This document outlines various evaluation parameters for dermal films, including thickness, weight variation, folding endurance, tensile strength, drug content uniformity, moisture content and uptake, water vapor transmission rate, swelling study, in vitro permeation studies using dialysis membrane, determination of flux and release kinetics, drug-polymer interaction studies, and stability studies. These parameters are used to thoroughly characterize and evaluate dermal films.

1. EVALUATION PARAMETERS FOR DERMAL
FILMS
PRESENTED BY-
POOJA GUPTA
M. PHARM 4TH SEM
DEPARTMENT OF PHARMACY
BARKATULLAH UNIVERSITY ,
BHOPAL

2. CONTENTS
• THICKNESS OF THE FILM
• WEIGHT VARIATION TEST
• FOLDING ENDURANCE
• TENSILE STRENGTH
• DRUG CONTENT UNIFORMITY
• MOISTURE CONTENT & MOISTURE UPTAKE
• WATER VAPOUR TRANSMISSION RATE
• SWELLING STUDY
• IN VITRO PERMEATION STUDIES USING DIALYSIS MEMBRANE
• DETERMINATION OF FLUX AND RELEASE KINETICS
• DRUG – POLYMER INTERACTION STUDIES
• STABILITY STUDIES

3. THICKNESS OF THE FILM-
The thickness of the dermal films was assessed at three different points using screw gauze or thickness gauge . For
each formulation, three randomly selected films were used.
WEIGHT VARIATION TEST-
In weight variation test of the film, three disks of 2x2cm2 was cut and weighed on electronic balance for weight
variation test.
FOLDING ENDURANCE-
The folding endurance was measured by manually for the prepared dermal films. A strip of the films (2x2cm) was
cut evenly and repeatedly folded at the same place till it is broken.
TENSILE STRENGTH-
The tensile strength of the film was evaluated by using the tensiometer . It consists of two load cell grips. The
lower one was fixed and upper one was movable. Film strips with dimensions of 2*2 cm were fixed between these
cell grips, and force was gradually applied till the film broke. The tensile strength was taken directly from the dial
reading in kg.

4. DRUG CONTENT UNIFORMITY-
A specific area of film (2 cm*2 cm) was dissolved in 100 mL methanol and shaken continuously for 24 h. Then
the whole solution was ultrasonicated for 15 min. After filtration, the drug was estimated spectrophotometrically
at wavelength in nm and determined the drug content.
MOISTURE CONTENT & MOISTURE UPTAKE-
The prepared films were weighed individually and kept in a desiccators containing anhydrous calcium chloride
for 24h. The films were re-weighed until a constant weight was obtained. Moisture content was calculated in
percentage based on the difference between the initial and the constant final weights of the film.
The percent moisture absorption test was carried out to check the physical stability and integrity of the films at
high humid conditions. In the present study the moisture absorption capacities of the film were determined in the
following manner. The films were placed in the desiccators containing 200ml saturated solution of potassium
chloride, to get the humidity inside the desiccators at 84% RH. After 3 days the films were taken and weighed
the percentage moisture absorption of the patch was found.
Percentage moisture absorbed = Final weight−Initial weight / initial weight in to 100

5. WATER VAPOUR TRANSMISSION RATE-
Glass vials of 5ml capacity were washed thoroughly and dried to a constant weight in an oven. About 1g of
fused calcium chloride was taken in the vials and the polymer films of 3.83cm2 were fixed over the brim with
the help of an adhesive tape. Then the vials were weighed and stored in a humidity chamber of 80-90% RH
condition for a period of 24h. The vials were removed and weighed at 24h time intervals to note down the
weight gain.
Water Vapor Transmission Rate = Final weight − Initial weight / Time × area
SWELLING STUDY
Completely dried films with a specified area (3.83cm2) were weighed and put in desiccators for 24h. They were
removed and exposed to relative humidity conditions of 75% (containing saturated solution of Nacl) in
desiccators. Weight was taken on a single pan balance periodically until a constant weight was obtained. The
swelling capacity of the films (in weight %) was calculated in terms of percentage increase in weight of
membrane over the initial weight of the specimen. The experiments were carried out in triplicate and the average
values were used for the calculation. The percentage degree of swelling (DS) was calculated as
DS (%) = WS- WD / WD×100
Where, WS and WD indicate the weight of the swollen and dry membranes respectively.

6. IN VITRO PERMEATION STUDIES USING DIALYSIS MEMBRANE -
In vitro permeation of dermal films through dialysis membrane with molecular weight was studied. The
membrane was mounted over a Franz diffusion cell and then placed dermal film. The receiver compartment of
the diffusion cell was filled with 15ml of phosphate buffer pH 7.4 and the setup was placed over a magnetic
stirrer at 370C. Samples of 3ml were withdrawn and replenished immediately from the receiver compartment at
1, 2, 3, 4, 6 and 12h. They were stored in refrigerated condition till the analysis was performed. The content of
samples was analyzed by UV-Visible spectrophotometer at nm.
DETERMINATION OF FLUX AND RELEASE KINETICS -
The flux (J) was calculated from the slope of the plot of cumulative amount of drug permeated per cm2 of skin at
steady state against the time using linear regression analysis. The steady state permeability coefficient ( KP) of
the drug through rat epidermis was calculated by using the following equation:
KP = J / C
Where, J= flux (µg/cm2/hour ); C= concentration of drug in the transdermal film.

7. The data obtained from the above permeation studies was fitted to zero order, first order and Higuchi models to
explain the pattern and the release mechanism from the formulations. Korsmeyer - Peppas model is one of the
mathematical expressions, used to understand the mechanism of drug release from these formulations. The Kors
meyer - Peppas equation is as follows;
Mt / Mα = Ktn
In which, Mt / Mα is the fractional amount of drug released at time t, K is a kinetic rate constant, and n is the
diffusional exponent that characterizes the mechanism of drug release.
DRUG – POLYMER INTERACTION STUDIES
To study the possible interaction between drug and polymers, Differential scanning calorimetry (DSC) study
was carried out on pure drug and the best formulation and the thermograms were obtained using DSC . The
analyses were performed under nitrogen (nitrogen flow rate 50ml/min) in order to eliminate oxidative and
pyrrolytic effects at a standard heating rate over a temperature range of 500C - 3500C.

8. STABILITY STUDIES
The sample films were sealed in aluminum packaging coated inside with polyethyl, and three sets were
stored in stability chamber (40±20C and 75±5% RH) for six months. Samples were collected after three
months of storage and evaluated. The results were under gone to statistical analysis with the help of paired
t-test to test the significance of difference at 0.05 level of significance. Then the similarity index was
calculated between permeation rates of best formulation before and after storage to prove. The similarity
factor (F2) is a logarithmic reciprocal square root transformation of the sum of squared error and is a
measurement of the similarity in the percent (%) of dissolution between the two curves.