1.4.2 Tablets used in the oral cavity (1-3)
The tablets under this group are aimed release API in oral cavity or to provide local action in this region. The tablets under this category avoids first-pass metabolism, decomposition in gastric environment, nauseatic sensations and gives rapid onset of action. The tablets formulated for this region are designed to fit in proper region of oral cavity.
188.8.131.52 Lozenges and troches
The tablet is a flat faced at least about 18mm in diameter and meant to suck and dissolves in the mouth. The compressed tablet is called troches and the tablets produced by fusion or candy molding process are called lozenges. Flavours and sweeteners are added to make tablets palatable. The tablet generally contains sucrose or lactose and gelatin solution to impart smooth taste. Lozenges for local action in mouth/ throat are: antiseptics, antibiotics, demulcents, antitussive agents or astringents. To produce systemic action: multivitamin tablet.
184.108.40.206 Sublingual tablets
They are to be placed under the tongue and produce immediate systemic effect by enabling the drug absorbed directly through mucosal lining of the mouth beneath the tongue.
Figure.11. Sublingual Tablets
The drug absorbed from stomach goes to mesenteric circulation which connects to stomach via portal vein. Thus, absorption through oral cavity avoids first-pass metabolism. The tablets are usually small and flat, compressed lightly to keep them soft. The tablet must dissolve quickly allowing the API to be absorbed quickly. It's designed to dissolve in small quantity of saliva. After the tablet is placed in the mouth below the tongue, the patient should avoid eating, drinking, smoking and possibly talking in order to keep the tablet in place. Swallowing of saliva should also be avoided since the saliva may contain dissolved drug. Bland excipients are used to avoid salivary stimulation. Due to inconvenience in administration, this dosage form is prepared only for those API(s) for which the only satisfactory nonparenteral method is this route. For example, Glyceryl trinitrate (vasodilator) and Isoprinosine sulphate (bronchodilator).
220.127.116.11 Buccal tablets
Completeness of drug absorption is desired but fast drug absorption is not intended. The tablets are designed not to disintegrate. They are flat elliptical or capsule shaped tablets as it can be easily held between gum and cheek. It's placed near the opening of parotid duct to provide the medium to dissolve the tablet.
Figure.12. Buccal Tablets
Since this tablet is to be kept for 30-60 minutes in oral cavity, care should be taken to see that all the ingredients are finely divided to avoid gritty or irritating sensation. This tablet is most often used when replacement hormonal therapy is to be administered. Antifungal drugs are preferred to be administered by this route. e.g., Miconazole - under preclinical trial - still not in market.
18.104.22.168 Dental cones
These tables are designed to be loosely packed in the empty socket remaining following a tooth extraction.
Figure.13. Dental Cones
Main purpose behind the use of this tablet is either to prevent multiplication of bacteria in the socket by employing a slow releasing antibacterial compound or to reduce bleeding by an astringent or coagulant containing tablet. It's formulated to dissolve or erode slowly in presence of a small volume of serum or fluid over 20-40 minutes period.
22.214.171.124 Mouth Dissolved tablets/ Rapidly Dissolving tablets (10)
Known to the FDA as orally disintegrating tablets, they are also called mouth-dissolving, fast-dissolving, rapid-melt, porous, orodispersible, quick dissolving. These kinds of tablets are preferred when fast action or relief is desired. Most commonly used drugs under this formulation are the agents active against Migraine. The tablets are designed to disintegrate as well as dissolve within one minute or some within 10 seconds of oral administration in limited quantity of saliva. They liquefy on tongue and patient swallows the liquid, without the need of water. A number of techniques are used to prepare these tablets, including lyophilization, soft direct compression. Matrices having an API and high porosity are also being prepared using sublimation process. Urea, urethane, ammonium carbonate, ammonium bicarbonate, hexamethylene, benzoic acid, naphthalene and camphor are commonly used for sublimation processing as they they volatize rapidly. After removal by sublimation, these inert volatile substances leave the matrices with a high porosity. Disintegrants and sugar based excipients, such as sodium starch glycolate, cross carmellose sodium, mannitol, xylitol, dextrose, fructose, maltose and polydextrose have been incorporated in almost all the orally disintegrating dosage forms (ODDFs). Loading of drug is made by preparing a blank and drug is post loaded. Generally the drug in solution is added after which the solvent evaporates. Taste masking poses numerous challenges since the drug product dissolves in mouth, any taste of drug must be covered, either by flavoring technique or by micro encapsulation or nanoencapsulation. A major drawback of most of these systems is that the packaging system needs a higher degree of protection due to the lower hardness and more friability of the porous nature of tablets, except the DuraSolv technology of CIMA Labs, which are suitable for rigors of bulk bottle packaging. Keep the orally disintegrating tablet in the blister pack inside the outer foil pouch until the patient is ready to take the medicine. Make sure that operator's hands are dry and peel open the blister to remove the tablet. Place the tablet on tongue and let it dissolve. These dosage forms have become a delivery system of choice for most patients as they provide comfort for administration throughout the day. Pharmaceutical companies, on the other hand, benefit from value addition in terms of product life-cycle management in today's market.