Overview Of Pharmaceutical Dispersible Tablet

Dispersible tablets (DT) as defined in European Pharmacopoeia are uncoated or film coated tablets containing active pharmaceutical ingredients (API) intended to be dispersed in water before administration giving a homogeneous dispersion. They disintegrate either rapidly in water to form stabilized suspension or disperse instantaneously in the mouth to be swallowed without the aid of water. Typically a dispersible tablet is dispersed in about 5 to 15 ml of water (e.g. in a tablespoonful or a glass of water) and the resulting dispersion is administered to the patient. Dispersible tablets are required to disintegrate within 3 min in water at 15 to 25. Also the dispersion produced from a dispersible tablet should pass through a sieve screen with a nominal mesh aperture of 710 µm.

Dispersible tablet

Orodispersible tablets (ODTs) are distinguished from classic sublingual tablets, which take more than a few minutes to dissolve in the oral cavity. Orodispersible tablets, quick disintegrating tablets, mouth dissolving tablets, fast disintegrating tablets, rapid dissolving tablets, and fast dissolving tablets are names used to describe orally disintegrating tablets.

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Prerequisite Of Oral Disintegrating Tablets

There are some prerequisite for oral disintegrating tablets which are mentioned as;

1. Tablets must disintegrate and disperse in the oral cavity without water intake

2. It can hold high drug quantities

3. It should be compatible with taste masking agents and excipients, and have optimum sensation effect

4. Leave minimum to no residue after administration

5. It should have optimum capacity to remain intact in formulation processes

6. It should be stable at the range of temperature and humidity

7. It should be adaptable and amenable to existing processing and packaging machinery

8. It should be manufactured at low cost

Suitability Of Drugs For Oral Disintegrating Tablets

1. Drugs to be used for sustained action are not suitable candidates for ODT

2. Drugs having very disagreeable taste are not suitable

3. Patients suffering from Sjogren's syndrome and those with less saliva secretion and not suitable for ODT dosage form

4. Drugs of very short half life and requiring frequent dosing are not appropriate candidates

5. Patients on anticholinergic therapy are not suitable for ODT

6. Drugs showing altered pharmacokinetic behavior if formulated in such dosage form with respect to their conventional dosage form are not suitable.

7. Drugs producing considerable amounts of toxic metabolites on first pass metabolism and in GIT and having substantial absorption in oral and pregastric areas are good candidates

8. Drugs permeable to upper GIT and oral mucosal epithelial cell lining are considered good candidates for ODT.

Excipients Required In Formulating ODTs

Excipients used in ODTs contain one superdisintegrant, a diluent/bulking agent, a lubricant and optionally swelling agent, a permeabilizing agent (depending upon drug nature), sweeteners and flavorings agents.

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Mechanism Of Drug Release

Disintegration takes place when a tablet breaks into fragments when it comes in contact with the fluid. This is followed by de-aggregation, disintegration beyond the original granule size into the primary particles. Dissolution occurs more rapidly from primary particles since the available surface area is large, but to a limited extent from the intact tablet, and the aggregates generated during tablet disintegration. The ODT should be dispersed or disintegrated in less than three minutes. The fundamental methodology used in development of ODT is the use of superdisintegrants like carboxy methyl cellulose, poly vinyl pyrrolidone and sodium starch glycolate.

Ideal Properties Of Dispersible Tablet

1. Exhibit low sensitivity to environmental conditions as humidity and temperature

2. Should maintain physical integrity and possess no friable loss with sufficient mechanical strength

3. Should have a pleasant mouth feel

4. Should leave minimum or no residue in the mouth after oral administration

5. The drug loading capacity of the dispersible tablets must be high

6. Increase in viscosity after dispersion

7. Should be adaptable and amenable to the existing processing and packaging machinery at low costs

8. Small to moderate molecular weight

9. Good solubility in water and saliva

10. Partially non-ionized at the oral cavity pH

11. Ability to diffuse and partition in to the epithelium of the upper GIT log p more than 1 or preferably more than 2

12. Ability to permeate oral mucosal tissue

13. The fast disintegration usually means disintegration of tablets in less than 1 minute, but it is preferred to have disintegration as soon as possible

14. The excipients should have high wettability, and the tablet structure should also have a highly porous network for fast dissolution

15. The disintegrated tablet should become a soft paste or liquid suspension, which can provide good mouth feel and smooth swallowing

16. A pleasant taste inside the mouth becomes critical for patient acceptance. Unless the drug is tasteless or does not have an undesirable taste, taste-masking techniques should be used. An ideal taste-masking technology should provide drugs without grittiness and with good mouth feel

16. The amount of taste masking materials used in the ODTs formulation should be kept as slow as possible to avoid excessive increase in tablet size

17. Drug properties for example; the solubility, crystal morphology, particle size, hygroscopicity, compressibility, and bulk density should not affect the final ODT performance and characteristics such as tablet strength and disintegration

18. Evade the first pass effect which increases the bioavailability of the fast dispersible tablets

19. Porosity

20. Hardness

21. Cost effective

22. Stable 

Advantages Of Oral Disintegrating Tablets

1. For pediatric patients and patient who cannot swallow

2. For API’s unstable if formulated in liquid formulation.

3. Increased bioavailability and faster onset of action compared to standard compressed tablet as it bypass the first-pass metabolism

4. Patients having prolonged illness who are prone to nausea sensation

5. Suitable for patient who don't have access to water like bedridden

6. The risk of asphyxiation is avoided

7. Enhance safety drug profile as toxic metabolites mediated by first pass hepatic metabolism is avoided

8. No pain as compared to chewable tablets and injection leading to compliance

9. Enables high drug loading

10. They have the advantage of solid dosage forms; they provide good stability, accurate dosing, easy manufacturing, small packaging size, and are easy to handle by patients

11. The pre-gastric drug absorption avoids the first-pass metabolism; the drug dose can be reduced if a significant amount of the drug is lost through hepatic metabolism. Hence drugs which are metabolised by first pass effect or metabolised by gastric enzymes, can also be administered

12. From the pharmaceutical industry’s point of view, ODTs can provide new dosage for msas a life cycle management tool for drugs near the end of their patent life

13. ODTs have the advantages of liquid formulations such as easy administration and no risk of suffocation resulting from physical obstruction by a dosage form

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Disadvantage Of Oral Disintegrating Tablets

1. Drugs with moderately larger doses are hard to formulate in the ODT

2. The hygroscopic properties of the formulation require additional moisture protection with a special packaging for the stability and adequate safety of the products

3. These tablets show low hardness and high friability, than conventional tablets, which make fragile tablets, which are difficult to handle, often require special packs in peel-able blisters

4. Drugs absorbed at a specific site cannot be administered in these dosage forms

5. Patients taking anticholinergic medicines at the same time may not be the best candidates for RDT die to decrease amount of saliva

6. For freeze-dried dosage forms, the dose of the drug product must be less than 60 mg for soluble drugs and less than 400 mg for Insoluble drugs

7. Bitter drugs are not easy to formulate as ODT’s except with the addition of taste masking materials