formulation and in vitro evaluation of colon …...technique. sodium starch glycolate was included...

Pharmaceutical Resonance 2020 Vol. 2 - Issue 2

© Published by DYPIPSR, Pimpri, Pune - 411 018 ( MH ) INDIA 34

RESEARCH ARTICLE

FORMULATION AND IN VITRO EVALUATION OF COLON TARGETED DRUG DELIVERY OF ACECLOFENAC

Mahesh D. Bhalsing1*, Shubhangi V. Shekade2 1* Pravara Medical Trust’s College of Pharmacy, Shevgaon, Dist Ahmednagar, India 2 Dept. of Pharmaceutics, Dr. D. Y. Patil Institute of Pharmaceutical Sciences and Research, Pimpri, Pune

Mahesh D. Bhalsingh Pravara Medical Trusts, College of Pharmacy, Shevgaon, Dist. Ahmadnagar, India

ABSTRACT :

Objective of the current study is to develop colon targeted drug delivery systems for aceclofenac. Guar gum (GG) and xanthan gum (XG) is used as a carrier in this drug delivery system. Matrix and compression coated tablets of aceclofenac were prepared by using various proportion of guar gum: xanthan gum like (1.25:1.25), (1.5:1) and (1.75:0.75). Above formulations of guar gum and xanthan gum were evaluated for post compression parameters. 14.52 -17.04% of the aceclofenac released from matrix tablets of aceclofenac within the 5 h dissolution study, in the physiological environment of the stomach and small intestine, depending on the proportion of guar gum: xanthan gum utilized in the formulation. Which results that the matrix tablet of aceclofenac failed to control the drug release within 5 h of the dissolution study. The compression coated formulations are developed to release less than 4 % of aceclofenac within 5 h dissolution study in the physiological environment of the stomach and small intestine. The dissolution study was continued in rat caecal contents, the compression coated tablet of aceclofenac released 63.75- 79.90% of aceclofenac after degradation by colonic bacteria at the end of 24 h of the dissolution study. The results showed that compression coated tablet CT3 with guar gum: xanthan gum (1.75:0.75) is most suitable to provide targeting of aceclofenac for local action in the colon owing to its minimal release of the drug in 1 st 5 h. No changes were seen either in physical appearance, drug content or in drug release pattern after storage at 40º C/ 75% RH for 3 months in the aceclofenac compression coated tablets.

Key words: Aceclofenac; Guar gum; Xanthan gum; Colon targeting; Compression coating

Introduction :

The oral route is taken into account to be most convenient for administration of medication to patients. After oral administration of conventional dosage forms usually dissolves in the stomach fluid or intestinal fluid and is absorbed from these regions of the GIT depends upon the physicochemical properties of the drug. It is a serious drawback in conditions where localized delivery of the drugs in the colon is required or in conditions where a drug needs to be protected from the hostile environment of upper GIT. Oral delivery of drugs to the colon is valuable in the treatment of diseases of colon

(ulcerative colitis, Crohn’s disease, carcinomas and infections) whereby high local concentration can be achieved while minimizing adverse effects that occur due to release of drugs in the upper GIT or unnecessary systemic absorption. The colon is attracting interest as a site where poorly absorbed drug molecule might have an enhance bioavailability. The region of colon is recognized as having somewhat less hostile surroundings with less diversity and intensity of activity than the stomach and small intestine. Additionally, the colon has a longer retention time and appears highly responsive to agents that enhance the absorption of poorly absorbed drugs. Apart from retarding or targeting dosage forms, a reliable colonic drug delivery could also be an important starting position for the colonic absorption of per-orally applied, undigested, unchanged and fully active peptide drugs. As the large intestine is comparatively free of peptidases such special delivery systems can have a better chance to get their drug sufficiently absorbed after per oral application [1].



Table 1. Formulation of Matr ix tablets

Aceclofenac is a non-steroidal anti-inflammatory drug that is effective in the treatment of painful inflammatory diseases. It has short half-life of 4 h [2].

Aceclofenac is a prostaglandin syntheses (cyclooxygenase) inhibitor, that which inhibits lipoxygenase and prostaglandin production, thereby inhibiting the inflammatory method [3]. Numerous approaches are used for targeting the drugs to the colon including, formation of a prodrug, multicoating time-dependent delivery systems, coating with pH-sensitive polymers, pressure-dependent systems and systems formulated making use of biodegradable polymers. Every system has advantages as well as shortcoming. However, biodegradable systems formulated making uses of naturally occurring polysaccharides are increasingly being developed. Natural polysaccharides remain undigested in the stomach and the small intestine and are degraded by the vast anaerobic micro flora of the colon [4].

Xanthan gum is known to have greater drug-release retarding property and synergistically enhanced the gel properties in the presence of galactomannan gums like guar. Guar gum is used in colon- specific drug delivery as matrix forming material and as compression coat.

The present investigation deals with development of novel colon targeted drug delivery system by using compression coating technique. Compression coating is a pharmaceutically accepted and industrially applied technique used in formulating tablets. The core tablet of aceclofenac was compression coated with guar gum and xanthan gum combinations to target into the colon, because after reaching the colon the polysaccharide gets degraded by the micro flora of the colon and drug will be release to the target site. The prepared core and compression coated tablets subjected for their different evaluation parameters and the stability studies were carried out according to the ICH guidelines.

2. Materials and methods :

2.1 Materials :

Aceclofenac was obtained as gift sample from Amoli Pharmaceutical Pvt.Ltd, Mumbai, India. Guar gum was procured from Loba. Chemicals. Mumbai, India. Xanthan gum was obtained as gift sample from Rajesh Chemicals, Mumbai, India. Sodium starch glycolate, Magnesium stearate, Microcrystalline cellulose, Talc were purchased from S.D. Fine Chemicals, Mumbai, India. All chemicals used in the experiment were of analytical grade.

2.2 Methods :

2.2.1 Preparation of aceclofenac matrix tablet [5] :

The formulation for matrix tablets of aceclofenac is given in Table 1. Matrix tablets of aceclofenac were prepared by wet granulation technique using starch paste as binder. Microcrystalline cellulose was used as diluents and mixture of talc and magnesium stearate was used as lubricant. Firstly all the ingredients were accurately weighed. Aceclofenac was separately passed through mesh (60) then Guar gum; xanthan gum and microcrystalline cellulose were sieved through mesh (44) and mixed with drug. Then powders were blended and granulated with starch paste. Then the granules were passed through mesh (22) and then granules were dried at 50o C for 2h. Then dried granules were passed through a mesh (22) and lubricated with a mixture of talc and magnesium stearate. The lubricated granules were compressed using 10 mm flat plain punches on compression machine.

Sr. Ingredients MT1 MT2 MT3

1 Aceclofenac 100 mg 100 mg 100 mg

2 Guar Gum 125 mg 150 mg 175 mg

3 Xanthan Gum 125 mg 100 mg 75 mg

4 starch 20 mg 20 mg 20 mg

5 Microcrystalline

Cellulose 25 mg 25 mg 25 mg

6 Magnesium

stearate 3 mg 3 mg 3 mg

7 Talc 2 mg 2 mg 2 mg

2.2.2 Preparation of aceclofenac core and compression coated tablets

The core tablets were prepared by direct compression technique. Sodium starch glycolate was included in the formulation to obtain aceclofenac tablets with fast disintegration characteristics. The formula for the core tablet is given in Table 2. Aceclofenac, microcrystalline cellulose and sodium starch glycolate were firstly sieved and weighed then mixed in the geometric fashion. Then mixture was lubricated with magnesium stearate and talc and then the mixture equivalent to 100 mg of aceclofenac (130mg) was weighed and then compressed by single station tablet punching machine using 8 mm flat punches, optimizing the hardness and die cavity of



the machine, so that the tablets will be of uniform hardness and with minimal weight variation [5].

The three formulations of compression coating (XG1, XG2, and XG3) for coating the core tablet are shown in Table 3 were prepared by wet granulation technique using starch paste as binder. Guar gum, xanthan gum and microcrystalline cellulose were sieved through mesh (44) and mixed with drug. Then powders were blended and granulated with starch paste. Then the granules were passed through mesh (22) and then granules were dried at 50o C for 2 h. The dried granules were passed through a mesh (22) and were lubricated with a mixture of talc and magnesium stearate. Then 47% weight of Coating mixture then kept in die cavity and then core tablet was placed on it in centered position and then remaining 53% of coating mixture was added to cavity and compressed in to tablets, by using the punches of 10mm diameter optimizing the hardness and die cavity of the machine, so that the tablets will be of uniform hardness and with minimal weight variation.

2.2.3 Evaluation of granules [6 - 8]

The granules of matrix tablet and compression coating was evaluated for their angle of repose, bulk density and compressibility index.

2.2.4 Evaluation of tablets [9 - 11]

2.2.4.1 Hardness

For each formulation, the hardness of 10 tablets were determined using the Monsanto hardness tester (Cadmach).

2.2.4.2 Friability

For each formulation, the friability of 20 tablets were determined using the Roche friabilator. Percent friability (F) was calculated as follows,

Sr. Ingredients Core Tablet

1 Aceclofenac 100 mg

2 Microcrystalline

cellulose 25 mg

3 Sodium starch

glycolate 3 mg

4 Magnesium

stearate 0.5 mg

5 Talc 1.5 mg

Table 2. Core Tablet Formulation

Sr. Ingredients XG1 XG2 XG3

1 Guar Gum 125 mg 150 mg 175 mg

2 Xanthan Gum 125 mg 100 mg 75 mg

3 Starch 20 mg 20 mg 20 mg

4 Microcrystalline

Cellulose 25 mg 25 mg 25 mg

5 Magnesium

stearate 3 mg 3 mg 3 mg

6 Talc 2 mg 2 mg 2 mg

Table 3. Composition of Compression coat Formulations

Initial Weight - Final Weight % F = —————————————— X 100

Initial Weight

2.2.4.3 Thickness

For each formulation, the thicknesses of 10 tablets were determined using Vernier caliper.

2.2.4.4 Weight variation Test

To study weight variation, 20 tablets from every batch were weighed using an electronic balance (AW-220, Shimadzu), and the test was performed as per the official method.

2.2.4.5 Drug content uniformity

Five tablets were weighed individually and triturated. Powder equivalent to the average weight of the tablet was weighed and drug was extracted in water for 6 hours. The solution was filtered through 0.45µ membrane. The absorbance was measured at 275 nm[12] after suitable dilution.

2.2.4.6 In Vitro Release Studies of matrix and compression coated tablet

The dissolution study of Matrix tablets of aceclofenac were carried out using a USP XXIII Electrolab six basket dissolution rate test apparatus (37°C at 100 rpm). In vitro drug release studies were carried out in three different media i.e. 0.1N HCl (pH 1.2) in 900ml as dissolution medium, as the average gastric emptying time is 2 h, for 3 h in phosphate buffer (pH 7.4) in 900ml dissolution medium, as the average small intestinal transit time is 3 h and then the dissolution was continued with the pH 6.8 phosphate buffer (control) for 19 h. At the end of the time periods, two samples each of 5 ml were taken, suitably diluted and analyzed for aceclofenac at 275 nm using a double beam UV/VIS Spectrophotometer.



Sr. Formulation

Code Drug: GG:

XG

1 CT1 1:1.25:1.25

2 CT2 1:1.5:1

3 CT3 1:1.75:0.75

Table 4. Compression Coating Tablets with Percent Gum content

The same dissolution procedure for compression coated tablets (CT1, CT2 and CT3) in the absence of rat cecal content were carried out as that of the matrix tablet. The dissolution procedures for CT1, CT2, and CT3 in the presence of rat caecal content were carried out in 0.1N HCl for 2 h and then continued with the pH 7.4 phosphate buffer for 3 h. Then the dissolution study was continued in the presence of rat cecal content to check the susceptibility of guar gum coats to the enzymatic action of colonic bacteria. The rat cecal content medium was prepared by isolating cecal content after opening rat abdomens. Weighed amount of cecal contents were transferred to 300 ml Ph 6.8 phosphate buffer with constant purging of carbon dioxide. To each of the dissolution vessels, 100 ml of cecal slurries was added. [13] The drug release studies were carried out in USP dissolution rate test apparatus (37°C at 100 rpm,) with slight modification. The basket containing tablet immersed in a beaker (capacity 150 ml, internal diameter 55 mm) containing 100 ml of dissolution medium [100 ml of pH 6.8 phosphate buffer containing 4% w/v of rat cecal content] was immersed in the water maintained in the 1000 ml vessel, which in turn, was in the water bath of the apparatus. The 5ml samples were withdrawn then the volume was made up to 10 ml with Phosphate buffer then filtered and the filtrate was analyzed for aceclofenac content at 275 nm and

the same volume was replaced to the dissolution medium [14].

2.2.4.7 Stability Studies [15]

The stability studies were performed as per ICH guidelines at the temperature of 40º C / 75% RH for 3 months. The samples were analyzed for drug content.

2.2.4.8 Statistical analysis

The cumulative percent of aceclofenac released from compression-coated tablets(n=3) in the dissolution medium at 24 h with and without rat cecal contents (control study) was compared, and the statistical significance was tested by using Student’s t-test. A value of P<0.05 was considered statistically significant.

3. Results and discussion

3.1 Evaluation of granules

The angle of repose for all formulation was in the range of 22.68º-24.52º i.e. less than 30(n=3), which indicates good flow properties of the granules. This was further supported by lower compressibility index values below15%, as shown in Table 5. These results indicated well to excellent flow properties.

3.2 Evaluation of tablets

Formulation code

LBD* (g/ml)

TBD* (g/ml)

Carr’s index* (%)

Angle of Repose*(º)

MT1 0.568±0.01 0.648±0.03 14.26±0.02 24.3±0.01

MT2 0.591±0.05 0.66±0.04 12.67±0.04 23.9±0.02

MT3 0.584 ±0.04 0.65±0.03 12.40±0.04 22.68±0.03

XG1 0.568±0.03 0.649±0.04 14.26±0.02 24.52±0.04

XG2 0.584±0.02 0.65±0.02 12.30±0.04 23.95±0.01

XG3 0.591±0.04 0.64±0.02 8.29±0.03 23.52±0.04

*Mean ± SD,n =3

Table 5. Evaluation of granules proper ties

Formulation code

Hardness* (Kg/cm2 )

Friability* (%)

Thickness* (mm)

Weight variation* (mg)

Drug Content* (%)

MT1 4.0±0.2 0.37±0.2 3.85±0.02 400±9 99.36±0.05

MT2 4.2±0.3 0.35±0.3 3.91±0.03 402±11 100.16±0.06

MT3 4.4±0.3 0.41±0.4 3.87±0.02 404±8 98.99±0.04

CT1 4.2±0.2 0.43±0.3 3.93±0.04 428±9 99.51±0.03

CT2 4.4±0.2 0.41±0.4 3.86±0.02 420±11 99.86±0.04

CT3 4.8±0.3 0.43±0.2 3.95±0.04 430±9 99.76±0.02

Core tablet 2.8±0.2 0.45±0.4 2.30±0.04 128±2 99.21±0.03

*Mean ± SD,n =3

Table 6. Evaluation of tablet proper ties



All the formulations showed uniformity in thickness and weight variation. The drug content for all the formulations was found to be between 98.99 to 100.16%. In the present study, the percentage friability for all the formulations was below 0.5% shown in Table 6. All the tablet formulations showed acceptable properties and complied with the in-house specifications for weight variation, thickness, drug content, hardness, and friability were within acceptable official limits.

3.3 Dissolution study

3.3.1 In vitro drug release studies of matrix tablets

When the matrix tablets were subjected to in vitro drug release studies, aceclofenac tablets MT1, MT2 and MT3 remained intact and slightly swollen at the end of 5 h and aceclofenac released from MT1, MT2 and MT3 were found to be 14.52%, 15.72%, and 17.04% respectively. Where as in next 19 h of dissolution study it was 62.40%, 64.40%, and 66.85% respectively is shown in Fig 1. The release of less percent of aceclofenac from the formulations MT1, MT2 than MT3 in 0.1N HCl, pH 7.4 phosphate buffer and pH 6.8 phosphate buffer without rat cecal content (control) was seen because of increased concentration of xanthan gum, which results in increased path length due to formation of viscous gel layer of more thickness. Hence, further studies on the in vitro dissolution of the formulations in rat cecal contents medium were not carried out on formulations MT1, MT2 and MT3 as they also released almost 15 to 17 % of its drug in physiological environment of stomach and small intestine. The results thus showed that the matrix formulations of aceclofenac MT1 MT2, MT3 of GG: XG failed to control the drug release in the physiological environment of stomach and small intestine.

Hence, it was planned to control the release of aceclofenac by preparing compression coated tablets of same GG: XG [1.25:1.25, 1.5:1and 1.75:0.75] ratios.

3.3.2 In vitro drug release study of compression coated aceclofenac tablets

In view of the unsuccessful delivery of the matrix tablets of aceclofenac in the physiological environment of colon, it was essential either to prevent or minimize the release of aceclofenac in the physiological environment of stomach and small intestine. Hence it was planned to apply guar gum and xanthan gum as a compression coat over the fast disintegrating aceclofenac core tablets. The core tablets of aceclofenac were found to have the required characteristics for colon targeting in the form of a guar gum and xanthan gum compression coat over the core tablet. The cumulative amount of aceclofenac released from tablets coated with coat formulations CT1, CT2 and CT3 (1.25:1.25, 1.5:1, 1.75:0.75 of GG: XG) was found to be less than 4% after 5 h of the dissolution study in 0.1 N HCl and Phosphate buffer pH 7.4.

Thus, guar gum and xanthan gum in the form of a compression coat is capable of protecting the drug released in the physiological environment of stomach and small intestine. To assess the integrity of the coats, drug release studies were carried out without the addition of rat caecal contents to pH 6.8 phosphate buffers. At the end of the 24 h of the dissolution study, all the tablets coated with coat formulations CT1, CT2 and CT3 were found intact and the percentage drug release was found to be 27.82%, 30.26% and 32.52%, respectively, as shown in Fig.2.This indicates that until the coat is degraded the gum will not permit the release of the bulk of the drug present in the core tablet. When the dissolution study was carried out in the presence of rat cecal content medium, the percent of aceclofenac released at the end of 24 h from CT1, CT2 and CT3 was 63.75%, 73.36% and 79.90% respectively is shown Fig 3. This is because of the presence of rat cecal content, the guar gum and xanthan gum coat gets degraded by colonic microbial enzymes present in the colon and thus complete drug release occur in the colon.

3.4 Comparison of dissolution profiles of compression coated formulation with and without rat cecal content.

In vitro dissolution studies were carried out in the absence of rat cecal content medium, the percent drug released from aceclofenac tablets coated with coat formulation CT1,CT2 and CT3 at the end of 24 h was found to be only 27.82%,30.26% and 32.52% respectively and the coat was remained intact. In the presence of rat cecal content the percent of drug release at the end of 24 h from the CT1,CT2 and CT3 Fig. 1: Dissolution profile of matr ix tablet without

rat cecal content



was found to be 63.75%,73.36% and79.90% respectively. A significant difference (P<0.001) was observed in the amount of aceclofenac released at the end of 24 h of the dissolution study is shown in Fig 4.

The coat in CT3 was almost degraded in the presence of rat cecal contents thereby releasing the drug into the dissolution medium. Since the xanthan gum content of coat in CT3 (75 mg) was lesser as compared to coat in CT2 (100 mg) and CT1 (125 mg) and the coat might have been completely hydrated and subsequently form smallest path length among all three formulations for movement of aceclofenac from core tablet towards the dissolution medium and resulting in the release of about 79.90 % of aceclofenac from CT3 was observed. The results showed drug release from compression coated formulation in the order of CT3> CT2> CT1.The compression coated formulation CT3 was completely degraded in stimulated colonic fluids whereas CT2 and CT1 formulations were less degraded in stimulated colonic fluids compared to CT3.

The higher proportion of xanthan gum in (CT1) 125 mg, only 63.75% of the drug was released at the end of 24 h of dissolution study. The gel strength of the swollen coat of xanthan gum might be too high and prevented the drug release from the formulation. The colonic bacterial action of the rat cecal medium might not be sufficient to enter in to a high strength gel barrier of the swollen CT1 compression coated formulation. Hence by decreasing the proportion of xanthan gum by 25 mg in CT2 gives only 73.36% of drug release. Therefore decreased the proportion of xanthan gum by 25 mg in CT3 than CT2 gives 79.90 % of drug release at the end of 24 h.

3.5 Stability study

In view of the potential utility of CT3 formulation for targeting of aceclofenac to colon, stability studies were carried out at 40°C / 75% RH for 3 months to assess their long term stability. There is no appreciable change in dissolution profile of CT3 formulation after storage at 40°C / 75% RH for 3 months as shown in Fig 5

Fig. 2: Dissolution profile of CT1, CT2 & CT3 in the absence of rat cecal content

Fig. 3: Dissolution profile of CT1, CT2 and CT3 in rat cecal content

Fig. 4: Percent of aceclofenac released from CT1, CT2 and CT3 formulation with and without rat cecal content

Fig. 5 : Release profile of CT3 before and after stability studies

Conclusion :

The present investigation was carried out to develop colon targeted drug delivery systems for aceclofenac for an effective and safe therapy of colonic diseases. Matrix tablets of aceclofenac MT1, MT2, MT3 (1.25:1.25, 1.5:1, 1.75:0.75 of GG: XG) formulation failed to release the drug in the physiological environment of colon. In view of this result, alternative colon targeted drug delivery systems were developed which could release minimal quantity of aceclofenac until colonic bacteria act upon the formulation. Fast disintegrating aceclofenac core tablets were compression coated with coat formulation containing various quantities of guar gum and xanthan gum in ratio (1.25:1.25, 1.5:1, 1.75:0.75) i.e.CT1, CT2 and CT3.The compression coated CT3 (1.75:0.75 of GG: XG) degraded in dissolution medium containing rat cecal contents



there by releasing 79.90 % of the drug is most likely to provide targeted delivery of aceclofenac to the colon. From the investigation it was clear that compression coated tablet proves to be a novel colonic delivery system as compared to colon targeted matrix tablets.

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