Oral solution drug delivery preparation

Gupta et al. prepared crosslinked chitosan microspheres by dropping a polysaccharide solution into a methanolic solution of NaOH and then adding a solution of glutaraldehyde for crosslinking. They demonstrated that the obtained microspheres were non-toxic and biodegradable, and therefore may be considered suitable candidates for oral drug delivery [130]. 

Microgel particles consisting of vinylpyrrolidinone copolymerized with acrylic acid have been prepared (61). These particles were designed to be used as an oral drug delivery vehicle. The microgel particles were loaded with a marker compound fluorescein isothiocyonate (FITC)-dextran and the release of this compound was monitored as a function of pH and temperature. The release of this compound was found to be slow in an acid solution but increased rapidly as the pH was increased. There was also a subsequent increase in FITC-dextran release when the particles were heated. At 4°C 18% of the FITC-dextrans were released while 50% was released at 37°C. The increase in the amount of FITC-dextran released is due to the microgel shrinking when heated. 

The delivery of freeze-dried preparations can be performed by different routes oral, nasal, anal, pulmonary, transdermal and parenteral. Of these routes, some do not require any treatment of the drug before it is administered, e.g. in the form of powders or tablets or in inhaling devices. For parenteral administration, however, whether by injection or infusion, the freeze-dried cake must be returned to a liquid state, a process referred to as reconstitution . The main vehicle will normally consist of water for injection or a solution, the concentration of which will establish isotonicity. The time required for the complete dissolution of the cake may in some cases be critical and should therefore be known. 

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