Evaluation of the ODF
The ODF is evaluated by various parameters such as thickness, the mechanical properties of the film, folding endurance, assay/drug
content as well as by studies of in-vitro disintegration, in-vitro dissolution, surface morphology, and taste (12, 13).
Thickness.
The thickness of strip can be measured by a micrometer at different locations. This measurement is essential to ascertain
uniformity in the thickness of the film as this thickness is directly related to the accuracy of the dose in the strip.
Mechanical properties of the film
. The mechnical propertis are tensile strength, percentage elongation, and elastic modulus.
Tensile strength.
Tensile strength is the maximum stress applied to a point at which the strip specimen breaks. It is calculated by the applied
load at rupture divided by the cross-sectional area of the strip as given in the equation below:
Percentage elongation.
When stress is applied, a film sample stretches, and this stress is referred to as strain. Strain is basically the deformation
of the film divided by the original dimension of the sample. As the plasticizer content increases, the elongation of film
is observed.
Tear resistance.
The tear resistance of a plastic film is a complex function of its ultimate resistance to rupture. A very low rate of loading
of 51 mm/min is employed. It is designed to measure the force to initiate tearing. The maximum stress or force (usually found
near the onset of tearing) required to tear the specimen is recorded as the tear resistance in newtons.
Young's modulus or elastic modulus. Young's modulus or elastic modulus is the measure of the stiffness of the film. It is represented as the ratio of applied
stress divided by the strain in the region of elastic deformation:
Hard and brittle strips demonstrate a high tensile strength and Young's modulus with less percentage elongation.
Folding endurance.
Folding endurance is determined by repeated folding of the film at the same place until the film breaks. The number of times
the film is folded without breaking is calculated as the folding endurance value.
Assay/drug content.
Assay/drug content is determined by any standard assay method described for the particular API in any of the standard pharmacopoeia.
In-vitro disintegration.
Disintegration time gives an indication about the disintegration characteristics and dissolution characteristics of the film.
For this study, the film, as per the dimensions required for dose delivery, was placed on a stainless-steel wire mesh containing
10 mL of distilled water. The time required for the film to break was noted as in-vitro disintegration time.
In-vitro dissolution.
In-vitro dissolution studies can be performed using the modifications to the standard basket or paddle apparatus described in any of
the pharmacopoeia because a conventional paddle apparatus may lead to floating of the film. The dissolution medium will be
selected as per the sink conditions and the highest dose of the API.
Surface morphology
. A study of surface morphology of the ODF is performed using the environment-scanning-electron microscopy method. The uniformity
of the film and absence of pores and striations indicate the good quality of the ODF.
Taste evaluation.
A taste evaluation study can be performed using a panel of human volunteers. The ODF should possess the desired sweetness
and flavor acceptable to the patient. In-vitro methods using taste sensors, a specially designed apparatus, and drug release by modified pharmacopoeial methods are used
for this purpose. Experiments using electronic-tongue measurements also have been reported to distinguish between the sweetness
levels in taste-masking formulation.
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