INTRODUCTION:

Poor aqueous solubility of drugs is a major limiting factor with many new drugs in their successful launch in market in spite of their potential pharmacokinetic activity. Poor solubility (less than 10 %) of a drug, leads to poor dissolution in the gastro intestinal tract (GIT) hence, incomplete and erratic absorption ultimately limits its clinical utility. Further, poorly soluble drugs are generally administered at much higher doses than the actual dose in order to achieve necessary drug plasma levels leading to increased adverse reaction & cost of therapy and often yields erratic pharmacological response and hence poor patient compliance. About 40% of drugs being in the pipeline of pharmaceutical companies are poorly soluble, which emphasizes the need of a technique to overcome such problems.¹ Poorly water-soluble drugs are associated with slow drug dissolution followed by slow absorption leading eventually to inadequate and variable bioavailability. Solubility, one of the key parameter in BCS, as well as dissolution rate is the most essential factors controlling the rate and extent of drug absorption.

A poorly water soluble compound is defined which get soluble less than 1part per 10000 part of water. A poorly water soluble drug, more recently, has been defined in general terms which require more time to dissolve in the gastrointestinal fluid than it takes to be absorbed in the gastrointestinal tract. Thus a greater understanding of dissolution and absorption behaviors of drugs with low aqueous solubility is required to successfully formulate them into bioavailable drug products.²

Meloxicam is a non-steroidal anti-inflammatory drug was selected as model drug as the drug has low aqueous solubility where its GIT absorption is limited by its dissolution in the gastrointestinal fluids exhibiting low bioavailability after oral administration.³ A number of approaches are practiced to improve the aqueous solubility of poorly soluble drugs viz., solid dispersion (solvent evaporation method, fusion process melt- mixing, freeze-dried, fusion-solvent method, kneading technique, co precipitation),⁴ spherical agglomeration,⁵ evaporative precipitation in aqueous solution,⁶ microcrystallisation,⁷ supersaturation,⁸ prodrug approach,⁹ polymorphism,¹⁰ complexation,¹¹ ph adjustment,¹² co-solvents,¹³, ¹⁴use of surfactant,¹⁵and particle size reduction.¹⁶These techniques result into polymorphic changes or changes in crystal structure or hydrophilicity or particle size changes due to formation of molecular dispersion. The formulations were evaluated by the evaluation techniques utilized also focused on studying these changes in drugs along with their solubility, dissolution and other properties. The solubility and in vitro study was evaluated by the spectrophotometer in the dissolution media. All these techniques can be easily accommodated at industrial level and the techniques can be easily incorporated in formulation operations in pharmaceutical industry.

MATERIALS AND METHODS:

Materials

Meloxicam was obtained as gift sample from Dr. Reddys Pharmaceuticals (Hyderabad, India). Povidone (PVP), poloxamer 407 and crospovidone were procured from Aurabindo laboratories (Hyderabad, India). Methanol and Acetone Chloroform were of AR grade (Qualigens, Mumbai, India).

Methods

Preparation of Spherical agglomerates

Spherical agglomerates were prepared by simple agglomeration technique, Meloxicam and carriers Poloxamer, Crospovidone and PVP were prepared in 1:1 weight ratios by following technique i.e. Approximately 3gm of Meloxicam in 6ml of acetone is added to a solution of poloxamer and crosspovidone in 100ml of distilled water separately. The mixture was stirred continuously using a mechanical stirrer Remi motors at 500rpm to obtain spherical agglomerates. The bridging liquid using Whatman filter paper no.1 and dried for 24 hrs at room temperature. The physical mixtures of the Meloxicam and selected polymers were prepared by triturating 1:1 ratio using mortar and pestle.

Table.No:1 List of formulae used to prepare spherical agglomerates and physical mixtures

S. No.	FORMULATION	CODE
1	Drug + PVP (1:1) spherical agglomerates	MEL:PVP SA
2	Drug + Poloxamer (1:1) spherical agglomerates	MEL:POL SA
3	Drug + Crosspovidone (1:1) spherical agglomerates	MEL:CRP SA
4	Drug + PVP (1:1) physical mixture	MEL:PVP PM
5	Drug + Poloxamer (1:1) physical mixture	MEL:POL PM
6	Drug + Crosspovidone (1:1) physical mixture	MEL:CRP PM

EVALUATION:

Fourier Transform Infrared Spectroscopy (FT-IR) studies

FTIR Spectroscopy was performed on each at the samples to determine the structure of the organic compounds and to identify the presence of specific functional groups within a sample. Furthermore drug polymer interactions were examined using the resulting spectra. The infrared spectra were obtained using a scale of wave numbers (cm^-1). The analyses were performed by using a thermo Nicolet nexus 470 FTIR ESP.3-5mg of sample was added to approximately 100mg of KBr. The mixture was then ground to a fine powder using a mortar & pestle and transparent discs formed using a pellet press. The discs were placed in FTIR spectroscopy apparatus and spectra were collected.

Particle size determination

Particle size determination was carried out using optical microscopy with a calibrated eye piece micrometer and stage micrometer by taking a small quantity of formulation on slide. About 100 spherical agglomerates size was measured individually, average was taken and their size range and mean diameter frequency was calculated.

Average Particle size is calculated by the formula,

Average Particle size= εnd/ n

Solubility studies

Pure drug (50mg), MEL: PVP SA, MEL: POL SA, MEL: CRP SA, MEL: PVP PM, MEL: POL PM and MEL: CRP PM under test was placed in a test tube containing 10ml distilled water. The samples were shaken at room temperature until equilibrium was achieved and the aliquots were filtered. The filtered samples were diluted suitably and assayed spectrophotometrically at 360nm.

Drug content uniformity

From each batch of the prepared spherical agglomerates 50mg were taken and analyzed for drug content. 50mg of spherical agglomerates was weighed and taken into a 50 ml volumetric flask; Methanol was added to make up the volume to 50 ml and mixed the contents thoroughly and kept aside for 4 hrs with occasional shaking to facilitate the extraction of drug from the solid mixture into solvent. The solution was filtered and diluted further with methanol and assayed for their drug content spectrophotometrically by measuring absorbencies at 360nm and the same was performed for physical mixtures.

Dissolution studies

The release of Meloxicam form spherical agglomerates was investigated in pH 6.8 phosphate buffer as a dissolution medium (900ml) using the paddle method specified in USP X XIV (model TD T6P-Electrolab).sample of 50mg spherical agglomerates were taken in the dissolution flask. A speed of 50 rpm and temperature 37+ 0.5° C was maintained through out the experiment. At fixed intervals, aliquots (5ml) were withdrawn and replaced with fresh dissolution media.

The concentration of drug released at different time intervals was then determined by measuring the absorbance using visible spectrophotometer at 360nm against blank and the same was performed for physical mixtures. The studies were carried out in triplicate.

RESULTS AND DISCUSSION:

Preparation of Spherical agglomerates

Spherical agglomerates of Meloxicam were prepared by simple agglomeration technique using a three solvent system. It includes a good solvent, a poor solvent and a bridging liquid. The selection of solvents depends on miscibility of the solvents and the solubility of in individual solvents. Accordingly acetone, water and chloroform are selected as a good solvent, poor solvent and bridging liquid. Chloroform has shown to be highly used in the preparation of spherical crystals. Hence this solvent system is used in the present study. Agglomerates were prepared by agitating the crystals in a liquid suspension and adding a bridging liquid, which wets the crystal surface causing binding. The addition of bridging liquid promotes the formation of liquid bridges between drug crystals.

The solidified spherical agglomerates were dried at room temperature. The manufacturing of a spherical agglomerates implies the creation of additional surface area and hence interface. As the Gibbs free energy change, associated with the formation of additional interface is positive, the spherical agglomerates formed are thermodynamically unstable and will tend to minimize their total energy by agglomeration. Kinetically, the process of agglomeration depends on its activation energy. This activation energy can be influenced by adding stabilizers to the system. A first requirement for a stabilizing system is that it provides wetting of the hydrophobic surfaces of the drug particles.

Fourier Transform Infrared Spectroscopy (FT-IR) studies

The drug and polymer interaction studies showed that there is no change in their physicochemical property during time of work. Hence, the polymers tested could be taken for further studies. In FTIR study, Meloxicam showed same characteristic bands between the same peaks were identified in the drug blended with polymers (PVP, Poloxamer and crosspovidone). The FTIR spectra of the physical mixture of the drug with polymers exhibited all the characteristic bands as in the spectrum of the individual Meloxicam, PVP, Poloxamer and crosspovidone excluding the possibility of any interaction, chemical and functional group change during the processing of the formulation spherical agglomeration is ensured.

Figure No.1 FTIR spectra of pure drug Meloxicam

Figure No.2 FTIR spectra of pure drug and Poloxamer spherical agglomerates

Figure No.2 FTIR spectra of pure drug and PVP spherical agglomerates

Figure No.4 FTIR spectra of pure drug and cross povidone spherical agglomerates

Particle Size Determination

Particle size determination was carried out using optical microscopy with a calibrated eye piece micrometer and stage micrometer by taking a small quantity of formulation on slide. About 100 microcrystal size of optimized formulation was measured individually, average was taken and their size range and average mean diameter was calculated and shown in the Table No.2

Table.No:2 Particle Size determination of Meloxicam spherical agglomerates

S.No.	Microcrystals	Average particle size
1	MEL:PVP SA	362.4 µm
2	MEL:POL SA	228.2 µm
3	MEL:CRP SA	296.8 µm

Drug Content Uniformity

The drug content was found to be good among the different batches of the prepared samples and ranged from 74.73% to 99.89 % .The drug content of the pure drug, spherical agglomerates (MEL: PVP SA, MEL: CRP SA, MEL: POL SA) and physical mixtures (MEL: PVP PM, MEL: CRP PM, MEL: POL PM) was found to be 47.04%, 98.69%, 73.73%, 91.65%, 98.94%, 99.19%. In comparison between three polymers used in the preparation of spherical agglomerates, poloxamer shows maximum drug content than PVP and Crosspovidone. Spherical agglomerates prepared with poloxamer were proved more efficient of all used polymers due to decrease in particle size by size reduction. This results in increase in surface free energy leads to increase in drug content.

Solubility studies

As water is a universal solvent, apparent solubility studies were carried out in deionised water. In solubility studies of the samples, the Spherical agglomerates prepared with poloxamer have showed highest solubility of the drug in water (31.25 mg/ml) as compared with the untreated drug (15.220 mg/ml) Table no-3. Spherical agglomerates prepared with poloxamer (MEL: POL SA) were proved more efficient of all used polymers due to decrease in particle size by size reduction. This results in increase in surface free energy leads to increase in solubility.

Table.No:3 Solubility Profiles of Meloxicam spherical agglomerates and physical mixtures

S. No.	FORMULATION	%SOLUBILITY (μg/ml)
1	Pure drug	15.220
2	Drug + PVP (1:1) spherical agglomerates	20.667
3	Drug + Poloxamer (1:1) spherical agglomerates	31.25
4	Drug + Crosspovidone (1:1) spherical agglomerates	26.30
5	Drug + PVP (1:1) physical mixture	18.23
6	Drug + Poloxamer (1:1) physical mixture	22.45
7	Drug + Crosspovidone (1:1) physical mixture	19.62

In-Vitro Dissolution Studies

The dissolution studies were carried out in pH 6.8 phosphate buffer which is mentioned as USP dissolution media. The spherical agglomerates prepared with polymers exhibited better dissolution rate when compared with plain drug, which indicates the deposition of polymer on the drug surface. The dissolution profile of the pure drug and the polymeric spherical agglomerates explains that the particle size reduction was an effective and versatile option to enhance the rate of dissolution. The spherical agglomerates prepared with poloxamer shown 97.95% drug release at the end of 90 min, while that with Crosspovidone and PVPshown 94.14%, and 87.54%, drug release after completion of 90 minutes. Whereas physical mixtures prepared with poloxamer shown 90.14% drug release at the end of 90 min, while that with Crosspovidone and PVPshown 94.14%, and 95.25%, drug release after completion of 90 minutes. Spherical agglomerates prepared with poloxamer (MEL: POL SA) were proved more efficient of all used polymers, Due to decrease in particle size by size reduction. This results in increase in surface free energy leads to fast release.

Table.No:4 Dissolution profiles of Meloxicam spherical agglomerates

S. No.	Time (min)	%Drug release of pure meloxicam	%Drug release of MEL:POL SA(1:1)	%Drug release of MEL:CRP SA(1:1)	%Drug release of MEL:PVP SA(1:1)
1	5	15.25	31.25	32.35	27.40
2	15	30.05	40.95	45.65	32.85
3	30	40.63	55.44	54.28	39.65
4	45	48.24	65.35	65.89	50.56
5	60	54.27	87.95	81.65	79.28
6	90	59.01	99.84	92.56	87.54

Table.No:5 Dissolution profiles of Meloxicam physical mixtures

S. No.	Time (min)	%Drug release of pure meloxicam	%Drug release of MEL:POL PM(1:1)	%Drug release of MEL:CRP PM(1:1)	%Drug release of MEL:PVP PM(1:1)
1	5	15.25	30.15	32.35	29.25
2	15	30.05	38.45	45.65	39.95
3	30	40.63	45.21	54.28	49.48
4	45	48.24	55.85	65.89	69.85
5	60	54.27	78.65	81.65	81.29
6	90	59.01	96.14	90.84	89.25

Figure No.5 Comparative Invitro Release Profile of Meloxicam spherical agglomerates

Figure No.6 Comparative Invitro Release Profile of Meloxicam physical mixtures

ACKNOWLEDGEMENT:

The authors wish to thank Dr.Reddy’s laboratories, Hyderabad for supplying gift samples of pure drug required for our research work. The authors are thankful to PRRM College of pharmacy, Kadapa for their valuable support in carrying out this work.

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Received on 14.01.2012 Accepted on 10.02.2012

Asian J. Pharm. Res. 2(1): Jan.-Mar. 2012; Page 32-36

ABSTRACT: