Overview, Advantage And Disadvantage Of Pharmaceutical Mouth Dissolving Tablets

Mouth dissolving tablets (MDT) can be defined as "a solid dosage form containing medicinal substances, which disintegrates rapidly, usually within a matter of seconds, when placed under the tongue. They are also called rapid dissolving tablets (RDT), orodispersible (ODT) or mouth-melt, quick dissolve, rapid melt, quick disintegrating, orally disintegrating, melt-in mouth, etc.

Mouth dissolving tablet

MDT has a pleasing mouth feel, and it does not require water to swallow. MDT easily dissolves or disintegrates in saliva within a few seconds (15 s to 3 min). Some MDT tablets are designed to dissolve in saliva remarkably fast, within a few seconds, and are called true fast-dissolving tablets (FDT). Others contain agents to enhance the rate of tablet disintegration in the oral cavity and are more appropriately termed as fast-disintegrating tablets, as they may take about one minute to disintegrate completely.

Having good hardness, dose uniformity, easy administration and serves as the first choice of dosage form for pediatrics, geriatrics and travelling patient. Preferred when fast action or relief is desired.

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Development And Design Of Mouth Dissolving Tablet

A number of techniques are used to prepare these tablets, including lyophilization, soft direct compression. For mouth dissolving tablet formulation the main criteria is to eliminate the bitterness of the tablet by adding sweetening agent or by sugar coating on the tablets. Taste masking poses numerous challenges since the drug product dissolves in the mouth, either by flavoring technique or by microencapsulation or nano-encapsulation.

Binders keep the composition of these fast‐melting tablets together during the compression stage. The right selection of a binder or combination of binders is essential to maintain the integrity and stability of the tablet.

To increase the tablet disintegration, superdisintegrants are added in it, which are very helpful to increase the bioavailability of tablet and to increase the disintegration property of tablet in saliva. Disintegrants are mainly added in the tablets by three methods. These methods are extra-granular, intra-granular and partially extra-granular and intragranular methods. MDT’s are mainly prepared by various methods like direct compression, wet granulation, solid dispersion and tablet molding etc.

Important Criteria For Excipients Used In The Formulation Of MDTs

1. It must be able to disintegrate quickly

2. Their individual properties should not affect the MDTs

3. It should not have any interactions with drugs and other excipients

4. It should not interfere in the efficacy and organoleptic properties of the product

5. When selecting binder a (single or combination of binders) care must be taken in the final integrity and stability of the product

6. The melting points of excipients used will be in the range of 30-350C

7. The binders may be in liquid, semi liquid, solid or polymeric mixtures

Mechanism Of Mouth Dissolving Tablets

To attain the tablet’s fast dissolving character, water should quickly egress into the tablet matrix to cause rapid disintegration and instant dissolution of the tablet. Increase in the porous structure of the tablet matrix and incorporating appropriate disintegrating agents or extremely water soluble agents in the tablet formulation are the fundamental approaches employed in current fast dissolving tablet technologies.

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Basically, the disintegrating major activity is to oppose the affectivity of the tablet binder and therefore the physical forces that act under compression to make the tablet. The mechanism by which tablet disintegrates into smaller particles and then produces a homogeneous suspension or solution is based on:

I) Capillary action

II) High swell ability of disintegrates

III) Capillary action and high swell ability

IV) Chemical reaction (Release of Gases)

Criteria For Drug Selection

The main criterias for a drug to be selected are as 

follows:

1. It should not have a bitter taste

2. The dose should be less than 20mg

3. Moderate molecular weight should be small

4. Should be of good solubility in water and saliva

5. Should have extensive First pass metabolism

6. Should have oral tissue permeability

Ideal Characteristics of MDTs

A MDT should have following properties:

1. A MDT should be dissolve or disintegrate in the mouth within few seconds

2. It should not require any liquid or water to show its action

3. It should not leave any residue in the mouth after the administration of the tablet

4. Be able to be manufactured in a simple conventional manner within low cost

5. It should be less effective by environmental conditions like humidity, temperature etc.

6. Have a pleasing taste

7. Be portable and easy to transport

8. Should compatible with sweetening agents for masking of taste

9. Should compatible for high drug loading

10. Have sufficient strength to withstand the rigors of the manufacturing process and post manufacturing handling

11. Be adaptable and amenable to existing processing and packaging machinery

12. Be portable without fragility concern and easy to transport

Unsuitable Drug Characteristic For MDTs

1. Short half-life and frequent dosing

2. Very bitter or otherwise unacceptable taste because taste masking cannot be achieved

3. Required controlled or sustained release

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Advantages Of Mouth Dissolving Tablets

1. Easy for administration to patients which cannot swallow the tablets like pediatric and geriatric, unconscious and mentally disabled patients

3. Accurate dose as compared to liquid

4. It shows pre-gastric absorption from the mouth, pharynx and esophagus hence it has a rapid rate of drug absorption

5. Does not require water to take the tablet during travelling

6. Quick disintegration and dissolution of drug tablet to produce rapid action

7. Bioavailability of drug can be increased by avoiding the passage of the drug from pharynx and esophagus through saliva passing down into the stomach

8. It has good mouthfeel property that helps to take the medicine easily than the bitter pills in pediatric patients

9. There is no risk of suffocation and choking during MDT uptake

10. It is helpful in some cases like motion sickness, during coughing etc

11. These MDT’s are stable for longer duration of time, till it is consumed

12. First pass metabolism is reduced, thus offering improved bioavailability and thus reduced dose and side effects

13. Suitable for sustained/controlled release actives

14. Allows high drug loading

Disadvantage Of Mouth Dissolving Tablets

1. Fast dissolving tablets are hygroscopic in nature so must be kept in a dry place.

2. Sometimes it possesses a mouth feeling.

3. MDT requires special packaging for properly stabilization & safety of stable product