Formulation and Evaluation of Buccal Tablet of Rasagiline Mesylate

Shilpa N. Shrotriya, Kishore N. Gujar, Bhakti R. Chorghe*

Department of Pharmaceutics, Sinhgad College of Pharmacy, Vadgaon (Bk.), Pune – 411 041, Maharashtra, India.

ABSTRACT:

The objective of the present investigation was to formulate and evaluate unidirectional, bilayered, buccoadhesive tablets of rasagiline mesylate using natural excipients. Caesalpinia pulcherrima polysaccharide (CSP), Tamarind seed polysaccharide (TSP) and Locust bean gum (LBG) were used as mucoadhesive agents in the formulation. The polysaccharides were isolated and were characterized for physicochemical properties such as solubility, pH, viscosity, test for carbohydrates, flow properties, microbial load, disintegration and swelling index. Differential scanning calorimetric (DSC) studies revealed that the polysaccharides were physically compatible with drug, rasagiline mesylate (RM). The formulation F12 containing CSP (15 mg), LBG (30 mg), TSP (30 mg) demonstrated bioadhesion force of 0.3941 ± 0.01 N, residence time of 120 ± 0.3 min, % drug release of 92.81 ± 0.2% and % drug diffusion of 92.01 ± 0.01% was selected as the optimized formulation. Thus, this study suggests that CSP, TSP and LBG in combination can act as potential mucoadhesive agents for buccal delivery.

KEYWORDS: Buccal tablet, Caesalpinia pulcherrima polysaccharide, Tamarind seed polysaccharide, Locust bean gum, Rasagiline mesylate, Mucoadhesion

1. INTRODUCTION:

Buccal delivery of drugs provides an attractive alternative to the oral route of drug administration, particularly in overcoming deficiencies associated with the oral administration. Buccal mucosa has an excellent accessibility, an expanse of smooth muscle and relatively immobile mucosa, direct access to systemic circulation through the internal jugular vein which bypasses the drugs from hepatic first pass metabolism¹. Various bioadhesive buccal formulations such as tablets, gels, patches and films have been developed using mucoadhesive polymers which can establish a strong adhesive contact with the buccal mucosa, allowing to increase residence time of delivery systems and to optimize drug bioavailability². Buccal tablet offers several advantages due to its small size, uncomplicated formulation process and cost effectiveness and improved patient compliance as compared to other dosage forms³. Both synthetic and natural polymers have been investigated extensively for the buccal drug delivery. Synthetic polymers are toxic, expensive, have environment related issues and need long development time for synthesis. However the use of natural polymers for pharmaceutical applications is attractive because they are economical, readily available, non-toxic and capable of chemical modifications, potentially biodegradable also biocompatible⁴. The present study involves the application of Caesalpinia pulcherrima seed polysaccharide (CSP), Locust bean gum (LBG) and Tamarind seed polysaccharide (TSP) as mucoadhesive polymers in the formulation of unidirectional release buccal tablet. TSP, CSP and LBG consists of galactose and xylose units in varying ratios^5-7.

Studies have revealed the use of these polysaccharides as thickening agents and stabilizing agents. Rasagiline mesylate is an antiparkinsonism drug, selective for MAO type B inhibition and used as a monotherapy in early parkinson’s disease and also as an adjunct therapy to levodopa. Rasagiline mesylate has bioavailability of ~36% due to the extensive first pass metabolism⁸. A Box-Behnken design was employed to identify and quantify the possible main and interaction effects of natural polymers and also to avoid increased number of trials⁹.The aim of present investigation was to identify optimal polymeric combinations of CSP, TSP and LBG for Rasagiline mesylate matrix preparation with optimum bioadhesion force, residence time, drug release and drug diffusion.

2. MATERIALS AND METHODS:

2.1 Materials

Rasagiline mesylate was a gift sample from Lupin Ltd. (Mumbai, India). Locust bean gum was procured from HiMedia Laboratories Pvt. Ltd. (Mumbai, India). Tamarind kernel powder was procured from Bhavna Gum Udyog (Ahmedabad, India). Dried seeds of Caesalpinia pulcherrima were purchased from local market of Pune, India. All other solvents and chemicals obtained were of analytical grade.

2.2 Methods

2.2.1 Isolation of polysaccharide from dried seeds of Caesalpinia pulcherrhima¹⁰

To 20 g of Caesalpinia pulcherrima kernel powder 200 mL of cold distilled water was added forming the slurry. The slurry was poured into 800 mL of boiling distilled water. The solution was boiled for 20 min under constant stirring within a water bath. The resulting thin clear solution was kept overnight to allow the majority of the containing proteins and fibers to settle out. The solution was then centrifuged at 5000 rpm for 20 min. The supernatant was separated and poured into double the volume of acetone via continuous stirring. The resulting product was then pressed between felt. The precipitate was again washed with acetone, and then dried at 50-60°C in an hot air oven. The dried material was ground, sieved and packed in air tight container.

2.2.2 Isolation of tamarind seed polysaccharide (TSP)¹¹

Slurry was prepared by suspending 20 g of fine kernel powder of tamarind seed into 200 ml of cold distilled water. The slurry was poured into 800 ml of distilled water and boiled for 20 minutes on a water bath; a clear solution obtained which was kept overnight. This clear solution was than centrifuged at 5000 rpm for 20 minutes to separate all the foreign matter. Supernatant liquid was separated and poured into excess of absolute alcohol with continuous stirring. Precipitate obtained was washed with 200 ml of absolute ethanol and dried at 50°C for 10 h and stored in a dessicator.

2.2.3 Characterization of polysaccharides

Isolated CSP and TSP were studied for physicochemical properties such as solubility, pH, viscosity, test for carbohydrates and polysaccharides, flow properties, microbial load, disintegration, swelling index and physical compatibility¹².

2.2.3.1 Swelling index¹³

About 1 gm (W₁) of CSP, TSP and LBG was accurately weighed and transferred to a 100 ml measuring cylinder. The initial volume of the powder in the measuring cylinder was noted. The volume occupied by the gum sediment was shaken gently and set aside for 24 h. The volume occupied (W₂) by the gum sediment was noted after 24 h. Swelling capacity of CSP, TSP and LBG was expressed in terms of swelling Index. Swelling Index was expressed as a percentage and calculated according to the following equation:

Swelling index = (W₂ – W₁)/W₂ x 100 (1)

2.2.3.2 Carr’s Index

To determine both bulk density and tapped density, 2 g of powder, previously shaken to break any agglomerates formed, was introduced into a 100 ml measuring cylinder. Initial volume was measured as bulk volume and the cylinder was placed on bulk density apparatus (Rolex, India). The tapping was continued until no further change in volume was noted. Bulk density and Tapped density were calculated using the following equation and Carr’s index was determined¹⁴:

Bulk Density = Weight of the powder / volume of the packing. (2)

Tapped Density = Weight of the powder / tapped volume of the packing (3)

The Carr’s index was calculated according to following formula:

Carr’s index =

Tapped density – Bulk density X 100 (4)

Tapped density

2.2.3.3 Microbial load¹³

About 1g of CSP, TSP and LBG were suspended in 10 ml of sterile water (inoculum). Inoculum (1 ml) was then transferred to separate petridishes 9 to 10 cm in diameter. After addition of the inoculum to the plate, 20 ml of agar medium (40-45°C) was poured into the each plate. Both the plates were gently rotated for thorough distribution of inoculum throughout the medium. Then the content was allowed to solidify at room temperature. These petri dishes were incubated for 48-72 h and colony forming unit of microorganisms per gram of specimen was counted visually.

2.2.3.4 In vitro disintegration study¹²

Pellets of individual gum and mucilage (100 mg) were prepared using hydraulic press and its disintegration pattern was observed by immersing them in glass petri dish, containing 25 ml phosphate buffer of pH 6.8 at room temperature. The morphological changes of each pellet were observed over a period of 4 h.

2.2.3.5 Physical compatibility test

Differential Scanning Calorimetry (DSC) studies:

The DSC thermograms of RM alone and along with natural polymers were recorded by using a DSC instrument (SIIO 6300 with auto sampler, Japan). Samples were accurately weighed onto aluminium pans and then hermetically sealed with aluminium lids. Thermograms were obtained at a scanning rate of 10°C/min conducted over a temperature range of 50-350°C in the environment of liquid nitrogen (flow rate – 60 ml/min).

2.2.3.6 Experimental design approach

A Box–Behnken experimental design was employed in this study to statistically optimise the polymer blends of buccal tablet for optimum mucoadhesivity, residence time, % drug dissolution and % drug diffusion. The Box–Behnken design was specifically selected since it requires fewer treatment combinations than a central composite design in cases involving three or four factors. The Box–Behnken design is also rotable and contains statistical “missing corners” which may be useful when the experimenter is trying to avoid combined factor extremes¹⁵. This property prevents a potential loss of data in those cases. Generation and evaluation of the statistical experimental design were performed with Design Expert V 8 Software. The concentrations of CSP (X₁), LBG (X₂), and TSP (X₃) were selected as independent variables and bioadhesion force (Y₁), in vitro drug release (Y₂), ex vivo diffusion (Y₃) was considered as dependent variables. A design matrix comprising of 15 experimental runs was constructed (Table 1).

General polynomial equation for non-linear quadratic model is,

Y = β₀+ β₁X₁+ β₂X₂ – β₃X₃ + β₄X₁X₂ + β₅ X₁X₃ + β₆ X₂X₃ + β₇X₁² + β₈ X₂² +β₉X₃² (5)

2.2.3.7 Preparation of unidirectional release bilayered buccal tablet

The unidirectional release bilayered buccal tablet was prepared by direct compression technique. Initially Rasagiline mesylate and the mucoadhesive polymers CSP, TSP and LBG were homogenously mixed using mortar and pestle. Then the other excipients present in the formulation viz. Avicel Ph 101 (diluent), sodium lauryl sulphate (penetration enhancer 2 mg/ tablet), HPMC K4M as a binder (6.5 mg/ tablet) sodium saccharine (sweetener) and talc (glidant) were added and again blended for 15 minutes. The blend was lubricated using magnesium stearate for 3-5 min. A multi station tablet compression machine (Model JM-6 General Machinery Company, Mumbai, India) with 8mm flat punch was used to prepare the tablet. The upper punch was then be removed and backing layer material, ethyl cellulose (20 mg) was added over it and finally compressed at a constant compression force¹⁶.

Table 1: Translation of coded values to actual values

Sr.No.	Variable levels		Low (-1)	Medium (0)	High (+1)	Response variables
1	Concentration of CSP (X₁)		0	15	30	Y₁: Bioadhesion force Y₂: Invitro drug release Y₃: Ex vivo diffusion studies
2	Concentration of LBG (X₂)		0	15	30
3	Concentration of TSP (X₃)		0	15	30
Batch	Independent variables				Actual values
Batch	X₁	X₂		X₃	X₁	X₂	X₃
F1	-1	-1		0	0	0	15
F2	1	-1		0	30	0	15
F3	-1	1		0	0	30	15
F4	1	1		0	30	30	15
F5	-1	0		-1	0	15	0
F6	1	0		-1	30	15	0
F7	-1	0		1	0	15	30
F8	1	0		1	30	15	30
F9	0	-1		-1	15	0	0
F10	0	1		-1	15	30	0
F11	0	-1		1	15	0	30
F12	0	1		1	15	30	30
*F13	0	0		0	15	15	15
*F14	0	0		0	15	15	15
*F15	0	0		0	15	15	15

*center point

2.2.4 Evaluation of buccal tablets

The formulated tablets were evaluated for their physical properties such weight variation, hardness, using Monsanto hardness tester, and percentage friability using Roche friabilator.

2.2.4.1 Surface pH

The surface pH of the prepared tablets was determined after soaking each tablet in distilled water (1ml) for 15 min. After the time of soaking the pH of the wet surface was measured by using the digital pH meter (Equiptronics, EQ-614, and India) ¹⁷. The experiment was performed in triplicate.

2.2.4.2 Swelling index¹⁸

Buccal tablets were weighed individually (W1) and placed separately in petri plates containing 5 ml of phosphate buffer pH 6.8. After the time interval of 15 min the tablets were removed from the Petri plates and excess surface water was removed carefully using filter paper. The swollen tablets were then reweighed (W2), and the swelling index was calculated using the formula mentioned in equation 1.

2.2.4.3 Determination of bioadhesion force

Texture Analyzer (CT3/100, Brookfield engineering labs, USA) equipped with a 100 g load cell was used for studying the bioadhesion force on a porcine buccal mucosa as a model membrane. The mucosal membrane was excised by removing the underlying connective tissue and washed with phosphate buffer (pH 6.8). The mucosal membrane was fixed between two circular discs at the lower perplex support. The upper circular disc had a cavity of 10 mm diameter through which mucosal membrane was exposed to the probe. The discs were lowered into the jacketed glass container filled with phosphate buffer pH 6.8 and maintained at 37 ± 1°C. The membrane was allowed to equilibrate at this temperature for 30 min. The buccal tablet was stuck to a double sided tape on the lower side of probe. The probe and circular cavity were aligned to ensure that tablet comes into direct contact with exposed surface of mucosal membrane. Before carrying out the investigation, exposed area of buccal tablet was moistened with phosphate buffer pH 6.8. The probe was lowered at a speed of 1 mm/s to contact the tissue with load of 90 g and contact time of 10 seconds and removed at the speed of 2 mm/s. Data collection and calculations were performed using Texture Pro CT V1.4 Build 17 software. The adhesive force and adhesiveness were used to evaluate the bioadhesive strength of tablet. Bioadhesion force (N) was calculated using formula¹⁹_:

Bioadhesion force (N)

= Bioadhesive strength (g) X 9.81(6)

1000

2.2.4.4 Determination of residence time

A locally modified (USP ED-2L, Electrolab, Mumbai) disintegration apparatus was used to determine the in vitro residence time. The porcine buccal mucosa was used for carrying out the test. The mucosal membrane was excised by removing the underlying connective tissue and washed with phosphate buffer pH 6.8. Porcine buccal mucosa, 3 cm long, was glued to the surface of a glass slide. One side of the tablet was wetted with one drop of phosphate buffer pH 6.8 and pasted to the mucosa by applying a light force with fingertip. The glass slide was vertically fixed to the apparatus and allowed to move up and down so that the tablet was completely immersed in the buffer solution at the lowest point and was out at the highest point. The beaker was filled with 500 ml of phosphate buffer pH 6.8 and was kept at 37± 1°C. The time required for the tablet to detach from the buccal mucosa was recorded as the residence time²⁰ .The experiment was performed in triplicate.

2.2.4.5 In vitro dissolution studies

In vitro dissolution of mucoadhesive buccal tablets of RM was studied in USP XXII type-II dissolution apparatus (TDT-08L, Electrolab) employing a paddle stirrer at 50 rpm using 500 ml of pH 6.8 buffer at 37 ± 0.5º C as dissolution medium. Aliquots of dissolution medium (5 ml) were withdrawn at specified intervals of time and analyzed for drug content by measuring the absorbance at 265 nm. The volume withdrawn at each time interval was replaced with fresh quantity of dissolution medium. Cumulative percent of RM released was calculated and plotted against time²¹.

2.2.4.6 Ex vivo diffusion studies

In vitro drug permeation through the sheep buccal mucosa was performed using Franz diffusion cell at 37±0.5°C. The freshly cut sheep buccal mucosa after removing underlying fat and loose tissues and washing with phosphate buffer pH 6.8 and distilled water was mounted between donor and receptor compartments. The receptor compartment was filled with phosphate buffer pH 6.8, and buccal mucosa was allowed to stabilize for 30 min in the receptor compartment by stirring on a magnetic stirrer (Whirlmatic, Spectralab, India) at 50 rpm and was maintained for the entire study. A 0.5 ml aliquot was withdrawn at predetermined time intervals of 10, 20, 30, 60, 90, 120, 150, 180 minutes and replaced with fresh medium. The aliquots were analyzed after appropriate dilution by UV spectrophotometer (1700, Shimadzu) at 265 nm²¹.

3. RESULTS AND DISCUSSION:

3.1 Characterization of isolated natural gum / mucilage

The polysaccharide from Caesalpinia pulcherrima and tamarind kernel powder was successfully isolated with the yield varying from 10-12 % for CSP and 7-10% for TSP. All the natural polymers were insoluble in cold water, warm water, phosphate buffer pH 6.8, ethanol, methanol and chloroform. The viscosity of CSP, LBG and TSP was found to be 1283±0.9cps, 2639 ± 3.01 cps, 3296 ± 2.09 cps respectively. Higher viscosity of TSP was due to its excellent hydration capacity. The pH of the gums and mucilage was found to be in the range of 5.2-7 which falls in the pH range of the buccal cavity i.e pH 5-7 (Patel, Liu and Brown, 2011), indicates that it would not cause irritation to the epithelium and mucous membrane of the buccal cavity. All the gums and mucilage showed positive test for carbohydrates and polysaccharides which indicates the presence of hydroxyl and carboxyl groups in the gums and mucilage. Presence of hydroxyl and carboxyl groups is essential for formation of covalent bonds with the mucin which will be responsible for mucoadhesion to occur.

3.1.1 Swelling index

The swelling index was found to be 21.22±2.4 for CSP, 39.92 ± 0.01% for TSP, 32.84 ± 0.01% for LBG. The higher swelling index of TSP might be due to its good water absorbing capacity.

3.1.2 Characterization of flow properties

Compression of tablet is dependent on flow properties of powder substance. LBG, CSP and TSP showed Carr’s Index of 16.26 ± 0.1%, 19.76±0.3, 18.07 ± 0.5% respectively. According to the standards mentioned in USP, TSP, CSP and LBG showed fair flow properties.

Figure 1: DSC thermogram of (A) RM (B) RM + CSP + LBG + TSP + HPMC K4M

3.1.3 Microbial load

The microbial load of all the gums and mucilage was found to be 130 CFU/gm, 110 CFU/gm and 99 CFU/g for CSP, TSP and LBG respectively. The reported colony forming unit in USP is not more than 200 CFU/gm (United States Pharmacopoeia-28, 2005). Therefore it was observed that microbial load of CSP, TSP and LBG falls into the limits specified by USP.

3.1.4 Disintegration test

The polymer pellets did not show any disintegration in the disintegration test in phosphate buffer of pH 6.8 over a period of 3 h. The non-disintegrating behaviour is helpful in maintaining the integrity of the buccal tablets during its stay in the buccal cavity and would lead to improved patient acceptance and compliance.

3.1.5 Physical compatibility test

Differential Scanning Calorimetry (DSC) studies

The DSC studies revealed no change in the endothermic peak of rasagiline mesylate when compared to physical mixture of rasagiline mesylate and excipients. So it can be depicted that the excipients and drug do not interact with each other (Figure 1).

3.2 Evaluation of buccal tablet

The thickness of all the tablets was found to be in the range of 2-2.3 ± 0.28 mm and the diameter was found to be 8 mm. Hardness of tablets of each formulation was found in the range of 4.3-6.2 kg/cm² which indicates good mechanical strength of all formulations. Tablets from each batch showed uniformity of weight as per I. P. limits. Average weight of the tablet was found to be 150 ± 2 mg for all batches. Friability testing showed percentage weight loss in the range of 0.71-0.9% for all the formulations which complies with the I.P. limits.

3.2.1 Determination of Surface pH

The delivery site of the tablet is buccal mucosa, if pH of tablet is more or less than the salivary pH it may cause irritation to the mucosa and may result in termination of treatment by a patient. Surface pH for all formulations was found in the range 6.58 to 7.4. Since range of the pH of tablet is near to the salivary pH (6.5 to 7.2), it will not cause irritation to mucosa.

3.2.2 Determination of swelling index

The swelling behaviour of a buccal tablet is an important property for effective bioadhesion and residence time. The swelling index for all the formulations ranged from 27.42±0.1 to 49.26±0.03 % (Table 2). Formulation F12 containing CSP (15 mg), LBG (30 mg) and TSP (30 mg) showed higher swelling index i.e. 49.26±0.03 %.which indicates that, as the concentration of LBG and TSP increased in the formulation the swelling index also increased and produced a less porous structure. The swelling index study indicated that rate of swelling was directly proportional to polymer content¹².

3.2.3 Residence time

The residence time increased with the increase in the polymer concentration. The F12 formulation showed maximum residence time of 120±0.30 min. The residence time was found high for F12 because of the higher interpenetration of TSP and LBG chains with that of the mucin which has increased its residence to the buccal mucosa (Table 2).

Table 2: Evaluation of buccal tablet formulations

Batch	Bioadhesion force ( N)±SD	Residence time (min)±SD	%Drug release ±SD	%Drug diffusion ± SD	Swelling index (%)± SD
F1	0.0942 ±0.10	35±0.10	98.49±0.80	98.21± 0.09	45.02±0.10
F2	0.1925±0.20	50±0.10	96.13±0.30	96.43±0.10	38.11±0.08
F3	0.2814±0.02	62±0.30	95.2±0.10	95.89±0.03	39.92±0.70
F4	0.3321±0.01	110±0.10	92.39±0.20	93.91±0.80	42.33±1.20
F5	0.0742±0.23	32±0.10	98.12±0.90	98.19±0.34	29.02±1.09
F6	0.1020±0.38	45±0.10	96.84±0.10	97.24±0.32	36.27±0.50
F7	0.2891±0.12	53±0.10	95.18±0.01	96.04±0.60	34.43±0.03
F8	0.3647±0.02	110±0.10	92.72±0.20	92.14±0.20	41.01±0.04
F9	0.0428±0.01	20±0.20	99.07±0.30	99.56±0.02	27.42±0.10
F10	0.1576±0.03	56±0.30	97.04±0.10	97.35±0.01	29.46±0.90
F11	0.2865±0.02	80±0.20	94.74±0.20	95.57±0.30	32.97±0.20
F12	0.3941±0.01	120±0.30	92.01±0.01	92.81±0.20	49.26±0.03
*F13	0.3048±0.01	105±0.40	94.54±0.40	94.23±0.10	45.16±0.90
*F14	0.3042±0.03	105±0.30	94.3±0.20	94.66±0.10	45.52±0.10
*F15	0.3067±0.10	100±0.20	94.82±0.82	94.95±0.10	45.16±0.20

Figure 2: Three dimensional response surface plot of bioadhesion force (Y₁)

The observation suggests that an increase in the concentration of X₁, X₂ and X₃ resulted in increase in bioadhesion force. The bioadhesion was high at the higher concentrations of X₃ and X₂ when compared to X₁This may be due to the enhancement of the hydrogen bonding capacity of the Tablet which subsequently produced a profoundly higher binding potential of two surfaces. Addition of CSP to the formulation did not show major increase in the bioadhesion force. Therefore it can be depicted that CSP has very low mucoadhesion properties.

3.3.2 Fitting of drug release data to the model

The statistical evaluation was performed by ANOVA and results are shown in Table 3. From the data it is evident that P value is less than 0.0500 in all formulations. The Model F-value of 51.67 implies the model is significant. There is only a 0.01% chance that a "Model F-Value" this large could occur due to noise. Values of "Prob > F" less than 0.0500 indicate model terms are significant. Values greater than 0.1000 indicate the model terms are not significant. In this case X₁, X₂, X₃, X₂X₃ are significant model terms.

Polynomial equation for response surface quadratic model,

Y₂ = +100.598 - 0.116 X₁- 0.186X₂ - 0.199X₃ - 2.222E-004X1X₂ - 2.588E-003X₁X₃ –6.111E 004X₂X₃ + 2.737E-

003X₁2 + 3.914E-003 X₂2 + 3.681E-003X₃2 (8)

The three dimensional response surface plot (Figure 3) shows that % drug release decreases when the polymers are taken in combination when compared to the individual concentration. The % drug release ranged from 92.14±0.20 to 99.56±0.02. Therefore it can be derived that the changing both the independent variables had significant effect on response Y₃. The observation suggests that an increase in the concentration of X₁, X₂ and X₃ resulted in decrease in % drug release. The drug release decreased in the higher concentration of polymer combinations. The drug release was found to be low in higher concentrations of X₃andX₂. This may be due to the higher swelling capacity of polymers which might not have allowed the drug to diffuse from the tablet matrix.

3.3.3 Fitting of diffusion data to the model.

The statistical evaluation was performed by ANOVA and results are shown in Table 3. From the data it is evident that P value is less than 0.0500 in all formulations. The Model F-value of 144.03 implies the model is significant. There is only a 0.01% chance that a "Model F-Value" this large could occur due to noise. Values of "Prob > F" less than 0.0500 indicate model terms are significant. Values greater than 0.1000 indicate the model terms are not significant. In this case X₁, X₂, X₃, X₁X₂, X₁X₃, X₂X₃, X₂² are significant model terms.

Polynomial equation for response surface quadratic model,

Y₃ = +95.200 - 0.097X₁ - 0.203X₂ - 0.050X₃ - 3.833E-003X₁X₂ - 4.388E-003X₁X₃ - 0.011 X₂ X₃ + 2.468E-003X₁2 + 7.824E-003X₂2 + 2.090E-003X₃2 (9)

Figure 4: Three dimensional response surface plot of % drug diffusion (Y₃)

Table 3: Coefficients for dependent variables

	Y₁		Y₂		Y₃
Coefficients	F value	p-value	F value	p-value	F value	p-value
Model	61.68	0.0001	51.67	0.0002	144.03	< 0.0001
X₁	24.48	0.0043	77.78	0.0003	200.04	< 0.0001
X₂	115.89	0.0001	87.87	0.0002	371.97	< 0.0001
X₃	352.49	< 0.0001	245.57	< 0.0001	483.41	< 0.0001
X₁X₂	1.74	0.2442	0.073	0.7978	15.37	0.0112
X₁X₃	1.76	0.2425	9.91	0.0254	20.15	0.0065
X₂X₃	0.040	0.8497	0.55	0.4908	141.04	< 0.0001
X₁²	24.51	0.0043	10.23	0.0240	5.88	0.0597
X₂²	12.90	0.0157	20.92	0.0060	59.12	0.0006
X₃²	29.83	0.0028	18.50	0.0077	4.22	0.0951

The three dimensional response surface plot (Figure 4) shows that % drug diffusion decreases when the polymers are taken in combination when compared to the individual concentration. The % drug diffusion ranged from 92.01 to 98.49% (Table 3).Therefore it can be derived that the changing both the independent variables had significant effect on response Y₄. The observation suggests that an increase in the concentration of X₁, X₂ and X₃ resulted in decrease in % drug diffusion. The drug diffusion decreased in the higher concentration of polymer combinations. The drug diffusion was found to be low in higher concentrations of X₃andX₂.Drug diffusion is in direct proportion to the drug release .This may be due to the to higher concentration of the polymer which upon swelling reduces the diffusion of the drug and also due to the excessive mechanical entanglement between the polymer chains.

3.3.4 Selection of optimized formulation

A Box-Behnken design was successfully employed for selection of optimized batch. The present work aimed at obtaining optimum bioadhesion force with drug release and diffusion of more than 90 %. Also it aimed at acquiring residence time upto maximum 2 h. Out of all the 15 formulations F12 satisfied the selected criteria. Formulation F12 containing CSP (15 mg), LBG (30 mg), TSP (30 mg) demonstrated bioadhesion force of 0.3941 ±0.01 N, residence time of 120±0.3 min, % drug release of 92.81±0.2% and % drug diffusion of 92.01±0.01% . Therefore formulation F12 was selected as the optimized formulation.

4. CONCLUSION:

Mucoadhesive buccal tablets of rasagiline mesylate using CSP, TSP and LBG were successfully prepared for unidirectional drug release and evaluated for various parameters. A Box-Behnken design was successfully employed for selection of optimized batch. The formulation F12 containing CSP (15 mg), LBG (30 mg) and TSP (30 mg) was identified to have maximum mucoadhesivity of 0.3941 ± 0.01 N. Therefore it can be concluded that TSP and LBG in their higher concentrations can be used for increasing the mucoadhesivity of the formulation. Formulation F9 containing CSP (15 mg) showed maximum % drug release and % drug diffusion of 99.07±0.30 and 99.56±0.02 respectively, but the mucoadhesivity and residence time obtained was very low i.e., 0.0428±0.01 and 20±0.20 respectively. Therefore, in order to satisfy the objectives of the study, formulation F12 containing CSP (15 mg), LBG (30 mg) and TSP (30 mg) which demonstrated bioadhesion force of 0.3941 ±0.01 N, residence time of 120±0.3 min, % drug release of 92.81±0.2% and % drug diffusion of 92.01±0.01% was selected as the best formulation. This formulation also showed residence time up to 2 h. The Box-Behnken design displayed the comparative study between the individual polymers in same concentration and their combinations. Comparison of individual polymer proved good mucoadhesivity of novel mucoadhesive agent, TSP. TSP in the combination with LBG and CSP showed 3-4 fold increase in the mucoadhesivity and also the drug release and diffusion was found to be optimum.

5. REFERENCES:

1. Jana S, Lakshman D, Sen KK and Basu SK. Development and Evaluation of Epichlorhydrin Cross-linked Mucoadhesive Patches of Tamarind Seed Polysaccharide for Buccal Application. Int. J. Pharm. Sci. Drug. Res. 2 (3); 2010: 193-198.

2. Abruzzo A, Bigucci F, Cerchiara T, Cruciani F, Vitali B and Luppi B. Mucoadhesive chitosan/gelatin films for buccal delivery of propranolol hydrochloride. Carbohydr. Polymers. 87; 2012: 581-88.

3. Boyapally H, Nukala RK, Bhujbal P and Douroumis D. Controlled release from directly compressible theophylline buccal tablets. Colloids Surf. B: Biointerfaces. 77 (2); 2010: 227-33.

4. Avachat AM, Dash RR and Shrotriya SN. Recent Investigations of Plant Based Natural Gums, Mucilages and Resins in Novel Drug Delivery Systems. Indian J. Pharm. Edu. Res. 45 (1); 2011: 86-99.

5. Singh S, Singh S, Bothara SB and Patel R. Pharmaceutical Characterization of Some Natural Excipient as Potential Mucoadhesives Agent. The Pharma Research, A Journal. 4; 2010: 91-104.

6. Dionisi M and Grenha A. Locust bean gum: Exploring its potential for biopharmaceutical applications. J. Pharm. Bioallied Sci. 4 (3); 2012: 175-85.

7. Mounika S, Narayanan V, Chandiran I, Manasa V, Sushma S, Mahita T and Pavani D. Pharmaceutical view of tamarind gum. The Pharma Professionals. 1 (2); 2011: 84-90.

8. Fernandez M, Negro S, Slowing K, Carbadillo AF and Barcia E. An effective novel delivery strategy of rasagiline for Parkinson’s disease. Int. J. Pharm. 419; 2011: 271-80.

9. Chopra S, Motwani SK, Iqbal Z, Talegaonkar S, Ahmad FJ and Khar RK. Optimisation of polyherbal gels for vaginal drug delivery by Box-Behnken statistical design. Eur. J. Pharm. Biopharm. 67; 2007: 120-31.

10. Jeevanandham S, Dhachinamoorthi D and Chandrasekhar KB. Drug Release Studies from Caesalpinia pulcherrima Seed Polysaccharide. Iranian J. Pharm. Res. 10 (3); 2011: 597-603.

11. Patel B, Patel P, Bhosale A, Hardikar S and Mutha S. Evaluation of Tamarind Seed Polysaccharide (TSP) as a Mucoadhesive and sustained release component of nifedipine buccoadhesive tablet and comparison with HPMC and Na CMC. Int. J. PharmTech Res. 1 (3); 2009: 404-10.

12. Gowthamarajan K, Jawahar N, Wake P, Jain K and Sood S. Development of buccal tablets for curcumin using Anacardium occidentale gum. Carbohydr. Polymers. 88; 2012: 1177-83.

13. Sarangapani S and Rajappan M. Pharmacognostical and Pharmaceutical characterization of Delonix regia – A novel matrix forming natural polymer. Int. J. Pharmacy. 2 (3); 2012: 564-73.

14. Lachman L, Liebermann JL and Kanig JL. Preformulation. In Lachman and Liebermann. The Theory and Practice of Industrial Pharmacy. Varghese Publishing House. 2009; 5th ed: pp. 353.

15. Munasur AP, Pillay V, Chetty DJ and Govender T. Statistical optimisation of the mucoadhesivity and characterization of multipolymeric propranolol matrices for buccal therapy. Int. J. Pharm. 323; 2006: 43-51.

16. Prasanth VV, Mudiyala S, Mathew ST and Mathapan R. Buccal tablet-As mucoadhesive drug delivery: An overview. J. Pharm. Res. 4 (3); 2011: 706-709.

17. Alanazi FK, Abdel Rahman AA, Mahrous GM and Alsarra IA. Formulation and physicochemical characterization of buccoadhesive films containing ketorolac. J. Drug Del. Sci. 17 (3); 2007: 183-92.

18. Shah VH, Pragna S and Shah GB. Design, Physicochemical Characterization and Pharmacokinetic Evaluation of Bilayered Buccal Tablets containing Statin Derivative. Res. J. Pharm. Biol. Chem. Sci. 3 (2); 2012: 227-39.

19. Avachat AM, Gujar KN and Wagh K. Development and evaluation of tamarind seed xyloglucan-based mucoadhesive buccal films of rizatriptan benzoate. Carbohydr. Polymers. 91; 2013: 537.

20. Vasantha PV, Puratchikody A, Mathew ST and Balaraman AK. Development and characterization of Eudragit based mucoadhesive buccal patches of salbutamol sulphate. Saudi Pharmaceutical J. 19; 2011: 207-14.

21. Azhar SA, Kumar PR, Sood V and Shyale S. Studies on directly compressed ondansetron hydrochloride mucoadhesive buccal tablets using gelatin, chitosan and xanthan gum along with HPMC K4M. J. Applied Pharm. Sci. 2 (5); 2012: 100-105.

Received on 06.08.2013

Modified on 30.08.2013

Accepted on 02.09.2013

Research Journal of Pharmaceutical Dosage Forms and Technology. 5(6): November-December, 2013, 345-354