POST FORMULATION TESTS(Tizanidine)

POST FORMULATION TESTS

        Some post formulation test of buccal tablet is following;

•         FTIR

•         Weight variation

•         Mucoadhesive strength

•         Dissolution test

•         Drug content uniformity

•         Surface pH

•         Swelling study

FTIR (Fourier transform infrared spectroscopy):

•         The light originates from the He-Ne laser

•         Half of the light is reflected 90 degrees and hits a fixed mirror, while the other half passes through the beam splitter and hits the moving mirror

•         The split beams are recombined, but having traveled different distances, they exhibit an interference pattern with each other

•         As they pass through the sample, the detector collects the interfering signals and returns a plot of response v. mirror displacement known as an interferogram. (19)

Weight variation test:

Ten buccal tablets of each formulation were weighed using an electronic balance and average weight of ten tablets and standard deviation were calculated. (20)

           %age deviation = average weight-individual weight    x 100 

                                                       Average weight                           

Specification:

Average Weight of Tablet, mg	Percentage Difference
130 or less	10
From 130 through 324	7.5
More than 324	5

Result:

         %age deviation of tablet is 99±0.45mg 

Mucoadhesive strength:

A modified balance method was used for determining the ex vivo mucoadhesive strength. Fresh sheep buccal mucosa was obtained from a local slaughterhouse and used within 2 h of slaughter. The mucosal membrane was separated by removing underlying at and loose tissues. The membrane was washed with distilled water and then with phosphate buffer pH 6.8 at 370C. The sheep buccal mucosa was cut into pieces and washed with phosphate buffer pH 6.8. A piece of buccal mucosa was tied to the glass vial, which was filled with phosphate buffer. The glass vial was tightly fitted into a glass beaker (filled with phosphate buffer pH 6.8, at 37 ± 10C) so that it just touched the mucosal surface. The buccal tablet was stuck to the lower side of a rubber stopper. The two sides of the balance were made equal before the study, by keeping a 5 gm weight on the right-hand pan. A weight of 5 gm was removed from the right-hand pan, which lowered the pan along with the tablet over the mucosa. The balance was kept in this position for 5 min contact time. The water (equivalent to weight) was added slowly with an infusion set (100 drops/min) to the right-hand pan until the tablet detached from the mucosal surface. This detachment force gave the mucoadhesive strength of the buccal tablet in grams. (7)

Result:

        Mucoadhesive strength of tablet is 4.92±0.11g

Dissolution Studies:

The United States Pharmacopeia (USP) XXIII rotating paddle method was used to study the drug release from the tablets. The dissolution medium consists of 500 ml of phosphate buffer pH 6.8. The release was performed at 37 ± 0.50C, with a rotation speed of 50 rpm. The buccal tablet was attached to the glass disk with instant adhesive (cyano acrylate adhesive). The disk was allocated to the bottom of the dissolution vessel. Five ml sample were withdrawn at predetermined time intervals and replaced with fresh medium. The samples were filtered through Whatman filter paper and analyzed after appropriate dilution by UV spectrophotometer at 320 nm. (20,7)

Result:

        Drug release of tablet is 87.84%

Drug content uniformity:

Ten buccal tablets from each formulation were crushed and mixed separately. From the mixture 4 mg of Tizanidine equivalent of mixture was extracted in 100 ml of methanol. Amount of drug present in extract was determined using UV spectrophotometer at 320 nm. This procedure was repeated thrice to get accuracy in the result. (21,7)

Result:

       Drug content of buccal tablet is 99.45±1.31%

Surface pH:

The surface pH of the buccal tablets was determined in order to predict the possible irritant effects of the formulation on the buccal mucosa. The buccal tablets were allowed swell at 37 ± 10C for 2 h in 40 ml phosphate buffer (pH 6.8). The surface pH of swollen buccal tablets was measured using pH paper. (22)

Result:

          Surface pH of tablet is 6.91±0.35

Swelling Study:

Three buccal tablets were weighed individually (W1) and placed separately in 2% agar gel plates with the core facing the gel surface and incubated at 370C ± 10C. At regular 1 h time intervals until 6 h, the tablet was removed from the Petri dish and excess surface water was removed carefully with filter paper. The swollen tablet was then reweighed (W2) and the swelling index (SI) were calculated using the formula given in equation. (23)

Swelling Index = [(W2-W1)/ W1] × 100

Result:

         Swelling index of tablet after 8hrs is 50.21±1.33