INTRODUCTION:

Colon specific drug delivery is desirable for the local treatment of variety of bowel diseases, for improving the systemic absorption of drug susceptible to acidic inactivation or enzymatic degradation in upper GIT¹. Sustained, targeted colonic delivery of drug is also useful in conditions like nocturnal asthma, angina and arthritishaving diurnal rhythm.² Various approaches that are utilized for the colonic drug delivery include³.

Coating with pH dependent system.

Time released dosage forms.

Carriers that are degraded exclusively by colonic bacteria.

Gums are natural plant hydrocolloids that are anionic or non-ionic plant polysaccharides. The plant polysaccharides such as amylose, inulin, pectin, guar gum remain unaffected in presence of gastrointestinal enzymes and once they reach in the colon they are acted upon by the vast microbial flora. The microbial action results in digestion of polysaccharides (gums) to monosaccharides units used as energy source by microbial flora⁴. Thus simplest way and interesting option is incorporation of drug in the gum matrix which will prevent the release in the upper GIT and upon action of microbial flora in colon the drug will get released.

This approach has good site specificity , therapeutic relevance and also the natural gums are biodegradable, non- toxic, approved falling under the category of “GRAS” (Generally Regarded As Safe) and with the use of these, the general problems associated with safety are resolved. The objective of present work was to formulate colon specific matrix tablet using Guar gum and Xanthan gum and also to study the suitability of the gums as coating material. The model drug used was 5-Amino Salicylic Acid, which is active moiety of Sulfasalazine, a prodrug, and the drug of choice for treatment of ulcerative colitis.⁵ The study was also aimed at to elucidate the release pattern from the matrix and coated tablets in presences of human feces containing 30% of bacteria as a source of microbial flora.

MATERIALS AND METHODS:

5-Amino Salicylic Acid was supplied generously by SUN Pharmaceutical Ltd Mumbai. Guar gum was provided by ACE gum Industries Mumbai. Xanthan gum from Cp Kelco Ltd. USA. All other excipients and reagents were of analytical grade and distilled water was used.

Preparation of Tablets:

The matrix tablets were prepared containing 200 mg of 5-Amino Salicylic Acid, Guar gum, Xanthan gum individually and in combination. The formulation details are given in Table 01

The tablets were prepared by wet granulation method. 10% starch paste was used as binding agent. Dibasic calcium phosphate was incorporated as filler excipient to maintain tablet weight constant. The damp mass prepared was passed

TABLE.NO.01 : FORMULATION OF 5-AMINO SALICYLIC ACID MATRIX AND COATED TABLET:

Sr. no	Ingredients mg/tab	G1	G2	G3	G4	G5	X1	X2	X3	XG1	XG2	XG3	P
1	5-Amino salicylic acid	200	200	200	200	200	200	200	200	200	200	200	200
2	Guar gum	22.5	45	67.5	90	135	-	-	-	45	90	67.5	--
3	Xanthan gum	-	-	-	-	-	45	90	135	90	45	67.5	---
4	Starch (as 10%paste)	45	45	45	45	45	45	45	45	45	45	45	30
5	Dibasic calcium phosphate	160	137.5	115	92.5	47.5	137.5	92.5	47.5	47.5	47.5	47.5	52.5
6	Talc	22.5	22.5	22.5	22.5	22.5	22.5	22.5	22.5	22.5	22.5	22.5	17.5
7	Total weight	450	450	450	450	450	450	450	450	450	450	450	300

Fig.No.01: Cumulative percent drug release from Guar gum matrix tablet.

Fig.No.02: Cumulative percent drug release from Xanthan gum matrix tablet.

through sieve # 8. The granules were dried at 45^oC for 8 hrs. The dried granules were passed through # 16. Prepared granules were lubricated with talc.

Granules were evaluated for angle of repose, % compressibility that was found to be within desirable limits.⁶

The granules were compressed into tablets on Cadmach single station tablet compression machine with 10mm concave punches. The total weight of matrix tablet was 450 mg. A batch of 1000 tablets was prepared for each formulation.

Coating of tablets:

The drug-loaded tablets without gums were coated in two batches, one with Guar gum and other with Xanthan gum. The composition of the coating solution used is given in Table. No. 02, and Table. No. 03. Operational variables for coating process are tabulated in Table no 04

Fig. No.03: Cumulative percent drug release from Guar gum and Xanthan gum combination matrix tablets.

Fig.No.04: Cumulative percent drug release from Guar gum and Xanthan gum coated tablets.

Evaluation of Tablets:

The prepared matrix tablets and the coated tablets were evaluated for hardness, friability, weight variation, content uniformity ⁷. Hardness of the tablet was tested with Monsanto Hardness tester. Friability of tablets was determined using Roche Friability Apparatus. Weight variation test was performed as per official method.⁸Thickness of tablet was measured with Venire Caliper. Drug content uniformity test for 5- amino salicylic acid was carried out by measuring the absorbance of samples at 330 nm using spectrophotometer (Systronic-117). The absorbance was compared with the calibration curve to determine the concentration of drug.

In Vitro Drug Release Studies:

Dissolution studies were carried out in USP dissolution apparatus XXI (Type I apparatus, 100 rpm, 37^oC) Initial drug release studies were carried out in 900ml of hydrochloric acid buffer pH 1.2 for 2 hrs. This was followed by 3 hrs study in phosphate buffer pH 6.8. As the media is supposed to contain the microorganisms for degradation of gums, a modification of the method and apparatus was done. The dissolution study was performed in 250 ml conical flask (instead of 900 ml vessel) immersed in the water present in outer jacket of dissolution apparatus maintained at 37 + 0.5 ^o C. The conical flask was corked and through it the rotating shaft with basket assembly was passed. At 6^th hr of study fresh human feces, 25 g ,were added to it to get the 10% fecal concentration in the media. Feces contain bacteria about 30% of its dry weight⁹ were used to simulate the colonic microbial environment for degradation of gums.

TABLE.NO.02: COMPOSITION OF GUAR GUM COATING SOLUTION

INGREDIENTS

QUATITY

Guar gum

Titanium dioxide

Polyethylene glycol- 600

Purified water upto

5 g

1 mg

1 ml

100 ml

TABLE.NO.03 : COMPOSITION OF XANTHAN GUM COATING SOLUTION

INGREDIENTS

QUANTITY

Xanthan gum

Titanium dioxide

Polyethylene glycol-600

Purified water upto

1 g

1 mg

1 ml

100 ml

Dissolution fluid was withdrawn at the one hour interval for 12 hr and samples were analyzed spectrophotometrically at 302 nm for buffer pH 1.2 and at 330 nm for phosphate buffer pH 6.8. Drug content was determined from standard curve in respective medias. The media was replenished with same amount of dissolution medium previously warmed at 37+ 0.5 ^oC.¹⁰

TABLE.NO. 04: THE PROCESS CONDITIONS MAINTAINED DURING COATING PROCESS.

Sr .No

Process parameters

Setting for coating pan

Equipment speed

Tilt angle of pan

Spray gun location

Air pressure

Gun to bed distance

Spray rate

Inlet air temperature

Exhaust

Hot air blowing

30 RPM

45^o

Top spray perpendicular to tablets

1 bar

8 cm

2-3 ml/min

35^o

Kept on

Continuously kept on

One set of study was carried out without the introduction of feces maintaining other conditions same to study the effect of microbial flora present in feces on degradation of the gums.

Statistical Data Analysis:

The release profiles of different batches were subjected for statistical analysis using KORSMEYER PEPPAS EQUATION¹¹.

Mt/M¥ = Ktⁿ

Where,

Mt/Mœ = fractional release of drug.

K = constant of geometrical and structural area of device.

n = diffusinal exponent.

t = time.

Fig. No. 05: Effect of feces on the release profile

Fig. No. 06: Stability study release profile.

Drug Excipients Interaction Study:

The IR analysis was done for the pure drug and the formulation XG3 having the equal proportion of both the gums used along with other excipients to study the drug excipient interaction.

Stability Studies:

The accelerated stability studies were carried out in B.O.D. incubator maintained at 45^o C temperature and relative humidity of 75 + 5 %. Sample of 10 tablets were kept in the incubator for 45 days and after specified time they were analyzed for the drug content and the release pattern.

RESULT AND DISCUSSION:

The of hardness of matrix tablet was found in range of 7.2 + 0.2 Kg/Cm² to 7.8+ 0.4 Kg/Cm²and that of coated tablet was 4.8 + 0.2 Kg/Cm² to 5.2 + 0.2 Kg/Cm². The friability was found in the range of 0.18 to 0.40 % for matrix tablet and that for coated tablet was 0.11 to 0.22 %.

The content of 5-amino salicylic acid in all formulations was 100 + 5 % of labeled amount. All the batches of prepared tablets were of good quality with respect to hardness, friability and drug content. The results obtained were within limit given in the official compendia.

TABLE.NO.05: EVALUATION OF 5-AMINO SALICYLIC ACID MATRIX AND COATED TABLETS

Batch no.	% Friability	Hardness (Kg/cm²) (Mean + .S.D.)	Weight variation (mg) (Mean +. S.D.)	Thickness (mm) (Mean + S.D.)	Content uniformity (%)
G1	0.37	7.2 + 0.2	457 + 12	3 + 0.1	99.48
G2	0.27	7.2 + 0.3	450 + 14	3 + 0.2	100.02
G3	0.40	7.4 + 0.2	449 + 12	2.8 + 0.1	100.46
G4	0.30	7.8 + 0.4	451+ 17	2.9 + 0.3	99.62
G5	0.18	7.8 + 0.3	459 + 14	3.1 + 0.3	99.14
X1	0.30	7.4 + 0.2	460 + 15	2.9 + 0.4	99.68
X2	0.32	7.4 + 0.3	458 + 08	3.1 + 0.3	100.76
X3	0.29	7.6 + 0.2	449 + 11	2.9 + 0.2	98.98
XG1	0.18	7.8 + 0.3	461 + 13	2.9 + 0.1	101.04
XG2	0.22	7.6 + 0.4	455 + 17	3 + 0.2	100.48
XG3	0.28	7.6 + 0.3	460 + 12	3.1 + 0.4	99.34
GC	0.11	4.8 + 0.2	391 + 07	4.2 + 0.3	99.56
XC	0.12	5.2 + 0.2	346 + 09	4.2 + 0.2	99.56

5-amino salicylic acid released from different formulations was slow and extended over longer period of time. The results of dissolution study of different formulations are shown in fig. 1, to fig 4.

From the fig 1 it was observed that guar gum in matrix tablet with concentration of 5 % has no relation with bacterial degradation and drug gets released rapidly where as at 15 % concentration of guar gum the release was maximum in the colonic simulated environment in presence of microflora of human feces. Increase in the concentration of guar gum to 20 %has not significantly altered the release pattern. At the concentration of 30 % the release was 50.78 % at 9 ^thhrs of study, which is very slow.

For Xanthan gum matrix tablet, fig 2, it was observed that with the increase in gum concentration there was decrease in drug release with time. The rise in the drug release in presence of microbial environment was not observed.

From fig 3, for the combination of guar gum and xanthan gum, it was observed that the drug release from the GG: XG (15:15) is much retarded as compare to other combinations. This can be explained on the basis that on exposing the tablet to the dissolution media, the gums with synergistic gelling properties form a viscous gel that slows down the further seepage of dissolution fluid in to the tablet. The initial delay in drug release can also be attributed to the time taken for the glassy to rubbery transition by the gum combination the drug present on the surface of the tablet accounts for the initial release seen.¹²

From the observation and graph it was observed that the drug release from the Xanthan gum coated tablet was very slow as compared to the guar gum coated tablet upto 6^th hr of study after which there was no considerable difference in the release pattern from both tablets. The release from the guar gum coated was purely because of the microbial degradation of the gums while Xanthan gum only acted as release-retarding material. The aqueous coating process was difficult due to viscosity of the gums and slow evaporation of the solvent used. Moreover the films formed where hard.

The effect of the microbial flora introduced in the form of human feces is seen from (fig 5). It was observed that the in the absence of feces the release was decreased greatly as compared to release in presence of feces. This indicates the activity of the microbial flora present in the feces towards the degradation the gums.

The drug released in absence of feces at the end of 12 hr was only 48.83%.

Statistical data analysis done using Korsmeyer Peppas Equation had shown the formulation G4 having the value of n=1.0668 has the best release pattern and it follows the zero order kinetics. Stability studies suggest no change in the physiochemical characteristics of the formulation G4. The drug content was within limit. The release pattern was also nearly same after 45 days. (Fig 6).

Thus it can be concluded that the prepared matrices using guar gum where enzymatically degraded by the colonic microbial flora. The Xanthan gum matrices retard the drug release and show release in the colonic environment. When the two gums were used in combination the Xanthan gum retarded drug release in the upper GIT while the Guar gum was enzymatically degraded by the colonic microflora. Thus the system acted as timed-release system as well as the enzyme-controlled system. Gums used as a coating material were not desirable because of viscosity problems in aqueous media.

ACKNOWLEDGEMENT:

Our sincere thanks to SUN Pharmaceutical Ltd. Mumbai, and Cadila pharmaceutical Ltd, Ahmedabad for generously providing the gift sample of 5- Amino Salicylic Acid. We are also thankful to ACE gum industries, Mumbai for providing the gift sample Guar gum, to CpKelco Ltd USA for complimentary sample of Xanthan gum. We are thankful to Dr.N.J.Gaikwad, Head, Department of Pharmaceutical sciences, Nagpur University for IR studies.

REFRENCES:

1) Chourasia, M.K.; Jain, S.K.; J.Pharm. Sci. 6 (1) 2003; p.33-66.

2) Yang, L., Chu, J.S.,Fix, J.A. Int.J.Pharm.235, 2002 p. 1—15.

3) Gazzaniga, A; Giordano; Sangalli, M.E; Zema, L; “Oral Colon –Specific Drug Delivery: Design Strategies”: S.T.P. Pharma Pratiques (France), V4, (5), 1994 p. 336.

4) Sinha V. R. , Kumria R., Int. J. Pharm., 224, 2001,p.19–38.

5) Eugene Braunwald; Kurt J. Isselbacher; Robert G.Petersdorf; Jean D. Wilson; Joseph B.Martin; Antony S. Fauci. Harrison’s Principles of Internal Medicine- 11^th Edn 1987 . Vol.2 Mc. Graw Hill Company. Newyork. p 1277-1290.

6) Leon Lachman; Liberman, H.A.; Kanig, J.L.; The Theory and Practice of Industrial Pharmacy; III edn.1990. Varghese publication House, Bombay. p.316-317.

7) Leon Lachman; Liberman, H.A.; Kanig, J.L.; The Theory and Practice of Industrial Pharmacy; III edn.1990. Varghese publication House, Bombay. p. 297-299

8) Indian Pharmacopoeia, Vol II, Govt. of India, Ministry of Health and Welfare, 1996, p.734-736.

9) www.britannica.com/eb/article-9033888/feces.

10) Jain, S.K.; Chourasia, M.K.; Dengre, R.; Indian J.Pharm. Sci. 2005, 67 (1): p. 43-50.

11) Sanford Bolton, Pharmaceutical Statistics, 3 ^rded. 1997, Marcel Dekker, p. 216-263.

12) Colombo P. , Bettini R. , Santi P. , Peppas N. A., Pharm. Sci. Technol. Today, 3 , 2000 , p.198–204.

Received on 14.03.2009 Modified on 17.05.2009

Research J. Pharm. and Tech.2 (4): Oct.-Dec. 2009; Page 705-709

HK Kunjwani1*, AM Manikrao1 ,Rajesh KS1, Sable VP3 and NH Indurwade2