Oral Routes Of Drug Administration Biology Essay


Oral routes of drug administration have wide acceptance up to 50-60% of total dosage forms. Solid dosage forms are popular because of ease of administration, accurate dosage, self-medication, pain avoidance and most importantly the patient compliance. The most popular solid dosage forms are being tablets and capsules; one important drawback of this dosage forms for some patients, is the difficulty to swallow. Drinking water plays an important role in the swallowing of oral dosage forms. Often times people experience inconvenience in swallowing conventional dosage forms such as tablet when water is not available, in the case of the motion sickness (kinetosis) and sudden episodes of coughing during the common cold, allergic condition and bronchitis. For these reason, tablets that can rapidly dissolve or disintegrate in the oral cavity have attracted a great deal of attention. Or dispersible tablets are not only indicated for people who have swallowing difficulties, but also are ideal for active people.

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Fast dissolving tablets are also called as mouth-dissolving tablets, melt-in mouth tablets, Orodispersible tablets, rapimelts, porous tablets, quick dissolving etc. Fast dissolving tablets are those when put on tongue disintegrate instantaneously releasing the drug which dissolve or disperses in the saliva. The faster the drug into solution, quicker the absorption and onset of clinical effect. Some drugs are absorbed from the mouth, pharynx and esophagus as the saliva passes down into the stomach. In such cases, bioavailability of drug is significantly greater than those observed from conventional tablets dosage form. The advantage of mouth dissolving dosage forms are increasingly being recognized in both, industry and academics. Their growing importance was underlined recently when European pharmacopoeia adopted the term " Orodispersible tablet" as a tablet that to be placed in the mouth where it disperses rapidly before swallowing.

According to European pharmacopoeia, the ODT should disperse/disintegrate in less than three minutes. The basic approach in development of FDT is the use of superdisintegrants like cross linked carboxymethyl cellulose (croscarmellose), sodium starch glycolate (primogel, explotab), polyvinylpyrollidone (polyplasdone) etc, which provide instantaneous disintegration of tablet after putting on tongue, their by release the drug in saliva.

The bioavailability of some drugs may be increased due to absorption of drug in oral cavity and also due to pregastric absorption of saliva containing dispersed drugs that pass down into the stomach. More ever, the amount of drug that is subjected to first pass metabolism is reduced as compared to standard tablet. The technologies used for manufacturing fast-dissolving tablets are freeze-drying, spray-drying, tablet molding, sublimation, sugar-based excipients, tablet compression, and disintegration addition.As a result of increased life expectancy, the elderly constitute a large portion of the worldwide populati today. These people eventually will experience deterioration of their physiological and physical abilities.

Recent developments in technology have presented viable alternatives for the patients who may have difficulty in swallowing tablets or liquids. Traditional tablets and capsules administered with an 8-oz, glass of water may be inconvenient or impractical for some patients. For example a very elderly patient may not be able to swallow a daily dose of antidepressant. An eight year old child with allergies could use a more convenient dosage form than antihistamine syrup. A schizophrenic patient the institution setting can hide a conventional tablet under his or her tongue to avoid their daily of dose of atypical antipsychotic. A middle-aged woman undergoing radiation therapy for breast cancer may be too nauseous to swallow her h2-blockers.

To overcome these drawbacks, mouth dissolving tablets (MDT) or orally disintegrating tablets; (ODT) has emerged as alternative oral dosage forms. These are novel types, of tablets that disintegrate/dissolve/disperse in saliva within few seconds. According to European pharmacopoeia, the orally dispersible tablet should disperse/disintegrate in less than three minute. The basic approach used in development of MDT is the use of superdisintegrants like cross linked carboxymethylceulose (crosscamellose), sodium starch glycolate (primogel,Explotab). Polyvinylpyrrolidone(polyplasdone) etc. Which provide instantaneous disintegration of tablet after putting on tongue, therepy releasing the drug in saliva. The bioavailability of some drugs may be increased due to absorption of drug in oral cavity and also due to pregastricabsortion of saliva containing dispersed drugs that pass down into the stomach. Moreover the amount of drug that is subjected to first pass metabolism is reduced as compared to standard tablet.

1.A) TABLETS :(7)

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Tablets may be defined as solid pharmaceutical dosage forms containing medicament or medicaments with or without suitable recipients & prepared either by compression or molding.

i)Advantages of tablets:

Some of the potential advantages of tablets are as follows.

They are the unit dosage form having greatest capabilities amongst all the oral dosage form for the dose precision and least content variability.

Their cost is lowest amongst all the oral dosage forms.

They are the lightest and the most compact amongst all the oral dosage form.

They are easiest and cheapest for packaging and transportation.

They lend themselves to certain special release profile products such as enteric or delayed release products.

Tablets are better suited to large-scale production than other unit oral dosage forms.

They have the best-combined properties of chemical, mechanical, microbiological stability amongst all the oral dosage forms.

ii) Classification of tablets:

Based on the route of administration or the function, the tablets are classified as follows.

1) Tablets ingested orally.

Compressed tablet

Multiple compressed tablet

Layered Tablet

Compression coated Tablet

Repeat action Tablet

Delayed action and enteric-coated Tablet

Sugar and chocolate-coated tablet

a) Film coated tablet

b) Chewable Tablet

2) Tablets used in the oral cavity.

Buccal Tablet

Sublingual Tablet

Troches and Lozenges

Dental cones

3) Tablets administered by other routes.

Implantation Tablet

Vaginal Tablets

4) Tablets used to prepare solution.

Effervescent Tablet

Dispensing Tablet

Hypodermic Tablet

Tablets Triturates

iii) Manufacturing Methods(7)

Tablets are manufactured by Wet granulation, Dry granulation or Direct compression method.

1) Wet Granulation: 

Wet granulation is the process in which a liquid is added to a powder in a vessel equipped with any type of agitation that will produce agglomeration or granules. These granules after drying are compressed to form tablets. 

2) Dry Granulation:      

    In this technique, there is no use of liquids. The process involves the formation of slugs. Then the slugs are screened or milled to produce granules. The granules formed are then compressed to form tablets. 

3) Direct Compression:

The term direct compression is used to define the process by which tablets are compressed directly from powder blends of active ingredient and suitable excipients, which will flow uniformly in the die cavity & forms a firm compact. 

Table No.1.1: Processing Steps Commonly required in the Various Tablet Granulation preparation techniques

Processing steps

Wet Granulation

Dry Granulation

Direct Compression

Raw materials





Compress (slug)



Wet mass














iv) Advantages of Dry Method :-

This process is more economical. It requires fewer manufacturing steps, less processing time & thus reduces labour cost & less process validation.

The processing steps required no need of moisture, heat, and high compaction pressure.

There is an optimization of tablet disintegration, in which each primary drug particle is liberated from the tablet mass & is available for dissolution.

Disintegrating agents like starch are more effective when processed by dry granulation compression than wet granulation technique

In the present aging society, easy-to-use dosage forms for elderly patient, whose swallowing function is often decreased, are in great demand. The use of conventional tablets, capsules, and liquid or syrup preparations were not always easy-to-use dosage forms for elderly patients because of there decrease motor function. Similarly the use of conventional tablets is challenging to pediatric, geriatric, and uncooperative patients who may have difficulty to swallow tablets and is also problematic when water is unavailable or when patients have a persistent cough or gag-reflux.

These problems have been addressed by the recent introduction of Fast disintegrating tablets(FDT) which also known as A quick-dissolving tablet (also known as fast-dissolving, fast-dissolving multiparticulate, rapid-dissolving, mouth-dissolving, fast-melting, orodispersing tablets) is an oral tablets that does not require water for swallowing. The tablets dissolve within 60 seconds when placed in mouth or in oral cavity.


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In recent decades, a variety of pharmaceutical research has been conducted to develop new dosage forms. Considering quality of life, most of these efforts have been focused on ease of medication. Among the dosage form developed to facilitate ease of medication, the rapid disintegrating tablet is one of the most widely employed commercial products.


A fast-dissolving drug delivery system in most cases is a tablet that dissolving or disintegrates in the oral cavity without the need of water or chewing. Most fast-dissolving drug delivery system films must include substances to mask the taste of the active ingredient. This masked active ingredient is then swallowed by the patients saliva along with the soluble and insoluble excipients.

These are also called melt-in-mouth, repimelt, porous tablet, oro-dipersible, quick dissolving or rapid disintegrating tablets. Oral Disintegrating tablets are also called as Oro-dispersible tablets, Quick disintegrating tablets , Fast disintegrating tablets, rapid dissolving tablets, Porous tablets and Rapimelts.


Figure 1.1: A- Disintegration of Oro dispersible tablet after 5 seconds

B- Disintegration of Oro dispersible tablet after 10 seconds

C- Disintegration of Oro dispersible tablet after 15 seconds

D- Disintegration of Oro dispersible tablet after 20 seconds

E- Disintegration of Oro dispersible tablet after 25 seconds

F- Disintegration of Oro dispersible tablet after 30 seconds

Recently, European Pharmacopoeia has used the term Oro-dispersible tablets that disperses readily and within 3 min in mouth before swallowing.

United State Food and Drug Administration (FDA) defined Oro-dispersible tablets as, "A solid dosage form containing medicinal substance of active ingredient which disintegrates usually within a matter of seconds ."

"Fast dissolving tablets is solid dosage form that contains medicinal substances And that disintegrate and dissolve rapidly without water (within seconds) ."

The need for delivering drugs to patients efficiently and with few side effects has prompted pharmaceutical companies to engage in the development of new drug delivery systems. A solid dosage form that dissolves or disintegrates rapidly in oral   cavity, resulting in solution or suspension without the need of water is known as fast dispersing dosage form or oral dissolving tablets. When this type of tablet is gone into the stomach, the 0.1N HCL will serve to rapidly dissolve the tablet.

Many patients find it difficult to swallow tablets and hard gelatin capsules and do not take their medicines as prescribed. Target populations for these new fast-dissolving/disintegrating dosage forms have generally been pediatric, geriatric, bedridden or developmentally disabled patients., who are traveling or who have little or no access of water are also good candidates for fast dissolving / disintegrating tablets. Other groups that may experience problems using conventional oral dosage form include the mentally ill, developmentally disable and patients who are uncooperative. A difficulty in swallowing (dysphagia) tablets or capsules is common problem among all age groups, especially in elderly and pediatrics. For this reasons, tablets that can dissolve or disintegrate in oral cavity, have attracted a great deal of attention.

Indeed, the oral dissolving tablet is an important and attractive alternative to liquid dosage form. . Syrups are best for pediatrics but they are bulky and drugs are not as stable in liquid form as in solid form like tablets.

Oro-disintegrating tablets are characterized by high porosity, and low hardness, when administered an in-situ suspension is created in the oral cavity as the tablet disintegrates and is subsequently swallowed. Some tablets are designed to dissolve in saliva remarkably fast, within a few seconds, and are true fast-dissolving tablets. Others contain agents to enhance the rate of tablet disintegration in the oral cavity, and are more appropriately termed fast-disintegrating tablets, as they may take up to a minute to completely disintegrate. When put on tongue, this tablet disintegrates instantaneously, releasing the drug, which dissolves or disperses in the saliva. Some drugs are absorbed from the mouth, pharynx and oesophagus as the saliva passes down into the stomach. In such cases, bioavailability of drug is significantly greater than those observed from conventional tablet dosage form. the disintegration time of these tablets depend largely on size and hardness parameters.

ii) Criteria for Fast dissolving Drug Delivery System(6)

The tablets should Not require water to swallow, but it should dissolve or disintegrate in the mouth in matter of seconds.

Be compatible with taste masking.

Be portable without fragility concern.

Have a pleasant mouth feel.

Leave minimum or no residue in the mouth after oral administration.

Exhibit low sensitive to environmental condition as temperature and humidity.

Allow the manufacture of the tablet using conventional processing and packaging

Equipments at low cost.

iii) Requirements of fast disintegrating tablets;

An ideal FDT should

Require no water for oral administration, yet dissolving/disperse/disintegrate in a matter of seconds.

Be harder and less friable.

Leave minimal or on residue in mouth after administration.

Exhibit low sensitivity to environment condition (temperature and humidity).

Allow the manufacture of tablet by using conventional processing and packing equipment.

iv) Advantages of FDT;

Ease of administration to patient who refuse to swallow a tablet, such as paediatric, geriatric, and psychiatric patient.

Convenience of administration and accurate dosing as compared to liquid.

No need of water to swallow the dosage form, which is highly convenient feature for patient who are travelling and do not have immediate access to water.

Good mouth feels property of MDT helps to change the basic view of medication as "bitter pill" particularly for paediatric patients.

Rapid dissolution of drug and absorption, which may produce rapid, onset of action.

Some drug are absorbed from the mouth and oesophagus as the saliva passes down into the stomach in such cases bioavailability of drug is increased.

Ability to provide advantage of liquid medication in the form of solid preparation.

Pregastric absorption can result in improved bioavailability and as a result of reduced dosage, improved bioavailability and as a result of reduced dosage improved clinical performance through a reduction of unwanted effect.

Achieve increased bioavailability/rapid absorption through pregastric absorption of drug from mouth, pharynx and oesophagus as saliva passes down.

The risk of chocking or suffocation during oral administration of conventional formulation due to physical obstruction is avoided, thus providing improved safety.

New business opportunity like product differentiation, product promotion, patent extension and life cycle management.

v) Disadvantages of FDT;

The tablets usually have insufficient mechanical strength. Hence, careful handling is required.

The tablets may leave unpleasant taste and/or grittiness in mouth if not formulated Properly

Tablets are very fragile and lack physical resistance. Because the tablets are very porous and low compression forces are used to prepare them. They cannot be packed in conventional strips or in bottles and special packaging is required.

Bitter drugs have to be taste masked by various techniques which in turn increases the time and cost of production

Their growing importance of fast Dissolving /disintegrating tablet was under lined recently when European Pharmacopoeia adopted the term "Oro-dispersible Tablet" as a tablet that to be placed in the mouth where it disperses rapidly before swallowing.

vi) salient feature of fast dissolving Drug Delivery System

Ease of administration for patients who are mentally ill, disabled and uncooperative.

Quick disintegration and dissolution of the dosage form.

Overcomes unacceptable taste of the drugs.

Can be designed to leave minimal or no residue in the mouth after administration and also to provide a pleasant mouth feel.

Allows high drug loading.

Ability to provide advantages of liquid medication in the form of solid preparation.

Adaptable and amenable to existing processing and packaging machinery

vii) possible benefits of orally disintegrating drugs.

1. Clinical:

Improved drug absorption.

Faster onset of action.

Minimized first pass effect.

Improved bioavailability.

2. Medicinal:

No tablet or capsule to swallow or chew.

Better taste, no water needed.

Improved safety and efficacy.

Improved compliance.

3. Technical:

More accurate dosing than liquid products.

Can use sugars and other excipients that are generally recognized as safe.

Improved stability because of unit-dose packaging.

Manufactured with common process and conventional equipment.

4. Business:

Lifecycle Management: re-formulation is a strategy to prolong market exclusivity as it may delay or reduce generic erosion at patent expiry.

Differentiation in a crowded market

For generic companies it offer the prospect of superior generic drugs in order to gain market dominance upon the expiration of patents

Cost effective drug development

1.3) Mechanism of tablet disintegrants(1)

The tablet breaks to primary particles by one or more of the mechanisms listed below:-

1. Capillary action

2. Swelling

3. Because of heat of wetting

4. Disintegrating particle/particle repulsive forces

5. Deformation

6. Release of gases

Enzymatic action

1 ) Capillary action

Disintegration by capillary action is always the first step. When we put the tablet into suitable aqueous medium, the medium penetrates into the tablet and replaces the air adsorbed on the particles, which weakens the intermolecular bond and breaks the tablet into fine particles. Water uptake by tablet depends upon hydrophilicity of the drug /excipient and on tableting conditions. For these types of disintegrants maintenance of porous structure and low interfacial tension towards aqueous fluid is necessary which helps in disintegration by creating a hydrophilic network around the drug particles.

2 ).Swelling:

Perhaps the most widely accepted general mechanism of action for tablet disintegration is swelling Tablets with high porosity show poor disintegration due to lack of adequate swelling force. On the other hand, sufficient swelling force is exerted in the tablet with low porosity. It is worthwhile to note that if the packing fraction is very high, fluid is unable to penetrate in the tablet and disintegration is again slows down.

Fig.no.1.2 : Disintegration of tablet by wicking and swelling

3 ).Heat of wetting (air expansion)

When disintegrants with exothermic properties gets wetted, localized stress is generated due to capillary air expansion, which helps in disintegration of tablet. This explanation, however, is limited to only a few types of disintegrants and can not describe the action of most modern disintegrating agents.

4. ). Disintegrating particle / particle repulsive forces

Another mechanism of disintegration attempts to explain the swelling of tablet made with 'non-swellable' disintegrants. Guyot-Hermann has proposed a particle repulsion theory based On the observation that non-swelling particle also cause disintegration of tablet. The electric Repulsive force between particle are the mechanism of disintegration and water is required for it. Researchers found that repulsion is secondary to wicking.

5. ). Deformation.

Hess had proved that during tablet compression, disintegranted particles get deformed and these deformed particles get into their normal structure when they come in contact with aqueous media or water. Occasionally, the swelling capacity of starch was improved when granules were extensively deformed during compression. This increase in size of the deformed particles produces a break up of the tablet.

Fig.1. 3. Disintegration by deformation and repulsion

6). Release of gases

Carbon dioxide released within tablets on wetting due to interaction between bicarbonate and carbonate with citric acid or tartaric acid. The tablet disintegrates due to generation of pressure within the tablet. This effervescent mixture is used when pharmacist needs to formulate very rapidly dissolving tablets or fast disintegrating tablet. As these disintegrants are highly sensitive to small changes in humidity level and temperature ,strict control of environment is required during manufacturing of the tablets .The effervescent blend is either added immediately prior to compression or can be added in to two separate fraction of formulation.

7 ). Enzymatic reaction

Here, enzymes presents in the body act as disintegrants. These enzymes destroy the binding action of binder and helps in disintegration.

Table.1.2. Disintegrating Enzymes.








Cellulose and it's derivatives



ix) Fundamentals of fast dissolving / disintegrating tablets:

For rapid dissolution or disintegration of dosage form, water must rapidly penetrate into the tablet matrix to cause quick disintegration & instantaneous dissolution of the tablet. Several techniques are used to achieve these fundamentals, to formulate mouth-dissolving tablet. Some of the techniques are described below.

1.4) Techniques for Preparing Fast disolving Tablets(8)

Many techniques have been reported for the formulation of Fast dissolving tablets or Orodispersible tablets.

1. Freeze drying / lyophilization

2. Tablet Moulding

3. Spray drying

4. Sublimation

5. Direct compression

6. Mass extrusion

1. Freeze-Drying or Lyophilization

Freeze drying is the process in which water is sublimed from the product after it is frozen. This technique creates an amorphous porous structure that can dissolve rapidly. A typical procedure involved in the manufacturing of ODT using this technique is mentioned here. The active drug is dissolved or dispersed in an aqueous solution of a carrier/polymer. The mixture is done by weight and poured in the walls of the preformed blister packs. The trays holding the blister packsare passed through liquid nitrogen freezing tunnel to freeze the drug solution or dispersion. Then the frozen blister packs are placed in refrigerated cabinets to continue the freeze-drying. After freeze-drying the aluminium foil backing is applied on a blister-sealing machine. Finally the blisters are packaged and shipped. The freeze-drying technique has demonstrated improved absorption and increase in bioavailability. The major disadvantages of lyophillization technique are that it is expensive and time consuming; fragility makes conventional packaging unsuitable for these products and poor stability under stressed conditions.

2. Tablet Moulding:

Moulding process is of two types i.e. solvent method and heat method. Solvent method involves moistening the powder blend with a hydro alcoholic solvent followed by compression at low pressures in moulded plates to form a wetted mass (compression moulding). The solvent is then removed by air-drying. The tablets manufactured in this manner are less compact than compressed tablets and posses a porous structure that hastens dissolution. The heat moulding process involves preparation of a suspension that contains a drug, agar and sugar (e.g. mannitol or lactose) and pouring the suspension in the blister packaging wells, solidifying the agar at the room temperature to form a jelly and drying at 30â-‹C under vacuum. The mechanical strength of moulded tablets is a matter of great concern. Binding agents, which increase the mechanical strength of the tablets, need to be incorporated. Taste masking is an added problem to this technology.

The taste masked drug particles were prepared by spray congealing a molten mixture of hydrogenated cottonseed oil, sodium carbonate, lecithin, polyethylene glycol and an active ingredient into a lactose based tablet triturate form. Compared to the lyophilisation technique, tablets produced by the moulding technique are easier to scale up for industrial manufacture.

In this technology, water-soluble ingredients are used so that tablet disintegrate and dissolve rapidly. The powder blend is moistened with a hydro alcoholic solvent and is moulded in to tablet using compression pressure lower than used in conventional tablets compression. The solvent is then removed by air-drying. Moulded tablets have a porous structure that enhances dissolution. Two problems commonly encountered are mechanical strength and poor taste masking characteristics. Using binding agents such as sucrose, acacia or poly vinyl pyrrolidone can increase the mechanical strength of the tablet.

To overcome poor taste masking characteristic Van Scoik. Incorporated drug containing discrete particles, which were formed by spray congealing a molten mixture of hydrogenated cottonseed oil, sodium bicarbonate, lecithin, polyethylene glycol and active ingredient into a lactose based tablet triturate form. Tablets prepared by this method are solid dispersions. Physical form of drug in the tablets depends on whether and to what extent it dissolves in the wetted mass. The drug can exist as discrete particles or micro particles in the matrix.  Different moulding techniques can be used to prepare mouth-dissolving tablets:

a. Compression Moulding: The powder mixture previously wetted with a solvent ike ethanol/water is compressed into mould plates to form a wetted mass.

b. Heat Moulding: A molten matrix in which drug is dissolved or dispersed can be directly moulded into orodispersable Tablets.

c. No vacuum lyophilization: This process involves evaporation of solvent from a drug solution or suspention at a standard pressure.

Moulded tablets possess porous structure, which facilitates rapid disintegration and easy dissolution. Moulded tablets offer improved taste due to water-soluble sugars present in dispersion matrix. But moulded tablets lack good mechanical strength and can undergo breakage or erosion during handling and opening of blister packs. However, adding sucrose, acacia or polyvinyl pyrrolidone can increase mechanical strength.

3. Spray Drying :

In this technique, gelatin can be used as a supporting agent and as a matrix, mannitol as a bulking agent and sodium starch glycolate or crosscarmellose or crospovidone are used as superdisintegrants. Tablets manufactured from the spray-dried powder have been reported to disintegrate in less than 20 seconds in aqueous medium. The formulation contained bulking agent like mannitol and lactose, a superdisintegrant like sodium starch glycolate & croscarmellose sodium and acidic ingredient (citric acid) and/or alkaline ingredients (e.g. sodium bicarbonate). This spray-dried powder, which compressed into tablets showed rapid disintegration and enhanced dissolution.

4. Sublimation:

To generate a porous matrix, volatile ingredients are incorporated in the formulation that is later subjected to a process of sublimation. Highly volatile ingredients like ammonium bicarbonate, ammonium carbonate, benzoic acid, camphor, naphthalene, urea, urethane and phthalicanhydride may be compressed along with other excipients into a tablet. This volatile material is then removed by sublimation leaving behind a highly porous matrix. Tablets manufactured by this technique have reported to usually disintegrate in 10-20 sec. Even solvents like cyclohexane;benzene can be used as pore forming agents.

The basis of this technique is to add inert solid ingredients that volatilize readily, (e.g. camphor, ammonium bicarbonate, naphthalene, urea, urethane etc) to other tablet excipients and the mixture is then compressed into tablets. Volatile material is then removed via sublimation, which generate a porous structure.

Koizumi et al applied the sublimation technique to prepare highly porous compressed tablets that were rapidly soluble in saliva. Mannitol and camphor were used as a tablet matrix material and subliming the material respectively.  Camphor was iminated by subliming in vacuum at 80 0C for 30 minutes to develop pores in the tablets.

Makino et al described a method of producing a fast dissolving tablet using water as a pore forming material. A mixture containing active ingredient and carbohydrates (glucose, manitol, xylitol etc) were moistened with water (1- 3 %w/w) and compressed into tablets. The water was then removed yielding highly porous tablet that exhibited excellent ;

Fig No 1. 4 Steps involved in Sublimation Technology

5. Direct Compression:

Direct compression represents the simplest and most cost effective tablet manufacturingtechnique. This technique can now be applied to preparation of ODT because of the availabilityof improved excipients especially superdisintegrants and sugar based excipients.

(a) Superdisintegrants:

In many orally disintegrating tablet technologies based on direct compression, the addition ofsuperdisintegrants principally affects the rate of disintegration and hence the dissolution. Thepresence of other formulation ingredients such as water-soluble excipients and effervescentagents further hastens the process of disintegration.

(b) Sugar Based Excipients:

This is another approach to manufacture ODT by direct compression. The use of sugar basedexcipients especially bulking agents like dextrose, fructose, isomalt, lactilol, maltilol, maltose,mannitol, sorbitol, starch hydrolysate, polydextrose and xylitol, which display high aqueoussolubility and sweetness, and hence impart taste masking property and a pleasing mouthfeel.Mizumito et al have classified sugar-based excipients into two types on the basis of molding anddissolution rate.

Type 1 saccharides (lactose and mannitol) exhibit low mouldability but high dissolution rate.

Type 2 saccharides (maltose and maltilol) exhibit high mouldability and low dissolution rate.

6. Mass-Extrusion:

This technology involves softening the active blend using the solvent mixture of water-soluble polyethylene glycol and methanol and subsequent expulsion of softened mass through the extruder or syringe to get a cylinder of the product into even segments using heated blade to form tablet. The dried cylinder can also be used to coat granules for bitter drugs and there by achieve taste masking.