INTRODUCTION:

Oral route is the most preferable route for delivering the drugs, since it has different advantage over the other route of administration¹. Though it has several advantages it also has some drawback; related with some patient who are unconscious, geriatrics, children and patients along with many health conditions such as trouble in swallowing or chewing the solid dosage forms². Most of the paediatric and geriatric patients are having a fear of taking solid dosage forms because of tablet size, chewing, surface form and taste.Due to the above disadvantages fast dissolving drug delivering has been invented in the years of 1970’s. it is as a substitute to tablets, capsules and syrups for paediatrics and geriatrics that has difficulty in swallowing oral solid dosage forms³. This type of solid dosage forms dissolve and disintegrate in oral cavity without using water⁴.

Oral drug delivery system is modified due to the development in the technology, that is transitions in the dosage forms from simple conventional tablet or capsules to modified release tablets or capsules to oral disintegrating tablets, from this fast dissolving films, out of all the above dosage forms this oral fast dissolving films is getting more scope⁵. In oral drug delivery system the new dosage form is oral fast dissolving films⁶. It is established based on the idea of the transdermal films. Oral films are the thin films which are placed on the tongue or mucosal tissue. It is wet by the saliva then rapidly disintegrates and dissolves to release the medication for oral mucosal and intra gastric absorption.

Oral dispersible films are defined as, these are the solid dosage forms containing thin polymeric strip incorporating and delivering pharmaceutical active ingredient and once placed in mouth dissolves in the short period of time without drinking water or chewing⁷.

Advantages:

· Easy to administer

· This type of drug delivery system is suitable for the paediatric, geriatric patients, who face difficulty in swallowing.

· Since oral cavity has large surface area, this type of drug delivery system has faster the disintegrating and dissolution rate.

· This do not require water for the administration, can be administered anywhere at any time.

· There are then flexible films, so easy to transport and storage.

· It’s useful in case of motion sickness, allergy, etc

· More bioavailability and more stability since it remain in solid dosage forms till it gets consumed.

· More accurate dosing is possible when compared to liquid dosage forms.

· Onset of action is more.

· Safe and drug is efficacious in less dose.

· Since oral cavity is high vascularised, drugs are absorbed fast and enter systemic circulation so that first pass metabolism is avoided⁸.

Disadvantages:

· It is difficult to incorporate high dose.

· Only limited amount of drug can be incorporated.

· Drug penetration enhancement is more.

· Uniformity of dose is a challenge.

· The techniques like iontophoresis can’t be applied in order to improve the bioavailability, as well as penetration for poorly absorbed drugs. Because they may cause damage to oral mucosa⁹.

Ideal characteristics of drugs to be selected to oral dispersible films:

· Drugs with pleasant taste should be used.

· Drugs having low dose up to 40mg can be incorporated.

· It should permeate through oral mucosa.

· It should be unionised at oral cavity pH.

· Small molecular weight drugs are preferable.

· It should have high stability and solubility in water and saliva¹⁰.

Formulation of oral dispersible films:

Active pharmaceutical ingredient:

Various active pharmac6eutical ingredients can be incorporated and delivered by oral dispersible films. 1-25% w/w of the drug is present in the oral dispersible films. Oral dispersible films usually prefer small molecular weight active ingredient. The active pharmaceutical ingredients are micronized for better dissolution as well as for the uniformity, so that texture of the film improves. Most of the active pharmaceutical ingredients have bitter taste this will make the formulation more unpleasant and also patients will dislike it, in order to mask the bitter taste of active pharmaceutical ingredient it is incorporated with the sweetening excipients this technique is called as obscuration technique.

Film forming polymer:

This is very important ingredient in the formulation of oral dispersible films. The oral dispersible film must be water soluble; it should disintegrate in the saliva for the better absorption. In order to formulate this polymer should be water soluble with low molecular weight and excellent film forming capacity. The polymer should be non-toxic non-irritant. It should have good wetting and spreading property, it should have good shear and tensile strengths, eg polyvinyl pyrolidine¹⁰.

Plasticizer:

It is a main ingredient in the formulation of the oral dispersible films. The flexibility of the strip as well as film forming property can be improved by the help of plasticizers.It also decreases the brittleness; it plays an important role in hanging the glass transition temperature of the polymer. The plasticizer is selected based on its compatibility with the polymer and type of solvent used in the solvent casting method. It is used up to 20%w/w. if the plasticizer used is not in a proper manner then it may lead to form cracking splitting peeling of strip etc, and also effect the absorption rate of the drug.

Colouring agents:

These are also important ingredients in order to improve the appearance of the formulation. It is used up to 1%w/w. eg: titanium dioxide.

Flavouring agents:

Flavouring agents are added in order to improve the acceptance by the patients. Up to 10% w/w concentration of flavours are added. Flavouring agents are selected on the basis of type of the drug incorporated. Age plays important role in the selection of the flavouring agents. Paediatric patients like chocolate and fruit flavours, but geriatric patients like orange and mint flavours. Flavouring agents are extracted from the plants fruits and flowers.eg: vanilla, orange, peppermint.

Saliva stimulating agents:

These are the agents which increases the production of the saliva. More the production of the saliva faster is the disintegration and absorption of the drug. Usually acids are used as saliva stimulating agents such an s citric acid, malic acid, lactic acid. These can be used as alone or in combination. It is used up to 2-6% w/w of weight of the strip.

Method of preparation:

Casting:

· Solvent casting

· Semisolid casting

Extrusion

· Hot melt extrusion

· Solid dispersion extrusion

Solvent casting method:

In this method ingredients are dissolved in water, then water soluble polymers are added, at the end drug is added and stirred to form homogeneous solution using magnetic stirrer. Set it aside for 8 hrs. Finally the solution is casted on the Petri plate and dried in air oven at 40-50ºC. Then film is peeled and cut.

Semisolid casting:

When acid insoluble polymers are to be used in the preparation of films, this method is applied. In this method gel mass is casted in to films, gel mass is obtained by adding solution of film forming to a solution of acid insoluble polymer present in ammonium or sodium hydroxide this is rolled dried and then cut.

Hot melt extrusion:

In this method the drug is mixed with carriers in solid form. Then the dried granular material is introduced. Then dried granular material is introduced into the extruder. The screw speed should set at 15 rpm in order to process the granules inside the barrel of the extruder for almost 3–4 min. The processing temperature should be 800ºC then pressed into a cylindrical calendar in order to obtain a film. There are certain profits of hot melt extrusion.

Solid dispersion extrusion:

In solid dispersion extrusion method immiscible components are extrude with drug and then solid dispersions are prepared. Finally the solid dispersions are shaped in to films by means of dyes.

Rolling Method:

In this method a solution or suspension of drug with film forming polymer is made and subjected to the roller. The solution or suspension should contain specific rheological consideration. Water, mixture of water and alcohol are used as solvent. The film is dried placing it on the rollers and cut in to required shapes and sizes.

Evaluation of oral dispersible films¹¹:

Thickness:

Thickness of the film is directly proportional to the drug content uniformity.it is measured using micrometre screw gauge or calibrated digital varnier callipers⁹.

Tack is the tendency of the strip to adhere to a surface. There are instruments also available for that test.

Tensile strength:

It is the maximum stress applied to a point at which the film breaks.it is calculated by using the formula, tensile strength = stress on the film × width of the film.

Percent elongation:

When stress applied on the film the film gets stretched this is called strain. This depends on the concentration of the plasticizer used.

% elongation = increase in length ×100

Young ‘modulus:

Young's modulus or elastic modulus is the measure of stiffness of strip. It is represented as the ratio of applied stress over strain in the region of elastic deformation as follows:-

Hard and brittle strips demonstrate a high tensile strength and Young's modulus with small elongation. It is also called as elastic modulus; it is the measure of stiffness of strip.

Tear resistance:

Tear resistance is the capacity of the film and it is the complex function of its resistance against the rupture. Very low rate of loading is employed and it is made to measure the force to initiate the tearing. The maximum stress or force required to tear the film is measured and recorded in units of newtons.

Folding endurance:

Folding endurance is determined by folding the film repeatedly at the same place until it breaks. The number of times film folded is noted and it is taken as endurance.

Organoleptic evaluation:

The product must be evaluated physiologically to tests the organoleptic characteristics. To check the organoleptic characters like odour taste controlled human taste panels are used, in-vitro methods like taste sensors, electronic tongue, specially designed apparatus can be used.

Surface pH of film:

Surface pH of the film is determined by placing the film on the surface of the agar medium of concentration 1.5%w/v. Then it is placed on the pH paper of range 1-11. The change in the colour of pH paper is observed, this will give the pH of the formulation¹².

Swelling property:

Here the swelling property of the film is studied. Using simulated saliva solution this study can be performed. Weighed stainless wire mesh is used to keep the film which is already weighed. Film sample which is placed in the mesh is submerged into 15 ml medium in a plastic container. The increased weight of the film is determined¹³.

Transparency:

The transparency of the film can be estimated by a simple UV spectrometer. Film samples are cut into small rectangular shapes and then it was placed in the internal side of the spectrometer cell . Transmittance can be obtained at 600 nm.

Assay:

It is used to measure the content uniformity. This is used to measure the concentration or amount of the active pharmaceutical ingredient present in the individual sample. This should be range between 85-115%.

Disintegration time:

Disintegration of the film is measured by USP disintegration apparatus. The disintegration time limit of 30 seconds is needed. There are 2 methods here 1. Slide frame method 2. Petri dish method. In both methods the film is made to dissolve with the help of water. Time taken to dissolve the entire film is noted this is considered as disintegration time⁸.

Dissolution test:

This test can be performed by using paddle apparatus or basket as written in the pharmacopoeia. The dissolution medium will be selected as per the sink conditions. This test is difficult to carry out because of the tendency of the film to float on the dissolution medium. 6.8 pH phosphate buffer, 0.1 N HCL, maintained at a temperature of 37± 0.5ºC at a speed of 50 rpm, samples of drug dissolved is collected and analysed using UV spectrophotometer¹².

Applications:

Oral films is the preferred method for drug delivery through buccal, sublingual, and mucosal route where rapid absorption is required which is used to treat pain, allergies, sleep difficulties, and central nervous system disorders.¹³

Oral soluble films:

it is used as breath strips, this is a novel drug delivery system and is widely accepted by the patients as vitamin supplements and personal care products¹⁴.

Topical use:

oral dispersible films can also be used as antimicrobial drugs analgesic drugs, for wound care or other application^{15, 16}

GIT disorder:

Hydrophilic and poorly water soluble molecules of different molecular weights are enclosed in the film they depend on the gastro intestinal pH ,they are used for the gastro intestinal disorders.¹⁷

CONCLUSION:

Oral dispersible film is a novel drug delivery system in the field of pharmaceutical science. It is gaining more acceptances because of their easy portability, better patient compliance and ease of administration. It is more important drug delivery system. Since it has fast disintegration and fast dissolution properties associated with better safety and efficacy. It is the best formulation in case of paediatric and geriatric patients. Major advantage of this drug delivery is administration without water. Its bioavailability is also more. It can be applied by oral as well as buccal routes. It is not only used for local effects it is also used for anaesthetics, allergy cold remedies and as vitamin supplies too. They can also be used as breath refreshers.

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Received on 30.08.2018 Modified on 02.10.2018

Research J. Pharm. and Tech 2019; 12(1): 425-428.

DOI: 10.5958/0974-360X.2019.00077.5