spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic...
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RESEARCH ARTICLE
Spherical crystallization of ezetimibe for improvementin physicochemical and micromeritic properties
Ashwini Patil • Yogesh Pore • Yogesh Gavhane •
Shitalkumar Patil • Sachinkumar Patil
Received: 30 September 2013 / Accepted: 29 January 2014
� The Korean Society of Pharmaceutical Sciences and Technology 2014
Abstract Spherical agglomerates of ezetimibe (EZT)
were prepared with hydrophilic polymers; polyvinyl pyr-
rolidone K30 (PVP) and/or poloxamer 188 (poloxamer) at
drug to polymer ratios of 1:1 (w/w) by spherical crystal-
lization technique, in order to improve its physicochemical
and micromeritic properties. Three different bridging liq-
uids; chloroform, dichloromethane and/or ethyl acetate
along with good solvent acetone and poor solvent water
were used to form six batches of agglomerates. Initial
characterization of all batches in terms of micromeritic and
physicochemical properties resulted in optimization of (A3,
EZT:PVP:ethyl acetate) and (B3, EZT:poloxamer:ethyl
acetate) batches and hence further investigated for drug–
polymer interaction, crystallinity and morphology using
FTIR, XRPD, DSC and SEM techniques. The results
indicated presence of hydrogen bonding, crystallinity and
spherical shape in agglomerates. Therefore, the optimized
agglomerates (B3) were directly compressed into tablet.
Unfortunately, drug release from the tablet was not satis-
factory, suggesting a need of disintegrant from dissolution
point of view. Therefore, these agglomerates were recom-
pressed incorporating certain excipients and evaluated as
per pharmacopoeia. The dissolution rate of prepared tablet
was similar to that of marketed tablet (p [ 0.05). It could
be concluded that spherical crystallization could be one of
the effective and alternative approaches for improved
performance of EZT and its tablet formulation.
Keywords Ezetimibe � Spherical crystallization �Spherical agglomerates � Physicochemical properties �Micromeritic properties
Introduction
In recent years, direct tableting has attracted the attention
of formulation experts, as it requires only few steps and is
convenient for process validation, good manufacturing
practices (GMP) and automation of production processes,
as compared to conventional tableting (Kawashima et al.
2003). Direct tableting involves simply mixing and com-
pression of powders which is possible without granulation
and drying and also wet granulation cannot be used with
sensitive drugs (Espitailier et al. 1997; Maghsoodi et al.
2008). It is a modern method in tablet manufacturing which
is desirable for saving the cost, time, equipments and
labour (Joshi et al. 2003). Directly compressible powder
with free flowing properties is preferred because of its
ability of forming stable compacts at low compression
force as well as it does not cause the problem of sticking
(Rasenack and Muller 2002a). For the successful direct
compression, the flowability and packability of drug is
essential. To achieve this goal spherical crystallization
technique has been developed by Kawashima for size
enlargement of the drug (Kawashima et al. 1994; Szabo-
Revesz et al. 2001).
In pharmaceutical industries, crystallization from solu-
tion is core technology and a part of wide processing
A. Patil � S. Patil � S. Patil
Department of Pharmaceutics, Ashokrao Mane College of
Pharmacy, Peth Vadgaon, Kolhapur 416112, Maharashtra, India
Y. Pore (&)
Department of Pharmaceutical Chemistry, Government College
of Pharmacy, Karad 415124, Maharashtra, India
e-mail: [email protected]
Y. Gavhane
Department of Pharmaceutics, Government College of
Pharmacy, Karad 415124, Maharashtra, India
123
Journal of Pharmaceutical Investigation
DOI 10.1007/s40005-014-0117-4
system such as solid–liquid separation and particle design
(Teychene et al. 2010). Spherical crystallization is an
efficient technique for particle design in which the process
of crystallization and agglomeration can be carried out
simultaneously in one step without using any binder (Ka-
washima et al. 1994; Deshpande et al. 1996; Usha et al.
2008). It is an agglomeration process that transforms the
drug crystal directly into spherical form which has been
successfully utilized for improvement in micromeritic
properties of crystalline drug. This technique can also be
used to improve solubility, wettability and dissolution rate
of poorly water soluble drug (Morishima et al. 1993;
Rasenack and Muller 2002b).
Two methods have been reported in literature for gen-
erating spherical crystals; spherical agglomeration (SA)
method and quasi-emulsion solvent diffusion (QESD)
method, which is also known as a transient emulsion (TE)
method. These two methods are widely employed for
spherical crystallization and distinguished by miscibility of
drug solvent complex with non-solvent (Ribardiere et al.
1996).
In the SA method, a drug solution in a good solvent is
poured into poor solvent provided the miscibility and
interaction or binding force between solvents are stronger
than interaction between drug and good solvent to precip-
itate out the crystals (Di Martino et al. 2000). A third
solvent which is added into the system while stirring and
preferentially wets the precipitated crystals, is termed as
‘bridging liquid’. This bridging liquid is immiscible with
poor solvent but is capable to collect the crystals suspended
in a system and forms a liquid bridge between the solid
crystal due to capillary negative pressure and interfacial
tension between the interface of solid and liquid. Thus the
nature of the bridging liquid plays an important role in the
agglomeration process (Rossetti and Simons 2003; Thati
and Rasmuson 2011). The selection and amount of the
bridging liquid are the most important parameters in
spherical crystallization. The formation of loose flocs or
compact pellets depends upon the amount of bridging
liquid (Thati and Rasmuson 2012). Thus, formation of
spherical crystal agglomerate is one of the best approaches
for preparing the solid dosage form (Szabo-Revesz et al.
2002).
Ezetimibe (EZT) (Fig. 1), chemically, 1-(4-flurophe-
nyl)-3(R)-[3-(4-flurophenyl)-3(S)-hydroxypropyl]-4(S)-(4-
hydroxyphenyl)-2-azatidinone, selected in the present work
is a lipid lowering compound that selectively inhibits the
intestinal absorption of cholesterol (Woodlinger 2005,
Dixit and Nagarsenker 2008). It is a white crystalline
powder having a poor aqueous solubility as well as poor
bioavailability (35–65 %) (Sancheti et al. 2009). Few
experiments have been reported for the improvement in
micromeritic and dissolution properties of EZT in the form
of co-crystal (Mulye et al. 2012) and spherical crystal (Patil
and Bhokare 2012). In this article, authors have attempted
the formation of spherical agglomerates for direct tableting
along with improvement in physicochemical properties of
EZT.
The objective of the current study was to improve the
physicochemical and micromeritic properties of poorly
water soluble EZT, via spherical crystallization technique.
Different hydrophilic polymers such as polyvinyl pyrrol-
idone K30 (PVP) and/or poloxamer 188 (poloxamer) and
different bridging liquids viz. chloroform, dichlorometh-
ane and/or ethyl acetate were employed to form various
batches of spherical agglomerates. Acetone and water
were used as good and poor solvent system respectively.
The prepared spherical crystals were characterized by
Fourier transformation infrared spectroscopy (FTIR),
X-ray powder diffractometry (XRPD), Scanning electron
microscopy (SEM), Differential scanning colorimetry
(DSC), flow properties, packability, saturation solubility
studies, drug content and dissolution studies. The com-
pressed tablet was prepared from agglomerated crystals of
EZT with excipients and its evaluation properties were
compared with the marketed tablet (EZEDOC 10 mg). For
the formulation of tablet only one batch (B3), having a
better flowability and dissolution properties was selected.
The performance characteristics of these tablets such as;
hardness, weight variation, drug content uniformity, fria-
bility test, disintegration time and dissolution rate were
further assessed.
Materials and methods
Materials
EZT, PVP and poloxamer were generously supplied by
Indoco Remedies, Mumbai, India as gift samples. All the
chemicals were of analytical grade and purchased from
Loba Chemie, Mumbai, India. Double distilled water used
throughout the experiment.
Fig. 1 Chemical structure of EZT
A. Patil et al.
123
Preparation of spherical agglomerates
In order to produce spherical agglomerates, a solution of
1gm of EZT in a 4 ml of acetone was poured into 40 ml of
distilled water containing 1 gm of PVP and/or poloxamer
and, 2 ml of bridging liquid (chloroform and/or dichloro-
methane and/or ethyl acetate) was added dropwise with
stirring at 750 ± 50 rpm at room temperature to form the
crystals. The crystals were collected by vacuum filtration
and dried in an oven at 40 �C for 12 h and further at room
temperature for 5 days. The crystals were stored in a des-
iccator at room temperature until further analysis. The
compositions of different batches of spherical crystals are
given in Table 1.
Powder flow measurement (flowability)
The flowability of pure EZT and agglomerated samples
was assessed by determination of the angle of repose, bulk
density, tap density, Carr’s index and Hausner’s ratio.
Angle of repose was determined by the fixed funnel
method whereas Carr’s index (CI) and Hausner’s ratio were
calculated from bulk density and tap density. Hausner’s
ratio was determined from the ratio of tap density and bulk
density. CI was calculated according to the following
equation (Nokhodchi et al. 2007a)
CI ¼ Tapped density�Bulk densityð Þ=Tapped density½ �� 100
ð1Þ
The mean of six determinations was reported.
Packability determination
In packability determination, pure EZT and/or agglomer-
ated sample was poured slowly and gently into measuring
cylinder and tapped for 100, 200, 300, 400, 500, 600, 700,
800, 900, and 1,000 times. The packability was calculated
according to Kawakita and Ludde equation as follows.
n=Cð Þ ¼ 1=abð Þ þ n=að Þ ð2Þ
where n is tap number, C denotes the volume reduction
which can be calculated according to Eq. (3), 1/a defines
the degree of volume reduction termed as compactability
and 1/b is a constant related to cohesion termed as
cohesiveness.
C ¼ V0�Vnð Þ =V0 ð3Þ
where, V0 and Vn are the powder bed volumes at initial and
nth tapping state respectively.
The plot of n/C verses n is linear and compactability 1/
a obtained from the slope a and the cohesivity 1/b obtained
from the intercept 1/ab of the plot of the modified
Kawakita and Ludde equation (Comoglu 2007).
Saturation solubility studies
Saturation solubility studies were performed according to
the method reported by Higuchi and Cannors (Higuchi and
Cannors 1965). The excess amount of pure drug and/or
spherical agglomerates were added in 10 ml of distilled
water and acetate buffer (pH 4.5) with 0.45 % sodium
lauryl sulphate (SLS) separately, taken in a screw cap tube
and shaken for 24 h in a rotary flask shaker at room tem-
perature. Appropriate aliquots were filtered through the
Whatman filter paper no. 41 and analyzed spectrophoto-
metrically at 232 nm (Shimadzu 1800, Japan).
Determination of drug content
For the determination of drug content, spherical agglom-
erates equivalent to 5 mg of EZT were dissolved in 20 ml
of methanol and the volume was adjusted to 50 ml with
distilled water. The solution was filtered through Whatman
filter paper no. 41, appropriately diluted and absorbance
was measured at 232 nm using double beam UV spectro-
photometer (Shimadzu 1800 Japan).
Dissolution studies
In-vitro dissolution studies were performed in 500 ml
acetate buffer (pH 4.5) with 0.45 % SLS at 50 rpm main-
tained at 37 ± 0.5 �C (Model Disso 2000 tablet dissolution
test apparatus, Lab India, India) using a paddle method.
EZT and its spherical agglomerates equivalent to 10 mg of
EZT was added to the dissolution media and samples were
withdrawn at appropriate time intervals. The dissolution
medium was replaced with an equal volume of the fresh
medium. The samples were filtered through the Whatman
filter paper no. 41, suitably diluted and analyzed at 232 nm
by UV spectrophotometer (Shimadzu 1800, Japan).
Table 1 Composition of spherical agglomerates
Drug ? polymer Bridging liquid Batch code
EZT ? PVP Chloroform A1
EZT ? PVP Dichloromethane A2
EZT ? PVP Ethyl acetate A3
EZT ? poloxamer Chloroform B1
EZT ? poloxamer Dichloromethane B2
EZT ? poloxamer Ethyl acetate B3
Spherical crystallization of ezetimibe
123
Scanning electron microscopy (SEM)
The morphology of pure drug, polymer and spherical
agglomerates were evaluated using Scanning electron
microscopy (SEM-Jeol Instruments, JSM-6360, Japan).
Samples were mounted on double-faced adhesive tape,
sputtered with gold. Scanning electron photographs were
taken at an accelerating voltage of 20 kV and obtained
micrographs were examined at X85, X100, X180, X200,
X250, X400 magnifications.
X-ray powder diffractometry (XRPD)
The XRPD patterns of all samples were recorded by using
Bruker D2 PHASER (Bruker AXS Analytical Instruments
Pvt. Ltd. Germany) X-ray powder diffractometer with Cu
as anode material, operated at a voltage of 30 kV and
current 10 mA. The samples were analyzed in the 2h angle
range of 5�–90�.
Differential scanning calorimetry (DSC)
The DSC thermograms of all formulations including pure
were recorded by using differential scanning calorimetry
(DSC 823E, Mettler Toledo, Switzerland). Approximately
2–5 mg of each sample was heated in the pierced alu-
minium pan from 30 to 300 �C at a heating rate of
10 �C min-1 under a stream of nitrogen at a flow rate of
40 ml min-1.
Fourier transformation infrared spectroscopy (FTIR)
The FTIR spectra were obtained from Shimadzu FTIR
spectrometer (IR Affinity 1 model, Japan) spectrometer.
The pellets of the drug and KBr prepared on KBr press.
The sample were scanned over the range of
4,000–500 cm-1.
Preparation of tablet from agglomerated crystals
The agglomerated crystals of only one batch B3
(EZT:poloxamer:ethyl acetate) were directly compressed
with specific concentrations of excipients given in the
Table 2 (Rowe et al. 2009) with hydraulic press (Techno-
search Instruments M 15, Thane, India) using 8 mm flat
faced punch and die set, at a pressure of 25 kg cm-2.
The advantages of direct tableting via spherical
agglomeration are reduced cost of production and limitation
in the processing steps. Further, no special equipment and
energy are required for this process. The drug crystals are
converted to spherical form to improve flowability, com-
pressibility, packability and to enhance physicochemical
characteristics of poorly water soluble drug. In addition to
that the properties of the particles such as shape, size, size
distribution, specific surface area can be manipulated by
crystallization processes (Hari Krishna et al. 2013; No-
khodchi et al. 2007a).
Evaluation of prepared tablets
The prepared tablets of EZT (batch B3) and marketed
tablet (EZEDOC 130 mg) were evaluated in terms of dis-
solution studies, disintegration time, friability test, weight
variation, uniformity of content, thickness, diameter and
hardness. Dissolution studies were conducted similarly as
that of formulations (United State Pharmacopoeia USP
2002). Disintegration test was performed by using disin-
tegration test apparatus (Labindia DT1000, India) (United
State Pharmacopoeia USP 2002). Friability test (Roche
friabilator, Labindia FT1020, India), weight variation,
uniformity of content test were performed as described
under procedure for uncoated tablet in Indian Pharmaco-
poeia (Indian Pharmacopoeia IP 2007). Thickness and
diameter were determined by using vernier caliper (Mitu-
toyo, Japan). Hardness was measured by using a Pfizer
hardness tester (Lachman et al. 1986).
Statistical analysis
The results were expressed as the mean ± standard devi-
ation and statistically analyzed using ANOVA wherever
necessary.
Results and discussion
Preparation of spherical agglomerates of EZT
For the preparation of spherical agglomerates, the selection
of good solvent, poor solvent and bridging liquid was
purely on the basis of the miscibility of solvents and
Table 2 Composition of tablet of EZT spherical crystals (Batch B3)
Ingredients mg per tablet
Spherical agglomerates equivalent to 10 mg of EZT 20
Microcrystalline cellulose 26
Sodium starch glycolate 11
Sodium lauryl sulphate 03
Magnesium stearate 02
Talc 02
Lactose 66
Total weight 130
A. Patil et al.
123
solubility of a drug in an individual solvent (Kawashima
et al. 1995). Since, EZT is soluble in acetone, slightly
soluble in chloroform, dichloromethane and ethyl acetate
but insoluble in water; acetone and water were used as a
good solvent and poor solvent respectively and chloroform,
dichloromethane and ethyl acetate were employed as
bridging liquids. In the absence of bridging liquid, finely
divided solid crystals were separated from each other.
However, after the addition of small amounts of bridging
liquid into the system, the solids appeared to be wetted and
formed a bridge between the solid crystals and finally
agglomerates into the spherical form.
When the amount of bridging liquid was decreased in
the system, the unwetted part of the crystal increased,
while, increasing the content of bridging liquid increased
the average diameter of agglomerated crystals. The opti-
mized concentration of good solvent and various bridging
liquid was found to be 2:1 (v/v). Further, different stirring
rates were tested and optimum stirring rate was found to be
750 rpm. At lower stirring rates the formation of lumps
were observed, while, high stirring rate destroyed the
agglomerates.
It has been well documented that the residual solvents
might influence the physicochemical properties of poly-
mers and drugs such as particle size, dissolution, wetta-
bility and glass transition (Tg) temperature. The residual
solvents could be considered to have plasticizing effect on
polymers and drugs in the formulations. The Tg might be
significantly lowered in the presence of residual solvents
leading to alteration of properties of a substance. This
ultimately can affect the dissolution and other physico-
chemical properties (Witschi and Doelker 1997; Passerini
and Craig 2001). Therefore, the drying time and drying
temperature which affect the rate of residual solvent loss
should be maintained appropriately so as to achieve max-
imum residual solvent loss and negligible retention as
specified in the limits (Witschi and Doelker 1997).
Here the spherical crystals were collected by vacuum
filtration and dried in an oven at 40 �C for 12 h and further
at room temperature for 5 days. This drying time was
considered to be sufficient for further analysis of spherical
crystals. Therefore, analysis of residual solvents was not
performed. Further, physical characterization studies
revealed that the crystallinity of the drug was retained in
spherical agglomerates resulting in improvement of desired
properties of drug. These results indicated maximum
residual solvent loss in the formulations.
Flowability determination
The micromeritic properties such as flowability of spheri-
cal agglomerates are shown in Table 3. It is evident that the
flowability in the terms of angle of repose, Hausner’s ratio
and Carr’s index for agglomerates was much improved
compared to that of pure drug alone. Statistical analysis
showed that the angle of repose, Hausner’s ratio and Carr’s
index for agglomerates reduced significantly as compared
to pure drug (p \ 0.001). However, no significant
Table 3 Flow properties of pure EZT and its spherical crystals
Batch
code
Hausner’s
RatioaCarr’s Index
(%)aAngle of Repose
(h�)a
EZT 1.40 ± 0.014 29.5 ± 0.68 40.89 ± 1.09
A1 1.14 ± 0.007b 13.5 ± 0.70b 21.9 ± 1.08b
A2 1.19 ± 0.002b 15.6 ± 0.85b 18.7 ± 1.12b
A3 1.16 ± 0.01b 14.5 ± 0.60b 17.8 ± 1.08b
B1 1.13 ± 0.005b 12.56 ± 0.62b 20.84 ± 1.15b
B2 1.19 ± 0.006b 16.61 ± 0.86b 22 ± 1.41b
B3 1.13 ± 0.009b 13.64 ± 0.90b 17.5 ± 0.70b
a Data shown as mean ± SD, (n = 6); SD standard deviationb Significant difference as compared to pure EZT i.e. significant
(p \ 0.001)
Table 4 Saturation solubility of pure drug and spherical
agglomerates
Batch code In water (lg ml-1)a In acetate buffer (lg ml-1)a
EZT 12.00 ± 0.007 4.32 ± 0.11
A1 103.94 ± 0.86b 21.98 ± 0.19b
A2 29.37 ± 0.72b 23.24 ± 0.67b
A3 106.51 ± 0.67b 21.95 ± 0.98b
B1 28.28 ± 0.86b 22.23 ± 0.41b
B2 87.20 ± 0.92b 21.29 ± 0.79b
B3 27.5 ± 0.70b 21.17 ± 0.57b
a Data shown as mean ± SD (n = 3), SD standard deviationb Significant difference as compared to pure EZT i.e. significant
(p \ 0.001)
Fig. 2 Compressibility studies of EZT and their spherical agglom-
erates by Kawakita equation
Spherical crystallization of ezetimibe
123
difference was observed for these properties between the
prepared agglomerates (p [ 0.05). Hausner’s ratio of
agglomerates was \1.25, which indicated improved flow-
ability of agglomerates. The poor flow properties of pure
EZT might be due to its irregular and stone shaped
appearance while agglomeration of EZT resulted in
spherical shape and enlargement of particle size with
improved flow properties as reflected in SEM micropho-
tographs (Hari Krishna et al. 2013; Sinko 2007; Subrah-
manyam 2000).
Saturation solubility studies
The solubility of pure drug and spherical agglomerates of
EZT are given in Table 4. The spherical agglomerates have
shown increased solubility in distilled water and acetate
buffer as compared to pure drug (p \ 0.001). A significant
increase in solubility of EZT in distilled water was
obtained in the case of PVP agglomerates, which contains
chloroform and ethyl acetate as bridging liquids. In case of
poloxamer agglomerates dichloromethane was found
appropriate bridging liquid for improvement in water sol-
ubility. The solubility of EZT in acetate buffer for all
formulations were appeared in the range of
21.17–23.24 lg ml-1 which were significant in compari-
son to pure EZT. The improvement in solubility was due to
alteration in crystal forms, different habit, surface
modification and hydrophilic and surfactant properties of
polymers. In some instances, solvents included in the
crystal form solvates, changing the surface properties and
the reactivity of drug particle and internal energy of par-
ticles, playing an important role in increasing solubility of
the drug (Patil and Sahoo 2011).
Packability determination
The plot of n/C Verses n is depicted in Fig. 2. The pack-
ability parameters a, b and correlation coefficient (R2)
obtained from Kawakita and Ludde equation were given in
Table 5. It was found that, in spherical agglomerates, the
value of the parameter ‘a’ in Kawakita and Ludde equation
reduced and the value of the parameter ‘b’ increased as
compared to pure drug alone. These results proved that the
packability of spherical agglomerates were improved than
pure drug and the agglomerated crystals were suitable for
direct tableting. It suggested that these agglomerates could
flow smoothly from hopper into the die cavity to attain
uniformity in weight which was necessary in direct tab-
leting. This improvement in packability and flowability
was due to size enlargement and spherical shape of these
agglomerates (Nokhodchi et al. 2007b).
Determination of drug content
Percentage drug contents of spherical agglomerates were
found to be in the range of 95.63 ± 1.94 to 100.00 ± 1.76
w/w.
Dissolution studies
The dissolution curves of pure EZT and its spherical
crystals in acetate buffer (pH 4.5) with 0.45 % SLS are
shown in the Fig. 3. The results indicated high improve-
ment in dissolution of spherical crystals as compared to
pure drug. It was observed that the dissolution rate of
crystals was increased significantly as compared to pure
drug (p \ 0.001). Table 6 shows % drug dissolved in
5 min (DP5), % drug dissolved in 45 min (DP45) and
Table 5 Parameters of packability of pure drug and spherical
agglomerates
Batch code a b R2
EZT 0.4612 0.0331 0.997
A1 0.1175 0.0696 0.998
A2 0.1191 0.0523 0.996
A3 0.0703 0.0719 0.998
B1 0.1113 0.0535 0.996
B2 0.1971 0.0535 0.996
B3 0.0662 0.0704 0.998
a and b are parameters in Kawakita equation; R2 correlation
coefficient
Fig. 3 The dissolution curve of
pure EZT and its spherical
crystals
A. Patil et al.
123
Table 6 Dissolution data of pure EZT and its spherical crystals in acetate buffer (pH 4.5) with 0.45 % SLS
System DP5a ± SD DP45
a ± SD DE5a ± SD DE45
a ± SD
EZT 14.98 ± 1.28 57.92 ± 1.3 1.69 ± 1.04 7.3 ± 0.70
A1 33.23 ± 3.28b 94.29 ± 1.0b 4.09 ± 1.20b 12.11 ± 0.78b
A2 38.96 ± 3.33b 90.04 ± 1.66b 4.90 ± 1.03b 12.35 ± 0.89b
A3 31.26 ± 2.92b 89.89 ± 1.49b 4.29 ± 0.68b 11.56 ± 0.62b
B1 37.28 ± 3.13b 98.8 ± 0.88b 5.28 ± 0.81b 13.72 ± 0.38b
B2 47.03 ± 1.85b 99.85 ± 1.2b 6.42 ± 0.75b 13.82 ± 0.27b
B3 41.19 ± 2.08b 100.15 ± 0.86b 5.79 ± 0.93b 14.30 ± 0.82b
SD standard deviation, DP % drug dissolved, DE dissolution efficiencya Data shown as mean ± SD (n = 3)b Significant difference as compared to pure EZT i.e. significant (p \ 0.001)
Fig. 4 SEM photomicrographs
of EZT and its spherical
agglomerates. EZT (a);
spherical agglomerates of EZT
with PVP (b); spherical
agglomerates of EZT with
poloxamer (c)
Spherical crystallization of ezetimibe
123
dissolution efficiency (DE5) and (DE45) at 5 and 45 min
respectively for all formulations.
The dissolution efficiency (DE) is defined as the area
under dissolution curve up to the time t expressed as per-
centage of the area of rectangle described by 100 % dis-
solution in the same time (Khan 1975). The dissolution
efficiency at 45 min was calculated as follows:
DE45 ¼AUC of dissolution curve at 45 minute
AUC of rectangle at time 45 minute
where, AUC is area under the curve The statistical analysis
of DE values of all formulations revealed a significant
improvement in the dissolution profile of spherical
agglomerates at 5 min (DE5) and 45 min (DE45)
(p \ 0.001) as compared to pure drug alone. The release of
pure drug was incomplete i.e. 57.92 % even in 45 min. The
reason for improvement in drug dissolution was greater
hydrophilicity and surfactant properties of polymers used,
absorption of incorporated polymer on the surface of
crystals and more porous structure of spherical crystals
than pure drug (Patil et al. 2012).
On the basis of dissolution data and micromeritic prop-
erties of spherical agglomerates, B3 batch was selected for
further compression into tablet as a trial and its evaluation
properties were compared with marketed formulation.
Scanning electron microscopy (SEM)
An examination of SEM microphotographs (Fig. 4) con-
firmed that the starting material was smaller in particle size
than any of treated crystals. The untreated EZT particles
were needle and irregular in appearance, which led to very
poor flow and difficulties in compression. It is clear from
the figures that the agglomerates of EZT with PVP and
poloxamer had a larger particle size and spherical shape
compared to pure drug. This would be one of the reasons
for the excellent flowability and packability of agglomer-
ation (Patil et al. 2012), since, the area of compact in the
powder bed for spherical agglomerates was smaller than
the needle shape crystals of EZT. The figures also indicated
that agglomerates produced in presence of poloxamer were
rough in the surface as compared to PVP agglomerates.
X-ray powder diffractometry (XRPD)
The XRPD pattern of pure drug, polymers and spherical
agglomerates are presented in Fig. 5. Table 7 shows peak
intensities of pure drug and spherical agglomerates at
various diffraction angles (2h�). The XRPD scan of pure
EZT showed intense peaks, clearly indicating the crystal-
line nature of pure drug (Mulye et al. 2012). In the XRPD
patterns of spherical agglomerates, it appeared that, the
drug was not transferred into amorphous form instead; it
had maintained its crystalline pattern into spherical
agglomerates also; although some peaks were found to be
slightly diffused. Thus, the crystallinity and spherical shape
would be suitable for direct tableting of the agglomerates.
Differential scanning calorimetry (DSC)
DSC thermograms of pure EZT, polymers and their cor-
responding formulations are shown in Fig. 6. The DSC
thermogram of pure EZT showed sharp endotherm at
164.37 �C (Fig. 6a) indicating crystalline nature of the
pure drug.
The thermogram of the PVP showed a broad endother-
mic peak at the 88.23 �C (Fig. 6b) corresponding to the
loss of water and an absence of melting endothermic peak
indicating the amorphous nature of PVP. The thermogram
of poloxamer showed sharp endotherm at 55.97 �C
(Fig. 6c) indicating its characteristic crystalline nature.
There were no appreciable changes in the thermograms
of spherical agglomerates compared to pure drug since
agglomerates have shown melting endotherms (EZT–PVP
agglomerates 165.42 �C, Fig. 6d; EZT-poloxamer
agglomerates 165.12 �C, Fig. 6e) which suggested that the
spherical agglomerates still exhibited crystalline nature.
These results were also supported by XRPD studies as
discussed earlier. These observations also confirmed an
absence of any chemical interaction of drug with additives
during the agglomeration process, further supporting the
results of IR spectroscopy.
Fig. 5 XRPD patterns of EZT and its spherical agglomerates. EZT
(a); PVP (b); poloxamer (c); spherical agglomerates of EZT with PVP
(d); spherical agglomerates of EZT with poloxamer (e)
A. Patil et al.
123
Fourier transformation infrared spectroscopy (FTIR)
FTIR spectrum of EZT (Fig. 7) is characterized by prin-
cipal absorption peaks at 3222.400 cm-1 (Broad, inter-
molecular hydrogen bonded, O–H stretch), 2966.166 cm-1
(Aromatic C–H stretch), 1881.263 cm (Weak combination
and overtone band of ring), 1714.505 cm-1 (C=O of lac-
tam), 1614 cm-1 (ring skeletal vibration band),
1445.420 cm-1 (C–N stretch), 1354.672 cm-1 (in plane
O–H bend), 1217.403 cm-1 (C–F stretch), 106500.6 cm-1
(C–O stretch of secondary alcohol) and 813 cm-1 (ring
vibration due to para-disubstituted benzene) (Mulye et al.
2012). In spherical agglomerates of EZT–PVP (Fig. 7d)
and EZT-poloxamer (Fig. 7e), the peaks of EZT at
3222.400 cm-1 were observed to be shifted to 3240.209
and 3235.908 cm-1 respectively as a result of hydrogen
bonding interaction between drug and polymer. No change
Table 7 Peak intensities of pure EZT and spherical agglomerates at various diffraction angles (2h�) in their XRPD patterns
EZT EZT–PVP spherical
crystals A3
EZT-poloxamer
spherical crystals B3
2h� Intensity 2h� Intensity 2h� Intensity
17.19 1077 17.18 1,249 17.18 1,194
18.28 1,878 18.64 4,272 18.62 4,058
19.66 1,941 18.72 3,762 18.68 4,186
23.23 2,373 19.29 4,868 19.37 5,162
19.33 4,952 19.39 5,077
19.35 5,013 19.43 4,384
27.05 1,015
Fig. 6 DSC thermograms of EZT and its spherical agglomerates.
EZT (a); PVP (b); poloxamer (c); spherical agglomerates of EZT with
PVP (d); spherical agglomerates of EZT with poloxamer (e)
Fig. 7 FTIR spectra of EZT and its spherical agglomerates. EZT (a);
PVP (b); poloxamer (c); spherical agglomerates of EZT with PVP (d);
spherical agglomerates of EZT with poloxamer (e)
Spherical crystallization of ezetimibe
123
in the rest of the peaks of EZT was noted indicating its
intact structure in both spherical agglomerated crystals.
Evaluation of prepared tablet formulation
Based on the micromeritic properties and dissolution profile
of spherical agglomerates, B3 batch (EZT:poloxamer:ethyl
acetate) was selected for tablet development and evaluation.
Initially, these spherical agglomerates were directly com-
pressed into a tablet and evaluated for the parameters as
discussed in experimental section. Unfortunately, drug
release from the tablet was not satisfactory during entire
period of dissolution studies, even after maintaining opti-
mum hardness. It was only 25 % within 45 min (detail data
not shown). The reason for low dissolution profile from the
tablet might be attributed to the role played by the hydro-
philic polymers as binders, during direct compression pro-
cess. This suggested a need of disintegrant from dissolution
point of view. Thus, these agglomerates were recompressed
incorporating certain excipients and evaluated as per phar-
macopoeia (Table 2). The evaluation parameters of pre-
pared tablet and marketed tablet (EZEDOC 10 mg) are
given in Table 8. The results of evaluation revealed that all
quality control parameters such as crushing strength, weight
variation, friability, content uniformity and disintegration
test of compressed tablets with excipients remained within
the desired limits as per pharmacopoeial standards and also
nearly similar to that of the marketed tablet.
The dissolution curve of prepared tablet and marketed
tablet in acetate buffer (pH 4.5) with 0.45 % SLS are
shown in the Fig. 8. Table 9 shows % drug dissolved in
5 min (DP5), % drug dissolved in 45 min (DP45) and dis-
solution efficiency (DE5) and (DE45) at 5 and 45 min
respectively for prepared tablet and marketed tablet.
The statistical analysis of DE values revealed no sig-
nificant difference between the dissolution profile of pre-
pared tablet and marketed tablet (p [ 0.05). The results
indicated that the dissolution profile of prepared tablet was
almost comparable with that of marketed tablet. The
compressed EZT tablet released 95.36 % of drug within
45 min while marketed tablet released 98.65 % of drug
within the same time. The results obtained from all eval-
uation parameters of the prepared tablet of EZT by using
spherical crystals was similar to the parameters of a mar-
keted tablet. These results supports that the formulation of
Table 8 Evaluation parameters of EZT spherical crystal (Batch B3) and marketed tablet
Evaluation parameters EZT-SCTa EZT-MTa
Thickness (mm) 2.98 ± 0.02 3.30 ± 0.01
Hardness (kg cm-2) 5.2 ± 0.26 5.4 ± 0.10
Diameter (mm) 8.0 ± 0.11 6.61 ± 0.17
Weight variation (%) 130 ± 2.11 130 ± 1.00
Friability (%) 0.22 ± 0.02 0.20 ± 0.015
Disintegration time (min) 10 ± 2.82 8.0 ± 1.41
Uniformity of content (label claim 10 mg) 98.81 ± 0.37 99.54 ± 0.27
SD standard deviation, EZT-SCT EZT tablet by spherical crystallization, EZT-MT marketed tablet of EZTa Data shown as mean ± SD (n = 3)
Table 9 Dissolution data of EZT-SCT and EZT-MT in acetate buffer (pH 4.5) with 0.45 % SLS
System DP5a ± SD DP45
a ± SD DE5a ± SD DE45
a ± SD
EZT-SCT 34.15 ± 3.69 95.36 ± 1.37 4.01 ± 1.08 12.36 ± 0.79
EZT-MT 33.04 ± 1.68 98.65 ± 0.66 5.35 ± 0.77 12.51 ± 0.57
SD standard deviation, DP: % drug dissolved, DE dissolution efficiency, EZT-SCT EZT tablet by spherical crystallization, EZT-MT marketed
tablet of EZTa Data shown as mean ± SD (n = 3)
Fig. 8 The dissolution curves of prepared tablet and marketed tablet
of EZT EZT-SCT: EZT tablet by spherical crystallization; EZT-MT:
marketed tablet of EZT
A. Patil et al.
123
tablet by using spherical crystallization technique is a good
alternative for marketing tablet in case of antihyperlipi-
demic drug EZT.
Conclusion
In the present investigation, EZT spherical agglomerates
were successfully prepared using spherical crystallization
technique with hydrophilic carriers. The altered size and
shape of prepared spherical agglomerates indicated modi-
fied crystal habit which could be responsible for significant
improvement in flowability, packability, solubility and
dissolution properties of EZT agglomerates. The microm-
eritic properties of agglomerates were significantly
improved, resulting in successful direct tableting. The
prepared tablet from spherical agglomerates showed simi-
lar physicochemical properties as compared to marketed
tablet suggesting an effective and alternative approach for
improved performance of EZT and its tablet formulation.
Acknowledgments Authors are grateful to Indoco Remedies,
Mumbai, India for providing gift samples of drug and polymers for
the research work. The authors are thankful to Shivaji University,
Kolhapur and Pune University, Pune, Maharashtra, India for provid-
ing analytical facilities. All authors express their sincere gratitude
towards Principal, Govt. College of Pharmacy, Karad, Maharashtra,
India for providing laboratory facilities and constant encouragement.
Conflict of interest Authors declare no conflict of interest.
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