Stability evaluation of celecoxib nanoemulsion containing Tween 80

Transcription

1 4 Thai J. Pharm. Sci. 32 (2008) 4-9 Original article Stability evaluation of celecoxib nanoemulsion containing Tween 80 F. Shakeel 1*, S. Baboota 2, A. Ahuja 2, J. Ali 2, M.S. Faisal 2 and S. Shafiq 3 1 Department of Pharmaceutics, Faculty of Pharmacy, Al-Arab Medical Sciences University, Benghazi, Libya 2 Department of Pharmaceutics, Faculty of Pharmacy, Jamia Hamdard, Hamdard Nagar, New Delhi , India 3 New Drug Delivery System (NDDS), Zydus Cadila Healthcare Ltd., Ahemdabad, India. *Corresponding author: Tel: address: faiyazs@fastmail.fm Abstract: The aim of the present study was to evaluate the stability of celecoxib (CXB) using novel nanoemulsion formulation. Optimized nanoemulsion formulation of CXB was prepared by low energy emulsification method. Stability studies were performed for the period of 3 months. Droplet size, viscosity and refractive index (RI) were determined during storage. Shelf life of nanoemulsion formulation was also determined by accelerated stability testing. It was found that droplet size viscosity and RI were slightly increased at refrigerator and room temperature. The changes in these parameters were not significant (p 0.05). The shelf life of nanoemulsion formulation was found to be 2.73 years at room temperature. These results indicated that stability of CXB can be enhanced in nanoemulsion formulation using Tween 80 as surfactant. Keywords: Celecoxib; Nanoemulsion; Stability; Tween 80

2 F. Shakeel et al. 5 Introduction Nanoemulsions are thermodynamically stable, transparent (or translucent) dispersions of oil and water stabilized by an interfacial film of surfactant and cosurfactant molecules having the droplet size less than 100 nm [1-3]. Nanoemulsions have a higher solubilization capacity than simple micellar solutions and their thermodynamic stability offers advantages over unstable dispersions, such as emulsions and suspensions, because they can be manufactured with little energy input (heat or mixing) and has a long shelf life [4-6]. Nanoemulsions also present advantages over other nano or micro carriers, namely higher storage stability, lower preparation cost, good production feasibility, thermodynamic stability, absence of organic solvents and no need of intensive sonication [7-8]. Stability of a dosage form refers to the chemical and physical integrity of the dosage unit and when appropriate, the ability of the dosage unit to maintain protection against microbiological contamination. An ideal drug product must be thoroughly characterized physically, chemically and microbiologically at the start of study and throughout the intended shelf life period [9]. Stability of drug product is one of the problems associated in the development of emulsions, microemulsions and nanoemulsions. Nanoemulsions have been known to enhance the physical as well as chemical stability of drugs [1-2, 10]. Therefore, the aim of the present study was to evaluate the stability parameters of celecoxib (CXB) using nanoemulsion formulation. Nanoemulsion formulation was prepared using nonirritant and pharmaceutically acceptable ingredients. Materials and methods Materials CXB was a kind gift sample from Ranbaxy Research Labs (India). Propylene glycol mono caprylic ester (Sefsol 218) was gifted from Nikko Chemicals (Japan). Diethylene glycol monoethyl ether (Transcutol-P) was gift sample from Gattefosse (France). Glycerol triacetate (Triacetin) was purchased from E-Merck (India). Tween 80 was purchased from Sigma Aldrich (USA). All other chemicals used in the study were of analytical reagent grade. Preparation of CXB nanoemulsion Various nanoemulsions of CXB were prepared by low energy emulsification method (aqueous phase titration method). Detail description of their preparation, physical stability, characterization and optimization is given in our previously published article [1]. Optimized nanoemulsion was prepared by dissolving 2% w/w of CXB in 10% w/w mixture of Sefsol-218 and Triacetin (1:1). Then 50% w/w mixture of Tween 80 and Transcutol-P were added slowly in oil phase. Then slow addition of distilled water was done to get the final preparation 100% w/w. Characterization of nanoemulsion Droplet size distribution of the nanoemulsion was determined by photon correlation spectroscopy (PCS), using a Zetasizer 1000 HS (Malvern Instruments, UK). Light scattering was monitored at 25 ÌC at a scattering angle of 90 Ì. The viscosity of the nanoemulsion was determined using Brookfield DV III ultra V6.0 RV cone and plate rheometer (Brookfield Engineering Laboratories, Inc, Middleboro, MA) using spindle # CPE40 at 25±0.3 Ì C. Refractive index of nanoemulsion formulation was determined using an Abbes type refractrometer (Precision Standard Testing Equipment Corporation, India). Stability studies Stability studies on optimized nanoemulsion were performed by keeping the sample at refrigerator temperature (4 ÌC) and room temperature (25 ÌC). These studies were performed for the period of 3 months. The droplet size, viscosity and RI were determined using methods described above during storage. Accelerated stability studies were also performed on optimized CXB nanoemulsion. Three batches of formulations were taken in glass vials and were kept at accelerated temperature of 30 ÌC, 40 ÌC, 50 ÌC and 60 ÌC at ambient humidity. The samples were withdrawn at regular intervals of 0, 1, 2 and 3 months and were analyzed for drug content by stability-indicating HPLC method at a wavelength of 250 µm [11]. Zero time samples were used as controls.

3 6 Thai J. Pharm. Sci. 32 (2008) 4-9 Analysis was carried out at each time interval by taking 50 µl of each formulation and diluting it to 5 ml with methanol and injecting into the HPLC system at 250 nm. In addition, samples of pure oil (combination of Sefsol 218 and Triacetin), pure surfactant and cosurfactant (S mix ) were run separately to check there was no interference of the excipients used in the formulations. The amount of drug degraded and the amount remaining at each time interval was calculated. Order of degradation was determined by the graphical method. Degradation rate constant (K) was determined at each temperature. Arrhenius plot was constructed between log K and 1/T to determine the shelf life of optimized nanoemulsion formulation. The degradation rate constant at 25 ÌC (K 25 ) was determined by extrapolating the value of 25 ÌC from Arrhenius plot. The shelf life (T 0.9 ) for each formulation was determined by using the formula: T 0.9 = K 25 Results and discussion Stability of a dosage form refers to the chemical and physical integrity of the dosage unit and when appropriate, the ability of the dosage unit to maintain protection against microbiological contamination. An ideal emulsion formulation must be thoroughly characterized physically, chemically and microbiologically at the start of study and throughout the intended shelf life period [9]. Therefore optimized nanoemulsion formulation was characterized for droplet size, viscosity and RI for the period of three months. During stability studies droplet size, viscosity and RI were determined at temperatures of 4 ÌC and 25 ÌC. These parameters were determined at 0, 1, 2 and 3 months. It was found that droplet size viscosity and RI were slightly increased at both temperatures (Table 1). These parameters were compared for statistical significance by one-way analysis of variance (ANOVA) followed by Tukey-Kramer multiple comparisons test using GraphPad Instat software (GraphPad Software Inc., CA, USA). The changes in these parameters were not significant (p 0.05). These results indicated that optimized formulation is stable and suitable for transdermal delivery of CXB. For accelerated stability studies, samples were withdrawn at regular intervals of 0, 1, 2, and 3 months. The samples were analyzed for their drug content by HPLC analysis at a wavelength of 250 nm [11]. The amount of CXB degraded and remaining in nanoemulsion formulation was determined at each time interval. The degradation of CXB was very slow at each temperature that could be stability of CXB in the form of nanoemulsion. Observations are given in the Table 2. Order of degradation was determined by graphical method at each temperature. The order of degradation was found to be first order (Figure 1). The correlation coefficients of first order degradation were significant as compared to correlation coefficients of zero order degradation at each temperature as shown in Figures 1 and 2 (p<0.05). Table 1 Droplet size, viscosity and RI of optimized nanoemulsion formulation during storage Time Temp Droplet size Viscosity mean RI ± SD b (months) ( ÌC) mean ± SD (nm) a ± SD (cps) a ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± a Mean ± SD, n= 3, b Mean ± SD, n= 6

4 F. Shakeel et al. 7 Log % drug remained o C R 2 = R 2 = o C 50 o C R 2 = o C R 2 = Time (months) Figure 1 First order degradation kinetics of CXB from nanoemulsion formulation at different temperatures Table 2 Degradation of optimized nanoemulsion formulation Time Temp Conc. found Conc. degraded % Log % (months) ( ÌC) (mg) (mg) Remained remained 0 30 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Table 3 Observation table for calculation of shelf life of nanoemulsion formulation Temp. Slope K x 10-3 Log K Absolute 1/T x10 3 ( ÌC) (month -1 ) Temperature

5 8 Thai J. Pharm. Sci. 32 (2008) 4-9 Drug remained (mg) o C R 2 = R 2 = o C R 2 = o C 60 o C R 2 = Time (months) Figure 2 Zero order degradation kinetics of CXB from nanoemulsion formulation at different temperatures Log K y = x R 2 = /T x 10 3 Figure 3 Arrhenius plot between Log K and 1/T for nanoemulsion formulation

6 F. Shakeel et al. 9 Therefore for first order degradation, Log % of drug remaining was plotted against time (Figure 1) and degradation rate constant (K) was calculated from the slope of the curve at each temperature. Observations are given in the Table 3. The degradation rate constant was calculated by the formula Slope = -K The effect of temperature on the degradation was studied by plotting log K v/s 1/T. (Figure 3). The value of K at 25 ÌC (K 25 ) was obtained by extrapolation of the plot and shelf life was then calculated by substituting K 25 in the following equation: T 0.9 = K 25 Where T 0.9 is the time required for 10 % drug degradation and is referred to as shelf life. The shelf life of optimized nanoemulsion formulation was found to be 2.73 years. Conclusion The droplet size, viscosity and RI of optimized nanoemulsion formulation were not significantly changed during 3 months of storage. Therefore it was concluded that prepared nanoemulsion was physically stable. The degradation of CXB after 3 months of storage was very low in the nanoemulsion formulation. The degradation of CXB was increased by increasing the temperature. The shelf life of nanoemulsion formulation was found to be 2.73 years at room temperature. Overall these results indicated that stability of CXB can be enhanced in nanoemulsion formulation using Tween 80 as surfactant. Acknowledgement The authors are thankful to University Grant Commission (UGC), New Delhi, India for providing financial support to this project. References [1] S. Baboota, F. Shakeel, A. Ahuja, J. Ali, and S. Shafiq. Design development and evaluation of novel nanoemulsions formulations for transdermal potential of celecoxib, Acta Pharm. 8: (2007). [2] S. Shafiq, F. Shakeel, S. Talegaonkar, F.J. Ahmad, R.K. Khar, and M. Ali. Development and bioavailability assessment of ramipril nanoemulsion formulation, Eur. J. Pharm. Biopharm. 66: (2007). [3] F. Shakeel, S. Baboota, A. Ahuja, J. Ali, M. Aqil, and S. Shafiq. Nanoemulsions as vehicles for transdermal delivery of aceclofenac, AAPS Pharm. Sci. Tech. 8: E104 (2007). [4] S. Baboota, A. Alazaki, K. Kohli, J. Ali, N. Dixit, and F. Shakeel. Development and evaluation of a microemulsion formulation for transdermal delivery of terbenafine, PDA J. Pharm. Sci. Tech. 61: (2007). [5] S. Shafiq, F. Shakeel, S. Talegaonkar, F.J. Ahmad, R.K. Khar, and M. Ali. Design and development of oral oil in water ramipril nanoemulsion formulation: In vitro and in vivo assessment, J. Biomed. Nanotech. 3: (2007). [6] S. Shafiq, F. Shakeel, S. Talegaonkar, J. Ali, S. Baboota, A. Ahuja, R.K. Khar, and M. Ali. Formulation development and optimization using nanoemulsion technique: a technical note, AAPS Pharm. Sci. Tech. 8: E28 (2007). [7] D. Paolino, C.A. Ventura, S. Nistico, G. Puglisi, and M. Fresta. Lecithin microemulsions for the topical administration of ketoprofen: percutaneous absorption through human skin and in vivo human skin tolerability, Int. J. Pharm. 244: (2002). [8] F. Shakeel, S. Baboota, A. Ahuja, J. Ali, and S. Shafiq. Celecoxib nanoemulsion for transdermal drug delivery: Characterization and in vitro evaluation, J. Disp. Sci. Tech., In press. [9] A.G. Floyd. Top ten considerations in the development of parenteral emulsions, Pharm. Sci. Tech. Today 2: (1999). [10] F. Shakeel, S. Baboota, A. Ahuja, J. Ali, and S. Shafiq. Skin permeation mechanism of aceclofenac using novel nanoemulsion formulation, Pharmazie, In press. [11] S. Baboota, F. Shakeel, A. Ahuja, J. Ali, S. Ahmed, and S. Shafiq. Development and validation of a stability-indicating HPLC method for analysis of celecoxib in bulk drug and microemulsion formulation, Acta Chromat. 18: (2007).