It is a solid unit dosage form of the medicament or medicaments with or without diluents and may be prepared by the molding or compression method and vary in size, weight, shape depending upon the route of administration and type of tablet.
Types of tablets:
Tablets have two types
1) Molded tablets
2) Compressed tablets
Have further three types:
a) Tablet triturate mold
b) Hypodermic tablet
c) Dispensing tablet
a) Tablet triturate mold:
Molded tablets are small disc shaped tablets which are prepared by forcing the soft mass into the cavities of mold. Generally potent medicaments and highly toxic drugs in small doses are used for preparing the molded tablets. The potent medicament is diluted with diluents like, lactose, dextrose, sucrose or a mixture of lactose and sucrose. The mixed powders are moistened with a suitable dilution of alcohol (generally so% alcohol) and mixed thoroughly so as to get a soft mass.
Soft mass prepared, pressed into the perforation of mold with spatula. This perforated plate of the mold filled with the mass, which is placed over another plate having exactly the same number of projecting pegs as that of perforation and these projecting pegs completely fit into holes. A little pressure is applied over top plate which will move the force downward, leaving the molded tablets on the projecting pegs.
b) Hypodermic tablets:
Hypodermic tablets are the soft, readily soluble tablets which are made in the tablet triturate mold. They are used for preparing solution to be injected, therefore in selecting the materials used for preparing the hypodermic tablets. Care must be taken that they should be completely and readily soluble and no insoluble particles should be present. They should be b=free from the bacterial contamination.
c) Dispensing tablets:
These tablets are prepared for providing an accurate and convenient quantity of drug that can be incorporated readily in compounding other dosage form. Tablets are solely designed to provide a convenient quantity for administration as a dosage form, because sometimes they contain very potent drugs which may prove fatal.
There are many further subdivisions of the compressed tablets that are given here.
a) Oral tablets:
These tablets are swallowed as such. They are placed over the tongue and swallowed with drink of water or any other suitable liquid. Most of them are formulated in such a way that they disintegrate in the stomach and dissolve in the gastric fluids thus absorption take place from there. Some of the tablets like enteric coated pass the stomach as such and disintegrates in the intestine from where absorption take place. Some time Mannitol can be used as sweetening agent.
Since the oral tablets are required to be disintegrated in the short time therefore either the medicament itself should be soluble in gastrointestinal fluids or disintegrating agents must be added in the formulation.
b) Chewable tablets:
These are the tablets which are requires to be broken and chewed in between the teeth before ingestion. These tablets are given to the children who have difficulty in swallowing and to the adults who dislike swallowing. A number of antacid tablets and multivitamins tablets are prepared as chewable tablets. These tablets do not require any disintegrating agent. In chewable tablets Mannitol is used as sweetening agents, it masks the bitter taste of the tablet. It is more 70% sweet than the sucrose. In the tablet it acts as a excipients.
c) Lozenge tablets:
These tablets effect on mucous membrane of throat. They can be prepared by molding as well as by compression method. In the formulation of lozenges no disintegrating agent is added. These tablets give smoothening and calming effect. It can be used in the throat pain and also irritation of the throat.Formulation must contain more sweetening agent and flavoring agent.
d) Enteric coated tablets:
These are the tablets which are required to be disintegrated in the intestine and not n the stomach. They are given coating which makes the tablet to pass the stomach as such a avoid stomach environment (acid and enzymes).
e) Soluble tablets:
These tablets are required to dissolve completely in liquid to produce solution of definite concentration. The solution prepared by dissolving the soluble tablets may include mouth washes, gargles, skin lotions, douches, antibiotics and certain vitamins.
f) Effarvasant tablets:
These tablets along with the active medicament contain other ingredients like, sodium bicarbonate, citric acid and tartaric acid which react in the presence of water liberating carbon dioxide and producing effervescence leading to disintegration of the tablet.
g) Sustain release/ repeated action tablets:
These are the tablets which after oral administration release the drug at a desires time and prolong the effect of the medicament.
These are small tablets meant for insertion under the skin by giving as small surgical cut into the skin, and cut is up to dermis and subcutaneous level. Implants are prepared to provide a slow and continuous release of drug over a long period of time ranging from three to six months, due to this reason drug used in the implants preparation are water insoluble.
i) Layered tablets:
These are the compressed tablets in which the granules of incompatible substances are compressed in to two or more layers successively in the same tablet.
j) Press coated tablets:
The granules of incompatible ingredients are compressed around the previously compressed tablet.
k) Film coated:
These are the compressed tablets which are given a thin coating of water soluble materials which protect the drug substances from atmospheric condition.
l) Sugar coated:
These are compressed tablets which are given a sugar coating to mask the bitter taste and odor of the drug as well as to protect the substance from atmospheric condition. This kind of tablets has some disadvantages like they are more venerable to the ecomposition by bacteria.
m) Buccal/ sublingual tablets:
These tablets are required to be placed below the tongue (sublingual) or in the side of cheek (Buccal). Generally these tablets contain those drugs which are destroyed, inactivated or not absorbed in the gastrointestinal tract, but are directly absorbed through mucosal tissue of the oral cavity.
Doctor of Pharmacy
University of Lahore