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Fast Dissolving Drug Delivery Systems: A Brief Overview

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1.1 Introduction to fast dissolving drug delivery system

Fast dissolving drug delivery systems have rapidly gained acceptance as an important new way of administering drugs. There are multiple fast-dissolving OTC and Rx products on the market worldwide, most of which have been launched in the past 3 to 4 years. There have also been significant increases in the number of new chemical entities under development using a fast-dissolving drug delivery technology.

Rapidly dissolving dosage forms have acquired great importance in the pharmaceutical industry because of their unique properties. Rapidly dissolving dosage forms are also called quick-dissolving delivery systems; quick-disintegrating, orally disintegrating, mouth dissolve dosage forms; or melt-in-mouth dosage forms. However, the function and concept of all these dosage forms are similar. In less than one minute, these dosage forms disintegrate or dissolve in the salivary fluids of the oral cavity, releasing the drug and inactive ingredients. Most of the drug is swallowed with the saliva where subsequent absorption takes place in the gastrointestinal tract. By definition, a solid dosage form that dissolves or disintegrates quickly in the oral cavity, without the need for the administration of water, is known as an oral fast-dissolving dosage form.

Salient Features of Fast Dissolving Drug Delivery System

  • Ease of administration for patients who are mentally ill, disabled and uncooperative.
  • Requires no water
  • Quick disintegration and dissolution of the dosage form.
  • Overcomes unacceptable taste of the drugs.
  • Can be designed to leave minimal or no residue in the mouth after administration and also to provide a pleasant mouth feel.
  • Allows high drug loading.
  • Ability to provide advantages of liquid medication in the form of solid preparation.
  • Adaptable and amenable to existing processing and packaging machinery
  • Cost- effective [5-9].

1.2 Characteristics of Fast Dissolving Delivery System [5] 1.2.1 Ease of administration

Fast Dissolving Delivery Systems are easy to administer and handle hence, leads to better patient compliance. Usually, elderly people experience difficulty in swallowing the conventional dosage forms (tablets, capsules, solutions and suspensions) because of tremors of extremities and dysphasia. Fast Dissolving Delivery Systems may offer a solution for these problems.

1.2.2 Taste of the medicament

As most drugs are unpalatable, mouth dissolving delivery systems usually contain the medicament in taste masked form. Delivery systems dissolve or disintegrate in patient's mouth, thus releasing the active ingredients which come in contact with the taste buds and hence, taste masking of the drugs becomes critical to patient compliance.

1.2.3 Hygroscopicity

Several fast dissolving dosage forms are hygroscopic and cannot maintain physical integrity under normal condition from humidity which calls for specialized product packaging [10].            

1.2.4 Mouth feel

Mouth feel is critical, and patients should receive a product that feels pleasant. Any large particles from the disintegrating tablet that are insoluble or slowly soluble in saliva would lead to an unpleasant gritty feeling. This can be overcome by keeping the majority of the particles below the detectable size limit. In some cases, certain flavors can imbibe an improved mouth feel perception, resulting in a product that is perceived as being less gritty, even if the only change is the flavor. Effervescence can be added to aid disintegration and improve mouth feel by reducing the dryness of a product [11, 12].

2. Introduction to fast dissolving oral thin film.

2.1 Definition

Thin film drug delivery is a process of delivering drugs to the systemic circulation via a thin film that dissolves when in contact with liquid, often referred to as a dissolving film or strip. Thin film drug delivery has emerged as an advanced alternative to the traditional tablets, capsules and liquids often associated with prescription and OTC medications. Similar in size, shape and thickness to a postage stamp, thin film strips are typically designed for oral administration, with the user placing the strip on or under the tongue or along the inside of the cheek. As the strip dissolves, the drug can enter the blood stream enterically, ducally or sublingually.

The first commercial non-drug product to use thin films was the Listerine PocketPaks breath freshening strips. Since then, thin film products for other breath fresheners, as well as a number of cold, cough, flu and anti-snoring medications, have entered the marketplace. There are currently several projects in development that will deliver prescription drugs utilizing the thin film dosage form [13].

2.2 Advantages of fast dissolving oral thin film

The design of thin film, often referred to as Pharm Film, as an oral drug delivery technology offers several advantages over other modes of drug delivery, such as ingestible tablets, chewable tablets, orally dissolving tablets, softgels, liquids or inhalants[14].

The sublingual and buccal delivery of a drug via thin film has the potential to improve the onset of action, lower the dosing, and enhance the efficacy and safety profile of the medicament.

All tablet dosage forms, softgels and liquid formulations primarily enter the blood stream via the gastrointestinal tract, which subjects the drug to degradation from stomach acid, bile, digestive enzymes and other first pass effects. As a result, such formulations often require higher doses and generally have a delayed onset of action.

Conversely, buccal and sublingual thin film drug delivery can avoid these issues and yield quicker onsets of action at lower doses.

Thin film is more stable, durable and quicker dissolving than other conventional dosage forms.

Thin film enables improved dosing accuracy relative to liquid formulations since every strip is manufactured to contain a precise amount of the drug.

Thin film not only ensures more accurate administration of drugs but also can improve compliance due to the intuitive nature of the dosage form and its inherent ease of administration. These properties are especially beneficial for pediatric, geriatric and neurodegenerative disease patients where proper and complete dosing can be difficult.

Thin film's ability to dissolve rapidly without the need for water provides an alternative to patients with swallowing disorders and to patients suffering from nausea, such as those patients receiving chemotherapy.

Thin film drug delivery has the potential to allow the development of sensitive drug targets that may otherwise not be possible in tablet or liquid formulations.

From a commercial perspective thin film drug delivery technology offers an opportunity to extend revenue lifecycles for pharmaceutical companies whose drug patent is expiring and will soon be vulnerable to generic competition.

Advantages of Oral Thin Film

  • Thin elegant film
  • Convenient dosing
  • Fast disintegration
  • Enhance stability
  • Quick dissolving
  • Improve patient compliance
  • Rapid release
  • Life cycle management
  • mucoadhesion
  • Taste masking
  • unobstructive
  • No risk of choking
  • Various sizes and shapes
  • No water needed

2.3 Need for fast dissolving thin film drug development

2.3.1 Taste masking

An important aspect of thin film drug delivery technology is the masking of the often bitter and poor taste of drug formulations[14].One method of taste-masking is encapsulation, the coating of drug particles with a polymeric covering sufficient to mask the taste of the drug particle while maintaining the ability to release the drug for absorption. Encapsulation is an efficient method for combining a high ratio of drug-to-non-drug elements in the taste-masked particle. Another method is the use of an ion exchange resin to bind the drug, forming a resinate that is less bitter than the drug alone. Shivang Chaudhary,final year M.S.Pharm student of Indian NAtional Institute of Pharmaceutical Education & Research (NIPER) has formulated Taste masked Quick melting oral strip(QMOS) for quick onset of erection, in which they got success in bitter taste masking of sildenfil citrate via its inclusion complexation within B-Cyclodextrin by simple kneading method.

2.3.2 Drug content uniformity

Drug content uniformity is a requirement for all dosage forms, particularly those containing low dose highly potent drugs. To uniquely meet this requirement, thin film formulations contain uniform dispersions of drug throughout the whole manufacturing process[15].Since this criteria is essential for the quality of the thin film and final pharmaceutical dosage form, the use of Laser Scanning Confocal Microscopy (LSCM) was recommended to follow the manufacturing process[16].

2.3.3 Avoiding drug degradation

Sensitive drugs may degrade over time in an aqueous environment. Thin film formulations must ensure that the integrity of the drug remains constant over time [17]. To overcome these challenges, developers of thin film have created highly specialized unique and often proprietary processes to deliver drugs on thin film [18].

2.4 Functionality of oral thin film

Pharmaceutical companies and consumers alike have embraced OTFs as a practical and accepted alternative to traditional OTC medicine forms such as liquids, tablets, and capsules. OTFs offer fast, accurate dosing in a safe, efficacious format that is convenient and portable, without the need for water or measuring devices [19]. OTFs are typically the size of a postage stamp and disintegrate on a patient's tongue in a matter of seconds for the rapid release of one or more APIs. The formulation of dissolvable films is customarily facilitated through aqueous polymer matrices that span a wide molecular weight (MW) range, thereby providing flexibility to achieve certain physical properties. With the selection of appropriate polymer excipients, these properties can be tailored to meet specific API-loading needs and dissolution rates.

To date, the commercial launch of OTFs is primarily in OTC products addressing therapeutic categories such as cough/cold, sore throat, and antacid/gas relief as well as a number of nutritional supplement applications [19].

In compliance with the appropriate monographs, current products deliver a specified API dose that is immediately released and ingested. Some drug forms are more easily used in OTFs than others (soluble versus non soluble), but we can expect API concentrations to increase as new OTF formulations are developed.

The capabilities of the base technology to create dissolvable films continue to evolve. For example, a common misconception of the OTF format is that it is limited with regard to the loading capacity of APIs. Some researchers reference a limit of 30 mg of API content as the maximum concentration. A more accurate statement would be that OTFs have the capability to load APIs up to 50% of the unit dose mass, as demonstrated by Novartis Consumer Health's Gas-X thin film, which contains 62.5 mg of simethicone per dose [20].

Some drug substances may be absorbed more rapidly through the oral mucosal and esophageal tissues via OTF formats during ingestion. Because the drug enters directly into the bloodstream and avoids hepatic first-pass metabolism, bioavailability may be improved, and the drug can be administered in smaller doses. Smaller doses translate to fewer side effects and potentially improved patient compliance. Oral mucosal delivery via OTFs could become a preferential delivery method for therapies in which rapid absorption is desired, including those used to manage pain, allergies, sleep difficulties, and central nervous system disorders.

Functional film properties controlled during manufacturing

  • Thickness
  • Width
  • Drug concentration
  • residual volatiles
  • tensile strnth
  • disintegration rates
  • dissolution rates

2.5 oral thin film as Strategic therapeutic categories

OTF formats can be considered for any therapeutic category in which an oral solid, liquid, or ODT format is currently offered. Ideal applications are those that use drug compounds that are potent and possess a narrow therapeutic range [21]. In addition, OTFs are proven to be a more beneficial platform for compromised populations such as children or the elderly where a quick, well-tolerated platform aids administration [22].

From a strategic standpoint, a group of therapeutic categories stand out as leading applications for the OTF format to expand beyond commercial OTC products on the market today (see sidebar, "Strategic therapeutic categories for oral thin films"). Development of a branded prescription OTF product for smoking cessation would set a precedent for the format, much like the launch of transdermal drug delivery patches for smoking cessation did in the 1990s.

Strategic therapeutic categories for oral thin films

  • Contraception
  • Hormone replacement
  • Pain management
  • Allergy and asthama
  • Nausea
  • Central nervous system disorders
  • Anti-inflammatory
  • Gastro-intestinal
  • Sleep aids
  • Veterinary medicines and vitamins

3. Drugs availability in market as a film/strip

The use of thin-film strips is of growing interest in the pharmaceutical sector following the success of Listerine PocketPaks® in the United States. Thin-film strip technology uses a range of water-soluble polymers and is reported to be able to incorporate watersoluble, insoluble, or taste-masked ingredients. The film is manufactured as a continuous sheet and then cut into individual doses prior to packing. The major limitations to this technology are the relatively low doses that can be accommodated (approximately 30 mg) and its moisture sensitivity thus requiring specific unit-dose packaging to protect the product and ensure shelf life. Thin-film technology has primarily been used in over the- counter (OTC) products.


4. Market trends

TCI's report also details the technology programs of 25 companies active in the development of Orally-Disintegrating Tablet technologies and 17 active in the development of Oral Film technologies. Technology Catalysts forecasts the market for drug products in oral thin film formulations to be valued at $500 million in 2007 and could reach $2 billion by 2010.

The first oral strip was developed by Pfizer (New York) as a mouth freshening product ("Listerine" pocket packs). "Chloraseptic Relief Strips" (distributed by Prestige Brands, Irvington, NY), Theraflu Thin Strips treat the most common symptoms of a cold in adults and children 12 and older and will be available in two cherry-flavoured treatment options: Long Acting Cough that quiets coughs for up to eight hours, and Multi-Symptom that, as well as tackling coughs, is said to provide temporary relief from a runny nose and sneezing, and soothes itchy, watery eyes and throat. Both will cost approximately $5.49 for a 12-strip pack.

Meanwhile, Triaminic Thin Strips, for children ages 6-12, will also be available in two treatment options: Long Acting Cough that quiets coughs for up to eight hours, in cherry flavor, and Cough & Runny Nose, in grape flavour. They will cost approximately $5.99 for a 16-strip pack, according to Novartis.

5. Formulation consideration

5.1. film forming polymer

A variety of polymers are available for preparation of OS. The polymers can be used alone or in combination to obtain the desired strip properties. The film obtained should be tough enough so that there won't be any damage while handling or during transportation. The robustness of the strip depends on the type of polymer and the amount in the formulation [23].

On the other hand, fast dissolving strip dosage formshould have the property to disintegrate in seconds when placed in mouth and deliver the drug to the oral cavity instantaneously. A list of polymers and their properties are given in Table 5 [24-30]. As the strip forming polymer (which forms the platform for the OS) is the most essential and major component of the OS, at least 45%w/w of polymer should generally be present based on the total weight of dry OS [31]. Of the various polymers available, pullulan, gelatin and hypromellose are most commonly used for preparation of OS. Pullulan is a natural polymer obtained from non-animal origin and does not require chemical modification. This polymer provides highly clear and homogenous films. It has low oxygen permeability and low water content which makes it most suitable for production of OS [32]. Many times, mixtures of polymers are used to improve hydrophilicity, flexibility, mouth-feel and solubility characteristics of OS.

Polyvinyl pyrrolidone films are brittle in nature and therefore copovidone is mixed with poly vinyl pyrrolidone for preparation of flexible fast disintegrating strips [33]. Combination of microcrystalline cellulose and maltodextrin has been used to formulate OS of piroxicam made by hot melt extrusion technique. In this case, microcrystalline cellulose is used to render the film non-sticky and smooth [34]. Microcrystalline cellulose was also used to decrease the disintegration time and improve the dissolution of drug from the OS [35].

Property of polymer

  • non-toxic
  • non-irritant
  • devoid of leachable impurities
  • good wetting property
  • spreadability property
  • readily available
  • Should not be very expensive
  • Should exhibit sufficient peel, shear and tensile strengths.

Various polymers can be employed to modulate the disintegration property of the oral strip. This is especially used in case of slowly disintegrable oral bioadhesive strips or patches that need to be retained in intact form for longer duration in the oral cavity. The bioadhesive polymer used in such formulations imparts the adhesive property to the strip such that it adheres to buccalmucosa to deliver the drug for prolonged period. Bioadhesive polymer should ideally adhere quickly to the buccal mucosa and should have sufficient mechanical strength. Polymers used for OS should have good shelf life and they should not aid in causing secondary infections in the oral mucosa or dental regions. It would be ideal to have a polymer that would have local enzyme inhibition action along with penetration enhancing property. The details of properties of bioadhesive or mucoadhesive polymers and their applications are discussed elsewhere [36-43]. Mucoadhesive polymers include polycarbophil, cellulose derivatives like hydroxypropyl methylcellulose, poly(acrylic acid) derivatives, sodium carboxymethyl cellulose, hydroxylethyl cellulose, hyaluronic acid, xanthan gum, locust bean gum, guar gum, carrageenan, sodiumalginate, chitosan, poly(ethylene oxide), poly (ortho esters), poly (hydroxyl butyrate), poly(cyano acrylates), polyphosphazenes, poly (vinyl alcohol) etc.

Second generation mucoadhesive polymers include thiolated polymers. They are multifunctional polymers consisting of hydrophilic macromolecules having free thiol groups on the polymer backbone. The polymer forms disulfide bonds with cysteine-rich subdomains of mucus glycoproteins. Corium International has developed a new class of adhesive hydrogels (Corplex„¢) [44].

There are a number of marketed products available that are based on mucoadhesion phenomena. Oramoist® is a Timed Release oral disk that adheres to the roof of the mouth and has a moisturizing effect for about 4 h [44]. It is recommended for dry mouth syndrome (xerostomia). Compeed® is another formulation that is intended to treat cold sore [46].



Polymer: Hydoxy propyl methyl cellulose (HPMC)

Synonym: Methocel, Metolose, Benecel (Hypromellose)

Description: It is a odorless, tasteless and white or creamy white fibrous or granular powder

Molecular weight: 10,000-1,500,000

Solubility: Soluble in cold water,forming a viscous colloidal solution, insoluble in chloroform, ethanol


Polymer: Hydroxy propyl cellulose

Synonym: Hydroxyl propyl ether, hyprolose, Klucel, Nisso HPC.

Description: It is a white to slightly yellow colored, odorless and tasteless powder. It is stable material

Molecular weight: 50,000-1,250,000

Solubility: It is freely soluble in water below 38 °C forming a smooth, clear, colloidal solution. Hydroxypropyl cellulose is soluble in many cold and hot polar organic solvents such as absolute ethanol, methanol, isopropyl alcohol and propylene glycol


Polymer: Starch and modified starch

Synonym: Amido, amylum, PharmGel, Fluftex W, Instant pure-Cote, Melogel etc.

Description: It is an odorless, tasteless, fine, white powder.

Molecular weight: 50,000-160,000

Solubility: It is insoluble in cold water and ethanol. It swells in water by about 5 to 10% at 37 °C


Polymer: Pullulan

Synonym: Pullulane, 1, 6 α linked maltotriose

Description: It is available as white, odorless tasteless, stable powder

Molecular weight: 8000-2,000,000

Solubility: It is soluble in hot as well as cold water


Polymer: Pectin

Synonym: Citrus pectin, Methopectin, pectin, pectinic acid 

Description: It occurs as a yellowishwhite, odorless powder with mucilaginous taste.

Molecular weight: 30,000-100,000

Solubility: It is soluble in water but insoluble in most of the organic solvents.


Polymer: Gelatin

Synonym:  Byco, cryogel, Instagel, Solugel

Description: It occurs as light amber to faintly yellow colored, vitreous, brittle solid. It is ordorless, tasteless.

Molecular weight: 15,000-250,000

Solubility: Soluble in glycerin, acid and alkali. Swells in water and softens. It is soluble in hot water


Polymer: Carboxy methyl cellulose

Synonym: Akulell, Blanose, Aquasorh

Description: It is white, odorless powder

Molecular weight: 90,000-700,000

Solubility: It is easily dispersed in water to form a clear or colloidal solution

5.2 Plasticizer

Plasticizer is a vital ingredient of the OS formulation. It helps to improve the flexibility of the strip and reduces the brittleness of the strip. Plasticizer significantly improves the strip properties by reducing the glass transition temperature of the polymer. The selection of plasticizer will depend upon its compatibility with the polymer and also the type of solvent employed in the casting of strip. The flow of polymer will get better with the use of plasticizer and enhances the strength of the polymer [47, 48].

Glycerol, Propylene glycol, low molecular weight polyethylene glycols, phthalate derivatives like dimethyl, diethyl and dibutyl phthalate, Citrate derivatives such as tributyl, triethyl, acetyl citrate, triacetin and castor oil are some of the commonly used plasticizer excipients. Typically the plasticizers are used in the concentration of 0-20%w/w of dry polymer weight [49-57]. However inappropriate use of plasticizer may lead to film cracking, splitting and peeling of the strip [58-60]. It is also reported that the use of certain plasticizers may also affect the absorption rate of the drug [61].

5.3 Active pharmaceutical ingredient

The active substance is may be from any class of pharmaceutically active substances that can be administered orally or through the buccal mucosa, respectively. The OS technology has the potential for delivery of variety of APIs. However since the size of the dosage form has limitation, high dose molecules are difficult to be incorporated in OS. Generally 5%w/w to 30%w/w of active pharmaceutical ingredients can be incorporated in the OS [62]. Multivitamins up to 10%w/w of dry film weight was incorporated in the OS with dissolution time of less than 60 s [32].

APIs can also be added as milled, micronized or in the form of nanocrystals or particles depending upon the ultimate release profile desired. It is always useful to have micronized API which will improve the texture of the film and also for better dissolution anduniformity in the OS [63].

Some of the examples of suitable drug molecule that can be incorporated in the OS are listed in table-6.


5.4 sweetening agent

Sweeteners have become the important part of the food products as well as pharmaceutical products intended to be disintegrated or dissolved in the oral cavity.

Natural sweeteners as well as artificial sweeteners are used to improve the palatability of the mouth dissolving formulations. Sweetening agent such as Sugar, dextrose, lactose, mannitol, sucrose, xylitol, malitol, acesulfame potassium, talin, glycyrrhizin, sucralose, aspartame, saccharin etc.

The classical source of sweetener is sucrose (derived from cane or beet in the form of liquid or dry state), dextrose, fructose, glucose, liquid glucose and maltose. The sweetness of fructose is perceived rapidly in the mouth as compared to sucrose and dextrose. Fructose is sweeter than sorbitol and mannitol and thus used widely as a sweetener.

The artificial sweeteners have gained more popularity in food and pharmaceutical preparations. Saccharin,cyclamate and aspartame are the first generation of the artificial sweeteners followed by acesulfame-K, sucralose, alitame and neotame which fall under the second generation artificial sweeteners. Acesulfame-K and sucralose have more than 200 and 600 time sweetness. Neotame and alitame have more than 2000 and 8000 time sweetening power as compared to sucrose. Rebiana which is a herbal sweetener, derived from plant Stevia rebaudiana (South American plant) has more than 200-300 time sweetness [64].The flavor quality of these artificial sweeteners is different than the natural sweeteners and may not be acceptable to the patients who are accustomed to the natural sugars. The amalgamation of sweeteners may lead to synergismand improvement in the taste of the formulations [65]. Aspartame was used for the preparation of oral strips of valdecoxib [66]. For the oral strip of piroxicam, maltodextrin was employed as sweetening agent [67]. Generally sweeteners are used in the concentration of 3 to 6 %w/w either alone or in combination [68].

5.5 flavoring agent

Perception for the flavors changes from individual to individual depending upon the ethnicity and liking. The selection of flavor is also dependant on the type of drug to be incorporated in the formulation. For example, mint flavor is generally added in products used for gastric related ailments like indigestion. The acceptance of the oral disintegrating or dissolving formulation by an individual by and large depends on the initial flavor quality which is observed in first few seconds after the product has been consumed and the after taste of the formulation which lasts for at least about 10 min [69].

Flavoring agents can be selected from synthetic flavor oils, oleo resins, extract derived from various parts of the plants like leaves, fruits and flowers. Flavors can be used alone or in the combination. Peppermint oil, cinnamon oil, spearmint oil, oil of nutmeg are examples of flavor oils while vanilla, cocoa, coffee, chocolate and citrus are fruity flavors. Apple, raspberry, cherry, pineapple are few examples of fruit essence type. The amount of flavor needed to mask

the taste depends on the flavor type and its strength. Preferably up to 10%w/w flavors are added in the OS formulations. Cooling agents like monomethyl succinate can be added to improve the flavor strength and to enhance the mouth-feel effect of the product. Other cooling agents likeWS3, WS23 and Utracoll II can also be used in conjunction with flavors [68, 70].

5.6 coloring agent

Coloring agents may include FD & C coloring agents, natural coloring agents, and natural juice concentrates, pigments such as titanium oxide, silicon dioxide and zinc oxide. (not exceeding concentration levels of 1%w/w) in OS .when some of the formulation ingredients or drugs are present in insoluble or suspension form [71,72].

5.7 stabilizing and thickening agent

The stabilizing and thickening agents are employed to improve the viscosity and consistency of dispersion or solution of the strip preparation solution or suspension before casting. Natural gums like xanthan gum, locust bean gum, carragenan and cellulosic derivatives can be used in the concentration up to 5%w/w as thickening agents and stabilizing agents [68]. Other ingredients such as surfactants and emulsifying agents are also added in small amount to improve the strip properties.

5.8 saliva stimulating agent

The purpose of using saliva stimulating agents is to increase the rate of production of saliva that would aid in the faster disintegration of the rapid dissolving strip formulations. Generally acids which are used in the preparation of food can be utilized as salivary stimulants. Citric acid, malic acid, lactic acid, ascorbic acid and tartaric acid are the few examples of salivary stimulants, citric acid being the most preferred amongst them.

These agents are used alone or in combination between 2 to 6%w/w of weight of the strip. Other OS ingredients such as sweeteners also act as salivary stimulants. Food grade sugars as well as synthetic sugars are useful salivary stimulants along with acidulents. Glucose, fructose, xylose, maltose, lactose are few examples of such sweeteners [73]. The resting salivary flow rate was 0.34 ml/min .but citric acid is capable to increase the salivary flow rate up to 1.68ml/min [73].

6. Method of manufacturing of oral thin film

One (or a combination) of the following processes may be used to manufacture the oral films [74].

  • Solvent casting
  • Hot-melt extrusion
  • Solid dispersion extrusion
  • Rolling

6.1 Solvent Casting

The oral film is preferably formulated using the solvent-casting method, whereby the water-soluble ingredients are dissolved to form a clear viscous solution. The API and other agents are dissolved in smaller amounts of the solution, and combined with the bulk. This mixture is then added to the aqueous viscous solution. The entrapped air is removed by vacuum. The resulting solution is cast as a film and allowed to dry, which is then cut into pieces of the desired size. Water-soluble hydrocolloids used to prepare films are: hydroxypropylmethyl cellulose (HPMC), hydroxypropyl cellulose (HPC), pullulan, sodium alginate, pectin and carboxymethyl cellulose (CMC) [75].

6.2 Hot melt extrusion

Hot melt extrusion (HME) is commonly used to prepare granules, sustained-release tablets, transdermal and transmucosal drug delivery systems. [76-77].Processing films by this technique, involves shaping a polymer into a film via the heating process rather than through the traditional solvent casting method. Melt extrusion was used as a manufacturing tool in the pharmaceutical industry as early as 1971. Since the turn of the century, many studies have been conducted on this process for the preparation of solid dispersion. Hot-melt extrusion method is used in the preparation of various dosage forms in the pharmaceutical industry such as preparation of sustained-release pellets. The drug carrier mix is filled in the hopper and is conveyed, mixed, and melted by the extruder. The die then shapes the melt in the required film form. Hot-melt extrusion include lower temperature and shorter residence time of the drug carrier mix (<2 minutes), absence of organic solvents, continuous operation possibility, minimum product wastage, good control of operating parameters, and possibility to scale up. Repka et al. prepared chlorpheniramine maleate (CPM) topical HPC films by hot melt extrusion technique using hydroxy propyl cellulose as polymer [76].

6.3 Solid dispersion extrusion

The term "solid dispersions" refers to the dispersion of one or more active ingredients in an inert carrier in a solid state in the presence of amorphous hydrophilic polymers and also using methods such as melt extrusion. A drug is first dissolved in a suitable liquid solvent and then this solution is incorporated into the melt of polyethylene glycol, obtainable below 70C without removing the liquid solvent. The selected solvent or dissolved drug may not be miscible with the melt of the polyethylene glycol. Also polymorphic form of the drug precipitated in the solid dispersion may get affected by the liquid solvent used [78].

6.4 Rolling method

In these method the film is prepared by preparation of a pre-mix, addition of an active and subsequent formation of a film [79] .The pre-mix or master batch which includes the film -forming polymer, polar solvent, and any other additives except a drug active is added to the master batch feed tank .Then a pre-determined amount of the master batch is controllably fed via a first metering pump and control valve to either or both of the first and second mixers. The required amount of the drug is added to the desired mixer through an opening in each of the mixers. After the drug has been blended with the master batch pre-mix for a sufficient time to provide a uniform matrix, a specific amount of the uniform matrix is then fed to the pan through the second metering pumps. The metering roller determines the thickness of the film and applies it to the application roller. The film is finally formed on the substrate and carried away via the support roller. The wet film is then dried using controlled bottom drying, desirably in the absence of external air currents or heat on the top (exposed) surface of the film.

7. Quality Control Of oral thin Film

7.1 Thickness

Thickness test is carried out using an electronic micrometer MI-1000 (Cheminstruments, USA). [80] It can be measured by micrometer screwgauge at different strategic locations. This is essential to ascertain uniformity in the thickness of the film as this is directly related to the accuracy of dose in the strip.

7.2 Tensile strength

Tensile strength is the maximum stress applied to a point at which the strip specimen breaks [81]. It is calculated by the applied load at rupture divided by the cross-sectional area of the strip. The "tensile strength" (psi) is the property of film that requires a load to cause load deformation failure of film. Tensile strength was evaluated according to ASTM International Test Method for Thin Plastic Sheeting (D 882-02) [82]. An electronic dynamometer AG/MC1 is used. The tensile strength and elongation at break were calculated as below:

Tensile strength (N/mm2) = Breaking force (N)/Cross-sectional area of sample (mm2)

7.3 Percent elongation

When stress is applied, a strip sample stretches and this is referred to as strain. Strain is basically the deformation of strip divided by original dimension of the sample. Generally elongation of strip increases as the plasticizer content increases [84].

%elongation =Increase in length of strip Ã- 100/ Initial length of strip

7.4 Disintegration Test

Disintegration time is defined as the time (second) at which a film breaks when brought into contact with water or saliva. The disintegration time is the time when a film starts to break or disintegrate.Thickness and mass play a role in determining the dissolvable film's physical properties [83-85].

The disintegration time limit of 30 s or less for orally disintegrating tablets described in CDER guidance can be applied to fast dissolving oral strips [86].

Although, no official guidance is available for oral fast disintegrating films/strips, this may be used as a qualitative guideline for quality control test or at development stage. Pharmacopoeial disintegrating test apparatus may be used for this study. Typical disintegration time for strips is 5-30 s [87].

7.5 Dissolution Test

Dissolution is defined as the amount of drug substance that goes into solution per unit time under standardized conditions of liquid/solid interface, temperature and solvent composition. Invitro method is carried out in modified USP XXIII apparatus (paddle over disk) and invivo dissoluition method is carried out in volunteers [80].

Dissolution testing can be performed using the standard basket or paddle apparatus described in any of the pharmacopoeia. The dissolution medium will essentially be selected as per the sink conditions and highest dose of the API [88].

7.6 Folding endurance

Folding endurance is determined by repeated folding of the strip at the same place till the strip breaks. The number of times the film is folded without breaking is computed as the folding endurance value [89].

7.7 Film flexibility

Film flexibility was determined by adapting the ASTM bend mandrel test (D 4338-97). Film was bended over a mandrel and examined for cracks over the area of the bend in a strong light.

7.8 Assay/drug content and content uniformity

This is determined by any standard assay method described for the API in any of the standard pharmacopoeia. Content uniformity is determined by estimating the API content in individual strip. Limit of content uniformity is 85-115%.

7.9 Organoleptic evaluation

Since the OS are intended to disintegrate rapidly or reside for more duration of time in the oral cavity, the product needs to have acceptable organoleptic palatable characteristics. The product should possess the desired features of sweetness and flavor which is acceptable to a large mass of population. For evaluation of psychophysical evaluation of the product, special controlled human taste panels are used. In-vitro methods of utilizing taste sensors, specially designed apparatus and drug release by modified pharmacopoeial methods are being used for this purpose. These in-vitro taste assessment apparatus and methodologies are well suited for high throughput taste screening of oral pharmaceutical formulations [90]. Experiments using electronic tongue measurements have also been reported to distinguish between the sweetness levels in taste-masking formulation [91].

7.10 Analytical techniques

7.10.1 Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis

Surface morphology of the films was observed using scanning electron microscopy (SEM). The films were mounted onto stubs, sputter coated with gold in a vacuum evaporator, and photographed using a scanning electron microscope (LEO1450VP, LEO Electron Microscopy Ltd., Cambridge, England). Additionally, EDX analysis was used for surface chemical analysis of the samples.The characteristic X-rays emitted and elemental information of the samples were recorded. The % w/w of each element reported was calculated by subtracting the Au element used as a coating material.

7.10.2 Fourier transform infrared (FTIR) spectroscopy

FTIR spectra of samples were recorded with an FTIR spectrophotometer (Spectrum One, PerkinElmer, Norwalk, CT) using the KBr disc method that has been previously used to investigate an interaction of materials in the films [92,93]. Each sample was pulverized, gently triturated with KBr powder at a weight ratio of 1:100, and then pressed using a hydrostatic press at a pressure of 10 tons for 5min. The disc was placed in the sample holder and scanned from 4000 to 450cmˆ’1 at a resolution of 4 cmˆ’1. Deconvolution procedure was performed in the wave number range of 2500-4000cmˆ’1 for resolving overlapping of OH stretching peaks by using IR spectroscopy software (Spectrum software, PerkinElmer, Norwalk, CT).

7.10.3 Powder X-ray diffractometry

Powder X-ray diffraction (PXRD) measurements of the samples were performed on a powder X-ray diffractometer (Jeol Model JDX-3530, Tokyo, Japan). The measurement conditions were a Cu radiation generated at 40 kV and 40mA as the X-ray source, angle 3-16-¦ (2_), and step angle 0.02-¦ (2_)/s. The peak position and the full width at half maximum (FWHM) of the basal spacing peak of MAS were recorded.

7.10.4 Differential scanning calorimetry (DSC)

DSC curves of the samples were recorded using a differential scanning calorimeter (DSC822, Mettler Toledo, Switzerland). Each sample (2-3 mg) was accurately weighed into a 40-_l aluminum pan and crimped without an aluminum cover. The measurements were performed over 30-350 -¦C at a heating rate of 10 -¦C/min.

8. Packaging Of Oral Thin Film

Expensive packaging, specific processing, and special care are required during manufacturing and storage to protect the dosage of other fast-dissolving dosage forms. Unlike these other quick-dispersing and/or dissolving oral delivery systems, the Quick-Dis„¢ system can be packaged using various options, such as single pouch, blister card with multiple units, and continuous roll dispenser, depending on the application and marketing objectives.

8.1 Single pouch

Soluble Film Drug Delivery Pouch is a peelable pouch for "quick dissolve" soluble films with high barrier properties. The pouch is transparent for product display. Using a 2 structure combination allows for one side to be clear and the other to use a cost-effective foil lamination. The foil lamination has essentially zero transmission of both gas and moisture. The package provides a flexible thin film alternative for nutriceutical and pharmaceutical applications. The single dose pouch provides both product and dosage protection.

8.2 Blister card with multiple units

The blister container consists of two components: the blister, which is the formed cavity that holds the product, and the lid stock, which is the material that seals to the blister. The film selection should be based upon the degree of protection required. Generally the lid stock is made of aluminum foil. The material used to form the cavity is typically a plastic, which can be designed to protect the dosage form from moisture.

8.3 Polyvinyl Chloride

The most commonly used blister material is polyvinyl chloride (PVC). This material, which provides a nominal or zero barriers to moisture, is used when the product does not require effective moisture protection.

8.4 Barrier Films

Many drug preparations are extremely sensitive to moisture and therefore require high barrier films. Several materials may be used to provide moisture protection such as Polychlorotrifluoroethylene (PCTFE) film, Polypropylene [94].

8.5 Continuous roll dispenser

An automatic drug tape dispensing and metering device and a disposable cassette containing a roll of drug tape housed in a small reusable portable dispenser unit. The dispenser contains a measurement device for carefully measuring the length of tape as it is dispensed. A counter monitors the remaining doses of drug tape remaining within the dispenser. A timer device may be provided to alert the patient that it is time for the medicament to be dispensed. As the lid of the dispenser unit is opened, the measured length of drug tape is severed from the roll by a cutter blade incorporated into the lid. The dosage and administration of the medicament to be given a patient may be set by adjusting the tape length released for each single dose and selecting the time intervals between dosages. The invention comprises also ingestible tapes of medicament.

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