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Page 1: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 2: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 3: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 4: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 5: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 6: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 7: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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

Page 8: Spherical crystallization of ezetimibe for improvement in physicochemical and micromeritic properties

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.

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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

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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.

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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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