FORMULATION, CHARACTERIZATION AND IN-VITRO EVALUATION OF
GASTERORETENTIVE
FLOATING
MICROSPHERES
CONTAINING
ESOMEPRAZOLE MAGNESIUM TRIHYDRATE.
A. Navya *; G. Sandeep
Department of Pharmaceutics, Padmavathi College of Pharmacy and Research
Institute, Periyanahalli, Tamilnadu.
Contact mail ID: navya2288@gmail.com
ABSTRACT
The present study involves the preparation and invitro evaluaton of floating
microsphreres
containing
Esomeprazole
Magnesium
Trihydrate.
Esomeprazole
microspheres are mainly designed to prolong the gastric retention time and also to
enhance the bio-availability of the drug. Floating microspheres were prepared by using
Emulsion Polymerization method. Preformulation studies were carried out before
formulation design. Total four formulations were prepared using two different polymers
viz., Hydroxy Propyl Methyl Cellulose and Chitosan in various ratios. Microspheres were
discrete, spherical, free-flowing and showed a good percentage of drug entrapment
efficiency. In-vitro dissolution test was carried out by using phosphate buffer pH 6.8. All
the formulations showed good dissolution profiles. Among all the formulation F3 showed
good dissolution profile with 91.8% of drug release in 12 hours. In-vitro release kinetic
data of Esomeprazole microspheres showed that the drug release mechanism was
diffusion controlled as the plots of Higuichi model was linear. All formulations exhibited
Non-Fickian diffusion (n value is in between 0.5 to 1) mechanism. Stability studies were
done for the selected formulation F3 which indicates that there is no change in drug
content of the formulation. In conclusion, the prolonged gastric retention time and
enhancd bio-availability of Esomeprazole Magnesium Trihydrate resulting from the
prepared floating microspheres, could contribute to the provision of a anti- ulcer effect.
Key words: Esomeprazole Magnesium Trihydrate, Chitosan, Hydroxy Propyl
Methyl Cellulose, Floating Microspheres, Gastric Retention time.
INTRODUCTION
Microencapsulation is a process by which very tiny droplets or particles of liquid
or solid material are surrounded or coated with a continuous film of polymeric material.
In microencapsulation particle size is ranging from several 10 microns to 5000 microns.
Microencapsulation provides the means of converting liquids to solids, of altering
colloidal and surface properties, of providing environmental protection and of controlling
the release characteristics or availability of coated materials.
Floating drug delivery systems are among the several approaches that have been
developed in order to increase the gastric residence time of dosage forms. [1,2,3] The
multiple unit system has been developed to identify the merit over a single unit dosage
form because the single unit floating systems are more popular. The multiple unit dosage
forms may be better suited because they are claimed to reduce the inter subject variability
in absorption and lower the probability of dose dumping. [4] Such a dosage form can be
widely distributed throughout the gastrointestinal tract (GIT), which afforded the
possibility of a longer lasting retention and more reliable release of the drug from the
dosage form. The present study is based on Esomeprazole Magnesium Trihydrate (ESM)
as a model drug. Esomeprazole Magnesium Trihydrate is a drug prescribed to treat
disorders caused by excess stomach acid. Available as the brand Nexium Esomeprazole
Magnesium Trihydrate is a proton pump inhibitor (PPI) similar to omeprazole. It is the Senantiomer of omeprazole.
Esomeprazole is a potent proton pump inhibitor used in the treatment of Gastro
esophageal reflux disease. (GERD)[5], Zollinger-Ellison syndrome promote healing of
erosive esophagitis. It has an absolute bioavailability of 60% and half-life about 1.5
hours. It undergoes significant 'first pass' metabolism. Esomeprazole is a specific
inhibitor of a proton pump (PPIs) of the parietal cells of the mucous layer of stomach. It
is accumulated and transformed into an active form in the secretory tubules where it
inhibits secretion of hydrochloric acid mostly excreted by the kidneys[6].
Esomeprazole Magnesium is marketed in India under the brand name of
Nexium[7]. Single doses of Esomeprazole of 20 - 60 mg produce approximately 40 - 60
% inhibition of Gastric acid.
MATERIALS AND METHODS
Esomeprazole is obtained as a gift sample from Micro Labs Pharma Pvt.Ltd.,
Bangalore. Chitosan was also obtained from Watson Pharma Pvt. Ltd., Thane. Hydroxy
Propyl Methyl cellulose was also obtained from Oxford Laboratories, Mumbai. Dichloro
Methane, Ethanol, n-Hexane, Sodium bicarbonate were obtained from S.D.Fine
Chem.Ltd, Hyderabad.
METHOD OF PREPARATION
Emulsion Polymerization Method
In this method, polymeric drug solution i.e, drug + polymer and solvent system
(DichloroMethane + Ethanol) of 10 ml is added to 10 % solution of egg albumin. This
polymeric phase is stirred continuously to form a uniform dispersion. In another beaker
86 ml of coconut oil containing 1 ml of 0.5% Sodium Lauryl Sulphate is taken which
forms the organic phase. The polymeric phase is added drop wise using needle into the
organic phase. It is continuously stirred for 2 hrs with a speed of 700 rpm using stirrer.
After stirring 1 ml of formaldehyde is added and obtained microspheres are washed thrice
with 20 ml of -hexane and the obtained final microspheres are stored in a dessicator.[8]
Table No.1 Formulation Design
Formulation
Drug(mg)
Hydroxy Propyl
Chitosan(mg)
Methyl Cellulose(mg)
F1
50
50
-
F2
50
75
-
F3
50
-
50
F4
50
-
75
EVALUATION
Flow Properties:
Angle of Repose
The flow characteristics are measured by angle of repose. Improper flow is due to
frictional forces between the particles. Angle of repose is defined as maximum angle
possible between the surface of the pile of the powder and the horizontal plane. Lower
the angle of repose the better the flow property
Tan ө = h/r
Ө = tan‾ 1 (h/r)
Where, h= height of pile
r= radius of base of pile
ө= angle of repose
Particle Size Determination
Sieving Method
Particles having size range between 50 and 1500 µm are estimated by
sieving method. Standard sieves of different mesh numbers are available commercially as
per the specifications of IP and USP. Sieves are arranged in a nest with the coarsest at the
top. A sample (50gms) of the powder is placed on the top sieves. This sieve set is fixed to
the mechanical shaker apparatus and shaken for a certain period of time (20 min).
The powder retained on each sieve is weighed. Frequently the powder is
assigned the mesh number of the screen through which it passes or on which it is
retained. It is expressed in terms of arithmetic or geometric mean of the two sieves.
Percentage Yield
The total amount of Microspheres obtained was weighed and the percentage yield
was calculated taking into consideration the weight of drug and polymer [9].
%Yield=(Practical yield / Theoretical yield) x100
Entrapment Efficiency
Drug entrapment efficiency of Esomeprazole was performed by accurately
weighing 100 mg of micro particles and suspended in 100ml of simulated intestinal fluid
of pH 7.4±0.1 and it was kept for 12hrs. Next day it was stirred for 15mins, and subjected
for filtration. After suitable dilution, Esomeprazole content in the filtrate was analyzed
spectrophotometrically at 301nm using Shimadzu UV-visible Spectrophotometer.
The absorbance found from the UV-spectrophotometer was plotted on
the standard curve to get the concentration of the entrapped drug. Calculating this
concentration with the dilution factor we get the percentage drug encapsulated in
microparticles[10].
Encapsulation efficiency = Estimated drug content/theoretical drug content × 100
In- vitroDissolution Studies
Dissolution studies were carried out for all the formulation, employing USP
XXIII apparatus (Basket method) at 37± 0.5˚C rotated at constant speed of 50 rpm using
0.1N HCl as the dissolution medium. A sample of microspheres equivalent to 100mg of
Esomeprazole was used in each test. An aliquot of the sample was periodically with
drawn at suitable time interval and the volumes were replaced with fresh dissolution
medium in order to maintain the sink condition. The sample was analyzed
spectrophotometrically.
Kinetics of Drug Release
In order to understand the mechanism and kinetic of drug release, the drug
release data of the in vitro dissolution study were analyzed with various kinetic model
like Zero order, First order, Higuchi’s, Korsemeyer Peppa`s and Coefficient of
correlation (r) values were calculated for the liner curves by regression analysis of the
plots.
Stability Studies
The formulations were stored in an oven at 30 ± 2˚C and 65% RH for a period of
six weeks. The samples were analyzed for drug content every week by spectrophotometer
at 301nm. Microspheres were individually wrapped using aluminium foil and packed in
amber coloured screw cap bottle and put at above specified condition in incubator for one
month. After one month microspheres were evaluated for in-vitro drug release.
Scanning Electron Microscopy
The samples were dried thoroughly in vacuum desiccator before mounting on
brass specimen studies. The samples were mounted on specimen studies using double
sided adhesive type, and gold palladium alloy of 120A˚ knees was coated on the sample
using sputter coating unit (Model E5 100 Polaron U.K) in Argon ambient of 8-10 Pascal
with plasma voltage about 20MA. The sputtering was done for nearly 3mins to obtain
uniform coating on the sample to enable good quality SEM images. The SEM was
operated at low accelerating voltage of about 15KV with load current of about 80MA.
The condenser lens position was maintained between 4.4-5.1.The objective lens aperture
has a diameter of 240 microns and the working distance WD=39mm.
RESULTS AND DISCUSSION
In this present work efforts have been made to develop floating microspheres of
Esomeprazole by emulsion polymerization method using Chitosan and Hydroxyl Propyl
Methyl Cellulose. Total four formulations were prepared and the detailed composition is
shown in Table No. 1. The prepared microspheres were subjected to determine angle of
repose, particle size, drug entrapment efficiency, In-vitro dissolution and stability studies.
Flow properties of the prepared microspheres were determined by conducting
Angle of repose, determination is shown in Table No. 2. All the formulations showed
angle of repose within the range of 22˚24 to 26˚51. Results indicating that they are having
good flow properties. Particle size was determined by sieving method results were
showed in Table No. 3. The particle size of formulations was mostly in the range of 600
µm.
The Entrapment efficiency was in the range of 79.66 to 88.97 shown in Table
No. 4.
The results of the in-vitro dissolution studies of formulations F1 to F4 are shown in
Table No.5. Among all the formulations F3 showed good dissolution profile with 91.8%
of drug release in 12 hours. Cumulative % Drug Release was shown in Figure No.1.
Drug release kinetic data for microspheres was shown in Table No. 6. All the
formulations exhibited anomalous (Non-Fickian) diffusion (n value is in between 0.5 to
1.0) mechanism. The drug release mechanisms were shown in the Figure No.2-5.
Morphology of the microspheres was investigated by scanning electron microscopy. The
photograph of formulations were taken by scanning electron microscope shown in the
Figure No.6. The microspheres prepared by this method were found to be spherical, free
flowing and it was observed by Scanning electron microscopy
Table No.2 Flow Properties of Esomeprazole Microspheres
S.No
Formulation
Angle of Repose
1
F1
25º 70’
2
F2
28º 29’
3
F3
29 º74’
4
F4
24 º32’
Table No.3 Particle size determination of Esomeprazole microspheres
Batch No.
Sieve
Sieve
Sieve
No.20(0.84mm)
No.25(0.600mm)
No.30(0.59mm)
840-1190µm
590-840µm
600µm
297-590µm
F1
0.07
0.08
0.44
0.22
F2
0.03
0.06
0.39
0.05
F3
0.02
0.1
0.74
0.14
F4
0.06
0.21
0.53
0.09
No.16(1.19mm)
Sieve
Table No.4 Entrapment Efficiency of Esomeprazole Microspheres
Formulation
Entrapment efficiency
F1
76.66
F2
81.38
F3
88.97
F4
83.42
Table No.5 Cumulative Percentage Release Profile of FormulationsF1-F4
Time
(hrs)
F1
F2
F3
F4
1
9.93
8.68
11.17
8.62
2
14.89
11.17
26.06
14.9
4
27.31
26.03
31.03
28.55
6
36.01
34.75
42.02
38.48
8
53.37
54.62
65.79
67.10
10
70.75
67.03
76.96
73.24
12
88.13
82.86
91.82
80.68
Figure No.1 Dissolution Profile For Formulations F1-F4
100
comparative dissolution profile of formulations
cumulative percentage release
90
80
70
F1
60
50
F2
40
F3
30
20
F4
10
0
0
2
4
6
8
Time (in hrs)
10
12
14
Table No.6 In- Vitro Release Kinetic Data For Esomeprazole Microspheres
Formulation
F3
Zero
First
Higuichi
Korsemeyer peppa`s Possible drug release
order
order
plots
plot
plots
plots
R2
R2
R2
0.8985
0.9955
0.9661
Figure No. 2 Zero Order Release
Model of Formulation F3
mechanism
R2
n
0.9741
0.7843
Non-Fickian, Higuichi
Figure No. 3 First order Release
Model of Formulation F3
log cumulative of % drug
remaining
Cumulative % Drug Release
2
120
100
80
y = 5.881x + 29.943
60
2
R = 0.8985
40
20
1.8
y = -0.0874x + 1.9525
1.6
2
R = 0.9955
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
0
0
5
10
5
15
10
15
Time (hours)
Time (hours)
Figure No. 5 Korsmeyer-Peppas
release model for formulation F3
120
100
80
60
y = 27.839x + 1.051
40
R2 = 0.9661
20
0
0
1
2
SQRT Time
3
4
Log Cumulative % Drug
Released
Cumulative % Drug Released
Figure No. 4 Higuchi release model
for formulation F3
2
1.5
y = 0.6644x + 1.3824
1
R2 = 0.9741
0.5
0
0
0.2
0.4
log Time
0.6
0.8
Table No.7 Stability Studies of Percentage Drug Content of Formulation F3
Drug content
before storage
Formulation
F3
Drug content after 30 days
Percent drug
Percent drug
content
content at 4˚C
Percent drug
Percent drug content at
content at room
humidity
temperature
30˚C ± 2˚C/ 65% RH
Drug content
Drug content
Drug content
Drug content
78.1
76.87
75.86
74.26
Figure No. 6 SEM of Microspheres
CONCLUSION
Esomeprazole Floating Microspheres were prepared successfully using chitosan
and Hydroxy Propyl Methyl Cellulose as release retardants in different proportions.
Preformulation studies of Esomeprazole were done initially and results directed for the
further course of formulation. Based on the preformulation studies different batches were
prepared using selected excipients. Prepared microspheres were evaluated for the flow
properties, drug entrapment efficiency, particle size determination, in-vitro dissolution
test. The entrapment efficiency was good. Among all the formulations F3 showed better
results. Enhanced drug release was observed in case of F3 than the other formulations.
Dissolution was carried out in phosphate buffer pH 6.8 at 301nm. All the
formulations were evaluated using different kinetic models i.e. Zero order kinetics, First
order kinetics, Krosmeyer peppa`s model and Higuichi kinetics. All the formulations
exhibited Non-Fickian diffusion mechanism. The drug release was diffusion controlled as
the plot of Higuichi model was found to be linear. The formulation F3 was selected as an
optimized formulation with 91.8% of drug release in 12 hours. Data for the stability study
indicate that there was no change in residual drug content for the selected formulation F3.
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