Orodispersible tablets, also known as orally disintegrating tablets, are tablet formulations that disintegrate rapidly in the oral cavity, usually within seconds to minutes, when placed on the tongue. No need of water or chewing is required for administration of these tablets. They disperse or dissolve in the mouth due to the penetration of saliva, resulting in a paste or thin gel that can be easily swallowed.
Orally disintegrating tablets offer important advantages over conventional tablet and capsule formulations for certain patient groups. They are very convenient for pediatric, geriatric and dysphagic patients who experience difficulty in swallowing conventional oral solid dosage forms. The Orodispersible tablets dissolve or disperse in the mouth within a short time, eliminating the need for water during the process of administration. This makes them very convenient solid dosage forms for such patient groups.
Formulation Technologies for Developing Orally Disintegrating Tablets
Several formulation technologies have been developed for manufacturing orally disintegrating tablets with rapid disintegration properties. Some of the major technologies include:
- Lyophilization or freeze-drying: It involves turning water into vapor sublimation from frozen state. The freeze-dried solid tablets produced using lyophilization have a porous structure that enables quick absorption of saliva for rapid disintegration.
- Moulding: It involves kneading the powder blend with a hydrophilic matrix former to form a dough, which is then compressed into tablets using low compression force. Common matrix formers used include starch, sugars and cellulose derivatives.
- Direct compression: It involves powder blends containing super disintegrants, swelling agents and other excipients that provide rapid disintegration of tablets upon contact with saliva. Commonly used super disintegrants are crosses-linked carboxymethylcellulose, sodium starch glycolate, etc.
- Cotton candy process: It involves melting sucrose or glucose on a rapidly rotating heated cylinder. The resulting floss-like structure has good hydrophilic and disintegration properties for use in rapid oro-dispersing tablets.
- Spray drying: Using this process, the active ingredient is first dissolved or suspended along with excipients in a volatile solvent. The solution or suspension is then atomized into a drying chamber, where solvent evaporation results in formation of porous micro particles. These microparticles can then be compressed into rapidly dispersing tablets.
Excipients Commonly Used in Orodispersible Tablets
Superdisintegrants are the key excipients that provide the rapid disintegration properties to orally disintegrating tablets. Apart from super disintegrants, other excipients commonly employed in orally disintegrating tablets include:
- Bulking agents like mannitol, sorbitol, xylitol, etc. provide hardness to the tablets alongside contributing to quick dispersion.
- Binding agents like starch, pregelatinized starch help in providing sufficient mechanical strength and cohesiveness to tablets during compression process.
- Saliva stimulating agents like citric acid, aspartame enhance production of saliva in the mouth to aid rapid disintegration of tablets.
- Flavors and sweeteners like peppermint, menthol, saccharin, aspartame provide taste masking and improve patient acceptability of tablets.
Evaluation Parameters for Orodispersible Tablets
Some key tests performed for evaluation of orally disintegrating tablets include:
- Disintegration time: As per pharmacopeial standards, orally disintegrating tablets should disperse within 3 minutes when placed on the tongue. Disintegration time is tested using a suitable disintegration apparatus.
- Wetting time: It is the time required for the tablet to completely disperse when kept in contact with simulated saliva fluid. Lower wetting time indicates better disintegration properties.
- Water absorption ratio: It is calculated as the ratio of weight of tablet after and before incubation in water or saliva fluid. Higher ratio indicates higher capacity for rapid disintegration.
- Compression force: Being delicate tablets, lower compression in tableting machine is used to avoid damage to porous structure.
- In vitro/in vivo dispersion/disintegration: Tests are done by placing tablets on tongue mimicking oral cavity conditions and observing disintegration under light microscopy or by visual observation.
- Dissolution/drug release studies: Done to check adequate bioavailability and drug release from orally disintegrating tablets during oral administration.
- Stability studies: Done according to ICH guidelines to check physical, chemical and microbial stability over long term storage period.
Application of Orodispersible Tablets in Various Therapeutic Categories
Orally disintegrating tablets have wide applications in several therapeutic areas due to advantages of convenient oral administration without water. Some major therapeutic categories where orally disintegrating tablets are frequently used include:
- Neurological disorders: Antidepressants, anti-parkinsonism, anxiolytics for neurological patients with dysphagia.
