbonate to produce gaseous carbon dioxide (CO2). The CO2disintegrates the tablet to produces a suspension of powdered material that is readily absorbed
· Modified release – coated or uncoated tablets that are designed to release the active ingredient when the desired activity or condition is reached. Examples: enteric coated, delay-release and prolonged release
· Enteric coated – also called as gastro-resistant, these tablets are resistant to acidic gastric juices. They are coated with a polymer material such as Cellulose acetate phthalate, Cellulose acetate trimellitate, or acrylate polymers.
· Prolonged release – also called as extended release or sustained release tablets. These tablets are formulated in such a way that the release of active ingredient is controlled over a prolonged period. Special excipients are needed to be able to produce prolonged release tablets.
· Soluble – tablets that are dissolved in water before being administered. These may be coated or uncoated.
· Tablets that are for mouth use – these tablets are formulated to release active ingredients when placed in the buccal cavity or mouth area. They are used when a patient has difficulty swallowing or when fast release into the bloodstream is required. Examples are buccal and sublingual tablets, lozenges and troches.
o Buccal – tablets placed in between the gingival (gums) and cheek area
o Sublingual – placed underneath the tongue
· Implantable/Other Route – tablets that are placed in other areas of the body instead of the mouth (example, rectal or vaginal tablets).
Advantages of tablets:
· Ease and convenience of use
· Fixed and metered dosages
· Bitter tasting drugs can be masked with coated tablets
· Unstable API can be administered through coated tablets
· Modified release of active ingredients ensures patient’s compliance and increases therapeutic effect
· Inexpensive form of dosage
· Stability of API
· Availability of drugs depends on several factors.
· Onset of action of drugs is less compared with direct route such as IV.
· Smaller and geriatric patients may find it harder to swallow tablets.