You are hereA REVIEW ON: FORMULATION AND EVALUATION OF FAST DISSOLVING TABLET

A REVIEW ON: FORMULATION AND EVALUATION OF FAST DISSOLVING TABLET


BY 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.

DUE TO 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 nonswelling particle also cause disintegration of tablets. The electric repulsive forces between particles are the mechanism of disintegration and water is required for it. Researchers found that repulsion is secondary to wicking.

DUE TO 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. This may be a mechanism of starch and has only recently begun to be studied.

DUE TO 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.

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

MARKETTED FORM OF FAST DISINTEGRAING TABLETS

Table 1.1

Product:

Manufactured By/For:

Active ingredient:

Category:

Indication:

Intended Age:

Abilify Discmelt

Otsuka America/
Bristol-Myers Squibb

aripiprazole

Atypical antipsychotics

Schizophrenia, Bipolar disorder, adjunct therapy for Major Depressive Disorder

13 years+ for Schizophrenia, 10 years+ for Bipolar disorder, adults for MDD

Alavert Quick Dissolving Tablets

Wyeth

Loratadine

Anti-histamines

Allergy

6 years+

Allegra ODT

Sanofi Aventis

Fexofenadine

Anti-histamines

Allergic rhinitis, Urticaria

6–11 years

Aricept ODT

Eisai Co.

Donepezil

Acetyl
cholinesterase inhibitors[2]

Alzheimer's disease

adults


 Benadryl FastMelt

Pfizer

Diphenhydramine

Anti-histamines

Allergy

6 years+

Calpol Fast Melts

McNeil Healthcare UK

Paracetamol

Analgesics

Pain

6 years+

Clarinex RediTabs

Schering-Plough

Desloratadine

Anti-histamines

Allergy

6 years+

Claritin RediTabs

Schering-Plough

Loratadine

Anti-histamines

Allergy

6 years+

Clonazepam ODT

Par Pharmaceutical

Clonazepam

Benzodiazepines

Anxiety, Panic Disorder, Seizure Disorders

6 years+

CONVENTIONAL TECHNIQUES USED IN THE PREPARATION OF ODT

LYOPHILIZATION
Lyophilization is a pharmaceutical manufacturing technology, which allows drying of heat sensitive drugs and biologicals at low temperatures under conditions that allow removal of water by sublimation. Lyophilization results in preparations, which are highly porous, with a very high spherical surface area, which dissolve rapidly and show improved absorption and bioavailability. The freeze-drying process consists of three phases.
1. Freezing to bring the material below its eutectic zone.
2. Sublimation drying or primary drying to reduce moisture to around 4%w/w of dry product.
3.   Desorption or secondary drying to reduce bound moisture to the required final value.

Tablets prepared by lyophilization are fragile and posses low mechanical strength, which make them difficult to handle and they also exhibit poor stability on storage under stressed conditions. Blank et al used a mixture of mannitol and one natural gum (e.g.; acacia guar or xanthan gum) as a carrier material, in formulation of lyophilized fast-dissolving tablets and found good stability in blister pack even when stored at high humidity conditions. Water penetrates through pores of network, resulting in rapid disintegration and / or dissolution of the dosage form.

SUBLIMATION
In this method highly porous and rapidly dissolving tablets, which includes the addition of a sublime salt to the tabletting components, compressing the blend and removing the salt by the process of sublimation. The active ingredient, a diluent(e.g.: lactose and trehalose), a sublime salt (e.g.: ammonium carbonate, ammonium bicarbonate and ammonium acetate), a binder and other excipients are blended and tablets are prepared. Then volatile salt is removed by sublimation, by exposing the tablets to reduced atmospheric pressure for a time sufficient to completely remove the salt.

Tablet prepared by fast dissolving, highly porous compressed tablets by sublimation technique. Mannitol is incorporated as diluent and camphor as sublime material. Tablets prepared by this method dissolve rapidly and possess sufficient hardness. Water can also be used as pore forming material for preparation of highly porous fast dissolving tablets. A mixture of active ingredient and a carbohydrate (e.g: sucrose, glucose, xylitol or mannitol) was wetted with suitable amount of water and compressed into tablets. The water is evaporated, producing highly porous tablets with good mechanical strength.

SPRAY DRYING
Spray drying is a process by which highly porous, fine powders can be produced. spray drying technique for preparing fast dissolving tablets. The composition contained a bulking agent (e.g.: mannitol and lactose), a disintegrant (e.g.: sodium starch glycolate and croscarmellose sodium), an acidic ingredients (citric acid), and /or alkaline ingredients (e.g.; sodium bicarbonate) which when compressed into tablets showed fast disintegration and enhanced dissolution. The fast dissolving tablets prepared from spray drying technique disintegrated within 20seconds.

MASS-EXTRUSION
This technology involves softening the active blend using the solvent mixture of water-soluble polyethylene glycol, using methanol and expulsion of softened mass through the extruder or syringe to get a cylinder of the product into even segments using heated blade to form tablets. The dried cylinder can also be used to coat granules of bitter tasting drugs and thereby masking their bitter taste.

TABLET MOULDING
In this method, the delivery system is prepared in the form of tablets using water-soluble additives, to allow the tablets to dissolve rapidly and completely in mouth. All ingredientsof the formulation are passed through fine mesh, dry blended, wetted with a hydro-alcoholic solvent and then compressed into tablets using low compression forces. The solvent present inside the tablets is removed by air-drying. The so formed moulded tablets contain a porous structure, which enhances dissolution. The moulded tablets prepared by above method possess low mechanical strength, to improve the mechanical strength, a binding agent like sucrose, polyvinyl polypyrrolidone, and cellulose polymers like hydroxypropyl methylcellulose may be added to the solvent system.

Masaki prepared intrabucally fast-disintegrating tablets using agar solution as binder and moulding the preparation into a blister pack. In this process, a suspension containing an active ingredient, agar and soluble sugars like lactose and/or mannitol is prepared and filled into the blister packing well, solidifying the preparation into a jelly form at room temperature, and dried at 30o C under a pressure of 700 to 760 mm Hg. The moulded tablets obtained by this method would have adequate strength with hardness greater than 2.0 kg/cm2.

In other process, the drug containing micro particles are combined with aneffervescent disintegrating agent, which on dissolution forms a tasteless drug suspension in the mouth. Although prompt release is preferred, the protective material utilized in the micro particle should not dissolve instantaneously in water or saliva. That is, the micro particle should resist dissolution and release for a period of time, typically a few seconds or so, sufficient to permit the patient to swallow the released microcapsules, the tablet disintegrates. A combination of polymers (cellulose and syntheticcellulose derivatives, Eudragit. RL30) along with release promoters like soluble sugar (mannitol and magnesium oxide) serves the purpose. The size of micro particles may preferably be between 150 to 500 µ (100 meshes to 35 meshes). The micro particles are then blended with effervescent disintegrant and other adjuvant like binder, diluent, lubricant, color and flavor, and granulated by compaction, extrusion or globulation, and compressed into tablets.

Fast-disintegrating tablets prepared by vacuum drying process are reportedby Van Scoik.  In this method, a frozen mixture containing a gum (e.g. Guar, tragacanth, carrageenan or xanthan gum), carbohydrates (mannitol, dextrose, maltose, sucrose or corn syrup), and a solvent was vacuum dried in a tablet shaped mould, which resulted in tablets with enhanced structural integrity than traditional moulded tablets.

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