258 Recent Patents on Drug Delivery & Formulation 2008, 2, 258-274 1872-2113/08 $100.00+.00 © 2008 Bentham Science Publishers Ltd. Orally Disintegrating Systems: Innovations in Formulation and Technology Honey Goel 1 , Parshuram Rai 2 , Vikas Rana 1, * and Ashok K. Tiwary 1, * 1 Pharmaceutics Division, Department of Pharmaceutical Sciences and Drug Research, Punjabi University, Patiala, India-147002. 2 Pharmaceutics Division, Shivalik College of Pharmacy, Naya Nangal, Punjab, India -140126 Received: May 21, 2008; Accepted: August 5, 2008; Revised: August 18, 2008 Abstract: Orally disintegrating systems have carved a niche amongst the oral drug delivery systems due to the highest component of compliance they enjoy in patients especially the geriatrics and pediatrics. In addition, patients suffering from dysphagia, motion sickness, repeated emesis and mental disorders prefer these medications because they cannot swallow large quantity of water. Further, drugs exhibiting satisfactory absorption from the oral mucosa or intended for immediate pharmacological action can be advantageously formulated in these dosage forms. However, the requirements of formulating these dosage forms with mechanical strength sufficient to with stand the rigors of handling and capable of disintegrating within a few seconds on contact with saliva are inextricable. Therefore, research in developing orally disintegrating systems has been aimed at investigating different excipients as well as techniques to meet these challenges. A variety of dosage forms like tablets, films, wafers, chewing gums, microparticles, nanoparticles etc. have been developed for enhancing the performance attributes in the orally disintegrating systems. Advancements in the technology arena for manufacturing these systems include the use of freeze drying, cotton candy, melt extrusion, sublimation, direct compression besides the classical wet granulation processes. Taste masking of active ingredients becomes essential in these systems because the drug is entirely released in the mouth. Fluid bed coating, agglomeration, pelletization and infusion methods have proven useful for this purpose. It is important to note that although, freeze dried and effervescent disintegrating systems rapidly disintegrate in contact with fluids, they do not generally exhibit the required mechanical strength. Similarly, the candy process cannot be used for thermolabile drugs. In the light of the paradoxical nature of the attributes desired in orally disintegrating systems (high mechanical strength and rapid disintegration), it becomes essential to study the innovations in this field and understand the intricacies of the different processes used for manufacturing these systems. This article attempts at discussing the patents relating to orally disintegrating systems with respect to the use of different formulation ingredients and technologies. Keywords: Orally disintegrating tablets, mouth dissolving tablets, fast disintegrating tablets, chewing gums, fast dissolving films, superdisintegrants. INTRODUCTION A vast variety of pharmaceutical research is directed at developing new dosage forms. Most of these efforts have focused on either formulating novel drug delivery systems or increasing the patient compliance. Among the dosage forms developed for facilitating ease of medication, the orally disintegrating systems have been the favorite of product development scientists. Table 1 [1-17] enlists the various drugs and ingredients formulated in to orally disintegrating tablets (ODT). The concept of orally disintegrating dosage forms has emerged from the desire to provide patients with more conventional means of taking their medication. Interestingly, the demand for ODT has enormously increased during the last decade, particularly for geriatric and pediatric patients who experience difficulty in swallowing conventional tablets and capsules. Hence, they do not comply with prescription, which results in high incidence of ineffective therapy [18]. In disease conditions such as motion sickness, sudden episodes of attacks of coughing and repeated emesis * Address correspondence to these authors at The Department of Pharma- ceutical Sciences and Drug Research, Punjabi University, Patiala, India; Tel: +91-09417457385; E-mail:aktiwary2@rediffmail.com; vikas_pbi@rediffmail.com. swallowing conventional tablets be comes difficult. Orally disintegrating dosage forms can serve as an effective alternative mode of drug delivery in such situations. When put in the mouth, these dosage forms disintegrate instantly to release the drug, which dissolves or disperses in the saliva. Thereafter, the drug may get absorbed from the pharynx and oesophagus or from other sections of g.i.t as the saliva travels down. In such cases, bioavailability is significantly greater than that observed from conventional tablet dosage form [19-22]. Hence, orally disintegrating systems may be anticipated to result in achievement of the required peak plasma concentration rapidly for drugs stable in the gastric pH. The orally disintegrating dosage forms could be suitable for neuroleptics, cardiovascular agents, analgesics, anti- allergics and drugs for erectile dysfunction. The US FDA approved products of this category are summarized in Table 2 [23]. In the light of the above, the present article aims at critically analyzing various formulation and technological developments with respect to orally disintegrating systems. ORALLY DISINTEGRATING TABLETS (ODTs) The performance of ODTs depends on the technology used in their manufacture. The orally disintegrating property of these tablets is attributable to the quick ingress of water into the tablet matrix, which creates porous structure and results in rapid disintegration. Hence, the basic approaches to