Optimization of Coating Solution for Preparation of Sustained Release Tablet

S Vaghasia, V Kanthiya, S Das*, R K Sethi and A Choudhury

Department of Pharmaceutics, GRY Institute of Pharmacy Borawan, Khargone- 451228(MP)

ABSTRACT

In this study, tablets were formulated by wet granulation technique taking Paracetamol as model drug. Three mucoadhesive polymers namely hydroxyl propyl methyl cellulose K4M, methyl cellulose and poly vinyl pyrolidone were used for preparation of coating solution (1%,2% and 3%) as well as for development of sustained release tablets. All the evaluation were carried out before and after coating like thickness and diameter, weight variation, friability, disintegration, swelling index, Mucoadhesive strength, drug content and in-vitro release study. All the physical evaluation parameters were increases after coating when compare with normal tablet. Normal tablets were showed 95% release within 30 min where coated tablets showed 98% release over a period of 6hr. in water and release was diffusion controlled confirmed by Higuchi’s plot. Thus, the present study concluded that, we can development of sustained release formulation can be possible by coating using the mucoadhesive polymers.

KEYWORDS: Punch, Coating, Diffusion, Sustained

INTRODUCTION

Tablet coating is a process of manufacturing which needs personnel attention during production of coated formulation because picking, roughness, bridging, blistering and cracking are the main problems arise if the dried condition is improper but it is a beneficial like mask the taste, odour, colour of drug, physical and chemical protection for the drug, control release of the drug from the tablet, improve product stability and modified drug release characteristics. Mainly two types of coating process are used in industry i.e. Film coating and Sugar coating but improper coating can affect the release of drug from the dosage form. To avoid this coating process, other techniques can be applied for the preparation of sustained release formulation using solid dispersion¹, using Indian resin², using mucoadhesive polymers³ and preparing matrices⁴ etc. but all the techniques raise the cost of production. In this study we develop or optimize the coating solution which can be used for the preparation of sustained release formulation with reduced cost.

MATERIAL AND METHOD

Paracetamol was gift sample of Aristo, Bhopal. Hydroxypropyl methylcellulose K4M (HPMC -K4M) and Methyl cellulose were supplied by Loba Chemie Pvt.Ltd., Mumbai and polyvinyl pyrrolidone was supplied by central drug house (p) Ltd. New delhi.

Drug–Polymer Interaction study:

Drug and polymer interaction study was carried out by using Fourier Transform Infrared (FTIR–8400S, Shimadzu Corporation, Japan). Samples were triturated with Potassium bromide and transformed into disk. Disk was applied to the centre of the sample holding device and scanned between 4000–400cm^–1 at a resolution of 2 cm^–1. The IR scans were processed using IR Solution and represented as percentage transmittance (%T) on a common scale.

TABLE I: COMPOSITION OF PARACETAMOL TABLETS AND COATING SOLUTION.

Ingradient	Quantity(mg)	Solution			Solution			Solution
Ingradient	Quantity(mg)	1%	2%	3%	1%	2%	3%	1%	2%	3%
Paracetamol	500	-----	-----	-----	-----	-----	-----	-----	-----	-----
Calcium carbonate	100	-----	-----	-----	-----	-----	-----	-----	-----	-----
Magnesium carbonate	75	-----	-----	-----	-----	-----	-----	-----	-----	-----
Zinc sulphate	24	-----	-----	-----	-----	-----	-----	-----	-----	-----
Magnesium stearate	0.5	-----	-----	-----	-----	-----	-----	-----	-----	-----
Talc	0.5	-----	-----	-----	-----	-----	-----	-----	-----	-----
Water (ml)	-----	30	30	30	30	30	30	30	30	30
Isopropyl alcohol(ml)	-----	70	70	70	70	70	70	70	70	70
HPMC(g)	-----	1	2	3	1	2	3	1	2	3
PVP(g)	-----	1	2	3	1	2	3	1	2	3
MC(g)	-----	1	2	3	1	2	3	1	2	3

TABLE II: PHYSICAL EVALUATION OF UNCOATED AND COATED PARACETAMOL TABLETS

Thickness

(cm)

Diameter

(cm)

Average Weight Variation (g)

Average Friability

Average Hardness

(kg/cm²)

Disintegrat-ion Time (min)

Drug Content (mg)

0.36

0.51

0.8

0.98

0.01

0.34

0.17

5.8

6.4

6.14

12.5

498

497

BC= Before coating, AC= After coating

Figure I: In-vitro release of Paracetamol from coated tablet

Preparation of mucoadhesive tablet:

Measure amount of paracetamol are mixed with the diluents for preparation of tablet with wet granulation technique taking 10% solution of starch and gelatin mixture as a binder. Solid mass was passing through 22 mesh size for preparation of granules. Finally mixed the talc used as a lubricating agent just prior to tablet punch. 700mg tablets were manufactured as per the formula given in table I using an instrumented tablet compression machine (Rimek Mini Press-I, Shakti Engineering). Each respective formulations was coated with 1%, 2% and 3% coating solution of HPMC, PVP and MC. Coating was done by dipping the tablets into the respective solution and immediately dried under the hot air flow⁵.

Physicochemical evaluation:

Thickness and diameter, hardness, disintegration and friability was carried out before and after coating using the instrument slide calipers, Monsanto hardness tester, disintegration apparatus and Roche friabilator respectively. Swelling index, Drug content, Bioadhesive strength and in-vitro release rate were also studied which are discussed below-

Figure II: Higuchi’s plot of coated tablets

Determination of Swelling index:

The water absorbing capacity (Swelling index) of tablets was determined by gravimetry. For this study 3 tablets were taken from each batch and initial weight (W1) was noted and tablets were kept on a 10 cm diameter wet filter paper disc, soaked in water in a petridish. After 24hr., the tablets were removed and wiped with tissue paper and reweighed (W2). The swelling index was calculated by the following formula^5-7.

Swelling index= (W2-W1)/W1

Drug content:

Drug content in the formulation was calculated by UV spectrophotometric method based on the measurement of absorbance 257nm in water. 700 mg tablets were kept in 25ml of water overnight so that the drug from tablets diffuses out. After filtration and suitable dilution the tablets solution was assayed spectrophotometrically (using a Shimadzu UV–1700, Shimadzu Corporation, Japan) ^5,
7-8.

Measurement of bioadhesive strength:

The bioadhesive strength of the tablets was measured using a modified physical balance. Goat intestine was used as a model membrane for measurement of bioadhesive strength and water as a moistening fluid. The surface of the mucosal membrane was first blotted with a filter paper and then moistened with 2-3 drops of water. The tablets were tied with thread and attached with the intestine. Another end of thread tied with one side of the physical balance. The weight required to detach the tablet from the mucosal surface was taken as the measure of bioadhesive strength ^{5, 7, 9}.

In-vitro drug release studies:

The release rates of prepared coated tablets of paracetamol were studied using the Veego dissolution test apparatus (USP II) rotating paddle method under sink conditions at 37±0.5ºc and 50 rpm. The tablets were placed in the basket and tested for drug release for 6hr in water^5-8.

RESULT AND DISCUSSION:

Paracetamol tablets were prepared by wet granulation technique and coating was done by mucoadhesive polymers like HPMC, PVP and MC. In IR study, principal peak of paracetamol was compare with the formulation. After comparing all the physical parameters of normal and coated tablets, it was seen that thickness and diameter was increases upto 0.2cm where hardness was increases upto 2kg/cm². Dinsintegration time was also increases with less friability. Drug contents of the tablets in all the batches showed 695mg to 698mg instead of 700mg. Detachment force measurement method is used for the determination of mucoadhesive strength of different formulations and it was observed that the HPMC had the highest bioadhesive strength (maximum 4gm). Coating trials yielded tablets without edge defects or surface imperfections. All the physical evaluation of tablets is given in Table II.

The release of Paracetamol (Figure I) from the tablets was studied in water in prescribed dissolution apparatus USP II. HPMC coated tablet showed 98% drug release in 6hr. where PVP and MC coated tablet showed 95% and 97% over a period of 4hr and 5hr respectively. On the basis of drug release profile, mechanism of drug release whether diffusion, swelling or erosion was confirmed by Higuchi’s plots (Figure II) shows the graphical representation of cumulative percentage drug release versus square root of time. The Higuchi’s plots were found to be linear with correlation coefficient values of 0.983, 0.975, 0.975 (HPMC 1%, 2%, 3%), 0.966, 0.917, 0.973(PVP 1%, 2%, 3%) and 0.948, 0.964, 0.956 (MC 1%, 2%, 3%). From the Higuchi’s plots it was concluded that the release of drug was diffusion controlled mechanism in all formulation.

CONCLUTION:

In this study good results were obtained after performing physical evaluation of coated tablets of paracetamol. Present study may be concluded that the films containing 500mg paracetamol coated with HPMC solution show good swelling, satisfactory drug content, promising mucoadhesive strength and convenient controlled drug release, thus seems to be a potential candidate for the development of sustained release formulation.

ACKNOWLEDGEMENT

Aristo, Bhopal for providing the free gift sample of the drug and services provided by GRY Institute of Pharmacy, Borawan are thankfully acknowledged.

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