The oral fast-dissolving systems are defined as oral drug delivery systems that dissolve or disintegrate within a few seconds to a few minutes of placement in the mouth and that do not require water to aid swallowing. Various technologies are used to achieve quick dissolution/dispersion in the oral cavity. This review focuses on the properties of the various fast-dissolving (orally disintegrating) technologies for systemic drug delivery.
Freeze-drying, molding, and compaction technologies are described. Zydis®, Quicksolv® and Lyoc® are prepared by freeze drying; FlashDose® is prepared by a molding/cotton-candy process; WOWTAB®, FlashTab® and Frosta® are prepared by granulation followed by compression; OraSolv®, DuraSolv®, OraVescent®, QDis™, Ziplets® and AdvaTab™ are prepared by direct compression. Differences between drug delivery systems with regard to their composition (excipients), structure and formulation are also reviewed. Employment of relatively consolidated technologies (lyophilization, compaction, and granulation) can shorten the formulation, development, and scaling-up processes. In addition, the properties of systems prepared using these technologies are critically compared. The advantages and the disadvantages of each type of dosage form in terms of dissolution and absorption rate, bioavailability, stability, mechanical strength, taste-masking properties, and patient compliance are emphasized. The implications of these differences for patient compliance and choice of technologies in drug formulation are highlighted.
Freeze-drying allows immediate dissolution of the tablets because of their high porosity, and enhances drug stability, especially for moisture-sensitive substances; on the other hand, a porous network is associated with low physical resistance and high friability, and special packaging is required in some cases. Use of the molding technology results in tablets with an appropriate dissolution time, even though they are characterized by poor mechanical properties (hardness). The fast-dissolving tablets based on compaction technologies utilize consolidated technologies (standard equipment and materials) and their production costs are low. Most of these tablets are characterized by good physical resistance (hardness), although this can result in an increase in the disintegration time.
Apart from its favorable anatomic and physiologic features that allow modulation of drug permeation, the high degree of vascularization, minimal enzymatic pool and potential to avoid first-pass metabolism make the oral cavity an ideal site for peptide/protein delivery and absorption using fast-dissolving formulations. Furthermore, the gentle preparation procedures and technologies (in particular lyophilization) used in the manufacture of oral fast-dissolving tablets are compatible with the delicate drug substances delivered by these formulations.