Flavored Oral Dispersible Films: A Comprehensive Review of Formulation Approaches and Regulatory Guidelines

Figure 1: Overview of oral cavity

(Image reproduced from the Source: https://cdn.ncbi.nlm.nih.gov/pmc/blobs/8545/11858154/94250c8a7532/molecules-30-00800-g003.jpg)

Furthermore, ongoing advances and new trends in ODF technology show its versatility as a platform for personalized medicine and targeted drug administration. However, issues such as drug loading restrictions, stability concerns, and regulatory considerations continue to be researched and developed ^[5,6].

In summary, flavored Orodispersible films represent a significant leap in oral drug delivery, successfully merging ease of use with improved clinical outcomes and user-focused design.

Composition of Flavored Oral Dispersible Films:

Flavored oral dispersible films (ODFs) are made up of a blend of film-forming polymers, active pharmaceutical ingredients (APIs), and excipients that work together to provide quick disintegration, acceptable mechanical strength, and increased palatability. The precise selection of these components is critical to obtain peak performance and

patient compliance^[3,5,7].

Film-forming Polymers:

The structural backbone of ODFs is made up of film-forming polymers, which are responsible for the formation of thin, flexible films Hydroxypropyl methylcellulose (HPMC), pullulan, and PVA are standard industry choices due to their superior film-forming properties, rapid wetting, and swift breakdown in the mouth ^[6–8]. The choice of polymer has a considerable impact on the film's dissolving rate and drug release properties ^[8] as shown in Table 1.

Table 1: List of the erodible polymers used in ODF:

Active Pharmaceutical Ingredient (API):

The Active Ingredient is used in modest doses and should be stable, uniformly dispersed, and compatible with various excipients. ODFs are ideal for powerful medications with a quick beginning of action, such as anti-allergic or antiemetic agents ^[3,9]. A homogeneous dispersion of the drug is vital for meeting strict pharmacopeial standards for dosage accuracy^[1].

Suitable drugs for formulation in ODFs include Chlorpheniramine, Loratadine, Phenylephrine, Diphenhydramine, Dextromethorphan, Ketoprofen, Sumatriptan, Zolmitriptan, Loperamide, Famotidine, Nicotine, Pseudoephedrine, Atorvastatin, Amlodipine, Sertraline, Ziprasidone, and Eletriptan^[10].

Plasticizers:

Plasticizers like glycerol, polyethylene glycol (PEG), and propylene glycol are used to upsurge film flexibility and decrease brittleness. They increase mechanical characteristics by reducing the polymer's glass transition temperature, which prevents cracking during handling ^[6,7].

Flavoring Agents:

Flavoring components are integral to pharmaceutical formulations for their ability to mask offensive organoleptic properties of APIs and increasing patient acceptance. Both natural and synthetic flavors, such as mint, citrus, and fruit flavors, are commonly used. Flavor selection is based on drug compatibility and processing stability ^[5,11]. Advanced flavor masking techniques, such as encapsulation, enhance palatability ^[2].

Sweetening agents:

Sweeteners including aspartame, sucralose, and mannitol are used to boost the flavor profile of ODFs. These compounds operate together with flavoring ingredients to effectively conceal bitterness and improve mouthfeel ^[7,8]. Some FDA-Approved Sweetening Agents are given in table 2 ^[10]

Table 2: list of sweetening agents

Saliva Stimulating Agents:

Saliva-stimulating chemicals, such as malic acid and citric acid, are used to speed up film degradation by boosting saliva output. This allows for quicker medication release and breakdown in the oral cavity ^[7].

Coloring Agents:

Coloring compounds are used to enhance the cosmetic appeal and patient acceptance of ODFs. To ensure safety and conformity with regulations, only certified food-grade colorants are used ^[8].

Techniques for formulating the Flavored Oral Dispersible Films (ODFs):

Oral dispersible films (ODFs) are manufactured using a variety of procedures with the goal of ensuring homogeneous drug distribution, quick disintegration, acceptable mechanical strength, and better patient acceptance. The proper procedure is determined by the physicochemical parameters of the drug and excipients, as well as the desired characteristics of the completed product.

Solvent Casting Method:

This method represents the most prevalent technique for the preparation of ODFs. This approach involves dissolving water-soluble polymers in a suitable solvent, followed by the amalgamation of plasticizers, active pharmaceutical ingredients (APIs), flavoring agents, and additional excipients. The resulting homogeneous solution is cast onto a flat surface and then dried to produce a thin film, which is then sliced into uniform units. This method facilitates the production of films characterized by uniform thickness, a smooth texture, and consistent drug distribution. However, it may not be suitable for moisture-sensitive medications due to the utilization of solvents ^[5–7].

Figure 2: Solvent casting method

(Source: https://www.mdpi.com/2380342)

Hot-Melt Extrusion (HME):

Hot-melt extrusion is a solvent-free technique where in polymers are melted and blended with the drug and excipients under precise temperature and pressure conditions. The consequential mixture is squeeze out through a die to form thin films. This method enhances the solubility and uniform distribution of poorly aqueous soluble drugs while obviating the requirement for solvents. Nevertheless, it may not be suitable for heat sensitive drugs due to the preeminent processing temperatures involved ^[3].

Semi-Solid Casting Method:

The semi-solid casting method entails the preparation of a viscous gel through the dissolution of water-soluble polymers, followed by the addition of acid-insoluble polymers to enhance film properties. The gel mass is then cast onto an appropriate surface and dried to yield films. This method backs to the production of films exhibiting improved mechanical strength and controlled disintegration properties ^[6,9].

Solid Dispersion Extrusion:

Using this method, the medication is created as a solid dispersion in a polymer matrix, which is then processed into films. By keeping the drug in an amorphous state, it increases the rate of solubility and bioavailability of poorly soluble medications. Additionally, it is important for masking flavour and enhancing medication release properties^[11].

Rolling Method:

This method consists of spreading a drug-containing solution or suspension onto a carrier using rollers, followed by drying and cutting into films. This technique is advantageous for large-scale production and ensures uniform thickness along with improved process control. However, it necessitates specialized equipment and precise regulation of processing parameters^[6].

Role of Flavoring Agents in Orodispersible Films (ODFs):

Flavoring agents serve a pivotal function in the preparation of oral dispersible Films (ODFs) by enhancing patient acceptability and compliance, particularly within pediatric and geriatric demographics. Given that ODFs rapidly disintegrate in the oral cavity, the taste receptors are directly exposed to the active pharmaceutical ingredient (API), rendering taste masking a significant formulation challenge. Numerous APIs possess an inherently bitter or unpleasant taste, which can adversely affect patient adherence if not properly addressed^[7,9].

Flavoring agents, in conjunction with sweeteners, are primarily utilized to mask the disagreeable taste of medications and to improve the inclusive organoleptic properties of the film. The selection of suitable flavors is contingent upon various factors, including the characteristics of the drug, compatibility with excipients, and stability throughout processing and storage. Commonly employed flavors include fruit-based options (e.g., orange, strawberry) and mint flavors, which provide a pleasant mouthfeel and immediate sensory appeal^[6,7].

Beyond the masking of bitterness, flavors also contribute to the perception of freshness and can influence the disintegration experience within the oral cavity. Advanced taste-masking techniques, such as microencapsulation and nanocarrier systems, are frequently employed alongside flavoring agents to further enhance palatability. For example, the inclusion of drug-loaded microparticles or nano capsules has demonstrated efficacy in reducing drug–taste receptor interactions, thereby augmenting the effectiveness of flavoring systems^[2,4]. Some of the flavouring agents are given in table 3 ^[12].

Table 3: list of flavouring agents used in ODFs:

Additionally, it is important to choose flavoring agents carefully so they do not negatively interact with the API or jeopardize the film's physicochemical stability. These agents' concentrations should be maximized to attain a balance between effective taste masking and formulation stability. Regulatory considerations necessitate that flavoring agents utilized in ODFs are safe, non-toxic, and compliant with established guidelines^[5].

In conclusion, flavouring agents are crucial to the creation of ODFs. significantly impacting patient compliance, product acceptability, and therapeutic outcomes their incorporation with modern taste-masking technology is advancing the creation of oral film formulations that are more efficient and patient-friendly^[11].

Evaluation Parameters of Flavored Oral Dispersible Films (ODFs):

The assessment of oral dispersible films is crucial for ensuring their quality, efficacy, and acceptability among patients. Usually, the following parameters are assessed:

Physical Appearance and Surface Morphology:

To ensure consistency in colour, transparency, smoothness, and the lack of air bubbles or flaws, the films should be visually inspected. Improving patient acceptability and compliance requires a consistent and attractive appearance^[7,9].

Thickness and Weight Variation:   

Film thickness is measured using a micrometer screw gauge at various points to verify uniformity. Weight variation is assessed by weighing individual films and calculating the average weight. Consistent thickness and weight are essential for ensuring dose accuracy and reliability ^[6,7].

Folding Endurance:   

A film is repeatedly folded at a predetermined spot until it breaks in order to measure folding endurance. The film's mechanical strength and flexibility are reflected in this characteristic. Better film integrity is indicated by a higher folding endurance value^[3,7].

Tensile Strength and Percent Elongation:

Tensile strength measures the maximum stress the film can endure before rupture, while percent elongation assesses the film's elasticity. These mechanical properties are critical for handling, packaging, and transportation ^[3,6].

Surface pH:   

The surface pH of the film is measured to identify compatibility with the oral mucosa. Ideally, it should approximate neutrality to prevent irritation within the buccal cavity ^[9,13].

Disintegration Time:   

For ODFs, disintegration time is a crucial factor. It is evaluated by submerging the film in distilled water or artificial saliva and timing how long it takes for it to completely disintegrate. ODFs should typically dissolve in 30 seconds ^[5,13].

In Vitro Dissolution Study:   

To assess the rate and degree of drug release, dissolving tests are carried out using conventional dissolution equipment. One major benefit of ODFs is that a faster rate of dissolution allows for a speedier commencement of action^[3,5].

Content Uniformity:   

Drug content uniformity is determined by dissolving individual films in an appropriate solvent and analyzing the drug concentration. This procedure guarantees that the active medicinal ingredient is present in each film at the recommended dosage^[3,14].

Moisture Content and Moisture Uptake:

The stability of the film is evaluated by measuring its moisture content. Excessive moisture can adversely affect mechanical properties and drug stability. Moisture uptake studies are conducted to analyze the film’s susceptibility to environmental humidity ^[6,13].

Organoleptic Evaluation (Taste and Mouthfeel):   

Organoleptic properties, including taste, flavor, mouthfeel, and aftertaste, are assessed through human volunteers or electronic tongue systems. Effective taste masking is critical, particularly for bitter pharmaceuticals, to enhance patient compliance ^[4,11,13].

Stability Studies:   

To assess changes in physical appearance, drug content, and disintegration characteristics over time, stability studies are carried out in compliance with regulatory criteria under a range of temperature and humidity settings^[5,13].

Regulatory Considerations:

In order to ensure the safety, effectiveness, and patient acceptability of flavoured oral dispersible films (ODFs), regulatory compliance is an essential part of their development. The FDA, EMA, and CDSCO are just a few of the national and international regulatory organizations that provide thorough standards for the approval and quality control of these dosage forms ^[5,7].

Flavouring agents used in ODFs are usually categorized as Generally Recognized as Safe (GRAS) compounds and are subject to safety regulations. These substances must be non-irritating, non-toxic, and compatible with other ingredients in the formulation. Additionally, in order to minimize potential negative effects, especially in paediatric and elderly populations, the amount of flavouring and sweetening chemicals must be under acceptable daily intake (ADI) levels^[5,7].

Figure.3: Safe level of sweeteners according to FDA