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 molding 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.
Type of Tablet
1. Uncoated tablet
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
2. Coated tablet
Tablets that have additional coating layer added. Examples of coatings include gums, sugar, plasticizers and waxes.
3. Dispersible tablet
Tablets that have film coats or uncoated tablets that form a uniform dispersion when it is suspended in water.
4. Effervescent tablet
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 CO2 disintegrates the tablet to produces a suspension of powdered material that is readily absorbed.
Ingredients: active medicament+ sodium carbonate / citric acid / tartaric acid
5. Modified release tablet
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
6. Enteric coated tablet
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.
7. Prolonged release tablet
Also called as extended-release or sustained-release tablets. These tablets are formulated in such a way that the release of active ingredients is controlled over a prolonged period. Special excipients are needed to be able to produce prolonged-release tablets.
8. Soluble tablet
Tablets that are dissolved in water before being administered. These may be coated or uncoated.
9. 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.
- Buccal tablets
- tablets placed in between the gingival (gums) and cheek area
- Sublingual tablets
- placed underneath the tongue
- Troches & Lozenges
- place in the side of a cheek for slow release of medicament absorbed directly into the buccal cavity- Bypass first-pass metabolism.
- Example: Local anesthetic, Antiseptic, antibacterial agent.
- Dental Cone
- compressed tablet placement in the cavity of the empty socket after teeth extraction.
10. Implantable tablets
Tablets that are placed in other areas of the body instead of the mouth (example, rectal or vaginal tablets).
11. Chewable tablet
These are placed into mouth & chewed & Finally swallowed. Chewable tablet has no requirement of Disintegration agents.
12. Hypodermic tablet
Tablet is dissolved with sterile water and administered by parenteral route/injection.
Advantages of tablets
- Ease and convenience of use
- 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 the therapeutic effect
- Inexpensive form of dosage
- Stability of API
- Most stable with respect to physical, chemical and microbiological attributes.
- Cheapest oral dosage form, easy to handle, use and carry out with attractive and elegant appearance.
- Cheap, easy to swallow and production does not require and additional processing steps.
- Low manufacturing cost as compared to other solid dosage forms and large-scale production is possible.
- An unpleasant taste can be masked by sugar coating.
- Packing and production is cheap and does not require more space for storage.
Disadvantages of Tablets
- The onset of action of drugs is less compared with the direct routes such as IV.
- Smaller and geriatric patients may find it harder to swallow tablets.
- Drugs which are amorphous and low-density character are difficult to compress into a tablet.
- Hygroscopic drugs are not suitable for compressed tablets.
- Drugs with low or poor water solubility, sloe dissolution, high absorbance in GI tract may be difficult to formulate.
- Sensitive to oxygen drugs may require special coating.
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