TYPES OF TABLETS

TYPES OF TABLETS

Tablets for oral administration

Sublingual tablets :

        These tablets are intended to be placed under the tongue and allowed to  dissolve and absorb. After absorption, the drug enters the systemic circulation without passing through the portal circulation, thus avoiding first-pass inactivation in the liver.Absorption of lipid-soluble molecules through the oral mucosa is rapid and the effect of drugs given in     this way may become apparent within 2 min. Nitroglycerin and organic nitrates are commonly administered by this route. Drugs that are destroyed by the gastrointestinal fluids or are subject to substantial presystemic metabolism may be  formulated into such tablets, Examples: Nitroglycerin, Methyltestosterone, Validol, etc.

Buccal tablets

        These  are small, flat, oval tablets, intended for buccal administration by inserting them into the buccal pouch (the space between the teeth and the cheek). They are dissolved or eroded slowly. Example:  Desaminooxytocine (Sandopart).

       

Chewable tablets

       These are large, hard tablets, difficult to swallow, intended to be crushed before ingesting. Example: Combantrin, Centrum junior, etc.

       Effervescent  tablets

       These contain sodium bicarbonate and an organic acid in addition to the drug substance. In the presence of water, these additives react liberating carbon dioxide which acts as disintegrator and produces effervescence. These tablets are soluble and they are taken readily and absorbed rapidly (e.g., Upsarin, Vit C, Supradin, etc.).

Sugar-coated tablets

      These are smooth, oval compressed tablets containing sugar coatings. Sugarcoating provides both protection and sweet taste but the coating operations take a long time. Example: Nifedipin,Vitaferro,

Film-coated tablets (FCT,)

 These are compressed tablets which are covered with a thin layer or a film of polymeric substances to protect their contents from moisture or to mask the taste of the ingredients

Enteric-coated tablets (ECT, )

      These are coated with substances that resist solution in gastric fluid but disintegrate in the alkaline contents of the intestine. Enteric coating is used for drugs with a gastric  irritant action, for drugs which are unstable in the acid medium of the gastric contents or if the drug should act on the intestine. (e.g., Voltaren, Salazopyrin).

Controlled-release tablets

These are formulated to release the drug slowly over a prolonged period of time. These dosage forms

have been referred to as prolonged-release (PR) or sustained-release (SR) dosage forms as well.

Tablets for parenteral administration

Inserts

These are intended for insertion into body orifices. Metronidazole, Isoconazole, Clotrimazole are

vaginal tablets (tabulettes vaginales).

Pellets (tablets for implantation)

are small, sterile tablets, used by implantation when prolonged and continuous absorption is

desired  (Estradiol, Disulfiram, etc.)

OTHERS

SINGLE  COMPRESSED TABLETS

These are manufactured  by just compressing the granules in particular geometery form.These are  designed to provide rapid disintegration and hence rapid drug release. After ingestion, the tabletswill disintegrate within the gastrointestinal tract. allowing the drug to dissolve in the gastric fluid and, ultimately, be absorbed systemically.

MULTIPLE COMPRESSED TABLETS

These are of two types

COMPRESSION COATED TABLETS

This type of tablet (compression coated tablet) has two parts, internal core and surrounding coat. The core is small porous tablet and prepared on one turret while coat is also formed by compression but is very smooth and  is usuallly  water soluble and disintegrates easily after swallowing, in order to achieve immediate release product.Some time delayed release tablets are made by this way.

MULTIPLE LAYERED TABLETS.

In this design the first layer is formed by a relatively light compression of the drug containing powder mix/granules. The next layer is then formed by compression of the powder/granule mix (containing drug) on top of the lightly compressed first layer. Additional layers are formed in a similar fashion. These May be used to incorporate more than one drug and separate them if any chemical  incompatibilities exist. Drug release behavior is not restricted to one type, this system may offer varied drug  release kinetics of the same or different drugs such as extended and immediate release.