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Chapter 5 Formulation and evaluation of self-
emulsifying formulations of itraconazole using pharmaceutically
accepted lipid-based excipients Page no. 157 to 191
Chapter 5 Itraconazole
Page 157
Chapter 5 Formulation and evaluation of self-emulsifying formulations of
itraconazole using pharmaceutically accepted lipid-based excipients Abstract
Poorly water-soluble drug, itraconazole offers a challenge in developing a drug product
with adequate bioavailability. The potential for lipidic self-emulsifying drug delivery
system to improve the oral bioavailability of itraconazole was investigated in fasted rats. A
series of itraconazole SEDDS were prepared in three groups based on oil:S/CoS mixture
ratios (1:9, 1:6 and 1:4) using Capryol 90 (oil), a mixture of Labrasol and Tween 20
(surfactants) and Transcutol P (co-surfactant). The multi-component delivery systems
were optimised by evaluating their ability to self-emulsify when introduced in simulated
gastric fluid, without pepsin, under gentle agitation and by determination of droplet size
and visual observation. Three formulations (F5, F21 and F27), one from each group were
selected based on droplet size and visual observation. Pseudo ternary phase diagram was
constructed to identify the efficient self-emulsification region. The effect of oil and
surfactants content on mean globule size of resulting emulsions was studied. The
optimized formulations were assessed for dissolution, in vitro diffusion, ex vivo stomach
and intestinal permeability along with the marketed capsule. From the data obtained in this
work, it was clear that oil to surfactant and co-surfactant ratio has the main impact on the
droplet size of the emulsion formed after dilution. However, the relation between droplet
size and in vivo absorption of itraconazole was futile. The order of AUC was 1:4 > 1:6 >
1.9 for oil:S/CoS mixture ratios. Following an oral administration of developed SEDDS
and marketed capsule to rats, a 1.7, 2.0 and 2.33-fold increase in bioavailability was
observed for F5, F21 and F27 respectively, compared with marketed capsule. The results
from this study demonstrate the potential use of SEDDS to provide an effective way of
improving oral absorption of lipophilic drugs.
Chapter 5 Itraconazole
Page 158
5.1. Introduction
In recent years, major advances in healthcare have led to an unwelcome increase in the
number of life-threatening infections due to true pathogenic and opportunistic fungi
(Richardson, 2005). Recently, there have been an increasing number of profound fungal
infections caused by fungi such as those belonging to the genus Candida, the genus
Aspergillus and the genus Cryptococcus. This is a particular complication encountered in
transplant patients, those administered a large quantity of antibiotics, anticancer drugs
(carcinostatic) or a steroidal agents over a long period, AIDS patients, or those suffering
from cancer in the terminal stage, and those with hematological malignancies undergoing
intensive chemotherapy and/or bone marrow transplantation (Bodey, 1992). Invasive
fungal infections are a major cause of morbidity and mortality in patients receiving bone
marrow transplants for leukemia as well as in immunocompromised cancer patients
(Anaissie, 1992).
Itraconazole (ITZ) is a broad spectrum antifungal agent and belongs to trizole group
indicated in the treatment of local and systemic fungal infections (Grant and Clissold,
1989).
Itraconazole is a synthetic anti-fungal drug, which is composed of a 1:1:1:1 racemic
mixture of four diastereomers (two enantiomeric pairs). Three chiral centers are present in
each diastereomer which possess a molecular formula of C35H38Cl2N8O4 and molecular
weight of 705.64 g/mol (Grant and Clissol, 1989; Jain and Sehgal, 2001). Itraconazole is
poorly soluble in aqueous media (less than 1 µg/mL in aqueous solutions at pHs of 1-12.7)
with a partition coefficient greater than 5 in octanol/water at pH 6. Thus, in spite of the
high antifungal activity, the bioavailability of unformulated crystalline itraconazole is
extremely low (Jung et al., 1999; Verreck et al., 2003). In order to enhance its solubility
and dissolution rate and thereby bioavailability, various formulations have been developed
and are briefly reviewed in Section II.
Histoplasmosis is a serious opportunistic infection in patients with AIDS and itraconazole
has demonstrated activity against Histoplasmosis capsulatum (Vyas and Bradsher, 2011).
Itraconazole is a weak base (pKa = 3.7) with high lipophilicity (log D > 5) (Peeters et al.,
2002) Its aqueous solubility is estimated at approximately 1 ng/mL at neutral pH and
approximately 4 μg/mL at pH 1, (Peeters et al., 2002) and thus it is ionized and water
soluble only at low pHs, as in gastric juice.
Chapter 5 Itraconazole
Page 159
Itraconazole is available as capsules or an oral solution, and doses of 200 mg daily or 200
mg twice a day are used therapeutically (Barone et al., 1993; Physician Desk Reference,
2000). Because it has relatively low bioavailability after oral administration, especially
when given in capsule form (Barone et al., 1998; Heykant et al., 1989), gastric acidity is
required for drug dissolution and adequate absorption with capsule formulations.
Decreased absorption has been observed in the fasting state and in patients with low
gastric acidity (Barone et al., 1993). Furthermore, in persons with AIDS, the absorption of
itraconazole from capsules was reduced by 50% compared with absorption in healthy
persons (Smith et al., 1992). Hypochlorhydria and thus a relatively high gastric pH, a
frequent complication of human immunodeficiency virus (HIV) infection, may be
responsible for this phenomenon (Welage et al., 1995).
Co-administration of acidic beverage with itraconazole may be an effective approach in
improving the bioavailability of itraconazole in patients with who are hypochlorhydric, as
AIDS patients (Lange et al., 1997a) or who are taking gastric acid suppressant (Lange et
al., 1997b). Higher consumption of sugar-sweetened beverages (like coca cola) is
associated with weight gain and increased risk for the development of type 2 diabetes
mellitus, and caffeine is a psychoactive substance. In such situation, co-administration of
vitamin C beverage and itraconazole may be useful for achieving maximum absorption of
itraconazole in patients with drug- or disease-related gastric hypochlorhydria (pH > 4)
(Bae et al., 2011). In addition, itraconazole has been also found to be a substrate of P-
glycoprotein (P-gp) (Balayssac et al., 2005; Wang et al., 2002). P-gp activity is an
important mechanism that decreases the oral bioavailability of drugs by limiting intestinal
absorption (Greiner et al., 1999; Yamaguchi et al., 2002).
In light of the aforementioned discussion, we explored the potential application of lipid-
based drug delivery system in the development of a self-emulsifying drug delivery system
(SEDDS) of itraconazole. SEDDS formulations containing itraconazole were developed
using different proportions of oil and surfactants (GRAS excipients) for oral
administration. Systems were evaluated for the quality of emulsion produced and mean
droplet size. Optimized formulations were further evaluated for dissolution, ex vivo
stomach and intestinal permeability across rat tissues and in vivo performance in rats.
Physicochemical properties of SEDDS and pharmacokinetic parameters were evaluated in
comparison to Itaspor® capsules
Chapter 5 Itraconazole
Page 160
The objective of the investigation was to develop and characterize the self-emulsifying
drug delivery systems of poorly water soluble drug, itraconazole with a view to improve
its solubility, dissolution rate , ex vivo permeation and in vivo absorption in animal model.
The formulations were developed by employing excipients with established long term
acceptability. The impact of excipients ratios and droplet size on bioavailability was also
studies for all the developed formulations.
5.2. Materials and methods
5.2.1. Materials
Itraconazole (ITZ) was a generous gift from Matrix Laboratories Ltd. (Hyderabad, India);
Isopropyl myristate (IPM), Propylene Glycol Dicaprylate/Dicaprate (Captex® 200) and
Glycerol Caprylate Caprate (Captex® 355) were obtained from Subhash Chemical
Industries (Pune, India); propylene glycol monocaprylate (Capmul MCM®), Capmul
MCM (8) were obtained from Abitec Corp., Janesville, WI. Propylene glycol
monocaprylate (CapryolTM 90), PEG-8 glycol caprylate (Labrasol®) and diethylene glycol
monoethyl ether (Transcutol P®) were provided by Gattefosse, France. PEG-35 castor oil
(Cremopho EL®) was obtained from BASF Corp., Germany. Glyceryl caprylate (Imwitor®
988) was provided by Sasol GmbH, Witten, Germany. PEG-20 sorbitan monolaurate
(Tween 20) and Tocopherol acetate were purchased from Merck (Mumbai, India).
Propylene glycol was purchased from Spectrochem (Mumbai, India). Capsule shells were
provided by Capsugel, Mumbai. Ketoconazole was purchased from HIMEDIA. All other
chemicals and solvents used were of analytical grade.
5.2.2. Solubility studies
The solubility of itraconazole in various oils, surfactants and co-surfactants was
determined. An excess amount of itraconazole was added to 5 ml of each selected oils and
surfactants and was shaken reciprocally at 25oC for 24 hrs. The supernatant portion of the
supersaturated solution was carefully withdrawn and suitably diluted with methanol, and
solubility of itraconazole was determined using HPLC (Jasco, Japan) at 263 nm (Shim et
al., 2006; Yang et al., 2008; Yoo et al., 2000). The HPLC system consisted of RP column
(LCGC Qualisil BDS C18; 5 µm 250 mm x 4.6 mm i.d) and acetonitrile: water (90:10) as
a mobile phase. A 40µL volume was injected into the column at a flow rate of 0.7mL/min
Chapter 5 Itraconazole
Page 161
5.2.3. Pseudo-ternary Phase Diagrams
The pseudo-ternary phase diagrams were constructed using water dilution method
(Djordjevic et al., 2004). Capryol 90 was used as the oil phase, mixture of Labrasol and
Tween 20 as the surfactant and Transcutol P as the co-surfactant. Phase diagrams were
constructed by a technique well described (Kommuru et al., 2001; Nazzal et al., 2002;
Taha et al., 2004) with ratios as mentioned in Table 5 and all preparations were diluted
100 times with 0.1N HCl. For each phase diagram at specific oil:Smix ratios (1:9, 1:6 and
1:4), mixtures of the oil, the surfactant and the co-surfactant were prepared, and the
mixture was diluted with 0.1N HCl, maintained at 37°C. Dilution medium was added drop
by drop while mixing on a cyclomixer, and the samples were marked as being optically
clear or turbid. Phase diagrams were then constructed using Tri plot v1-4 software (David
Graham and Nicholas Midgley, Loughborough, Leicestershire, UK).
5.2.4. Preparation of itraconazole self-emulsifying formulations
A series of itraconazole SEDDS were prepared with fixed concentration of itraconazole
(25 mg) and varying concentrations of Capryol 90, Labrasol, Tween 20 and Transcutol.
Itraconazole was dissolved in Capryol 90 and then mixture of Labrasol, Tween 20 and
Transcutol were accurately weighed and added to itraconazole oily solution. The mixture
was slightly heated on water bath for 5-10 mins at 60°C until a transparent preparation was
obtained.
5.2.5. Characterization of Self emulsifying formulation
5.2.5.1. Visual observation and droplet size determination
0.05 mL formulations were diluted in 5 mL of dilution media (0.1N HCl) maintained at
37°C, 100 times dilution. Visual observation of the samples was recorded as previously
reported (Craig et al., 1995; Khoo et al., 1998). Globule Size of the same diluted samples
was measured by Zetasizer ZS 90 and measurements are shown in Table 5.3.
5.2.5.2. Characterization of selected formulations
Droplet size, polydispersity index and zeta potential were measured on Zetasizer ZS 90
after 100 times dilution in different media viz. Distilled water (DW), 0.1N HCl and
phosphate buffer saline pH 6.8 (PBS) maintained at 37°C. Drug content was measured by
HPLC.
Chapter 5 Itraconazole
Page 162
Formulations were also evaluated for dissolution study, in vitro diffusion study, ex vivo
stomach and ex vivo intestinal permeability study in rats. In vivo study was also carried out
for developed itraconazole SEDDS and extemporaneous suspension of market capsule.
5.2.5.3. Drug content
SEDDS formulation equivalent to 25 mg of itraconazole was taken and diluted in
methanol. Volume was made up to 25 mL with methanol (1mg/mL). 0.2 mL was
withdrawn from the above solution and to it 4.8 mL of methanol was added and mixed
well. 5 mL of 0.1 N HCl was added to above mixture and mixed well (20 µg/mL).
Samples were prepared in triplicate and absorbances were taken at 258 nm on UV visible
spectrophotometer (Shimadzu UV-2450, Japan) keeping equal mixture of methanol and
0.1N HCl (1:1) as a reference. Placebo was also treated in the same way to check
interference, if any.
5.2.5.4. Spectroscopic characterization of optical clarity
The optical clarity of aqueous dispersions of SEDDS formulation was measured
spectrophotometrically. Composition was prepared according to the design and diluted to
100 times with 0.1N HCl (USP 30) (USP 30/NF25). The % transmittance of solution was
measured at 650 nm, using distilled water as a reference (Cirri et al., 2007; Subramanian et
al., 2004; Zhang et al., 2008).
5.2.5.5. Morphological characterization
The morphology of self emulsifying formulation was observed by using a transmission
electron microscope (TEM) (Phillips Tecnai 20, Holland) at an acceleration voltage of 200
kV and typically viewed at a magnification of 43,000×. The size of the colloidal structures
was determined using AnalySIS® software (Soft Imaging Systems, Reutlingen, Germany).
Formulations were diluted with distilled water 1:25 and shaken. Carbon-coated copper
grids were glow-discharged (Edwards E306A Vacuum Coater, England) and 10 µL of
sample adsorbed on to these holey film grid and observed after drying.
5.2.5.6. Determination of droplet size and zeta potential
Droplet size and zeta potential of the formed emulsion were determined by photon
correlation spectroscopy that analyzes the fluctuations in light scattering due to Brownian
motion of the particles, using a Zetasizer ZS 90 (Malvern Instruments, UK). Light
scattering was monitored at 25°C at a 90° angle.
Chapter 5 Itraconazole
Page 163
5.2.5.7. Dissolution study
Dissolution studies of itraconazole capsule and itraconazole SEDDS filled in hard gelatine
capsule (size # “000”) was carried out using USP XXIII Dissolution apparatus I (basket
type) at speed of 50 rpm in 900mL for 100 mg marketed capsule and 225 mL for 25 mg
SEDDS 0.1 N HCl at 37 ± 0.5 °C. Aliquots of 5 mL were removed at 2, 5, 10, 15, 30, 45,
60, 75 and 120 min. Volume of aliquots was replaced with fresh dialyzing medium each
time. These samples were analyzed quantitatively for amount of itraconazole released at
corresponding time by using UV-visible spectrophotometer (Shimadzu UV-2450, Japan)
at 255 nm.
5.2.5.8. In vitro diffusion study
In vitro diffusion studies were performed for the formulations developed (F5, F21 and
F27), using a dialysis technique (Dixit et al., 2010; Kang et al., 2004; Patil et al., 2004).
The dialyzing medium was 0.1N HCl. One end of dialysis tubing (Dialysis membrane 70,
HIMEDIA; MWCO 12,000-14,000 daltons; pore size: 2.4 nm) (7 cm in length) was
clamped and then 1.1 mL (≡25 mg of drug) of self-emulsifying formulation was placed in
it. The other end of the tubing was also secured with dialysis closure clip (HIMEDIA,
Mumbai) and was allowed to rotate freely in 225 mL of dialyzing medium and stirred
continuously with magnetic bead on magnetic plate at 37°C. Aliquots of 5 mL were
removed at different time intervals. Volume of aliquots was replaced with fresh dialyzing
medium each time. These samples were analyzed quantitatively for itraconazole dialyzed
across the membrane at corresponding time by using UV-visible spectrophotometer at 255
nm.
For marketed formulation (Itaspor®-INTAS, pellets in capsule), capsules were crushed in
mortar with pestle. From the crushed pellets, blend equivalent to 25 mg (113.975 mg
blend) was weighed and made suspension by adding 3 mL of DW and was filled in
dialysis membrane. The membrane was sealed from both the end with the help of dialysis
closure clips and was placed in 225 mL of 0.1N HCl
5.2.5.9. Ex vivo stomach permeability study
Male Sprague-Dawley rats (250-300 g) were euthanized in carbon-dioxide vacuum
chamber. All experiments and protocols described in this animal study were approved by
the Institutional Animal Ethics Committee of B V Patel PERD Centre, Ahmedabad, India
and were in accordance with the guidelines of the Committee for Purpose of Control and
Chapter 5 Itraconazole
Page 164
Supervision of Experiments on Animals, Ministry of Social Justice and Empowerment,
Government of India. To check the stomach permeability, the stomach part was isolated
carefully and taken for the ex vivo permeation study. Then this tissue was washed with
physiological acid solution containing 100 mM HCl and 54 mM NaCl to remove the
mucous and gastric contents. Then the tissue was rinsed with 100 mM HCl. The method
employed was modified from experimental procedures well described in the literature
(Gharzouli et al., 1995; Hung and Neu, 1997; Shah and Khan, 2004).
SEDDS formulations, 0.4 mL (equivalent to 10 mg of drug) were injected into the
stomach and tissues were tightly closed with the help of threads. Similarly 2 mL
extemporaneous suspension of market capsule (Itaspor®-INTAS) equivalent to 10 mg of
drug was filled in stomach tissue and was placed in a beaker with constant stirring and
temperature of 37° C on a magnetic stirrer. The receiver compartment was filled with 30
mL of 100 mM HCl. The absorbance was measured at 255 nm, keeping the respective
blank. The percent permeation of drug was calculated against time and plotted on a graph.
5.2.5.10. Ex vivo intestinal permeability study
This was carried out by the method well described in the literature (Araya et al., 2006;
Ghosh et al., 2006). Male Sprague-Dawley rats (250-300 g) were euthanized in carbon-
dioxide vacuum chamber. All experiments and protocols described in this animal study
were approved by the Institutional Animal Ethics Committee of B V Patel PERD Centre,
Ahmedabad, India and were in accordance with the guidelines of the Committee for
Purpose of Control and Supervision of Experiments on Animals, Ministry of Social Justice
and Empowerment, Government of India. To check the intestinal permeability, small
portion of small intestine was isolated and used for the ex vivo permeability study. The
tissue was thoroughly washed with pH 6.8 phosphate-buffered saline (USP 30) (USP
30/NF25) to remove any mucous and lumen contents.
One mL SEDDS formulations were diluted to 5 mL with distilled water (outside mixing
for 1 minute by vortex mixer), the resultant sample (5 mg/mL) was injected into the lumen
of the duodenum using a syringe, and the two sides of the intestine were tightly closed
with the help of threads. Extemporaneously suspension was prepared from market capsule
(Itaspor®-INTAS), and 1 mL equivalent to 5 mg of drug was filled in stomach tissue
similar to that of SEDDS formulations. Then the tissue was placed in a beaker with
constant stirring and temperature of 37°C on magnetic stirrer. The receiver compartment
Chapter 5 Itraconazole
Page 165
was filled with 30 mL of phosphate-buffered saline containing 20% PEG 400. The
absorbance was measured at 258 nm, keeping the respective blank. The percent diffusion
of drug was calculated against time and plotted on a graph.
5.2.6. HPLC analysis
See Chapter 4 Sec. 4.2.6. HPLC method development and validation
5.2.7. Bioavailability studies
Bioavailability studies were performed in male Wistar rats weighing 280 to 350 g. All
experiments and protocols described in this study were approved by the Institutional
Animal Ethics Committee of Sri Dhanvantary Pharmaceutical Analysis and Research
Centre, Surat, India and were in accordance with guidelines of the Committee for Purpose
of Control and Supervision of Experiments on Animals, Ministry of Social Justice and
Empowerment, Government of India. Two groups were made for the study, and four rats
were kept in each group. The animals were kept under standard laboratory conditions,
temperature at 25 ± 2°C and relative humidity (55 ± 5%). The animals were housed in
polypropylene cages, four per cage, with free access to standard laboratory diet (Lipton
feed, Mumbai, India) and water ad libitum. The animals were fasted overnight prior to the
experiment but had free access to water.
The formulations (SEDDS and extemporaneous suspension prepared from marketed
capsule (Itaspor®)) were given orally using feeding snode. Dose for the rats was selected
as reported (Shin et al., 2004; Van Cauteren et al., 1987) and calculated based on the
weight of the rats (30mg/kg body weight) according to the surface area ratio (Akhila et al.,
2007; Paget and Barnes, 1964). The animals were anesthetized using ether and blood
samples (approximately 500 μL) were collected from the retro-orbital vein using a
heparinized needle (18-20 size) at 0 (pre-dose), 1, 2, 4, 8, 12, 16 and 24 hours after oral
administration of formulations. The blood samples were collected into a vacutainer tube
(13 x 75mm, 2mL, Accuvac, BD, NJ), mixed and centrifuged on a laboratory centrifuge at
5000 rpm for 20 min at ambient temperature. The supernatant plasma was carefully
separated and kept at –20°C (Thermo Scientific, USA) until analysis was carried out using
validated HPLC.
5.2.7.1. Plasma analysis
Frozen plasma samples were thawed just prior to extraction. A 100 µL of plasma sample
was transferred in 2 mL centrifuge tube (Tarson, Kolkata, India). To that 300 µL of
Chapter 5 Itraconazole
Page 166
acetonitrile containing Ketoconazole as an internal standard (Vaughn et al., 2006) (200
ng/mL in acetonitrile) was added and vortex-mixed for 1 min. The tube was centrifuged at
15,000 rpm for 20 min at 4° C. The organic layer was carefully decanted and was
transferred to clean tube and dried under nitrogen stream at ambient temperature. The
residue was reconstituted with a 100 µL aliquot of mobile phase, consisted of a mixture of
5 mM sodium phosphate buffer pH 5.7 and ACN (38:62 v/v) and 50 µL was injected
directly onto the HPLC column at a flow rate of 1.0 mL/min.
Plasma concentration versus time data of itraconazole for rats was analyzed using standard
non-compartment analysis. The area under the plasma concentration-time curve (AUC0→t)
from zero to 24 hour was estimated by the linear trapezoidal method (Han and Lee, 1999;
Lee and Ku, 1999). The relative bioavailability (F) of SMEDDS to the suspensions was
calculated using the following equation:
F = (AUCtest /AUCreference) × 100%
5.2.8. Statistical analysis
Statistical analysis for the determination of differences in diffusion, permeability and in
vivo absorption profiles of itraconazole SEDDS and the marketed preparation was
assessed by the use of Student’s t-test. The pharmacokinetic data between different
formulations were compared for statistical significance by Student’s t-test. Statistical
probability (P) values less than 0.05 were considered significantly different.
5.2.9. Stability studies
Chemical and physical stability of itraconazole SEDDS (F5, F21 and F27) were assessed
under various storage conditions namely room temperature (RT), 30±2°C/65±5% RH and
40±2°C/75±5% RH as per ICH guidelines (ICH Q1A(R2)) in ICH certified stability
chambers (Humidity Chamber, EIE Instruments Ltd., Ahmedabad, India).
Itraconazole SEDDS equivalent to 25 mg was filled in a glass vial with a rubber closure
and aluminium-crimped tops. Eight such glass vials of each F5, F21 and F27 were filled
and stored at various aforementioned storage conditions up to 3 months. Samples were
removed at 0, 1, 2 and 3 months of interval and checked for itraconazole content (by
HPLC), droplet size, polydispersity index and zeta potential after diluting formulation to
100 times with three different media viz. Distilled water (DW), 0.1N HCl and phosphate
buffer saline pH 6.8 (PBS) maintained at 37°C.
Chapter 5 Itraconazole
Page 167
5.3. Results and discussion
5.3.1. Screening of oil and surfactants
The solubilities of itraconazole in various oils and surfactants are presented in Table 5.1.
Among the selected oils that were screened, maximum solubility of itraconazole was
found in Capryol 90 followed by Captex 200, IPM and Captex 355. Among the surfactants
(Table 5.1), Transcutol P followed by Tween 20 showed reasonable solubilizing potential
for itraconazole. Transcutol P proved to be the best solublizer for itraconazole.
Before selecting Transcutol P as a co-surfactant, propylene glycol was also screened for its
efficiency in preparation of a good self emulsifying system. During the formulation
development of Nevirapine, it was found out that Labrasol has poor water uptake capacity
which was improved by adding Tween 80. In the case of itraconazole, Tween 20 was tried
for the development of self emulsifying system.
A series of trials were taken with three different ratios of Oil: Smix (1:9, 1:6 and 1:4).
Capryol 90 was selected as an oil phase, mixture of Labrasol and Tween 20 as a surfactant
and Transcutol P as a co-surfactant. The ratios 9:1, 1:1, 2:1and 4:1of surfactant to co-
surfactant were tried with 1:1, 1:2 and 1:3 ratios of Labrasol:Tween 20 as a surfactant
(Table 5.2).
Table 5.1: Solubility of itraconazole in various oils and surfactants at 25°C (n =3)
Oil /Surfactant Solubility (mg/mL) Isopropyl myristate 0.206 ± 2.07 Captex 200 1.008 ± 2.08 Captex 355 2.127 ± 1.97 Tocopherol acetate 5.22 ± 1.87 Capryol 90 22.132 ± 1.58 Tween 20 3.709 ± 1.04 Labrasol 7.147 ± 1.65 Transcutol 4.6 ± 1.48 Capmul MCM 7.4533 ± 1.15 Capmul MCM (8) 5.8483 ± 1.43 Imwitor 988 6.5708 ± 1.25 Cremophor EL 4.0015 ± 1.21 Propylene glycol 1.1804 ± 0.55
Chapter 5 Itraconazole
Page 168
Table 5.2: Formulation development trials
1 2 3 4 5 6 7 8 9 10 11 12 Oil:Smix 1:9 1:9 1:9 1:9 1:9 1:9 1:9 1:9 1:9 1:9 1:9 1:9 S/CoS 9:1 9:1 9:1 1:1 1:1 1:1 2:1 2:1 2:1 4:1 4:1 4:1 Lab+T20 1:1 1:2 1:3 1:1 1:2 1:3 1:1 1:2 1:3 1:1 1:2 1:3 ITZ(mg) 25 25 25 25 25 25 25 25 25 25 25 25 13 14 15 16 17 18 19 20 21 22 23 24 Oil:Smix 1:6 1:6 1:6 1:6 1:6 1:6 1:6 1:6 1:6 1:6 1:6 1:6 S/CoS 9:1 9:1 9:1 1:1 1:1 1:1 2:1 2:1 2:1 4:1 4:1 4:1 Lab+T20 1:1 1:2 1:3 1:1 1:2 1:3 1:1 1:2 1:3 1:1 1:2 1:3 ITZ(mg) 25 25 25 25 25 25 25 25 25 25 25 25 25 26 27 28 29 30 31 32 33 34 35 36 Oil:Smix 1:4 1:4 1:4 1:4 1:4 1:4 1:4 1:4 1:4 1:4 1:4 1:4 S/CoS 9:1 9:1 9:1 1:1 1:1 1:1 2:1 2:1 2:1 4:1 4:1 4:1 Lab+T80 1:1 1:2 1:3 1:1 1:2 1:3 1:1 1:2 1:3 1:1 1:2 1:3 ITZ(mg) 25 25 25 25 25 25 25 25 25 25 25 25 Smix = Mixture of surfactants and co-surfactant; Lab = Labrasol; T20 = Tween 20; ITZ = itraconazole
5.3.2. Characterisation of formulation development trials
5.3.2.1. Visual observation: The prepared self emulsifying systems of itraconazole were
diluted 100 folds with 0.1N HCl and checked for optical clarity. When the ratio of oil:Smix
was 1:2, prepared systems exhibited turbidity and they were dropped from the study.
Obviously, as the proportion of oil phase increases, the optical clarity of the formulations
becomes poor on dilution.
Table 5.3: Visual observation and droplet size of formulation development trials as shown in Table 5.2
Trial No.
Size (nm)
PdI Visual Observation
Trial No.
Size (nm)
PdI Visual Observation
1 149.2 0.159 Bluish Tinge 19 185.0 0.293 Slight Turbid 2 56.87 0.151 Poor quality 20 141.0 0.277 Bluish Tinge 3 98.77 0.309 Poor quality 21 95.39 0.4 Slight Bluish Tinge 4 162.6 0.248 Bluish Tinge 22 182.4 0.264 Bluish Tinge 5 118.2 0.172 Slight Bluish Tinge 23 121.0 0.208 Bluish Tinge 6 38.85 0.639 Poor quality 24 147.1 0.976 Poor quality 7 163.7 0.275 Bluish Tinge 25 200.3 0.401 Turbid 8 56.89 0.56 Poor quality 26 167.5 0.252 Bluish Tinge 9 18.13 0.6 Poor quality 27 130.2 0.156 Bluish Tinge
10 142.5 0.206 Bluish Tinge 28 546.1 0.392 Turbid 11 25.33 0.205 Poor quality 29 320.3 0.116 Turbid 12 53.14 0.403 Poor quality 30 255.0 0.265 Turbid 13 158.8 0.199 Bluish Tinge 31 452.6 0.136 Turbid 14 105.0 0.278 Slight Bluish Tinge 32 189.3 0.278 Bluish Tinge 15 40.68 0.256 Poor quality 33 180.0 0.239 Bluish Tinge 16 251.7 0.142 Turbid 34 360.9 0.206 Turbid 17 159.9 0.264 Bluish Tinge 35 205.5 0.341 Bluish Tinge 18 155.6 0.259 Bluish Tinge 36 203.1 0.331 Bluish Tinge
Chapter 5 Itraconazole
Page 169
When oil:Smix ratio was 1:9, S/CoS ratio of 9:1 with Labrasol to Tween 20 ratio of 1:1
gave bluish tinge. The effect of various ratios of surfactant to co-surfactant along with
different ratios of Labrasol to Tween 20 has been shown in the Table 5.3.
5.3.2.2. Droplet size measurement: The droplet size of formulations developed with
Oil:Smix ratios were in the range of 18.13 nm – 149.2 nm, 40.68 nm – 251.7 nm, 180 nm –
546.1 nm for 1:9, 1:6 and 1:4, respectively.
A comparative study of data obtained from the droplet size measurements and visual
observations were made. Those formulations which gave bluish tinge and good optical
clarity were selected. In the first group (Formulation trials 1-12), formulations 1, 2, 5, 7
and 10 gave bluish tinge with droplet size in the range of 118.2 nm – 149.2 nm. The
formulation 5 with lowest droplet size (118.2 nm) was selected. Similarly, in the second
group 8 formulations were compared for their droplet size and the formulation 21 with
lowest droplet size of 95.39 nm was selected. Formulation 27 with droplet size of 130.2
nm was selected among the 5 formulation with good optical clarity.
5.3.3. Construction of pseudo-ternary phase diagrams
The regions which showed bluish tinge were identified as transparent and isotropic
mixtures. The percentage of three different phases i.e. oil, water and the mixture of
surfactant and co-surfactant were calculated and plotted with the help of Tri plot v1.4
software for fabrication of ternary plot. The points (formulation trials) which showed
bluish tinge were joined with the line and were shaded (Figure 5.1). It can be seen that, the
formulations which showed bluish tinge in 1:9, 1:6 and 1:4 ratios of Oil:Smix were not
more than 203.1 nm. The formulation prepared within these regions (dark shaded) may
give droplet size in micron size.
Figure 5.1: Psuedoternary phase diagram of Oil to Smix ratios of 1:9, 1:6 and 1:4
Chapter 5 Itraconazole
Page 170
5.3.4. Characterization of selected formulations
The droplet size, polydispersity index and zeta potential of SEDDS formulation after 100
times dilution in different media is shown in Table 5.4. Size distribution by intensity in
various media for F5 is shown in Figure 5.2 (a), (b) and (c). Data shows that there is not
wide variation in size of droplets in distilled water and 0.1N HCl. The droplet size
increases in phosphate buffer. The size of droplets increases as the percentage of oil
increases. The droplet size follows the order of F27 > F21 > F5.
The polydispersity index is most poor in phosphate buffer. Zeta potential was also
measured of the same diluted samples and shown in the Table 5.4. Drug content of
SEDDS formulations was measured and is shown in Table 5.4. Table 5.4: Characterization of developed formulations
Droplet size D (nm) Polydispersity Index (PdI) Zeta potential (mV) Drug content (%) F5 F21 F27 F5 F21 F27 F5 F21 F27 F5 F21 F27
DW 417.3 201.0 194.4 0.147 0.226 0.211 -6.10 3.54 -7.15 101.06 ± 0.72
100.85 ± 0.44
100.54 ± 0.62 0.1NHCl 152.1 175.2 179.0 0.256 0.491 0.486 3.47 4.72 1.16
PBS 501.3 539.6 742.2 1.0 1.0 1.0 -2.11 -7.25 -3.16
Figure 5.2(a): Droplet size distribution of itraconazole SEDDS F5 after dilution in distilled water
Chapter 5 Itraconazole
Page 171
Figure 5.2(b): Droplet size distribution of itraconazole SEDDS F5 after dilution in 0.1N HCl
Figure 5.2(c): Droplet size distribution of itraconazole SEDDS F5 after dilution in phosphate buffer saline pH 6.8
Chapter 5 Itraconazole
Page 172
Size distribution by intensity in various media for F21 are shown in Figure 5.3 (a), (b) and
(c).
Figure 5.3(a): Droplet size distribution of itraconazole SEDDS F21 after dilution in distilled water
Figure 5.3(b): Droplet size distribution of itraconazole SEDDS F21 after dilution in 0.1N HCl
Chapter 5 Itraconazole
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Figure 5.3(c): Droplet size distribution of itraconazole SEDDS F21 after dilution in phosphate buffer saline pH 6.8
Size distribution by intensity in various media for F27 are shown in Figure 5.4 (a), (b) and
(c).
Figure 5.4(a): Droplet size distribution of itraconazole SEDDS F27 after dilution in distilled water
Chapter 5 Itraconazole
Page 174
Figure 5.4(b): Droplet size distribution of itraconazole SEDDS F27 after dilution in 0.1N HCl
Figure 5.4(c): Droplet size distribution of itraconazole SEDDS F27 after dilution in phosphate buffer saline pH 6.8
The TEM picture is shown in Figure 5.5. The microemulsion droplets were observed to be
spherical and homogenous with large population of the smaller droplet in the size range of
less than 200 nm. The droplet size of formed emulsion determined by TEM is in
correlation with that of measured by photon correlation spectroscopy (PCS).
Chapter 5 Itraconazole
Page 175
Figure 5.5: Transmission electron microscopic image of itraconazole self emulsifying systems after dilution showing size of some oil globules. (Scale: 500 nm). (a) SEDDS F5, (b) SEDDS F21 and (c) SEDDS F27
Statistically there was significant difference in the dissolution profiles of all developed
formulations and market formulation at P < 0.05 and can be seen in Figure 5.6.
(a) (b)
(c)
Chapter 5 Itraconazole
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Figure 5.6: Dissolution profiles of itraconazole SEDDS and marketed capsule in 0.1N HCl (n=6)
In vitro diffusion profiles (Figure 5.7) shows that there was no significant difference
between the formulations with F5 & F21. For all other formulations there was a significant
difference in their diffusion profiles at P < 0.05
Figure 5.7: In vitro diffusion profile of itraconazole SEDDS and extemporaneous suspension of marketed capsule in 0.1N HCl (n=6)
-20
0
20
40
60
80
100
120
0 20 40 60 80 100 120 140
% C
umul
ativ
e dr
ug re
leas
ed
Time (min)
Dissolution profiles of SEDDS and Market Capsule in 0.1N HCl
SEDDS F5
SEDDS F21
SEDDS F27
MKT Capsule
0
10
20
30
40
50
60
0 1 2 3 4 5 6
% c
umul
ativ
e dr
ug d
iffus
ed
Time (Hours)
In vitro diffusion study of Itraconazole SEDDS and Market Capsule
SEDDS F5
SEDDS F21
SEDDS F27
MKT Capsule
Chapter 5 Itraconazole
Page 177
There was significant difference in stomach permeability between all other formulations at
P < 0.05, except F5 & F21 and F21 & F27 (Figure 5.8).
Figure 5.8: Ex vivo stomach permeability of itraconazole SEDDS and extemporaneous suspension of marketed capsule in 100 mM HCl (n=3)
Significant difference (P < 0.05) was also seen in ex vivo intestinal permeability of
developed SEDDS and marketed formulation except for formulation F5 and F21 (Figure
5.9).
Figure 5.9: Ex vivo intestinal permeability of itraconazole SEDDS and extemporaneous suspension of marketed capsule in pH 6.8 PBS (n=3)
0
5
10
15
20
25
30
35
0 0.5 1 1.5 2 2.5 3 3.5
% c
umm
ulat
ive
dru
g pe
rmea
ted
Time (Hours)
Stomach permeability study of Itraconazole SEDDS and Marketed Capsule
SEDDS F5
SEDDS F21
SEDDS F27
MKT Capsule
0
10
20
30
40
50
0 1 2 3 4 5 6
% c
umul
ativ
e dr
ug p
erm
eate
d
Time (Hours)
Intestinal permeability study of Itraconazole SEDDS and Market Capsule
SEDDS F5
SEDDS F21
SEDDS F27
MKT Capsule
Chapter 5 Itraconazole
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5.3.5. Bioavailability Studies
Typical chromatograms obtained showing peaks for ITZ at 1 h after administration of
marketed suspension and SEDDS F5, F21 and F27 are shown in Figure 5.10 (a) 5.10(b),
5.10(c) and 5.10(d), respectively. Table 5.5 summarises mean pharmacokinetic parameters
for various formulations.
Figure 5.10(a): Typical chromatogram obtained while analyzing plasma for ITZ level after administration of the extemporaneous suspension of marketed capsules at 1 h
Chapter 5 Itraconazole
Page 179
Figure 5.10(b): Typical chromatogram obtained while analyzing plasma for ITZ level after administration of the SEDDS F5 at 1 h
Figure 5.10(c): Typical chromatogram obtained while analyzing plasma for ITZ level after administration of the SEDDS F21 at 1 h
Chapter 5 Itraconazole
Page 180
Figure 5.10(d): Typical chromatogram obtained while analyzing plasma for ITZ level after administration of the SEDDS F27 at 1 h
Figure 5.11 depicts the plasma concentration profile of itraconazole after oral
administration of SEDDS and extemporaneous suspension of marketed capsule to rats.
Figure 5.11: Plasma concentration profile of itraconazole after oral administration of SEDDS and extemporaneous suspension in rats (n=4 and 30 mg/kg)
0
50
100
150
200
250
300
350
400
450
0 5 10 15 20 25 30Itra
cona
zole
pla
sma
conc
entr
atio
n (n
g/m
ml)
Time (Hours)
Marketed Capsule
SEDDS (F5)
SEDDS (F21)
SEDDS (F27)
Chapter 5 Itraconazole
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There was no significant difference in AUC0→t for extemporaneous suspension with F5
and F21, but F27 was statistically significant different from extemporaneous suspension.
AUC0→∞ of F5 and F27 was significantly different from extemporaneous suspension, but
there was no significant difference between extemporaneous suspension and F21. Cmax of
extemporaneous suspension and F5 was not significant different, but there was a
significant difference in Cmax of extemporaneous suspension with F21 and F27.
The relative bioavailabilities of itraconazole SEDDS F5, F21 and F27 were 170.56%,
204.55% and 233.91%, respectively when compared to extemporaneous suspension. It
was found that there was no significant difference between F5, F21 and F27 with regard to
AUC0→t, AUC0→∞ and Cmax.
The three self emulsifying formulations were prepared, containing varying amounts of oil
and surfactants and as mentioned previously the droplet size followed the order F27 > F21
> F5. However, the formulations developed in this study contained varying concentrations
of oil and surfactants. The observed bioavailability indicated that there was little
correlation of AUC and Cmax with respect to droplet size of formed emulsions. The
observed results are in agreement with few researchers groups in different laboratories.
Yap & Yuen (2004) observed that droplet size difference (1.5 and 10.6 µm) between two
SEDDS containing varying amounts of soybean oil, Tween 80 and Labrasol did not affect
the bioavailabilities of tocotrienols.
In several cases avoidance of drug precipitation could be the predominant factor governing
improvement of oral bioavailability from lipid vehicles than the size of the droplet size. It
has been well documented that the influence of droplet size on bioavailability has been
observed for several molecules for e.g. Vitamin (Julianto et al., 2000), cyclosporine (Trull
et al., 1995), and halofantrine (Khoo et al., 1998); while it is limited for some others, e.g.,
atovaquone (Sek et al., 2006), danazol (Porter et al., 2004), and ontazolast (Hauss et al.,
1998). A very limited number of studies have focused on the influence of the
particle/droplet size of comparable formulations on the absorption and bioavailability.
The formulation F5 showed least particle size having maximum amount of surfactant.
Contrary to expectations that smaller particle size increases absorption, this did not lead to
higher bioavailability. Formulation F21 with slightly bigger droplet size compared to F5
showed higher bioavailability (204.55%). The maximum bioavailability (233.91%) was
shown by F27 with least concentration of surfactant and maximum concentration of oil.
Chapter 5 Itraconazole
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The study revealed that the bioavailability decreased when concentration of oil was
decreased from 17.27% to 8.77%.
Formulation F5 exhibited faster absorption and higher Cmax but lower bioavailability
(170.56%) compared to F21 (204.55%) and F27 (233.91%). This indicates that having a
highly dispersed system improves absorption rate which is due to higher amount of
surfactants, but is not enough to ensure higher bioavailability (Nielsen et al., 2008).
It has been observed and reported that lipid systems which contain more amount of
surfactant or hydrophilic excipients are more prone to drug precipitation. Using such
excipients may improve solvent capacity, drug loading and in vitro performance but may
decrease in vivo absorption due to precipitation of drug on oral administration (Pouton,
2006).
The role of droplet size in the performance of the formulation in vivo is generally less
important than the assumption. The possible reason for this is that as soon as the dispersed
formulation leaves the stomach it encounters digestive power of the small intestine. The
fate of the drug after the formulation has been digested is more important than the initial
particle size. Esters can be rapidly hydrolyzed in the presence of pancreatic lipase and
most commonly used surfactants are ethoxylated esters that are rapidly hydrolyzed. The
physical state of the degradation products will be changed significantly by contact with the
mixed bile salt micelles and the drug will partition between the various phases in the gut
lumen, or could precipitate out if the total solvent capacity is reduced as a result of
lipolysis (Pouton, 2006).
Table 5.5: Relative bioavailability and pharmacokinetic parameters of itraconazole after oral administration of itraconazole SEDDS and extemporaneous suspension to the rats (n=4)
MKT SEDDS (F5) SEDDS (F21) SEDDS (F27) AUC0→t (ng.h/mL)
3037.268 ± 198.86
4111.651 ± 1567.14
3521.983 ±1030.00
4664.412 ± 228.138
AUC0→∞ (ng.h/mL)
5264.334 ± 1705.79
8978.953 ± 3191.02
10768.64 ± 8767.113
12314.27 ± 5551.154
Cmax (ng/mL) 171.956 ± 5.715 276.80 ± 138.645
243.499 ± 44.90 304.848 ± 78.942
Tmax (h) 1.0 ± 0.0 1.5 ± 0.577 1.5 ± 0.577 1.5 ± 0.577 Relative bioavailability (%)
--- 170.56 204.55 233.91
Chapter 5 Itraconazole
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5.3.6. Stability studies
No change in the physical parameters such as homogeneity and clarity was observed
during the stability studies. Droplet size, polydispersity index and zeta potential remained
unchanged, as compared to initial characterization at 0 month (Table 5.4), even after
keeping the formulations at different environmental storage conditions for 3 months,
indicating the physical stability of developed formulations (Table 5.6, 5.7 and 5.8). No
decline in the drug content was observed at the end of 3 months indicating that drug
remained chemically stable in SEDDS.
Table 5.6: Stability studies of itraconazole SEDDS F5 at various storage conditions Storage conditions → 25 ± 2°C (RT) 30 ± 2°C/65 ± 5% RH 40 ± 2°C/75 ±
5%RH Parameters ↓ Medium↓ 1 M 2 M 3 M 1 M 2 M 3 M 1 M 2 M 3 M Droplet Size D (nm)
DW 389.21 372.83 380.41 379.19 389.17 386.45 397.5 386.3 388.47
0.1N HCl 134.35 146.49 149.83 144.9 144.39 151.38 146.3 144.3 147.35
PBS 448.29 459.82 451.96 439.33 479.7 455.26 487.4 477.32 472.21
Polydispersity index (PdI)
DW 0.152 0.153 0.162 0.182 0.145 0.167 0.224 0.314 0.287
0.1N HCl 0.189 0.235 0.226 0.211 0.244 0.212 0.263 0.273 0.278
PBS 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Zeta Potential (mV)
DW -8.3 -4.62 -6.43 -6.42 -5.72 -6.85 -7.75 -6.82 -7.05
0.1N HCl 5.32 4.28 6.19 4.75 5.39 6.21 5.73 6.71 6.62
PBS -3.29 -3.81 -4.21 -3.64 -5.39 -6.63 -3.49 -4.62 -5.26
Drug Content (%) 104.54 ± 1.6
102.02 ± 1.82
100.70 ± 0.46
101.21 ± 1.09
100.60 ± 2.77
100.90 ± 0.30
100.3 ± 0.6
100.8 ± 1.55
103.03 ± 0.60
Table 5.7: Stability studies of itraconazole SEDDS F21 at various storage conditions Storage conditions → 25 ± 2°C (RT) 30 ± 2°C/65 ± 5% RH 40 ± 2°C/75 ±
5%RH Parameters ↓ Medium↓ 1 M 2 M 3 M 1 M 2 M 3 M 1 M 2 M 3 M Droplet Size D (nm)
DW 194.46 200.37 201.33 198.28 182.39 187.63 199.4 200.46 199.84
0.1N HCl 181.2 169.25 167.46 159.86 161.3 163.02 170.6 170.5 173.25
PBS 492.52 482.46 478.36 483.52 503.2 491.73 532.6 489.4 491.06
Polydispersity index (PdI)
DW 0.232 0.321 0.233 0.321 0.142 0.21 0.253 0.216 0.224
0.1N HCl 0.476 0.472 0.389 0.462 0.392 0.288 0.421 0.472 0.418
PBS 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Zeta Potential (mV)
DW 5.23 4.47 5.46 4.78 3.58 5.21 5.63 4.68 4.82
0.1N HCl 6.43 6.73 7.21 7.53 6.48 6.75 5.89 5.49 6.25
PBS -5.38 -6.37 -6.61 -4.82 -5.38 -5.44 -6.72 -5.94 -5.58
Drug Content (%) 102.42 ± 1.84
101.91 ± 2.61
101.61 ± 0.63
99.79 ± 0.17
100.80 ± 0.46
100.30 ± 1.51
99.79 ± 0.46
100.20 ± 1.49
100.0 ± 0.30
Chapter 5 Itraconazole
Page 184
Table 5.8: Stability studies of itraconazole SEDDS F27 at various storage conditions Storage conditions → 25 ± 2°C (RT) 30 ± 2°C/65 ± 5% RH 40 ± 2°C/75 ± 5%RH
Parameters ↓ Medium↓ 1 M 2 M 3 M 1 M 2 M 3 M 1 M 2 M 3 M Droplet Size D (nm)
DW 199.3 188.58 180.89 192.3 192.5 190.55 198.7 189.7 199.96
0.1N HCl 183.53 171.36 183.62 179.28 168.3 172.36 181.5 177.8 180.84
PBS 648.27 649.36 662.57 684.29 669.5 671.05 668.5 678.2 675.42
Polydispersity index (PdI)
DW 0.283 0.253 0.261 0.197 0.325 0.268 0.184 0.227 0.231
0.1N HCl 0.457 0.453 0.432 0.456 0.462 0.338 0.473 0.428 0.436
PBS 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Zeta Potential (mV)
DW -9.1 -5.82 -7.83 -8.75 -6.11 -7.84 -9.28 -7.92 -6.98
0.1N HCl 2.87 2.08 3.42 3.62 3.72 4.21 4.51 4.88 5.35
PBS -4.42 -5.28 -4.88 -5.38 -5.27 -5.33 -4.62 -6.72 -5.69
Drug Content (%) 102.12 ± 1.21
102.12 ± 0.80
101.31 ± 1.06
100.50 ± 1.14
100.40 ± 0.46
100.10 ± 0.76
100.10 ± 0.46
100.10 ± 0.69
100.3 ± 0.8
D (nm) = diameter in nanometer; DW = distilled water; PBS = phosphate buffer saline pH 6.8; RT = room temperature; M = month; RH = relative humidity
5.4. Conclusion
In the recent years the utilization of lipid excipients for the enhancement of oral
bioavailability of poorly soluble drugs has attracted attention. Self-emulsifying drug
delivery systems containing itraconazole were formulated using various ratios of
oil:S/CoS mixture in an attempt to increase its release rate and bioavailability. Three
formulations containing itraconazole were developed through the construction of pseudo-
ternary diagrams, droplet size determination and visual inspection. F5 consisted of 8.77%
of Capryol 90, 13.31% Labrasol, 32.15% of Tween 20, 43.32% Transcutol; F21 consisted
of 12.4% Capryol 90, 12.5% Labrasol, 45.3% Tween 20 and 27.23% Transcutol; F27
consisted of 17.27% Capryol 90, 15.73% Labrasol, 57% Tween 20 and 7.5% Transcutol.
Itraconazole was 2.4% in all three SEDDS formulations. After oral administration to rats,
the SEDDS F5, F21 and F27 containing itraconazole had a relative bioavailability of
170.56%, 204.55% and 233.91% compared with the extemporaneous suspension prepared
from marketed capsules. The order of droplet size of formed emulsion was 1:4 (F27) > 1:6
(F21) > 1:9 (F5) for ratios of oil: Smix. Although the three self-emulsifying formulations
with different ratios of oil:Smix did show differences in exposures of itraconazole in rats,
the results were not in consistent with strong dependence on emulsion droplet size and oral
absorption. Contrary to expectations, the droplet size of the formed emulsion played very
little role in in vivo absorption of itraconazole from developed self emulsifying
formulations. The possible explanation for this observation can be a very high lipophilicity
of itraconazole (log P 5.66). Such drugs have more affinity toward lipophilic domain of
the formulation and remain in a solubilised state for better absorption. When the drug
Chapter 5 Itraconazole
Page 185
solubilisation capacity at interface has been increased with the use of surfactants, dilution
with physiological fluid may lead to migration of surfactant form the oil/water interface
and can result in reduction in drug loading capacity and precipitation. This phenomenon
may be responsible for the decrease in bioavailability as the proportion of surfactant
increased. In conclusion, the data overall showed little apparent correlation between
emulsion droplet size and oral absorption in rats, but statistically (P < 0.05) there was no
significant difference between all the three formulations with respect to AUC and Cmax.
The results obtained illustrate the magnitude of bioavailability enhancement that can be
achieved through rational design of lipid-based formulations.
Chapter 5 Itraconazole
Page 186
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