INTRODUCTION:

Type 2 diabetes mellitus is a heterogeneous disorder characterized by multiple defect in the liver, pancreatic β-cell, and peripheral tissue such as adipose tissue and skeletal muscles. Recently various developed and developing countries move towards combination therapy for treatment of various diseases and disorders requiring long term therapy such as diabetes and hypertension. They are combination therapy which has various advantages over mono therapy such as problem of dose related side effects which are minimized¹.

Bi- layer tablets are novel drug delivery systems where combination of two or more than two drugs in a single piles having different release profiles which improves patient compliance, and prolongs the drug actions. The major therapeutic goals in subjects with glucose control, to optimize blood glucose control, to normalize lipid disturbances to reduce overweight and elevated blood pressure. Multilayered tablet concept has been utilized to develop sustained release formulations. The advantages of pharmacokinetics rely on the criterion that drug release from the fast releasing layer leads to a suddenly rise in blood concentration². The bi-layer tablet is suitable for sequential release of two drugs in combination, of two separate incompatible substances and also for sustained release tablet formulation in which one layer is immediate release as initial dose and second layer is sustained release dose¹. The objective of this research was to develop a combination drug therapy for antidiabetic tablet formulation having different mechanism of action to complement each other and together effectively lower the blood glucose levels. Metformin is first-line choice of drug for oral biguanides². Metformin has an oral bioavailability and is absorbed slowly. Glimepiride is the third generation sulfonylurea drug useful for control of diabetes mellitus, type-II. Glimepiride are pre-clinical investigation of the suggested a number of potential benefits over sulfonylurea currently available of lower dosage, rapid onset possibly due to less stimulation of insulin secretion and extra pancreatic effects. More recently the process has been adapted for preparation of pharmaceutical matrix systems providing immediate or sustained release. Melt granulation has been employed as a novel technique for the formulation of oral solid dosage forms in pharmaceutical industries in the last decade³. Bilayer tablet comprising of immediate release, sustained release tablets utilizes diluent like dibasic calcium phosphate and lactose, then lubricant are magnesium stearate, talc. etc. This study aims to formulate the bilayered tablets of Glimepiride and Metformin hydrochloride by using Rice bran wax as binder⁴.

MATERIALS AND METHODS:

Table No. 1: MATERIAL:

Sr. No.	Ingredient	Name of Suppliers	Function Category
1	Metformin HCL	Balaji laboratories	API
2	Rice bran wax	Research-Lab Fine Chem. Industries, Mumbai	Binder
3	PEG 6000	Research-Lab Fine Chem. Industries, Mumbai	Solvent
4	Dibasic calcium phosphate	Research-Lab Fine Chem. Industries, Mumbai	Diluent
5	Magnesium phosphate	Research-Lab Fine Chem. Industries, Mumbai	Lubricant
6	Talc	Research-Lab Fine Chem. Industries, Mumbai	Lubricant
7	Glimepiride	Gift Sample	API
8	Lactose	Research-Lab Fine Chem. Industries, Mumbai	Diluent
9	Red iron oxide	Research-Lab Fine Chem. Industries, Mumbai	Coloring agent

Table No.2: Formulation table of sustained release layer

Sr. No.	Ingredient	M1	M2	M3	M4	M5	M6	M7	M8	M9
1	Metformin HCL	500mg	500mg	500mg	500mg	500mg	500mg	500mg	500mg	500mg
2	Rice bran wax	4%	5%	6%	7%	8%	9%	10%	11%	12%
3	PEG 6000	10%	10%	10%	10%	10%	10%	10%	10%	10%
4	Dibasic calcium phosphate	q.s	q.s	q.s	q.s	q.s	q.s	q.s	q.s	q.s
5	Magnesium stearate	1%	1%	1%	1%	1%	1%	1%	1%	1%
6	Talcum	1%	1%	1%	1%	1%	1%	1%	1%	1%
	TOTAL	800mg	800mg	800mg	800mg	800mg	800mg	800mg	800mg	800mg

Table No.3: Formulation table of immediate release layer

Sr. N0	Ingredient	G1	G2	G3	G4	G5	G6	G7	G8	G9
1	Glimepiride	1mg	1mg	1mg	1mg	1mg	1mg	1mg	1mg	1mg
2	Lactose	88.5mg	89.5mg	90.5mg	91.5mg	92.5mg	93.5mg	94.5mg	95.5mg	96.5mg
3	Red iron oxide	0.5mg	0.5mg	0.5mg	0.5mg	0.5mg	0.5mg	0.5mg	0.5mg	0.5mg
4	Magnesium stearate	1mg	1mg	1mg	1mg	1mg	1mg	1mg	1mg	1mg
5	Talcum	q.s	q.s	q.s	q.s	q.s	q.s	q.s	q.s	q.s
	TOTAL	100mg	100mg	100mg	100mg	100mg	100mg	100mg	100mg	100mg

CHARACTERIZATION OF BILAYER TABLETS:

Precompression parameter:

Angle of repose:

The diameter of the powder cone was measured and the angle of repose was calculated using the following equation,

Where, h = height

r = radius

Density:

The bulk density and tapped bulk density were determined and calculated using the following formulas⁷.

Particle size distribution:

The particle size distribution was measured using sieving method.

Photo-microscope study:

Photo-microscope image of TGG and GG was taken by photo-microscope.

Moisture sorption capacity:

Moisture sorption capacity was performed by taking 1 g of disintegrate uniformly distributed in petri-dish and kept in stability chamber at 37+1°c and 100% relative humidity for 2 days investigated for the amount of moisture absorb⁸.

Compressibility:

The compressibility index was calculated by using formulation,

Hausner’s Ratio:

It is calculated by the formula,

Post compression parameters:

General appearance:

The general appearance of a tablet, its visual identity and overall “elegance” is essential for consumer acceptance. General appearance includes tablet shape, size, color, presence or absence of an odour.

Weight variation:

Twenty tablets were selected at random and the average weight was determined. Not more than two of the individual weight deviate from the average weight by more than the percentage deviation as per IP and none deviates by more than twice the percentage. IP official limits of percentage for all trials is 5%⁹.

The following percentage deviation shown in tablet in weight variation is allowed.

Table No. 4: Weight Variation Parameters

Average weight tablet	Percentage deviation
130 mg or less	± 10
>130 mg and < 324 mg	± 75
324 mg or more	± 5

Tablet Thickness:

For the production control, the adequate standardization of punch and die tooling was done. The thickness was measured by placing 10 tablets in holing tray and measuring the total thickness within ±0.01mm using digital Vernier caliper¹⁰.

Hardness:

The compressional force relationship, with uniform tooling, made the tablets hardness which is a useful tool for physically controlling tablet properties during a production operation. The hardness of the tablets was determined by using Monsanto type hardness tester. For adequate mechanical stability 4-6 kgs/tablet hardness is required¹¹.

Friability:

Friability is the measure of tablet strength. 20 tablets were weighed accurately and placed in the tumbling apparatus that revolves at 255 pm dropping the tablets through a distance of six inches with each revolution. After 4 min, weight of tablets and the percentage loss in tablet weight was determined^{12, 13}.

Disintegration test of immediate release layer:

The tablet disintegration was carried by placing one tablet in each tube of the basket and top portion of the tube was closed with disc and run the apparatus containing 0.1 N HCL and maintained at 37±0.1°C as the immersion liquid. The assembly was raised and lowered between the cycle per minute. The time taken for the complete disintegration of the tablet with number of palpable mass remaining in the apparatus was measured and recorded¹⁴.

Dissolution studies:

The dissolution study was performed on dissolution test apparatus. The dissolution medium used was 900 ml 0.1 N HCL for first 2 hrs. And buffer pH 6.8 for the next 10 hrs. at 37±0.1°C. The paddle speed was kept constant at 50 rpm. Each time 5 ml of sample withdrawn the interval of the sample of 10 min, 30min, 1hrs, and 2hrs for glimepiride and 5ml sample were withdrawn for metformin HCL for thereafter at interval of 1 hrs.¹⁵. The withdrawn sample were analyzed spectrophotometrically at 226nm for glimepiride and 233nm for metformin HCL. The sample amount of fresh 0.1N HCL and phosphate buffer pH 6.8 was used to replace the amount withdrawn for respective dissolution media. Percent cumulative drug release of both drugs from the tablet was calculated¹⁶.

RESULT AND DISCUSSION:

Precompression evaluation:

FTIR studies:

Compatibility studies were performed using FTIR. Drug- excipient compatibility studies were conducted with the objectives of selecting the compatible ingredients for tablets.

Figure No.1: FTIR Spectrum of metformin HCL

Figure No.2: FTIR Spectrum of Glimepiride

Standard Curve:

Standard Curve of Metformin HCL in water:

Figure No.3: Standard Curve of Metformin HCL in water

Standard Curve of Glimepiride in 0.1N HCl

Figure No.4: Standard Curve of Glimepiride in 0.1N HCl

Calibration curve:

a) Calibration curve of metformin HCl in water:

Calibration curve of metformin HCl was determined by plotting absorbance/concentration (mcg/ml) at 233 nm. The results obtained the linear regression analysis was done on absorbance data points. A straight line generated to facilitate the calculation of amount of drug, the equation is as follows:

Figure No.5: Calibration curve of Metformin hydrochloride in 0.1 N HCl

Figure No.6: Calibration curve of Glimepiride in 0.1 N NaOH

Pre-compression parameters:

Immediate release layer:

The precompression parameters performed for the immediate release layer of bilayer tablets by wet granulation technique are mentioned. For the evaluation if immediate release layer the bulk and tapped density values of the formulations laid between 0.440 g/cm³-0.488 g/cm³. As per pharmacopeia limits, the bulk and tapped density must be less than 1.2 g/cm³ which indicates a good packing. Therefore, the prepared batches passed the limit prescribed by pharmacopoeia and good packing ability. The value of the angle of repose was found to be 23°-45’-28°-45’ which indicates satisfactorily acceptable flow property, hausner’s ratio, Carr’s index were found to be in range 1.08-1.16 and 5.51- 15.91 respectively, which describes acceptable flow property as well as good packing ability. The results for granule characteristics are represented in table:

Table 5: Pre-compression studies of immediate release.

Sr. No.	Batches	Bulk Density (gm/ml)	Tapped Density (gm/ml)	Carr’s Index (%)	Hausner’s Ratio	Angle of Repose (ɵ)
1	G1	0.410	0.40	10.48	1.10	25.17
2	G2	0.40	0.39	10.26	1.12	25.11
3	G3	0.41	0.39	14.56	1.45	26.07
4	G4	0.41	0.40	8.19	1.081	27.36
5	G5	0.41	0.47	9.20	1.092	25.7
6	G6	0.41	0.39	5.51	1.055	23.45
7	G7	0.42	0.40	9.66	1.096	28.45
8	G8	0.41	0.39	12.55	1.143	27.56
9	G9	0.47	0.46	11.12	1.159	25.21

Table 6: Pre-compression studies of sustained release.

Sr. No.	Batches	Bulk Density (gm/ml)	Tapped Density (gm/ml)	Carr’s Index (%)	Hausner’s Ratio	Angle of Repose (ɵ)
1	M1	0.482	0.45	4.77	1.047	28.33
2	M2	0.50	0.48	5.54	1.055	26.12
3	M3	0.47	0.45	3.6	1.036	22.3
4	M4	0.45	0.43	2.1	1.021	24.37
5	M5	0.50	0.48	2.78	1.038	25.24
6	M6	0.49	0.48	2.6	1.026	23.01
7	M7	0.49	0.46	4.83	1.048	26.90
8	M8	0.50	0.45	3.16	1.031	24.53
9	M9	0.49	0.46	11.4	1.024	20.90

Table 8: Post compression parameter of bilayer tablets:

Sr. No.	Batch	Diameter (mm)	Thickness (mm)	Hardness (kg/cm²)	Weight variation	Friability	Drug Content Metformin	Drug content Glimepiride
1	F1	16.5	5.7	6.7	910	0.55	94.3	92.40
2	F2	16.5	5.5	5.8	905	0.79	94.01	90.10
3	F3	16.7	5.1	5.6	895	0.12	96.25	93.30
4	F4	16.5	5.5	6.9	915	0.20	94.92	94.70
5	F5	16.4	5.6	5.8	900	0.11	96.61	94.50
6	F6	16.8	5.8	5.53	922	0.23	95.37	95.23
7	F7	17	5.9	6.52	898	0.31	97.19	93.18
8	F8	16.2	5.4	5.86	910	0.23	95.82	95.01
9	F9	16.8	5.5	6.5	900	0.15	97.17	98.12

Table 9: The % cumulative drug release of F1 – F9 formulation and comparison with commercial product 2 (Glimepiride)

Time (min)	% cumulative drug release
	G1	G2	G3	G4	G5	G6	G7	G8	G9	Commercial product 2
0	0	0	0	0	0	0	0	0	0	0
15 min	65.22	69.11	73.78	75.68	77.69	80.24	81.34	83.13	88.55	65.65
30 min	75.59	75.25	71.06	73.46	78.56	82.46	85.14	88.06	89.78	80.58
60 min	77.90	78.45	78.56	80.47	82.80	85.56	87.38	90.56	91.26	86.36
120min	78.46	79.97	81.36	83.33	85.56	87.90	89.90	92.37	98.50	98.17

Table 10: The % cumulative drug release of F1 – F9 formulation and comparison with commercial product 1 (Metformin HCl)

Time (Hrs.)		% cumulative drug release
	M1		M2	M3	M4	M5	M6	M7	M8	M9	Commercial product 1
0	0		0	0	0	0	0	0	0	0	0
1hrs	35.22		37.36	40.92	42.22	45.37	48.25	48.36	49.11	51.34	35.23
4hrs	44.27		47.22	53.11	55.48	58.45	61.27	64.23	67.39	70.12	60.56
8hrs	52.69		55.97	58.02	62.97	65.77	69.22	71.11	75.38	83.03	84.12
12hrs	68.22		73.45	75.88	81.33	84.37	87.78	89.25	93.92	97.21	97.12

In vitro-drug release:

The percentage of drug release of bilayer tablets in mg when compare with metformin innovator and glimepiride was found to be 97.17 and 98.12% and the result are shown in table 9 and 10.

The percentage drug release for formulation F9 shows the better drug release 97% of metformin and 98% of glimepiride.

Figure No.7: Drug release profile

CONCLUSION:

The study involved in designing and fabricating an oral bilayer antidiabetic tablet formulation which has first impulse of the dose in the shortest time possible and second dose is a prolonged time at a constant rate for the duration of more than 12 hrs. The formulation was found to be highly optimized and demonstrated highest cumulative drug release where the metformin followed either zero-order or first order and glimepiride followed anomalous diffusion. Therefore, the designed formulation will offer a therapeutic regimen and provide patient friendly postprandial type-II diabetes mellitus management.

ACKNOWLEDGEMENT:

We are grateful to the teacher’s and principal of Loknete Dr J. D. Pawar College of Pharmacy, Manur, Tal. Kalwan for their helpful guidance.

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

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Received on 03.06.2021 Modified on 19.06.2021

Asian J. Res. Pharm. Sci. 2021; 11(4):273-279.

DOI: 10.52711/2231-5659.2021.00043

Batch code	Disintegrating time (min)
G1	4:10
G2	6:20
G3	7:15
G4	8:10
G5	5:20
G6	7:20
G7	8:10
G8	7:50
G9	8:20