INTRODUCTION:

Poor dissolution characteristics of relatively insoluble drugs have long been a problem to pharmaceutical Industry. No. of modern drugs are poorly soluble in water and aqueous fluids. Their absorption and bioavailability require improvement in the dissolution rate and efficiency. Among the various methods for improving the dissolution rate and bioavailability, cyclodextrin (CD) complexation was found to be very successful with a number of poorly soluble drugs¹.

Cyclodextrins have mainly been used as complexing agents to increase the aqueous solubility of poorly water-soluble drugs and to increase their bioavailability and stability². The most common cyclodextrins are α -cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, which consist of six, seven, and eight glucopyranose units, respectively. Among α-, β-, γ-; β-CD was used for the study, as it has bigger cavity size and is the least toxic among the other natural cyclodextrin³.

Most of the Nonsteroidal anti inflammatory drugs belong to class II category under Biopharmaceutical classification system (BCS II) i.e., they are inherently highly permeable through biological membranes, but exhibit low aqueous solubility. They need enhancement in solubility and dissolution rate for improving their bioavailability. In the present investigation studies were carried out on cyclodextrin complexes of Meloxicam for enhancing the dissolution rate. Meloxicam, chemically 4-hydroxy-2-methyl-N-(5-methyl-2-thiazolyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide, is a potent non-steroidal anti-inflammatory drug (NSAID) of the enolic acid class of the oxicam derivatives which exhibits preferential inhibition of cyclo-oxygenase-2 (COX-2) and inhibits prostaglandin synthesis⁴. It is very effective for the treatment of rheumatoid arthritis, osteoarthritis, and other joint diseases. Meloxicam does not have known cardiovascular toxicity at doses of less or equal to 15 mg/day, which are recommended for the treatment of osteoarthritis and rheumatoid arthritis. Its therapeutic benefits combined with a good gastrointestinal tolerability are well documented in comparison with other NSAIDs, however, its oral administration can produce some side effects, such as stomach ache and indigestion, so Meloxicam is not suitable for the treatment of rheumatological patients with gastric ulcers⁵. Meloxicam shows similar efficacy for reducing pain and inflammatory symptoms but lesser toxicity than other NSAIDs^6,7,. Meloxicam possesses appropriate physicochemical properties for potential transdermal delivery. It is highly potent, and the oral dose (7.5–15mg/d) of Meloxicam is the lowest of any of the NSAIDs⁸. It has a low molecular weight (354.1), low polarity and low daily therapeutic dose. In order to avoid irritation of the gastrointestinal tract, minimize systemic toxicity and achieve a better therapeutic effect, one promising method is to administer the drug via the skin⁹. However, the skin is a natural barrier, and only a few drugs can penetrate the skin easily and in sufficient quantities to be effective. Therefore, in recent years, numerous studies have been conducted in the area of penetration enhancement^9,10. Penetration enhancers improve the ability of skin to absorb drugs by altering the lipid domain of the stratum corneum (SC) and the protein elements of the tissue, or they may increase the partitioning of a drug into the SC^11,12. A few investigations had reported the topical delivery of Meloxicam such as using penetration enhancers¹³, hydrogels¹⁴ and microemulsions¹⁵.

The specific aims of the present investigation were to enhance solubility of Meloxicam by by forming inclusion complex of Meloxicam with beta cyclodextrin, formulate a topical gel of Meloxicam- β-CD complex and evaluate it for different physicochemical properties, diffusion across goat abdominal skin.

MATERIALS AND METHODS:

The materials used include Meloxicam (gift sample from Cipla Pharmaceuticals, Kurkumbh), β-cyclodextrin (gift sample from Macleods Pharma, Kachigam, Daman), HPMC-E-6 (gift sample from Piramal limited, Ahmedabad). Carbopol 940, DMSO, oleic acid and all others chemicals of analytical reagent grade were procured from S.D Fine Chemicals Ltd, Mumbai.

Preparation of Meloxicam- β -Cyclodextrin Complex

Kneading Method:

Calculated amounts of Meloxicam and β-CD were accurately weighed and transferred in a glass mortar, triturated with a small volume of distilled water and methanol (1:1 volume ratio) and then kneaded for 60 minutes. The product was kept at room temperature for 24 hrs. Distilled water and methanol (1:1 volume ratio) was used as wetting agent to achieve better interaction of Meloxicam with β-CD during kneading method. The kneaded formulations were prepared at 1:0.5, 1:1, 1:2, 1:3, 1:4 and 1:5 molar ratios. The complex in the ratio 1:2 showed better complexation, so the complex in ratio 1:2 was used for the formulation of gel.

Preparation of gel:

Gels were prepared by using different polymers as shown in table-1. The polymer and purified water I.P. were taken in a mortar and allow soaking for 24 hrs. Meloxicam was dissolved in solvent blend of Chloroform: Dichloromethane and other additives were added. The trituration was continued to get homogenous dispersion of drug in the gel. pH of gel was adjusted with triethanolamine when carbopol gels were prepared. The permeation enhancers like sodium lauryl sulphate and dimethyl sulfoxide were incorporated in different concentrations. Gels containing Meloxicam- β-CD complex were prepared by the same procedure as above by adding complex in place of plain Meloxicam.

Preformulation studies

Preformulation studies were performed on free drug and complexes to assess the suitability of the complexes for the dosage forms. Solubility of the drug and the complex in phosphate buffer pH 7.4 were determined. The results were as shown in table 2. FT-IR studies of the pure drug, β-CD and drug-β-CD complex were recorded using Fourier Transform Infrared (FTIR) spectroscopy (Jasco FT-IR-460 Plus). Thermo grams of the pure drug, β-CD and β-CD complex were recorded by analyzing the samples by DSC using METTLER-DSC-30S, Mettler Toledo India Pvt. Ltd., Switzerland, using crucible Al 40µL, at of 10°C /min heating rate, under nitrogen environment. The temperature range used was 0 – 400°C. The DSC thermograms of Meloxicam exhibited an endothermic peak at 263 corresponding to its melting point. β-cyclodextrin alone showed a broad endothermic representing a loss of water molecule, a dehydration process. The thermograms of complexes are different from the pure drug; thereby giving clear evidence that there is formations of the complex. As the concentration of the β-cyclodextrin is increased in the in the complex it was observed that the height of endothermic peak at 263 diminished gradually and it disappeared at the concentration of 1:5, indicating complex formation at all these concentrations. However, maximum deflection in the peak height was found to occur while changing the concentration ratio from 1:1 to 1:2, indicating maximum inclusion at this concentration. Hence, other characterizations were performed in complexes bearing drug:β-cyclodextrin, 1:3, 1:4 and 1:5 in molar concentration. The molecular volume of β-cyclodextrin is 346 Å where as molar volumes of, Meloxicam is 412 Å, which is greater than the molecular volume of β-cyclodextrin. Therefore two molecules of β-cyclodextrin may be required for making true inclusion complex. Practically, it has been found that for making inclusions, two molecules of β-cyclodextrin were to enclose one molecule of drug. On the basis of molecular volume itself it is suggestive that drug could not be covered by the cavity of one molecule of β-cyclodextrin. Therefore for further studies 1:2, drug: β-cyclodextrin ratio were used. The prepared complexes were studied for its solubility in phosphate buffer pH 7.4.

Evaluation of gels

The prepared gels were evaluated for physical appearance, pH, spreadability, extrudabilty, drug content, and in vitro release study across goat abdominal skin which was obtained from slaughter house. The physical appearance and homogeneity of the prepared gels were tested by visual observations. Results were mentioned in table 3. The spreadability¹⁶ of the gel formulations was determined. The pH of the gel formulations was determined using a pH meter. For assay of the drug in gels, 1 gm of gel was accurately weighed and transferred to 100 ml volumetric flask to which about 70 ml of 0.1 N NaOH was added, after vigorous shaking the volume made up to 100 ml with 0.1 N NaOH. The content was filtered through a suitable filter paper. An aliquot 1ml was pipetted out from the filtrate and suitably diluted in phosphate buffer pH 7.4. The content of Meloxicam was determined by using Systronics 2203 UV/visible spectrophotometer, at 366 nm against blank. The blank solution was prepared in the same manner as above, using gels without the drug. The tests were carried out in triplicate. The viscosity of the gel formulations was determined using Brookfield viscometer model (LVDV-II+) with spindle no. CP52 at the temperature of 37⁰ C. The in vitro drug release from gel formulations was studied across goat abdominal skin using modified Keshery Chien diffusion cell. The receptor compartment was filled with the solution of 100 ml phosphate buffer of pH 7.4 and maintained at 37 ± 0.5⁰C with constant magnetic stirring. Gel formulation equivalent to 10 mg of Meloxicam was spread uniformly on the surface of goat abdominal skin (previously washed thrice) and was fixed to the one end of tube such that the preparation occupies inner circumference of the tube. The samples (1ml) were collected from the receptor compartment at predetermined time interval and replaced by equal volume of fresh receptor solution to maintain constant volume allowing sink condition throughout the experiment. The amounts of Meloxicam in the sample were assayed spectrophotometrically by Systronics 2203 UV–visible spectrophotometer at 366 nm. In-vitro cumulative % release from gel containing pure drug and complex was given in table-4.

RESULTS AND DISCUSSION:

The present study involves the study of release of drug from gels prepared using inclusion complexes of β-cyclodextrin to increase the solubility of Meloxicam. The solubility of the drug was found to be increased considerably by complexation. The results were as shown in table 2.The drug and complexes were characterized for solubility, DSC, FT-IR studies. The IR spectras were shown in fig. 1. Thermograms of pure drug, β-CD and β-CD complex were shown fig 2. The results of in-vitro drug release across the goat abdominal skin using fabricated Keshary-Chien diffusion cell were indicated in table 4 and graphically shown as graph 1.

CONCLUSION:

Dissolution profile of Meloxicam was improved by complexation with β-CD by kneading method. This complex with the ratio of 1:2 (drug: complex) has contributed for better drug release profile. The physicochemical of properties of complex was amenable for gel formation. Gel formulations prepared with carbopol 940 and HPMC E-6 showed good homogeneity. However, the carbopol 940 based gel (formulation DCG-2) proved to be the formula of choice, since it showed the highest percentage of % drug content, % drug release and good rheological properties. In vitro release of Meloxicam from gel was enhanced because of inclusion complex.

Table 1: Formulation Table of gels

Sr. No.	Ingredients	Formulations
Sr. No.	Ingredients	DG 1	DG 2	DG 3	DG 4	DCG 1	DCG 2	DCG 3	DCG 4	DG 5
1.	Meloxicam (mg)	7.5	7.5	7.5	7.5	--	--	--	--	7.5
2.	Drug-β-CD complex (mg)	--	--	--	--	55.96	55.96	55.96	55.96	--
3.	HPMC E 6 (mg)	--	--	5	5	--	--	5	5	5
4.	Carbopol – 940 (mg)	1	1	--	--	1	1	--	--	1
5.	TEA (ml)	0.5	0.5	--	--	0.5	0.5	--	--	0.5
6.	SLS (ml)	250	--	250	--	250	--	250	--	250
7.	DMSO (ml)	--	5	--	5	--	5	--	5	5
8.	Oleic acid (ml)	5	--	5	--	5	--	5	--	5
9.	Chloroform (ml)	4	4	6	6	5	6	4	6	5
10.	Dichloromethane (ml)	6	6	4	4	5	4	6	4	5
11.	Purified water (Ml) (q.s.)	100	100	100	100	100	100	100	100	100

Note: DG 1, DG 2, DG 3, DG 4, DG 5: Gel containing plain Drug, DCG 1, DCG 2, DCG 3, DCG 4: Gel containing Drug-β-CD complex

Table 2: Solubility analysis of pure drug and of complex

	Solubility (mg/ml)	Concentration (mg/10ml)	Molar conc. of Meloxicam.	Enhancement in solubility
Plain drug in PBS	0.246	2.460	0.001005	1 fold
Drug- β-CD complex	1.005	10.00	0.002906	4.065 folds

_{Table 3 -: Evaluation of Meloxicam Gel Formulations}

Formulation Code	pH	Drug Content %	Viscosity (cps)*	Spreadability (gm.cm/sec) ± S.E.*	Extrudability Pressure(gm./cm²)±S.E*
DG 1	6.8 ± 0.19	98.33	9352	18.37	250 ± 1.59
DG 2	6.3 ± 0.15	98.18	9146	19.00	221 ± 2.41
DG 3	6.1 ± 0.16	99.74	8420	25.53	345 ± 1.35
DG 4	6.6 ± 0.12	98.65	8366	26.71	412 ± 2.796
DCG 1	6.1 ± 0.13	99.48	8530	20.42	232 ± 2.63
DCG 2	6.5 ± 0.11	99.84	8634	19.57	210 ± 1.41
DCG 3	6.9 ± 0.13	98.31	9664	21.71	359 ± 1.33
DCG 4	6.1 ± 0.13	98.51	8258	20.65	410 ± 2.74
D5G 5	6.8 ± 0.14	99.32	9282	22.33	396 ± 1.75

Table-4: Percent release of Meloxicam from Gel Formulations through goat abdominal skin

Sr No.	Time (hr)	Square root of time	Percent Cumulative Drug Release ± S.E.*
Sr No.	Time (hr)	Square root of time	DG 1	DG 2	DG 3	DG 4	DCG 1	DCG 2	DCG 3	DCG 4	DG 5
1	0	0	0	0	0	0	0	0	0	0	0
2	01	1.000	2.38 ± 0.32	3.42 ± 0.76	2.46 ± 0.32	6.30 ± 0.44	4.64 ± 0.66	7.22 ± 0.98	4.54 ± 0.64	4.76 ± 0.46	5.82 ± 0.54
3	02	1.414	3.45 ± 0.54	5.46 ± 0.48	7.42 ± 0.24	16.22 ± 0.64	12.42 ± 0.44	14.86 ± 0.44	9.32 ± 0.22	8.82 ± 0.88	6.64 ± 0.64
4	03	1.732	8.42 ± 0.45	10.14 ± 0.48	8.62 ± 0.48	24.62 ± 0.54	20.86 ± 0.22	23.64 ± 0.42	14.44 ± 0.42	16.46 ± 0.26	12.24 ± 0.64
5	04	2.000	13.34 ± 0.35	18.46 ± 0.42	14.62 ± 0.64	34.54 ± 0.48	32.32 ± 0.44	32.66 ± 0.54	18.48 ± 0.98	26.84 ± 0.86	20.98 ± 0.64
6	05	2.236	15.38 ± 0.64	24.42 ± 0.52	16.46 ± 0.42	48.82 ± 0.46	46.64 ± 0.78	40.64 ± 0.22	30.44 ± 0.44	36.98 ± 0.64	30.86 ± 0.46
7	06	2.449	19.56± 0.23	34.96 ± 0.42	20.22 ± 0.44	60.66 ± 0.44	54.42 ± 0.48	58.42 ± 0.22	36.66 ± 0.88	50.64 ± 0.62	39.64 ± 0.54
8	07	2.645	23.58± 0.22	44.86 ± 0.32	26.42 ± 0.46	72.88 ± 0.42	62.22 ± 0.44	72.24 ± 0.66	46.94 ± 0.66	61.24 ± 0.86	48.64 ± 0.64
9	08	2.828	29.42± 0.34	46.64 ± 0.24	34.64 ± 0.66	76.38± 0.20	68.38 ± 0.66	88.66 ± 0.64	60.88 ± 0.66	68.86 ± 0.62	56.86 ± 0.88

* Values indicate mean of three determinations

Graph 1 : Graphical representation of In vitro release of Meloxicam from gels formulations through goat abdominal skin

a. Release from DG 1, DG 2, DG 3, DG 4

b. Release from DCG 1, DCG 2, DCG 3, DCG 4, DG 5

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Received on 16.03.2013 Modified on 01.04.2013

Research J. Pharm. and Tech 6(7): July 2013; Page 790-793