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INTRODUCTION
The oral cavity has been a preferred site for quick medication absorption. As these formulations are affordable and simple to administer for people who struggle or are unable to swallow oral conventional dose forms, the development of this medication delivery into newer, unique dosage forms for certain classes of drugs has been popular. These systems were designed to be readily framed according to their design (Carmen et al., 2023). Among these formulations, Mouth Dissolving Tablets (MDTs) are the one. MDTs are also referred as oro-dispersible tablets, melt-in-mouth tablets, fast melting, fast disintegrating, fast dissolving, and so on (Tundlayat et al., 2024). Due to their special qualities, these dosage forms, which are both conventional as well as patented, are in high demand from manufacturers and patients alike (Giulia et al., 2022; Khatri et al., 2018; Narkevich et al., 2018). Currently, a third of people experience dysphagia, sometimes known as trouble swallowing. Little ones also have trouble in ingesting solid dosage forms. Children's immature neurological and muscular systems might also make it difficult for them to swallow (Van den et al., 2015). Travelling individuals who may not have easy access to water plainly suffer with taking their medications.
Aforementioned difficulties can be easily treated with these dosages (Logemann, 1995; Ryan et al., 2001; Vaqar et al., 2012; Willig et al., 1994). Regarding the same as orally disintegrating, the development of the MDT was informed by the development of orodispensing technology in previous decades. To create an effective oral dissolving tablet, formulations using a variety of processes, such as direct compression, moisture-activated wet granulation, and lyophilization, must be used (Ghourichay et al., 2021). A good dosage of Active Pharmaceutical Ingredients (API) (0.5 to 600 mg) with enough mechanical strength and temporal dispersion is made possible by these tablets.
The goal of the Mouth Dissolving Drug Delivery System idea was to increase patient compliance (Bala et al., 2013). These dosage forms minimise the need for water during administration by rapidly disintegrating and/or dissolving, releasing the medication as soon as they come into exposure to saliva. This feature alone makes them extremely appealing to patients who are younger and older (Mahajan et al., 2011; Nagar et al., 2011; Parmar et al., 2012; Peh and Wong, 1999). All age groups frequently experience difficulty swallowing traditional tablets and capsules, but elderly and dysphagic patients are particularly likely to experience this. This dysphagia issue is associated with a variety of medical conditions, including stroke, Parkinson's disease, AIDS, thyroidectomy, head and neck radiation therapy, and other neurological disorders like cerebral palsy (Bhidayasiri et al., 2022; Jena et al., 2024; Schindler et al., 2021; Stocchi et al., 2019; Umemoto and Furuya, 2020; Warnecke et al., 2016; Yap and Camm, 2003). According to one study, the biggest obstacle to taking tablets for 26% of the 1576 patients was their size, with surface, shape, and taste coming in second and third.
ADVANTAGES AND DISADVANTAGES
Advantages and limitations are interpreted in Figure 1.
NECESSITY OF DEVELOPING MDTS
Non-invasive delivery technologies are still needed due to patient dissatisfaction with traditional methods. The key target demographics are children and the elderly, who struggle to take regular tablets (Reddy et al., 2011).
PHENOMENON OF MOUTH DISSOLVING
When designing mouth-dissolving tablet formulations, super-disintegrants are significantly more carefully considered. They provide rapid disintegration of the tablet by causing swelling and water absorption (Figure 2). The swelling process of the super-disintegrants wets the surface of the carrier, facilitating tablet dissolving and increasing dissolution rates (Baby et al., 2024). Super-disintegrants' performance is dependent on both the density of the generated matrix and the swelling capacity of the dissolving media (Figure 3). The larger swelling capacity and density of the matrix lead to a greater degree of disintegration (Masih et al., 2017).
In this procedure, porous tablets with good mechanical strength and fast dissolution have been created. Other tablet excipients were combined with inert solid substances, and the mixture was compacted into tablets. Sublimation produced a structure with pores. The tablets sublimate in 10-20 sec (Arya and Chandra, 2010; Kumar and Devi, 2022; Kushagra et al., 2016; Mishra et al., 2024). The majority of APIs utilised in MDT formulations cause systemic impacts instead of local impacts. Drug and excipient properties should not have a significant impact on tablet properties. However, certain drug properties, alike; particle size, crystal structure, solubility, compressibility, along with hygroscopicity, can alter final MDT features. The most prevalent chemicals synthesised as MDTs are antihypertensives, anti-inflammatories, antifungals, analgesics, antibiotics, and antilipidemic (Nannjkar and Shinde, 2020). There are various standards for pharmaceuticals used in MDT formulation that qualify MDTs as an acceptable and optimal dosage form. For example, the medicine should be ionised, disseminated, and permeated through the mucosa, leaving no residue in the oral cavity. Moreover, the API's molecular weight should be less than 500 Da. For daily use, active ingredients should be less than 50 mg, having agreeable taste, a short half-life, and odour. Resilience to extreme climatic conditions, low production costs, along with compatibility with prevailing processing and packaging techniques rendering them increasingly attractive to both patients and industry (Babu and Akhtar, 2020; Nand et al., 2010; Nilesh and Prakash, 2024; Roy et al., 2022).
FORMULATION AND MANUFACTURING PROCESSES
Mechanism of Superdisintegration
Tablet disintegration occurs through four major methods, as listed below.
Swelling
Tablet disintegration is often attributed to swelling. Tablets that have extensive porosity show poor disintegrating effect attributed to insufficient swelling force. In contrast, tablets with poor porosity exhibit considerable swelling force.
Porosity and Capillary action
Capillary action is the initial stage in disintegration. Placing the tablet in aqueous media weakens the intermolecular connection, causing it to break down into fine particles. Tablet water uptake is determined by the hydrophilic properties of the drug/excipient along with the tableting process. Disintegrants exhibiting a porous structure and low interfacial tension form a hydrophilic network surrounding drug particles, which aids in disintegration (Figures 4 and 5).
Particle Repulsive Force
Another disintegrant mechanism explains why nonswellable tablets swell. Guyot-Hermann conveyed a particle repulsion theory built around the discovery that tablets dissolve whenever no swelling particles are detected. Disintegration is induced by electric repelling interactions among particles, which actually require water. Researchers discovered that wicking comes first, then repulsion.
Deformation
During tablet compression, fragmented particles distort and return to their natural structure when exposed to watery medium or water. Deforming starch granules during compression can improve their swelling capacity. The increased size of distorted particles causes the tablet to break.
TECHNIQUES USED FOR FORMULATION OF MDTS ARE
Freeze Drying,
Molding,
Phase Transition Process,
Cotton Candy Process,
Spray Drying,
Mass Extrusion,
Nanonization,
Direct Compression,
Fast Dissolving Films,
Sublimation,
Melt Granulation.
PATIENT ACCEPTANCE AND COMPLIANCE
The pharmaceutical formulation is an important factor in treatment compliance. The MDT formulations are very appropriate. This medication may aid patients who have difficulty swallowing, including the elderly and young, as well as those with underlying illnesses. The MDT formulation is preferable for people who loathe capsules/pills, as well as those who are bedridden. However, energetic people who are engaged or travelling may get benefit from this briefing, which does not require water (Albert et al., 2006). For many patients, a fast-dissolving effective formulation that does not require water outperforms pills and capsules. Medications swallowed without water by bedridden patients may stick to the oesophageal membrane and disintegrate prematurely, potentially causing an oesophageal lesion (Channer and Virjee, 1985; D’arcy, 1984; Ergun and Miskovitz, 1992). MDT formulations have been favoured over conventional presentations, indicating a requirement for a modified to typical dose forms. This basic formulation can boost patient acceptability of prescribed medications, resulting in better compliance. MDTs have the advantage of dissolving quickly in the oral cavity (15-120 sec), resulting in rapid absorption as well as therapeutic action. Some MDTs are especially engineered for being absorbed through the oesophagial mucosa along with buccal areas, accelerating bioavailability over standard dosage forms. These tablets have received emphasis not only for their efficacy, but also for their ability to overcome obstacles caused by other oral medicines such as chewing tablets, effervescent pills, gums, suspensions (Vishal et al., 2022).
MARKET TRENDS AND FUTURE PROSPECTS
MTDs have witnessed increased demand over the last decade, and the field has grown considerably in the pharmaceutical industry. Many medications are best administered orally. Recent technological advances have encouraged scientists to create MDTs that improve patient compliance and convenience. These pills dissolve or disintegrate in the mouth, removing the need for extra water and making it easier to consume active pharmacological components. The formulation's success and practicality prompted the development of additional MDT technologies. MDTs are solid unit dosage forms that quickly dissolve in the mouth lacking drinking or chewing (Parkash et al., 2011). MDTs, or orally disintegrating tablets, are particularly useful for youngsters and the elderly who have difficulties in swallowing traditional pills and capsules. MDTs can be manufactured in a variety of ways, with product success dependent on drug compatibility and excipient selection in the delivery system. Universal research has been performed to develop super disintegrating chemicals and test new formulation procedures. Despite the multitude of current MDTs, there is still room for refining and invention in order to standardise novel technologies. This comprises taste masking, instant disintegration/dissolution, and quick release. MDTs have substantial advantages as solid dosage forms and may be created for most present drugs in the near future.
CONCLUSION
Over the last decade, MDTs have developed popularity. MDT formulations require quick disintegration, dissolving, or melting in the tongue. This can be accomplished by creating a porous tablet matrix or by using superdisintegrants and/or effervescent excipients. Clinical trials have demonstrated that MDTs improve patient compliance, have a faster onset of action, and boost bioavailability. However, many people are not aware of this distribution strategy. As a result, chemists are charged with sharing information about this system. Because of its low mechanical strength, this dose form should be used with caution. The packaging of MDTs is crucial. MDTs require a particular amount of saliva for disintegration and dissolution, hence patients with dry mouth should not be provided them.This dosage type is most suited for young patients who do not have primary teeth and elderly patients who have lost their teeth for good. Many MDTs have been tested and found to have strong discriminating power. In the near future, this delivery mechanism is likely to become equally significant as current distribution systems.