Development and Evaluation of Sustained Release Matrix Tablets Using Natural Polymer as Release Modifier


LP Hingmire*, VN Deshmukh and DM Sakarkar

Department of Industrial Pharmacy, S. N. Institute of Pharmacy, Pusad. Dist: Yavatmal- 445 204. MS. India.

* Corresponding Author E-mail:



In  the  present  investigation,  an  attempt  has  been  made  to  increase  therapeutic  efficacy,  reduce  frequency  of administration, and improve patient compliance, by developing sustained release matrix tablets of diclofenac sodium using natural polymers such as Xanthan gum, locust bean gum, sodium alginate. Sustained release matrix tablets of diclofenac sodium, were developed by using different drug: polymer ratios, such as 1:0.5; 1:1 and 1:1.5. Xanthan gum, locust bean gum, sodium alginate, combination of locust and xanthan, locust and sodium alginate were used as matrix former, the tablets were compressed by direct compression method using 8 mm flat faced punches. Compressed tablets were evaluated for uniformity of weight, content of active ingredient, friability, hardness, thickness, swelling index and in vitro dissolution using paddle method, and swelling index. All the formulations showed compliance with pharmacopoeial standards. Among these formulations, formulation containing combination of locust bean gum and Xanthan gum (6:4) showed sustained release of drug for 12 hours with release of 98.95 %. Optimized formulation was subjected toaccelrated stability studies. Thus, locust bean and Xanthan gum combination can be used as an effective matrix former, to extend the release of diclofenac sodium.


 KEY WORDS              Sustained release, Xanthan gum, locust bean gum, sodium alginate, diclofenac sodium.                     



Matrix system is the most innumerable method used in the development of Sustained release formulations. It is the release system, which prolongs and control release of drug that is dissolved or dispersed. In fact, a matrix is defined as a well-mixed composite of one or more drugs with a gelling agent i.e. hydrophilic polymers.1 the natural polymers are been extensively used in the field   of   drug   delivery   because   they   are   readily available, cost effective, eco-friendly, capable of multitude of chemical modifications, potentially degradable and compatible due to their natural origin. Past research was done on various natural gums like agar agar, guar gum, chitosan, for potential pharmaceutical and biomedical applications.


Diclofenac  sodium  is  a  most  widely  used  NSAID, useful in the treatment of rheumatic disorders, and is characterized by rapid systemic clearance, and thus warrants the use of a Sustained Release formulation for prolonged action, and to improve patient compliance.2,3

Various experimental reports such as solubility, pH, half life, indicated diclofenac sodium as a good candidate for SR formulation.4,5  Few SR formulations of diclofenac sodium   (100   mg)   are   also   available   commercially.


In this study locust, Xanthan gum, Sodium alginate were used  alone  and  combination  of    locust  bean  gum  with xanthan and  sodium alginate  were  used  as  a  hydrophilic matrix polymers for controlling release of sparingly water soluble diclofenac sodium was studied, together with different factors affecting drug release, from the hydrophilic matrix tablets.



Diclofenac sodium (DS) was obtained as gift sample from Alkem   Laboratories   Mumbai.   The   Locust   bean   gum, Xanthan gum, was obtained from Crystal colloids Ltd. Mumbai. Sodium alginate Sulbha gums Bangalore other materials used was of analytical grade, and procured from commercial sources.


Determination of Viscosity of combination of different gums by brook field viscometer

Before  using  the  combination  of  gums  the  viscosity  of 0.5%w/v solution of gums individuals and in combinations were determined, Using brook field viscometer with spindle No.3 at 37 o C. The highest viscosity combination was considered suitable for good polymer for dosage form. (Fig-1)


Preparation of sustained release matrix tablet using natural gums6

Matrix tablets were prepared by direct compression method.  Table-1  shows  composition  of  each  tablet formulation. The formulations are composed of various concentrations of natural gum in the ratios as drug and polymers 1: 0.5, 1: 1 and 1: 1.5 in various percentages. The drug and excipients weighed separately and passed through  100-  mesh  sieve.  Drug  was  added  to  the lactose and the polymer mixture and then blended for 20 min.  at last the lubricants were added and subjected to compression using 8 mm standard flat punch (single punch tablet machine) in to tablets.



Figure:1 Viscosity of various gums in combination with Locust bean gum, AA: Agar agar, SA: Sodium alginate, GG: Guar gum, GGh: Gum Ghutti.


Evaluation of post compression parameters7, 8

All prepared matrix tablets were evaluated for uniformity of weight and drug content, as per I.P. Friability, hardness, thickness, was determined.


In-vitro dissolution study 9

In-Vitro drug release studies for  all  formulations as well as marketed formulation were carried out using dissolution test apparatus USP Type-II at 50 rpm. The dissolution medium consisted of 900 ml of Standard buffer pH 1.2 for the first 2 hrs, followed by pH 6.8 for remaining period of time. Temperature maintained at 37°C ± 0.5°C. Aliquots of 5ml were withdrawn at predetermined time intervals and an equivalent amount of fresh dissolution fluid equilibrated at the same temperature was replaced. Aliquots withdrawn were diluted up to 50 ml with buffer, filtered and analysed by measuring the absorbance at 278 nm.


Kinetic treatment to dissolution data

In order to investigate the mode of release from tablets, the release data of optimized formulation was analyzed with  the  following  mathematical  models:  Q  =  Kot (Zero order kinetic), ln (100-Q) = lnQo-K 1 t (First order kinetic) and Q = Kptn (Korsmeyer and Peppas equation), where, Q is the percent of drug released at time t and Ko and K 1 are the coefficients of the equations. Kp is constant incorporating structural and geometric characteristics of the release device, and n is the release exponent indicative of mechanism of release


Figure 2: Viscosity of various gums in combination with Locust bean gum, GA: Gum Acacia, GT: Gum tragacanth, XG: Xanthan gum, GK: Gum karaya.


Swelling study 10, 11

As the release of drug is proportionate to matrix form, the swelling index was determined by equilibrium weight gain method.   The   study   was   carried   out   in   the   USP/NF dissolution   apparatus   I.   The   polymer   matrices   were accurately weighed, placed in dissolution baskets, immersed in pH 6.8 phosphate buffers and maintained at 37± 0.50C in the dissolution vessels. At regular intervals of 2, 4, 6, 8, 10 and 12 hours, the pre-weighed basket matrix system was withdrawn from the dissolution vessels, lightly blotted with a tissue paper to remove excess test liquid and re-weighed. The swelling index was estimated at each time point using following equation:


(Ws – Wi)

Swelling Index =                               X 100



Where, Ws is the weight of the swollen matrix at time t, Wi is the initial weight of matrix.

Accelerated Stability Study: 12

For determination of stability of prepared different formulations, accelerated stability studies were carried out on optimized formulation. Tablets were stored at 40 ± 2°C/75 ± 5 % RH for duration of one month. After completion of one month sample was withdrawn and tested for different tests such as thickness, hardness, drug content and in-vitro drug release.



The   formulated   matrix  tablets   met   the   pharmacopeial requirement of uniformity of weight. All the tablets conformed to the requirement of assay, as per I.P. Hardness,

% friability, and thickness, drug content were well within acceptable limits.


Table 1: Matrix tablet Formulation table.

(mg)	Drug	Xanthan
Gum	Locust  Bean
gum	Sodium
Alginate	Locust+  Xanthan
Gum (6:4)	Locust +Sodium
Alginate (9:1)	Lactose	Mg.
Stearate	Total Wt
F1	100	50	-	-	-	-	147	3	300
F2	100	100	-	-	-	-	97	3	300
F3	100	150	-	-	-	-	47	3	300
F4	100	-	50	-	-	-	147	3	300
F5	100	-	100	-	-	-	97	3	300
F6	100	-	150	-	-	-	47	3	300
F7	100	-	-	50	-	-	147	3	300
F8	100	-	-	100	-	-	97	3	300
F9	100	-	-	150	-	-	47	3	300
F10	100	-	-	-	50	-	147	3	300
F11	100	-	-	-	100	-	97	3	300
F12	100	-	-	-	150	-	47	3	300
F13	100	-	-	-	-	50	147	3	300
F14	100	-	-	-	-	100	97	3	300
F15	100	-	-	-	-	150	47	3	300


In-vitro dissolution study:

All   the   formulations   were   subjected   to   in-vitro dissolution studies and results are shown in Fig 3-7. From dissolution study it revealed that the formulation F1, F2 and F3 containing Xanthan gum alone showed 101.05±0.65 for 7 hours, 102.43±0.32 for 9 hours and 98.12±0.45 for 10 hours respectively. This showed that as  concentration of  natural gum as  release  modifier increases the rate of drug release from tablet decreases.


This may be because of an increase in polymer concentration causes an increase in the viscosity of the gel as well as the formation of gel layer with a longer diffusional path.   This may cause as decreased in the effective   diffusion   co-efficient   of   the   drug   and therefore a reduction in the drug release rate.


Similarly formulation F4, F5 and F6 containing Locust bean gum alone showed 94.37±0.12, 92.67±0.52 and 87.34±0.21 in 12 hours respectively. Formulation F7, F8 and F9 containing Sodium alginate alone showed 102.34±0.78 for 9 hours, 99.24±0.78 for 9 hours and 104.74±0.96 for 11 hours respectively.


From this result it was found that Locust bean gum retard more drug as compared to Xanthan gum and Sodium alginate. Hence drug release retardation from these three gums was found to be in following order.


Locust bean gum > Sodium alginate > Xanthan gum

Results also showed that, formulation F10, F11 and F12 containing combination of Locust bean gum and Xanthan gum in the ratio of 6:4 showed 103.85±0.15 for 11 hours, 98.95±0.42 for 12 hours and 87.64±0.85 for 11 hours. Similarly, formulation F13, F14 and F15 containing  combination Locust bean gum and Sodium alginate in the ratio of 9:1 showed 107.64±0.23 for 11 hours, 90.24±0.42 for 12 hours and 85.12±0.17 for 12 hours. This showed that combination of Locust bean gum and Xanthan gum showed more drug retardation than that of combination of Locust bean gum and sodium alginate. Hence drug release retardation from these combinations of gums was found to be in following order


(Locust bean gum+ Xanthan gum) > (Locust bean gum+ Sodium alginate)


Figure 3: Dissolution profile of formulation F1, F2, F3 and marketed product


Figure   4:   Dissolution   profile   of   formulation   F4,   F5,   F6 marketed product


Figure 5: Dissolution profile of formulation F7, F8, F9 marketed product



In-vitro drug release of all formulations (F1-F15) was also compared with the marketed preparation. The results showed that the drug release profile of formulation F11 resembles with that of marketed formulation. Hence formulation F11 containing combination of Locust bean gum and Xanthan gum in the   ratio   of   6:4   was   considered   as   optimized formulation used for further study.


Figure 6: Dissolution profile of formulation F10, F11, F12 and marketed product


The kinetic treatment reflected that release data of F11 showed R2 value of 0.9542 and 0.9920  for first order, and zero order equation respectively, indicating that release  of  drug  follows  zero  order  kinetic  Further Korsmeyer and Peppas equation resulted into the value of n = 0.3490, which is close to 1, indicating that the drug release was approaching zero order kinetics. Accelerated stability study on F11 formulation showed that there  was  no  considerable change in  thickness, hardness  and  drug  content  also  there  was  no  any difference found between dissolution profile before and after stability. Hence tablet prepared by using natural gums as release modifier was found to be stable.



The  authors are  grateful  to  Alkem  Laboratories Mumbai

providing gift sample of diclofenac sodium. Crystal colloid, for locust bean gum, xanthan gum, sulbha gums and sodium alginate.


Figure7: Dissolution profile of formulation F13, F14, F15 and marketed product



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Received on 09.06.2008    Modified on 10.07.2008

Accepted on 25.08.2008   © RJPT All right reserved

Research J. Pharm. and Tech. 1(3): July-Sept. 2008; Page 193-196