INTRODUCTION:

For systemic delivery of drug molecule through pharmaceutical products from various dosage forms, the oral drug delivery system is the commonly used route of administration from the all routes of administration. Oral route is observed as most natural route of administration. Because of ease of swallowing, patient taking and cost effective formulation process the oral route is simple, suitable and safe route than other.^1-3

The problem in this system is low and varying bioavailability, due to the factors such as poor aqueous solubility, slow dissolution rate, low intestinal permeability, and instability in GI milieu, high first-pass metabolism through liver and/or intestine varying GI transit, and P-gp mediated efflux. Due to this it may be produced irreproducible clinical response or a therapeutic failure in some cases because of sub therapeutic plasma drug levels.^4-5

Enteric coated systems (ECS) uses polymeric coatings that are insoluble in the gastric media and hence, avoid drug release in the stomach. They dissolve at various pH ranging between 4.8 and 7.2^.6-8 The enteric coating material is act as barrier for controlling the oral drug delivery in the digestive system where it is absorbed. The word “enteric” shows small intestine; hence enteric coatings avoid delivery of drug before it comes in contact with the small intestine^.9-10

Colon is advantageous for specific local treatment of a different bowel diseases like ulcerative colitis, Crohn’s disease, Colon targeted drug delivery is required for the drug release to produce safe and effective treatment for the colonic disorders.^11-12

Lopramideis used for the control and indicative relief of acute diarrhea and chronic diarrhea relate with inflammatory bowel disease or gastroenteritis, and loperamide also used to overcome the volume of release from ileostomies.

Peristaltic activity on the circular muscles and longitudinal muscles of the intestinal wall are inhibited by Loperamide. It is extensive calcium channel blocker and connected to opioid mu-receptors. Bioavailabilty of Loperamide is 0.3%. Half life of Loperamide is 9.1 to 14.4 hours (average 10.8 hours)¹³. Rajeswari P. et al., (2016)Developed colons targeted drug delivery system by utilizing Chitosan as a carrier for Mesalamine by using wet granulation method. The formulated tablets were checked for Hardness, Weight variation, Drug uniformity, Friability and In-vitro Drug release study. All the parameters were found to be in the limits. Matrix tablets carrying Chitosan released 99.99% of mesalamine in simulated colonic fluid. The results of in-vitro study shows that the enteric coating matrix tablets containing Chitosan act as carrier and xanthum gum act as binder are most preferable to release the drug selectively in colonic site. The final formulation of mesalamine for colon-specific drug delivery gives pH, time and enzyme controlled release. Formulation F6 showed 99.29% at the end of 24 hrs and emerged as best formulation.

MATERIALS AND METHODS:

Loperamide drug was procured as a gift sample from Shasun chemicals, Chennai. Excipients like Eudragit S100, Ethyl cellulose, Lactose (DCL 21), Talc, Magnesium stearate, Eudragit FS 30D, Tri Ethyl Citrate, Purified talc, Purified water purchased from Thermocil Fine Chem, pune. All other excipients are analytical grade.

Preformulation study:

The organoleptic properties, solubility study, flow property, melting point and compressibility of the drug and excipients were determined.

Drug-Excipients Compatibility study:

A. Physical observation:

Drug molecule was mixed well with all excipients in binary proportion and less portion of this mixed powder was kept in a 2ml of cleaned and dried vial. Temparature at 40^oC ± 2^oC / 75 ± 5% RH the vials are placed in stability chamber for observation purpose. Mixtures were also placed at 2^oC-8^oC, 50^oC and room temperature (Control). Physical observation was done visually at the initial stage, after 15 days and after 1 month at 40^oC ± 2^oC / 75 ± 5% RH. Changes in colour of Loperamide API and combination of drug and excipients was observed.

B. Chemical compatibility studies by FT- IR:

The pure drug sample, drug-excipient mixtures of the formulation were chosen for the study. After a time interval of 30 days from formulation of the mixtures of drug-excipients the FT-IR spectra’s of the above samples were studied for observing incompatibility. The spectra’s were obtained by making Potassium bromide pellets under dry condition by using pellet press technique. The spectra of the bulk drug sample and that of the drug-excipient mixtures were contrast to examine the incompatibility problems. If there are no changes in peaks of mixture when compared to pure drug, it shows there is no any chemical interaction.

Bulk density :

The granules are accurately weighed and shifted into a 50 ml measuring cylinder by using funnel. The unsettled visible volume, to the closest graduated unit filled by the powder granules was measured.

ρ_bulk = m/Vo

m = Is the Mass of the blend

Vo = Untapped Volume

Tapped density:

The measuring cylinder holding a weighed quantity of powder granules (after measuring bulk density) was placed in tapped density tester (Electro Lab USP II) for 500 taps.

ρt = m/Vt

m = Is the Mass of the weighed granules

Vt = Final tapped volume of granules

Powder Compressibility index :

1) Carr’s compressibility index: Compressibility index are a measure of the tendency for arch formation.

ρt - ρbulk

CI = ------------------ X 100

ρt

ρbulk = Bulk density

ρt = Is Tapped density

2) Hausner’s ratio: He showed that coarse spheres powder, had proportion upto 1.2; whereas extra cohesive, less free flowing granules such as flakes have values more than 1.6.

ρt

Hausner’s ratio = ------------------ X 100

ρbulk

ρ_bulk = Bulk density

ρ_t= Tapped density

3) Particle Size Analysis: Particle size distribution of the drug was estimated by sieving method. The sieves are fixed on top of one another in increasing order. The test powder, for example 10gm, was placed on the top sieve. The sieves are subjected to a standard period of time for blending. The weight of material remain on each sieve was exactly determined.

Formulation of colon targeted matrix tablet of Loperamide:

Direct compression method were used for formulation of colon targeted matrix tablet of Loperamide. All the batch formulations in these studies are prepared by direct compression method. (Table-1).

Table 1: composition of formulation batches

Sr. No	Ingredients	Quantity of ingredients (mg/tab)
Sr. No	Ingredients	F1	F2	F3	F4	F5	F6
1	Loperamide	250	250	250	250	250	250
2	Eudragit S-100	80	60	50	35	20	14
3	Ethyl cellulose	60	55	40	25	15	10
4	Lactose (DCL 21)	50	75	100	130	154	165
5	Talc	5	5	5	5	5	5
6	Magnesium stearate	5	5	5	5	6	6
Total weight (mg)		450	450	450	450	450	450

A required quantity of excipients was weighed accurately. The Loperamide, Eudragit S100 and ethyl cellulose were sifted using 60 # mesh. Lactose (DCL 21) sifted through 40 # mesh.The sifted powders were mixed in polythene bag for ten minutes.The above dried granules were lubricated by using Talc. Talc is sifted through 40# mesh and magnesium stearate, sifting through 60# mesh after that mixed for 5 minutes in polythene bag. Then final lubricated mixture was compressed at an average weight of 450 mg using punch size 14.2 mm.

Coating of tablets:

Composition of Ingredient for Enteric Coating:

6% coating has been given for all the formulations to shelter the drug from acidic environment.

Preparation of Enteric Coating solution:

A required quantity of Eudragit FS 30 D was weighed accurately and stirred. Mean while Triethylcitrate was added to it, purified talc was triturated separately in a mortar. And added to the solution and stirred. Finally the volume was making up to needed quantity with purified water. Filtered the above solution with #100 mesh.

Evaluation of Post-Compression Parameters:

Weight Variation Test:

Twenty tablets were taken randomly and weighed individually. For weight variation test calculate average weight and check the each tablet weight to the average weight.

Hardness:

Tablet hardness of all the formulated tablets was measured using a Monsanto hardness tester.

Thickness:

Tablet thickness must be limited within a ±5% difference in standard value. Thickness of all the formulated tablets was measured using digital verniercalipers.

Friability:

For this test finaly prepared twenty tablets were weighed correctly and put in the friabilator and apparatus was operated for 100 rounds or 4 minutes. After that tablets are de dusted and weighed. The 0.5 to 1% is weight loss limit for regular uncoated tablets. The weight loss was measured by using formula.

Weight loss

F(%) = -------------------------- X 100

Initial Weight

Disintegration Test:

The apparatus is operated without disks, using simulated gastric fluid (pH 1.2) at 37⁰C for 2 hrs. The tablets are then removed and must indicate no proof of disintegration, breaking or softening. Disks are then added and the apparatus is operated by use of simulated intestinal fluid (pH 7.4) at 370C for a period of time limit mentioned in the monograph. The product passes the test if all tablets are disintegrated.

In-Vitro Dissolution Studies:

The release rate of Loperamide from tablets were determined using USP Dissolution Testing Apparatus 2 (paddle method). The test was done by using 900ml of 0.1N HCL at 370+0.50C and 100rpm for first 2 hrs. Then replaced with 7.4 pH phosphate buffer and continued for 24hrs. A liquor volume of 5ml was remove at regular intervals and replaced with fresh buffer diluted. The samples were replaced with new dissolution medium. The drug release is determined from the absorbance of the sample and standard.

FTIR and DSC analysis:

FTIR analysis:

In order to get proof on the feasible interaction of Loperamide with constituents at molecular level, Drug and formulation F6 powder in 1:1 molar proportion were prepared in KBr (Potassium Bromide) disks and perform FTIR study by using Perkin Elmer Spectrum one, FTIR spectrophotometer (1600 series, Perkin-Elmer Inc, Norwalk, CT). The scanning area starts from 450 cm⁻¹ to 4000 cm⁻¹and the resolution was 1 cm⁻¹.

DSC (Differential Scanning Calorimetry):

Physical Interaction studies between drug – Loperamide (Lp) and excipients were studied by DSC. About 2mg of each sample Loperamide and powder blend of drug and additives were heated separately in a sealed aluminum pan (capacity – 4µl) under nitrogen flow (30ml/minute) at a scanning rate of 5^oC /minute from 40ºC to 600ºC using Differential Scanning calorimeter (Spectrum one, Perkin Elmer, Model Sd 10, Norwalk, CT). Empty aluminium pan was utilised as a reference for this study. The heat flow act as role of temperature was measured for each sample of drug and excipients.

Assay (By UV method):

Preparation of standard solution:

Weigh accurately 100.0mg of Loperamide working standard in a clean, 100ml volumetric flask and 10ml of Acetonitrile. Shake well to dissolve and make up the volume to 100ml with phosphate buffer. Mix well and dilute 5ml with of this solution to 50ml with Phosphate buffer. Further dilute 5ml of the resulting solution to 50ml with phosphate buffer.

Preparation of sample solution:

Weigh accurately about 190mg of crushed tablet powder in a clean, 200ml volumetric flask and add 10ml of acetonitrile. Shake well and make up the volume to 200 ml with Phosphate buffer. And dilute 5ml with of this solution to 50ml with Phosphate buffer. Further dilute 5ml of the remaining solution to 25ml with phosphate buffer

Procedure :

Measure the absorbance of both the standard and sample preparation at 222nm using Phosphate buffer as blank. Assay was calculated from the following formula.

Stability Studies:

The reason for stability testing is to give proof on how the quality of a drug substance or drug products changes with the time due to effect of a variety of environmental conditions like temperature, humidity, and light enabling recommended for storage conditions and shelf life.

RESULTS AND DISCUSSION:

Preformulation Studies:

The colour, solubility, melting point and moisture content of the API were evaluated. All are within the limit of the monograph.

Flow properties of Loperamide :

A. Angle Of Repose Of Loperamide:

The angle of repose of API was calculated upto 380.56΄± 0.69. Hence the drug belongs to fair flow and requires glidants to improve the flow property.

B. Bulk Density and Tapped Density of Loperamide:

The average bulk density and tapped density was calculated upto 0.453 ± 0.01 and 0.614 ± 0.003g/ml respectively.

C. Powder Compressibility And Hausner’s Ratio

Based on Compressibility index and Hausner’s ratio, it indicates the Loperamide (API) belongs to poor flow property.

Table 2: summary of micromeritic properties of pure drug

Sr. No.	Test	Values
1	Angle of repose (Degree)	380.56΄± 0.69
2	Bulk Density (g/ml)	0.453±0.01
3	Tapped Density(g/ml)	0.614± 0.003
4	Compressibility index (%)	26.22
5	Hausner’s ratio	1.35

Particle Size Distribution:

From the particle size analysis it was concluded that the particles size of the API was found to be moderately coarse powder.

Drug - Excipients Compatibility Studies:

From the drug excipients compatibility study, it was detect that there was no characteristic change or interaction between drug and excipients. Thus it was concluded that the excipients selected for the formulation were compatible with Loperamide.

Figure 1 : FTIR spectra of loperamide with excipient

Table 3: micromeritic properties of lubricated powder blend

Formulation Code	Bulk density (gm/cm3)	Tapped density (gm/cm3)	Carr’s Index (%)	Hausner’s ratio	Angle of repose (degree)
F1	0.35±0.02	0.40 ± 0.01	11.73±0.79	1.12 ±0.15	29⁰58’±0.53
F2	0.31±0.03	0.35 ± 0.05	12.10±0.54	1.13 ±0.28	33⁰23’±0.35
F3	0.37 ± 0.01	0.42 ± 0.06	13.63±0.38	1.13 ±0.12	30⁰96’±0.19
F4	0.38 ± 0.07	0.40 ± 0.08	11.57±1.05	1.14± 0.85	31⁰26’±0.60
F5	0.35 ± 0.10	0.44 ± 0.06	12.60±0.86	1.12 ±0.74	29⁰35’±0.48
F6	0.41± 0.06	0.46± 0.01	12.98±0.65	1.13 ±0.24	31⁰.05’±0.25

Table 4: results for evaluation of finished product (uncoated tablet)

Parameters	F1	F2	F3	F4	F5	F6
Average weight (mg)	450±1.18	450±0.89	450±2.00	450±0.61	450±2.68	450±0.21
Thickness (mm)	3.4± 0.16	4.2±0.09	4.7± 0.14	5.9± 0.12	5.7±0.01	5.9 ± 0.16
Hardness (kg/cm2)	12.6 (± 0.15)	9.4 (± 0.22)	6.2 ( ± 0.30)	5.2 ( ± 0.32)	6.0 ( ± 0.30)	5.8( ± 0.11)
Friability (%)	0.36	0.41	0.39	0.31	0.35	0.33
Disintegration time (min)	-	24’46’’	17’42’’	14’45’’	8’42’’	7’18’’
Assay (%)	99.34	99.2	98.51	99.85	99.53	100.21

DISCUSSION:

The thickness of the tablets is in between 3.4 to 5.9mm. The formulated tablets in all the trials having good mechanical strength with adequate hardness in the scale of 12.6 to 5.2kg/cm². The friability of the tablets was calculated within 1%. All the above trail formulations have passed the friability test. The average weight of all the formulations was calculated upto 450mg. It is within the permissible range. The percentage of drug content from all batches of the tablets ranging from 98.5 to 100.21 which are within the acceptable limits.

A. ablet evaluation parameter :

Table 5: results for evaluation of enteric coated tablet (f6):

Trial

Thickness

(mm)

Weight variation (mg)

Disintegration

time(min)

Assay (%)

Drug release (%)

6.2±0.02

477±0.21

218’63’’ ±1.98

99.92 ± 0.08

98.51

DISCUSSION:

Loperamide tablet of the above trial (F6) was satisfied of all the parameters. The coated tablets were studied for the above tests such as thickness, disintegration test, weight variation, assay and in-vitro studies.

B. FTIR analysis:

Figure 2: FTIR spectrum of loperamide formulation f6

DISCUSSION:

FTIR analysis of coated formulation F6 showed no significant change in major functional groups wavelengths of Loperamide.

C. DSC Analysis:

Figure 3: DSC thermo gram of loperamide and formulation f6

DISCUSSION:

Sharp endothermic peak at 228.93 ⁰C indicated melting point and morecrystalline structure of Loperamide. While in case of formulation curved endothermic peak indicates loss of crystalline structure of drug

Figure 4: In vitro dissolution of formulation f6

Table 6 : In vitro dissolution data for enteric coated formulation

Dissolution Media	Sampling Time	Cumulative% drug release in different trials
Dissolution Media	Sampling Time	F3	F4	F5	F6
Simulated Gastric Fluid (0.1 HCl)	2 Hrs	1.07	1.60	1.83	2.00
Simulated Intestinal Fluid (7.4pH Phosphate Buffer )	5 Hrs	7.43±0.32	8.804±0.13	10.09±0.78	11.58±0.13
	8 Hrs	10.09±0.78	12.74±0.43	16.76±0.13	20.72±0.43
	12 Hrs	26.97±0.52	26.97±0.52	36.82±1.35	49.76±0.57
	16 Hrs	45.18±0.95	61.24±0.52	72.21±0.95	81.51±0.57
	20 Hrs	61.24±0.57	72.19±0.43	84.31±0.57	90.71±0.95
	24 Hrs	78.22±0.78	82.43±0.57	92.65±0.95	98.51±0.78

DISCUSSION:

The concentration of Eudragit S 100 and Ethyl cellulose was further decreased to 14mg/unit and 10mg/unit and increased the Lactose DCL21 concentration to 165mg/unit. The tablets of this trial are subjected to in-vitro dissolution study. The percentage of drug release showed 98.51±0.78 at 24 hrs. This trial was taken as confirmatory trial and subjected as stability studies.

Stability Studies:

Discussion:

The F6 formulation of enteric coated tablets was carried out for the stability study, it was kept in 400C± 20C /75±5% RH for the interval of three months. Percentage of drug release and assay was determined. The data’s does not showed much variation during stability studies. The results show that the product was stable.

CONCLUSION:

The loperamide enteric coated matrix tablets were prepared by using the selected additives quantities by using direct compression method. The finaly prepared tablets were examined for both pre-compression and post-compression parameters as per need of standards. And the results were obeyed with the pharmacopoeia specification. The finally prepared Loperamide tablets were coated with enteric polymer Eudragit FS 30D by pan coating method. From all the batches, formulation F6 showed 98.51% drug release at 24 hrs. From the results obtained, it can be says that formulation F6 containing enteric coated matrix tablet of Loperamide would be a hopeful formulation to achieve the aim which cure inflammatory bowel diseases (ulcerative colitis) without any gastric irritation or ulcers, which is helpful for patients having pre-history of ulcerative colitis.

ACKNOWLEDGEMENTS:

The authors thank the Shasun chemicals, Chennai India for providing Loperamide as gift sample.

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Received on 30.07.2019 Modified on 08.08.2019

Research J. Pharm. and Tech 2020; 13(3):1447-1452.

DOI: 10.5958/0974-360X.2020.00264.4