الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Soluble diluents such as sugars were found to offer an advantage in ODT manufacturing over insoluble diluents, involving absence of feeling of roughness imparted by the latter type (87). However, compressed tablets of water soluble materials such as mannitol did not dissolve rapidly in mouth owing to difficulty of water penetration into a low porosity matrix (87). Consequently, increasing porosity of the soluble matrix via sublimation is presumed to be a good choice. One of the techniques exploited for ODT manufacturing is, therefore, based on sublimation as a post compression treatment (87). Herein, volatile ingredients are involved in the tablet matrix; and the tablets are then exposed to sublimation process (i.e. heating under vacuum). In this way, the sublimable agent will evaporate leaving behind a porous matrix, which enhances tablet disintegration. The volatile ingredient may therefore be called ”pore-forming agent”. In patent studies conducted by Roser and Blair (91), inert solid ingredients that displayed high volatility (e.g. ammonium bicarbonate, benzoic acid, camphor, and urea) were compressed along with other ingredients into tablets and were then removed by sublimation. Makino et al (92) reported a method using water as a pore forming agent, while Koizumi et al (87) utilized camphor as a subliming agent for ODT preparation.
Sublimation is a post-compression treatment that can be employed using available equipment, facilities and inexpensive materials. It is therefore amenable for large scale production. High tablet porosity resulting from sublimation technique is a major pathway for rapid disintegration. Yet, major drawbacks of this technique include high tablet friability and residual sublimable material that, therefore, should be inert. In addition, the efficiency of sublimation should be high enough to produce sufficient evaporation and porosity.
Camphor is a crystalline, ketonic substance (figure 2) that is highly volatile even at ambient temperature (93, 94), and therefore used as a pore forming agent in ODT manufacturing (87). Melting takes place at a temperature ranging from 175 °C to 179 °C. The powder is slightly soluble in water and very soluble in alcohol (93).