Evaluation of transdermal patch of carvedilol Thickness of patches 85 Patch thickness was measured using Micrometer Screw Gauge at three different places and the mean value was calculated Weight variation 85 Weight variation was studied by taking individual weight of ten randomly selected patches for each formulation prepared in different batches The weights were taken in electronic digital balance Drug content 85 Accurately weighed patches were individually dissolved in minimum quantity of methanol and volume was made up to 100 ml with pH 7 4 phosphate buffer saline solution 10 ml was transferred to volumetric flask and volume was made up to 100 ml The absorbance was recorded at 243 nm The blank solution was prepared in the similar way except that the patches without drug were used Percentage Moisture content 86 The prepared films were weighed individually and to be kept in a desiccators containing fused calcium chloride at room temperature for 24 hrs After 24hrs the films are to be reweighed and determine the percentage moisture content from the below mentioned formula Percentage Moisture uptake 86
The weighted films were kept in desiccators at room temperature for 24hrs containing saturated solution of potassium chloride in order to maintain 84 RH After24hrs the films are to be reweighed and determine the percentage moisture uptake from the below mentioned formula Swelling index87 The patches of 2x2cm² was weighed and put in a Petri dish containing 10 ml of double distilled water and were allowed to imbibe Increase in weight of the patch was determined at preset time intervals until a constant weight was observed The degree of swelling S was calculated using the formula S Wt Wo Wo x 100 Where S is percent swelling Wt is the weight of patch at time t and Who is the weight of patch at time zero Folding endurance88 The folding endurance is expressed as the number of folds number of times the film is folded at the same place either to break the specimen or to develop visible cracks This test is important to check the ability of sample to withstand folding This also gives an indication of brittleness less folding endurance indicates more brittleness Folding endurance of the film was determined by repeatedly folding a small strip of film 2cm x 2cm at the same place till it broke The number of times the film could be folded at the same place without breaking gave the value of folding endurance Percent Elongation at break and Tensile strength 88 A small film strip 4 x 1cm was cut on a glass plate with a sharp blade One end of the film was fixed by placing in the film holder Another end of the film was fixed with the help of forceps having triangular ends to keep the strip straight while stretching and a hook was inserted
A thread was tied to the hook passed over the pulley and a small pan attached to the other end to hold the weights A small pointer was attached to the thread which travels over the graph paper affixed on the base plate To determine elongation and tensile strength the film was pulled by means of a pulley system Weights were gradually added to the pan to increase the pulling force till the film was broken The elongation was determined simultaneously by noting the distance traveled by the pointer before break of the film on the graph paper The weight required to break the film was noted as break force Percent elongation at break and tensile strength was calculated using the following formulae Percent elongation at IB Io X 100 Io Where Io Original length of film IB Length of film at break when stress is applied Tensile Strength Break force 1 L a b L Where a b and L are width thickness and length of strip respectively L is the elongation at break Break force weight required to break the film kg Tensile Strength 89 The tensile strength was determined by the apparatus designed as shown in fig 5 2 The instrument was designed such that it had horizontal wooden platform with fixed scale and attachments for two clips that holds transdermal patch under test Out of the two clips one was fixed and other was movable Weights were hanged to one end of pulley and the other end of pulley was attached with movable clip The wooden plat form was such fitted that it would not dislocate while the test is running
Three strips of patch were cut having 2cm length and 2cm breadth The thickness and breadth of strips were noted at three sites and average value was taken for calculation The rate of change of stress was kept constant with the increment of 0 5g per 2 minutes The elongation was observed and the total weights taken were used for calculation The tensile strength was calculated by using following formula Where L Length b Thickness a Width ΔL Elongation at break Fig 5 1 Assembly for tensile strength In vitro permeation studies 90 The experiment was conducted according to the protocol approved by the institutional animal ethics committee IAEC NO NIPS 05 29 2016 at the department of pharmacology NRI Institute of Pharmacy Bhopal For in vitro evaluation of TDDS albino rat was selected because of its easy availability and suitability A Franz diffusion cell was used in this experiment The Franz diffusion cell was fabricated from borosilicate glass and consisted of two compartments i e receptor and donor The cell had lower jacketed halve through which water maintained at 37 5 C was circulated and this lower halve had an effective receptor volume of 50ml and skin surface area of 3 14 cm2 The two halves of the cell were secured in place with the help of strong metallic clips The receptor solution was stirred by a Teflon bead of 12 mm length on a magnetic stirrer Selection of animal For In vitro evaluation of TDDS al
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