Solubility Enhancement of Poorly Water Soluble Drug by Using β Cyclodextrin

Aceclofenac complex is prepared by kneading method of inclusion complexation. The aim of present work is to improve the solubility and dissolution properties of a poorly water soluble drug aceclofenac, by inclusion complexation technique. Two components namely β cyclodextrin and span 60 were used in this study,  β CD is used as complexing agent and span 60 as surfactant which helps in increasing solubility and dissolution. The prepared Aceclofenac complex is evaluated in terms of compatibility, solubility, dissolution behavior with the help of FTIR, DSC, In vitro dissolution studies. The complexation parameter of β CD had an impact on the solubility of drug. The solubility of complexes was progressively improved when compared to pure Aceclofenac drug in water. The prepared Aceclofenac complexes were subjected to dissolution study.  At the end of 60 min of dissolution study 22.32±0.42 of pure drug was dissolved. The prepared complexes showed 85.35±0.71 at 60 min. The percent of drug dissolved increased for the complexes prepared with high concentration of β CD.  The study showed that complexing property of β CD and surfactant action of span 60 has its influence on both solubility and dissolution of the prepared inclusion complexes. MDT and % DE was evaluated for the all the prepared complexes. Aceclofenac complexes prepared with high concentration of β CD showed lower MDT and higher % DE compared to pure Aceclofenac. The pure and complexed Aceclofenac were characterized by DSC studies. DSC studies showed that there was no appreciable change in the melting endotherm of prepared complexes compared to that of pure drug. The drug release from the above follows Korsemeyer-Peppas model and release mechanism was Non- Fickinian. 
Keywords: Aceclofenac, inclusion complex, kneading method, complexing agent, solubility, dissolution.


Introduction
Oral delivery system is the most convenient and commonly employed route of drug delivery system as it is easiest way of drug delivery system and also for its high patient compliance, least sterility constraints, cost effectiveness and flexibility in the design of dosage form. As a result, many of the drug companies are more intended to produce bioequivalent oral drug products. The major challenge associated with these delivery systems is its poor bioavailability i.e. it depends on several factors including aqueous solubility, permeability, dissolution rate and pre systemic metabolism. The most frequent causes of low bioavailability are attributed to poor solubility and low permeability. 1 In order to achieve a better/desired therapeutic effect of a drug, it must reach a reasonable significant concentration in plasma, which is mainly corelated with the solubility of drugs in GIT fluids. Except pinocytosis all other mechanisms of drug absorption requires presence of drug concentration in the solution form. Solubility is the main parameter for drug dissolution and drug absorption 2 . Nearly one-third of the drug which are developed are water insoluble and one-half of the developed drug will fail in trials because of their under privileged pharmacokinetics i.e. their poor water solubility. Therefore, it is essential to enhance the drug dissolution is the rate limiting step for various lipophilic drugs 3 . Solubility can be defined as the spontaneous interaction of two or more substances to form a homogeneous molecular dispersion. Drug solubility is the one in which the maximum concentration of the drug dissolved in the solvent under specific standard conditions. The need of drug solubility is to increase the drug absorption rate.

Inclusion Complexation
Inclusion complexation is a traditional technique of enhancing the solubility of poorly aqueous soluble drugs. The method involves the formation of complex with the cyclodextrin and the drug molecules. The complexation occurs when an aqueous solution of the cyclodextrin is shaken with the drug molecule or its solution. In aqueous solution the hydrophobic cavity of cyclodextrin are occupied by water molecules, which can be replaced by appropriate drug molecule that are less polar than water.
The formation of complexes by inclusion complexation method involves several techniques. They are Physical blending/ grinding method, kneading method, co precipitation, solid dispersion, neutralization, lyophilization, melting, microwave irradiation method, spray drying 7 .

Materials and Methods
Aceclofenac was obtained as a gift sample from Sangus Life Science Pvt.ltd Bengaluru. Cyclodextrin was obtained as a gift sample from HiMedialaboratories Pvt. Ltd. Mumbai. Span 60 was obtained from Ozone International, Mumbai. Distilled water and phosphate buffer pH 6.8 were collected from laboratory.

Determination of λmax of drug:
A diluted solution of aceclofenac in phosphate buffer solution (pH 6.8) was scanned for absorption maxima against blank between 200-400 nm using UV-visible spectrophotometer (UV-1700. Shimadzu, Japan). The maximum absorbance was found to be 275nm.

Preparation of phosphate buffer solution (pH 6.8):
Dissolved 28.80 gm of disodium hydrogen phosphate and 11.45 gm of potassium dihydrogen orthophosphate in sufficient water to produce a 1000 ml in volumetric flask.

Calibration curve of Aceclofenac in phosphate buffer solution (pH 6.8)
Accurately weighed Aceclofenac (100 mg) was transferred into a 100 ml volumetric flask, dissolved and adjusted the volume up to 100 ml with phosphate buffer solution (pH 6.8) to get stock solution A. From the stock solution A, 10 ml was pipetted out into a 100 ml volumetric flask and volume was made up to mark with phosphate buffer solution (pH 6.8) to get stock solution B. From the stock solution B, known volume were pipetted out and made up to 10 ml with phosphate buffer solution (pH 6.8)of aliquots such as 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, 3.6 and 4.0 ml are pipetted out and made up to marin 10 ml volumetric flask to get 4-40 µg/ml concentration solutions and absorbance was recorded at 275 nm by UV-visible spectrophotometer (UV-1700. Shimadzu, Japan) 8 .

Preparation of Complexes:
Complexation of drug and β-CD by kneading method: The required quantity of β cyclodextrin and span 60 was weighed and little amount of water added to get paste like consistency. To the paste, weighed quantity of Aceclofenac was added the mixture by kneading in a mortar. Then this mixture was transfer into Petri dish and completely dried in hot air oven at 60 o C for 48h. Dried product was passed through sieve no #80 to obtain fine powder. Total weight of the powder was taken. 9

Evaluation Studies of Inclusion Complexes
Solubility studies:

Solubility studies of Pure Drug
Solubility analysis was done which include the selection of suitable solvent system to dissolve the drug. Dissolve accurately 10mg of drug in 10ml of water, 10 ml of 0.1N HCL and 10 ml of Phosphate buffer pH 6.8 in 100ml conical flask separately. The samples were kept on rotary shaker at 100rpm for 24 hours. After that the volumes were made up to100ml mark with respective solvents, then filter the solutions. The filtrate was analyzed at 275nm by using UV -visible spectrophotometer (UV-1700. Shimadzu, Japan).

Solubility studies of prepared inclusion complexes
Solubility analysis was done which include the soluble of complexes in water. Dissolve accurately 10mg of F1, F2, F3, F4 and F5 in 10ml of water in 100ml conical flask separately. The samples were kept on rotary shaker at 100rpm for 24 hours. After that the volumes were make up to 100ml mark with water then filter the solutions. The filtrate was analyzed at 275nm by using UV -visible spectrophotometer (UV-1700. Shimadzu, Japan). 12

In vitro dissolution studies:
Dissolution studies were performed with different formulation of Aceclofenac complexes and compared with the pure Aceclofenac drug.
The dissolution studies were performed in distilled water using USP II paddle dissolution apparatus at 50rpm. Dissolution medium consisted of 900ml distilled water maintained at 37±0.5 o C. At a specific time intervals (5 to 60 min), an aliquot was withdrawn and replenished with fresh medium. Amount of dissolved drug in each aliquot was measured on a UV-Visible spectrophotometer (UV-1700. Shimadzu, Japan) at 275 nm using suitable blank. All the trails were conducted in triplicate and the average (± S.D) reading was noted. 13

Results
Calibration Curve of Aceclofenac:   Values are mean ±SD, n=3    Values are mean ± SD, n=3