Chitosan and Hydroxy Propyl Methyl Cellulose as a Carrier for Aceclofenac for Prolonged Release

Numerous natural polymers either alone or in combination with other polymers were found effective in controlling the drug release. In this study the attempts were made to combine chitosan (degree of deacetylation 84.14 %) and as hydroxylpropyl methylcellulose (HPMC K 15M) to retard the release of aceclofenac in tablet formulation. The tablets were prepared by wet granulation and evaluated for pre and postcompression parameters. All the pre-compression parameters were found within the limit. Hardness and friability values were found in the range of 4.30-4.89 kg/cm and 0.1-0.6% respectively. These results proved the good mechanical strength of the formulations. The drug content was found in the range of 97.56 – 99.10 %. Weight variation was found within the official limit. The percent drug release and swelling index was found to be dependent on the concentration of polymer. With increasing the concentration of both the polymers the swelling index Original Research Article Katedeshmukh et al.; JPRI, 33(32A): 173-182, 2021; Article no.JPRI.69212 174 was increased and drug release decrease. Highest concentration of both the polymers was found to retard the drug release up to 8 h. The effect of Chitosan and HPMC on drug release was evaluated by design expert software to achieve the optimized formulation. The response of the drug release after 4h was considered to check the drug release. It was found that the enhanced concentration of both the polymers had negative effective on the drug release. The formulation containing highest concentration of the chitosan and HPMC was found be fit in the limits of optimized formulations. The optimized formulation was found to be stable at accelerated stability storage conditions.


INTRODUCTION
Tablets are solid dosage forms containing a single dose of single or multiple active pharmaceutical ingredients obtained by compressing uniform volumes of particles and intended for oral administration. They are most commonly prescribed dosage form offering convenience of drug administration, providing tablet to tablet drug uniformity and stability over extended and diverse storage conditions [1].
Advancement in tablet production technology has resulted in newer modified release oral dosage forms. Sustained-release tablets are one of such dosage forms which are designed to control drug release profile at a specific rate to obtain desired concentration of drug either in blood plasma or site of action [2]. They provide several advantages such as reduced frequency of dosing, sustained concentrations of drugs in blood, uniform drug delivery, reduced adverse effects, enhanced efficacy of drug at the desired site of action, increasing the time of action and enhanced patient compliance over conventional oral tablet dosage forms. Sustained release has received the attention of researchers because of feasibility in dosage form in providing release of the medication for extended time period and obtaining desired therapeutic action after administration of single dose [3].
Sustained release oral tablet dosage forms are formulated by coating the tablets by the polymers involved in retarding the drug release in order to regulate the solubility rate or by encapsulating the drug in the form of microparticles of different sizes using polymers to control the dissolution rate. Several natural polymers such as natural gums, natural silk, mucilages, natural rubber, proteins, starch, cellulose etc. obtained natural sources are used in the formulation of sustained release tablets [4].
Chitosan, a naturally occurring polysaccharide is one of such natural polymers used in the formulation of sustained release tablets. It is a deacetylated chitin derivative, comprising copolymers of N-acetylglucosamine and glucosamine. Chitosan is a most widely used biodegradable and biocompatible cationic polymer because of its properties such as reduced toxicity and improved patient compliance. Structurally it possesses 1-4 linked 2-acetamido-2-deoxy-β-D-glucopyranose as well as 2-amino-2-deoxy-β-D-glucopyranose [5].
Solubility of chitosan is critically associated with its deacetylation degree, molecular weight and the pH value of its aqueous solution. Chitosan is practically insoluble in water and common organic solvents but can be easily solubilised in acidic aqueous solutions below pH 6.3. Low degree of deacetylation (55-70%) makes chitosan completely insoluble in water, Medium deacetylation degree (70-85%) is renders it partly soluble in water while high degree of deacetylation (85-95%) enhances solubility of chitosan in water. Ultrahigh degree of deacetylation (95-100%) of chitosan is difficult to achieve. Reducing the molecular weight of chitosan by inducing degradation is plays an important role in enhancing its aqueous solubility in water [6].
Cellulose ethers such as hydroxylpropyl methylcellulose (HPMC), are widely used as the basis for sustained release hydrophilic matrix tablets. Its characteristics as gelling agent are very useful in the formulation of sustained release tablets as it forms an erosion and diffusion resistant gel layer by hydration which is involved in control drug release [7].
Acceclofenac being a nonsteroidal antiinflammatory drug (NSAID), is used for the treatment of pain and several inflammatory disorders such as rheumatoid arthritis osteoarthritis and ankylosing spondylitis. Aceclofenac inhibits the cyclo-oxygenase enzyme (COX) involved in prostaglandins (inflammatory mediators) synthesis responsible for pain, fever inflammation and swelling. Aceclofenac being a BCS Class II drug exhibits poor water solubility which leads to dissolutionrelated absorption problems [8].
The present investigation aims to develop the sustained release tablet formulation to retard the release of acelofenac. It has short half-life of 2-4 h hence to reduce the dosing frequency it is need to develop sustained release formulation. The chitosan (degree of deacetylation 84.14 %) and HPMC K 15M were used in combination to retard the release of aceclofenac. The effect of these polymers on drug release was studied.

Material
Aceclofenac was obtained as gift sample from Aarti Drugs, Mumbai. Chitosan (degree of deactetylation (84.14%, molecular weight 540 kDa) was procured as gift samples from India Sea Foods, Kerala. HPMC was obtained from Anshul Life Sciences, Mumbai as gift sample. All the solvent used for the study were of analytical grade.

Methods
Matrix tablet containing Chitosan and HPMC K 15M was prepared by wet granulation method. 3 2 factorial design was used to prepare the different batches by selecting Chitosan and HPMC K 15M as independent variables and drug release was chosen as dependent variables. All the batches prepared with 100 mg of Aceclofenac and various concentration of chitosan and HPMC as shown in Table 1. Briefly, all the ingredients were weighed and passed through sieve no 40. Further homogeneous mixing was carried out and granules were prepared by starch paste as binder. Wet granules were dried by tray dryer at the temperature of 40-50 0 C and passed through sieve no 30. Before compression granules were lubricated with talc and magnesium stearate and flow characteristics of granules were evaluated. The compression was carried out by 10 station tablet compression machine (Karnavati Co. Ahmedabad), 8mm punch was used to obtain the weight of 250 mg of each tablet [9].

Preparation of matrix tablets containing chitosan and HPMC K 15M
Matrix tablet containing Chitosan and HPMC K 15M was prepared by wet granulation method. 3 2 factorial design was used to prepare the different batches by selecting Chitosan and HPMC K 15M as independent variables and drug release was chosen as dependent variables. All the batches prepared with 100 mg of Aceclofenac and various concentration of chitosan and HPMC as shown in Table 1. Briefly, all the ingredients were weighed and passed through sieve no 40. Further homogeneous mixing was carried out and granules were prepared by starch paste as binder. Wet granules were dried by tray dryer at the temperature of 40-50 0 C and passed through sieve no 30. Before compression granules were lubricated with talc and magnesium stearate and flow characteristics of granules were evaluated. The compression was carried out by 10 station tablet compression machine (Karnavati Co. Ahmedabad), 8mm punch was used to obtain the weight of 250 mg of each tablet [9].

Evaluation of granules
The prepared granules were evaluated for different flow properties as follows: [10].

*All weights in mg 2.2.2.2 Tapped density
The samples were taken for the evaluation of bulk density were subjected to tapped density test apparatus and tapping was done for 100 times and volume occupied by granules were noted.
Tapped density = Mass of granules/ Tapped volume

Carr's index
The Carr's compressibility index was determined by the values obtained for bulk and tapped densities by the following formula, Carr's index (%) = (Tapped density-Bulk density/Tapped density) X 100

Hausner's ratio
It was calculated by the formula, Tapped density/ Bulk density.

Evaluation of tablets
Prepared tablets were evaluated for the following parameters as listed in Indian Pharmacopoeia [11].

Weight variation test
It was carried out by randomly weighing 20 tablets individually and calculating the average weight. Later the weight of each tablet was compared with average weight. Tablet was considered as passed the test when they did not deviate ± 7.5% of average weight.

Hardness test
Pfizer hardness tester (Model PTB 411, Dolphin instruments) was used for the determination of the hardness of the tablets.

Friability test
The Friability of the tablets was determined using Roche friabilator (model-EF-2, Electrolab). 10 tablets were weighed and subjected to Roche friabilator for 25 revolutions per minute and after the test tablets were de-dusted and reweighed. The friability was calculated by using formula: % Friability = (1-Weight of tablet before the test/ Weight of tablet after the test) X 100

Thickness test
The crown-to-crown thicknesses of five tablets from each batch were determined using a digital vernier caliper (Mituyoto) and average values were calculated.

Swelling behaviour of matrix tablets
One tablet from each formulation was kept in a petri dish containing pH 6.8 phosphate buffer. The matrices obtained were circular in shape with 8-mm diameters. Hence, concentric circles were drawn with diameters of 7, 8, 10, 12, 14, 16, 18, 20mm. The paper was laminated to make it hydrophobic. On either side of this piece, special arrangements were made to facilitate the raising and lowering of the assembly. The concentric circles were drawn to measure the increase in the radial direction, and the diameter of the outermost circle arbitrarily was fixed at 20 mm as the matrices underwent total disintegration/dissolution above this parameter [12].

In-vitro drug release studies
The In-vitro dissolution studies were carried out using USP TDT-08L (Electro lab, Mumbai.) apparatus at 37±0.5 o C and at 50 rpm for 8 hrs.
The dissolution medium used was 900 mL phosphate buffer pH 6.8. At predetermined interval 10 mL of sample was withdrawn from the dissolution medium and replaced with fresh medium to maintain sink condition. After filtration and appropriate dilution, the sample solutions were analysed by UV-visible spectrophotometer [13].

Statistical Analysis
It was carried out by ANOVA by using design expert software.

Stability Studies
Stability study was carried out as per ICH guidelines on selected formulations. The formulations were selected on the basis of cumulative % drug release at 4 hrs. analysed Design Expert software. Parameters mainly % drug contents and cumulative drug release were measured [14].

RESULTS AND DISCUSSION
Tablets containing Aceclofenac were prepared to study the effect of chitosan and HPMC 15M on the drug release. Tablets were prepared by wet granulation technique and evaluated for flow properties; the result is summarized in Table 2. Flow properties are important for uniform flow of material from hopper to die. Poor flow properties results in the weight variation and content uniformity of tablet. Carr's index in the range of 5-15 was desirable to achieve excellent flow properties whereas value of Carr's index greater than 40 showed extremely poor flow properties.
Hausner's ratio near about 1.2 and 1.6 was indicative of low inter-particular friction and more cohesive forces respectively [15,16].

Evaluation of Tablets
Prepared tablets were evaluated for different parameters as per the pharmacopoeia. Hardness and friability are indicative of mechanical strength of the tablet. The mechanical strength is important factor for tablet which generally denotes capability of tablet to withstand the force during transportation and handling of tablets.
Hardness of the tablets depends on compactness of granular mass and the compression force. For the different batches hardness and friability value ranged from 4.03-4.89 Kg/cm 2 and 0.1-0.6% respectively. These values were indicative of good mechanical strength as hardness values between 4-5 Kg/cm 2 and friability less than 1% are desired for good mechanical strength [17]. Weight variation and content uniformity test was important to determine the uniformity of the weight of tablet and uniform drug distribution within the tablet respectively. These parameters were very important for uniform dose distribution and ultimately bioavailability of the drug. These depend on uniform mixing and flow properties of the powder or granules [18]. The results of evaluation were shown in Table 3.

Swelling behaviour of matrix tablets
After exposure to media the penetration of the solvent into the tablet resulted in hydration swelling and formation of gel. The larger exposure area of the radial surface increases the process of swelling. The extent of swelling was measured in terms of radial swelling of the tablet. These measurements are represented graphically in Fig. 1.

Fig. 1. Radial swelling of formulations
It was observed that chitosan matrices preferentially undergo radial swelling. This could be attributed to the acetyl substitution on the polymeric backbone. This substitution would be contributing towards radial relaxation favourably. These results were in agreement with the research carried out by the Nunthanid et. al. [19]. HPMC was also contributing the swelling of the matrices. HPMC enhances the water uptake rate by the tablet resulting in rapid swelling and transition from glassy to rubbery state. This transition leads to disentanglement of the polymer chains [20]. The graph showed that with highest concentration of both the polymer swelling was also increased (Formulation VI).

In-vitro drug release studies
The effect of degree of deactylation of chitosan on the release of aceclofenac was studied along with the effect of combination of chitosan with HPMC. The release of drug with respect to time is shown in Fig. 2.
Chitosan and HPMC were combined in different concentration and release of the drug was determined. It has been observed that highest concentration of both the polymer could retard the drug release for 8 hrs. and individual polymer at highest concentration could retard the drug release for 6-7 hrs. The various combinations at low concentration of polymer could retard the drug release up to 6 hrs. The combination of low and high concentration of polymer could retard the drug release up to 7 hrs. These results might be attributed to formation of viscous gel layer depending on the polymer concentration and subsequent release of the drug. At higher concentration the drug release rate is low due to formation of more viscous layer that hinder the diffusion of drug [21]. Formulations having n values close to 0, release become increasingly matrix type. This is due to resulting in formation of matrix. The system no longer remains a reservoir, barrier membrane diffusion controlled one but transforms into a monoblock of drug and polymer. In case of HPMC matrix tablets, the release pattern in 6.8 phosphate buffer, shows n values depicting matrix or first order. In this case the contribution of the polymer degree of deacetylation plays very important role. The disruption of release controlling mechanism leads to significant changes in n values. For HPMC matrix the n value was less than 0.5 indicating Peppas or Higuchi or Matrix pattern. For these formulations, the n value is further away from 0.5 towards zero indicates diffusion through membrane as predominant mechanism of drug release as against the swelling controlled drug release seen in case of chitosan matrix [22].

Optimization
The effect of chitosan (X1) and HPMC K15M (X2) on drug release was evaluated by using design expert software. The data was statically analysed by ANOVA. All the responses observed for nine formulations prepared were fitted to various models using Design-Expert® software and following graphs were obtained.
It was observed that the best-fitted model was linear for the response drug release at 4 h. The values of R2, adjusted R2, predicted R2, SD and % CV are given in Table 4, along with the regression equation generated for each response. The results of ANOVA in Table 5 for the dependent variable demonstrate that the model was significant for the response variable. It was observed that independent variables X1 (Chitosan concentration) and X2 (concentration of HPMC K15 M) had a negative effect on drug release (Y). The coefficients with more than one factor term in the regression equation represent interaction terms. It also shows that the relationship between factors and responses is not always linear. When more than one factor are changed simultaneously and used at different levels in a formulation, a factor can produce different degrees of response.

Stability Studies
The selected formulations were kept for Accelerated stability at 40°C±2°C and 75% RH ±5% RH. The samples were withdrawn at a regular time interval. The formulations were tested for different parameters like % drug contents and cumulative drug release were measured and the results of accelerated stability studies are shown in Table 6.