Metronidazole Encapsulation within Chitosan Coated Eudragit RL Microsphers for Site Specific Delivery
R. Sivakumar1*, V. Ganesan1, Markand Viyas2, N.N. Rajendran2 and M. Kommala3
1The Erode College of Pharmacy, Erode – 638112 (TN)
2Swamy Vivekanandha College of Pharmacy, Tiruchengode - 637 205, India.
3Mohamed Sathak A.J. College of Pharmacy, Chennai-600 119
*Corresponding Author E-mail: rrsk1879@gmail.com
ABSTRACT:
The purpose of the work was to formulate and evaluate mucoadhesive microspheres containing metronidazole for the potential delivery of the drug to the colon. Microspheres were prepared by emulsion solvent evaporation method and filled into capsules for polymeric coating. These preparations were characterized for micromeritics study, morphology, percentage drug content, encapsulation efficiency, Percent mucoadhesion and in vitro drug release study. All the microspheres were spherical in shape smooth surface with a mean diameter 58.9 µm – 205.1 µm. The release mechanism were anomalous (non-fickian) diffusion mechanism. The prolonged colonic residence time and enhanced metronidazole stability resulting from the mucoadhesion microspheres of metronidazole might make contribution of complete eradication of amoebiasis.
KEYWORDS: Metronidazole, Colon targeting, Mucoadhesive microspheres, Eudragit RL, Chitosan.
INTRODUCTION:
Targeted drug delivery should be the preferred method of administration of bio active agents in the treatment of disorders. This method offers an attractive way to deliver desired therapeutic agents directly to specific sites. Oral targeted delivery of medicine has been specially used for the treatment of gastrointestinal disorders1. Recently, dosage forms that precisely control the release rates and targets to a specific body site have made an enormous impact in the formulation and development of novel drug delivery systems. Microspheres form an important part of such novel drug delivery systems2 Metronidazole is belonging from Anthelmentic class of Anti bacterial and Anti-protozoal agents which is mainly used to treat the parasites which are mainly responsible for the amoebiasis. The colon is the main site of the residence for the parasites. So, in case of amoebiasis it is necessary to eradicate the parasites to cure the disease3-4.The primary aim of the study was to develop the mucoadhesive microspheres containing metranidazole for colon targeting. The study concerns the use of Eudragit RL and chitosan to prepare mucoadhesive microspheres.
EXPERIMENTAL:
Materials:
Metronidazole was obtained as a gift sample from Unique pharmaceuticals (Mumbai, INDIA). Chitosan was obtained as a gift sample from the central institute of Fisheries Technology (Cochin,). Eudragit RL was obtained as a gift sample from Micro Labs (Hosur). All other chemicals obtained were of Analytical grade.
Methods:
Preparation of Mucoadhesive Microspheres:
All mucoadhesive microspheres were prepared by emulsification-solvent evaporation method using internal phase containing 20 ml of acetone and Eudragit RL Metronidazole. The external phase was consisted of liquid paraffin containing Span 80. At first, the internal phase was prepared at 60◦ C and added to the external phase at room temperature. The microspheres were separated from liquid paraffin by filtration using Whatmann filter, washed three times with 50 ml of petroleum ether, and air dried. The resultant microspheres were further coated by dipping into 5% of Chitosan solution and finally dried.
These mucoadhesive microspheres were filled in the hard gelatin capsule shell and the shell was coated with Eudragit RL solution by dipping and drying method to exactly target the colon5-6. The composition of coating polymer contain Eudragit L 100 (8%), Dibutyl phthalate (2%) and methanol (80%).
Calculation of controlled release dose:7
Required dose = Conventional dose (1+0.693×τ / t1/2) : τ = Duration of Dose
Required dose = 200(1+0.693×12/6) t1/2 = Half life of drug
Required dose = 477 mg of Metronidazole
Production Yield:8
The dried microspheres were collected and weighed accurately. The percentage yield was then calculated using formula given below
Particle Size Analysis:8
Microsphere size determination was done by optical microscopy method. Approximately 300 microspheres were counted for particle size using optical microscope (Labomed CX RIII, Ambala, INDIA.
Morphology:
The morphology of microspheres were observed under a Scanning Electron Microscope (SEM). The instrument used for this study was (Hitachi-SEM Model S – 450, JAPAN)).Scanning Electron Microscope. The microspheres were mounted directly on to the SEM sample stub, using double-sided sticking tape, and coated with gold film (thickness 200 nm) under reduced pressure (0.001 torr) and photographed
Drug Content:8
Accurately weighed 100 mg microspheres, crushed in glass mortar and pestle and the powdered microspheres were suspended in 100 ml of phosphate buffer pH 7.4. After 12 hours the solution was filtered and the filtrate was analyzed for the drug content using UV –Visible spectrophotometer at 276.6nm.
Encapsulation efficiency:
The encapsulation efficiency of thee microspheres were calculated using the following formula8
Vitro release studies:8
Dissolution studies were carried out for all the formulations, employing USP XXIII Basket type apparatus at 50 rpm at 37 + 0.5°C using 900ml of 0.1N HCl as the dissolution medium for first 2 h and followed for phosphate buffer ( pH 6.8) for another 3 h and in the phosphate buffer pH 7.4 up to 12 h. A sample of microspheres equivalent weight to 477 mg of Metronidazole was used in each test. An aliquot of the sample was periodically with drawn at suitable time interval and the volume was replaced with fresh dissolution medium. The sample was analyzed spectrophotometrically at 276.6 nm.
Release kinetics of drug:9
The drug release data of the in-vitro dissolution study were analyzed with various kinetic model like zero order, first order, Higuchi’s, Peppa’s and Coefficient of correlation (r) values were calculated for the linear curves by regression analysis of the above plots.
In vitro wash-off test: 9-12.
The mucoadhesive property of microspheres was evaluated by an In vitro wash-off method. Freshly excised piece of intestinal mucosa (2 x 2 cm) from goat were mounted on to glass slides (3 x 1 inch) with cyanoacrylate glue. Two glass slides were connected with a suitable support, about 25 microspheres were spread on to each wet rinsed tissue specimen and immediately thereafter the support was hung on to the arm of a USP tablet disintegrating test machine. When the disintegrating test machine was operated, the tissue specimen was given slow, regular up-and-down moment in the test fluid (Phosphate buffer pH7.4) at 37 ± 0.5°C. At the end of the 5 h the machine was stopped and number of microspheres still adhering to tissue was calculated. The studies were carried out in triplicate.
RESULTS AND DISCUSSION:
Micromeritics study:
The angle of repose was found in the range of ~230 to ~250 which revealed that the microspheres of all the batches had well flow characteristics and flow rates. The bulk density was in the range of 0.484 gm/cm3 to 0.599 gm/cm3. The microspheres prepared by this method were found to be discreet, spherical, free flowing and it was observed by Scanning Electron Microscopy (SEM) Fig 1.The size of the mucoadhesive microspheres was determined by the optical microscopy method. The microspheres were uniform in size with a size range of 58.9mm to 205.1mm. Table 1.
Fig.1 SCM Photograph of the Metronidazole Microspheres
Table 1. Characterization of Metronidazole microspheres
|
Code |
Percentage yield (%) |
Drug content (%) ± S.D. |
Encapsulation efficiency (%) |
Percent Mucoadhesion |
|
MF1 |
72.66±5.3 |
77.99±0.995 |
86.81±2.6 |
70.33±2.3 |
|
MF2 |
70.27±3.5 |
72.08±0.721 |
84.12±5.1 |
70.01±4.3 |
|
MF3 |
70.81±2.8 |
77.11±0.821 |
81.60±3.7 |
59.33±3.4 |
|
MF4 |
71.64±6.3 |
75.39±0.823 |
79.35±4.2 |
68.33±5.8 |
|
MF5 |
72.54±4.7 |
71.97±0.121 |
78.21±3.8 |
61.00±5.2 |
|
MF6 |
79.30±5.9 |
83.37±0.845 |
77.41±4.0 |
66.10±2.7 |
Percentage Yield, Drug Content and Encapsulation Efficiency:
In this present work efforts have been made to develop mucoadhesive microspheres of Metronidazole using emulsion solvent evaporation technique using Eudragit RL along with mucoadhesive polymer Chitosan. The percentage yield of microspheres of all formulations was found in the range of 70.27% to 79.30%.The drug content values of mucoadhesive microspheres were found in the range of 71.97% to 83.37%, the determination of drug content showed that even if the polymer composition
was changed the process was highly efficient to give microspheres having maximum drug loading. The drug encapsulation efficiency was found in the range of 77.41% to 86.81%.
In vitro Wash-off Test:
Mucoadhesive Microspheres of Metronidazole exhibited good mucoadhesive properties in the in vitro wash off test. The results of wash off test were shown in Table 1. The MF1 formulation has more adhesive strength than others.
In vitro Release Study:
The drug release was retarded by increasing the polymer concentration due to increased viscosity and strength of matrix formed due to Eudragit RL and Chitosan. The solubility of Eudragit RL is fully depended on the pH of the medium. It will dissolve at the range of pH 6 to pH 8. In vitro drug released at the end of 12 hours showed that MF1 released the 82.77% of drug MF2 released 81.63% of drug MF3.released 79.17% of drug MF4 released 77.91% of drug MF5 released 76.48% of drug, and MF6 released 74.97% of drug. So it was found that the drug release from microspheres was decreased by increasing the polymer concentration Fig 2.
Fig.2. In vitro Release Profile of Metronidazole Microspheres
Release Kinetics:
For the first order kinetics the r values were found in the range of 0.8421 to 0.8929, For the zero order kinetic the r values found in the range of 0.9696 to 0.9822. So that all the formulations exhibited zero order drug release kinetics. Among these formulation MF1 showed best r value (0.9822) for the zero order kinetics.
In order to understand the complex mechanism of drug release from the mucoadhesive microspheres, the in vitro Metronidazole release data were fitted to korsmeyer-peppa’s release model and interpretation of r values enlightens in understanding the release mechanism from the dosage form. The r values thus obtained were ranged from 0.9666 to 0.984. All the prepared formulations exhibited anomalous (non-fickian transport) diffusion mechanism. The drug release was diffusion controlled as the plot of Higuchi’s model was found to be linear (r > 0.9778). These formulations are also showed as good ‘r ’values of zero order kinetics indicating the Metronidazole release from these mucoadhesive microspheres were by both diffusion and erosion mechanisms.
CONCLUSION:
All the formulations exhibited anomalous (non-fickian transport) diffusion mechanism and follow zero order kinetic. The formulation MF1 was selected as best formulation; with 82.77% of controlled drug release at the end of 12 hours with maximum mucoadhesion properties, hence such a design can be used for colon targeted drug delivery of metronidazole to eradicate the parasites from the colonic region. Finally it is concluded that by increasing polymer concentration the drug release from microspheres will be slow.
ACKNOWLEDGEMENTS:
Authors wish to acknowledge Dr. M. Karunanidhi, Chairman and Secretary, Vivekanandha groups of educational institution for his support.
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Received on 10.12.2010 Modified on 11.01.2011
Accepted on 17.01.2011 © RJPT All right reserved
Research J. Pharm. and Tech. 4(6): June 2011; Page 993-996