http://informahealthcare.com/drdISSN: 1071-7544 (print), 1521-0464 (electronic)

Drug Deliv, Early Online: 1–10! 2014 Informa Healthcare USA, Inc. DOI: 10.3109/10717544.2013.879753

ORIGINAL PAPER

Solid self-nanoemulsifying drug delivery system (S-SNEDDS) fororal delivery of glimepiride: development and antidiabetic activityin albino rabbits

Abdul Bari Mohd1, Krishna Sanka1, Srikanth Bandi1, Prakash V. Diwan1, and Nalini Shastri2

1Department of Pharmaceutics, School of Pharmacy, Anurag Group of Institutions, Hyderabad, Andhra Pradesh, India and 2Department of

Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad, Andhra Pradesh, India

Abstract

Context: This study presents novel self-nanoemulsifying drug delivery system potential of oraldelivering which leads poorly aqueous soluble drug glimepiride.Objective: The objective of this study was to prepare solid self-nanoemulsifying drug deliverysystem (S-SNEDDS) for the improved oral delivery of glimepiride and to evaluate its therapeuticefficacy in albino rabbits.Results and discussion: The droplet size analyses revealed a droplet size of less than 200 nm. Thesolid state characterization of S-SNEDDS by scanning electron microscopy (SEM), X-ray powderdiffraction and differential scanning calorimetry (DSC) revealed the absence of crystallineglimepiride in the S-SNEDDS. The in vitro dissolution studies revealed that the significantimprovement in glimepiride release characteristics. The effect of S-SNEDDS on therapeuticefficacy of glimepride was assessed in albino rabbits by monitoring blood glucose levels andcompared with free drug suspension, L-SNEDDS. The S-SNEDDS showed significant (p50.05)increase in in vitro drug release and therapeutic efficacy as compared with free drug.Conclusion: This study demonstrated that S-SNEDDS is a promising novel drug delivery systemof glimepride to enhance oral delivery.

Keywords

Aerosol 200, dissolution, glimepiride, oraldelivery, solid carrier, S-SNEDDS

History

Received 12 November 2013Revised 29 December 2013Accepted 29 December 2013

Introduction

The oral delivery of many new drug molecules is recurrently

associated with complications of low water solubility or high

lipophilicity which leads to poor and highly variable oral

bioavailability and the absence of dose proportionality

(Kyatanwar et al., 2010). This class of drug compounds can

be classified as low solubility and high permeability Bio

Pharmaceutical Classification System (BCS) class II drugs. In

these drugs, dissolution of the drug is the rate limiting step in

the absorption process. To triumph over these obstacles,

numbers of formulation approaches are reported including the

use of surfactants (Allaboun et al., 2003; Balakrishnan et al.,

2004; Chakraborty et al., 2009), lipids (Yeap et al., 2013),

permeation enhancers (Burcin et al., 2010; Beg et al., 2011),

formation of salt (Li et al., 2005; Serajuddin, 2007),

co-crystallization (Shan & Zaworotko, 2008; Qiao et al.,

2011; Chadha et al., 2012), solid dispersions (Serajuddin,

1999), inclusion complexes with cyclodextrins and modified

cyclodextrins (Miyake et al., 2000; Veiga et al., 2000; Wang

et al., 2000; Bannwart et al., 2001; Carrier et al., 2007;

Gamsiz et al., 2010a,b; Gamsiz et al., 2011; Badr-Eldin et al.,

2008; Kumar et al., 2013), nanosuspensions (Patravale et al.,

2004), and colloidal vesicles like liposomes (Nazzal et al.,

2002a; Manconi et al., 2013; Yang et al., 2013), and niosomes

(Khazaeli et al., 2007; Bayindir & Yuksel, 2010; Sezgin-

Bayindir et al., 2013; Jin et al., 2013)

In modern years, self-nanoemulsifying drug delivery

systems (SNEDDS) are the most popular and commercially

feasible lipid-based formulation approach for improving oral

bioavailability of poorly water soluble and lipophilic drugs

(Pouton, 2006; Date, 2007; Shweta et al., 2011). SNEDDS are

precisely defined as an isotropic multi-component drug

delivery systems composed of a synthetic or natural oil,

surfactant, and co-surfactant that have a unique ability of

forming fine oil in water micro- or nano-emulsion upon mild

agitation followed by dilution in aqueous media such as

gastro-intestinal fluid. As SNEDDS self-emulsifies in the

stomach and presents the drug in minute droplets of oil

(55 mm), it improves drug dissolution through presenting a

large interfacial area for partitioning of the drug between

the oil and the GIT fluid. The other advantages include

increased stability of drug molecules and ease of administer-

ing the final formulation as gelatin capsules (soft gelatin

capsules in the case of liquid self-nanoemulsifying drug

delivery system (L-SNEDDS) and hard gelatin capsules in

the case of solid self-nanoemulsifying drug delivery system

(S-SNEDDS)).

Address for correspondence: Dr. Nalini Shastri, Department ofPharmaceutics, National Institute of Pharmaceutical Education andResearch (NIPER), Hyderabad 500 037, AP, India. Tel: +40 23073741.Fax: +40 23073751. Email: svcphod@yahoo.co.in

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Glimepiride,1-[[p-[2-(3-ethyl-4-methyl-2-oxo-3-pyrroline-

1-carboxami-do) ethyl] phenyl] sulphonyl]-3-(trans-4-methyl-

cyclohexyl) urea is the first third-generation sulphonyl urea.

It is a very potent sulphonyl urea employed for concomitant use

with insulin for the treatment of non-insulin-dependent (type

II) diabetes mellitus. It produces hypoglycemia by stimulating

release of insulin from pancreatic b cells and by increasing the

sensitivity of peripheral tissue to insulin. It also supports the

movement of sugar from the blood into the cells that need it.

Glimepiride shows low, pH-dependent solubility. It exhibits

very poor solubility at 37 �C (50.004 mg/ml) in acidic and

neutral aqueous media and it belongs to ‘‘BCS Class II’’ drugs

(Lobenberg & Amidon, 2000). It is likely to show low and

irregular bioavailability following oral administration due to

the low water solubility (Amidon et al., 1995; Grunenberg

et al., 1995). Hence administering glimepiride by oral appears

as a tough challenge due to its poor absorption pattern and

rapid and unpredictable hepatic first pass metabolism.

The present study deals with formulation of an Aerosol�

200 based SNEDDS of a poorly water soluble drug

(glimepride). The main objective of this study was to

investigate solid self-nanoemulsifying drug delivery system,

as a potential drug delivery system for glimepiride. S-

SNEDDS (consisting of Tween� 80/PEG and 400/Mygliol�

812) was characterized with regard to morphological analysis,

solid state characterization as well as its in vitro drug release

and therapeutic efficacy in albino rabbits.

Materials

Glimepiride was kindly gifted by Dr Reddy’s Labs, Hyderabad,

India. Miglyol� 812 (Capric Triglyceride), Cotton seed oil,

Aerosol� 200 (Dioxosilane), and Cremophor� RH 40

(Macrogolglycerol hydroxystearate) were gift samples from

Bari’s Pharmaceuticals, Hyderabad, India. Tween� 80

(Polyoxyethylene sorbitan monooleate), PEG 400 (polyethyl-

ene glycol 400), Span� 20 (Sorbitan monolaurate), oleic acid,

soya bean oil, ethyl alcohol, and HPLC grade methanol were

purchased from Merck Specialties Pvt. Ltd., Mumbai, India.

Span� 80 (Sorbitan monooleate), propylene glycol, and

potassium dihydrogen phosphate were obtained from SD-

Fine Chemicals Ltd., Mumbai, India. All other chemicals and

materials were of analytical grade.

Methods

Operating conditions of HPLC for glimepiride analysis

Glimepiride was determined by high-pressure liquid chroma-

tography (HPLC) using HPLC system (UFLC prominence

HPLC, Shimadzu, Kyoto, Japan) with a PDA detector

(SPD20A) at a wavelength of 228 nm and a manual injector

with injection volume setting at 20 ml. The mobile phase

consists of Acetonitrile: 0.2 M phosphate buffer (pH 7.4) was

pumped at a flow rate of 1 ml/min. The drug was separated by

Gemini C18, 100� 4.6 mm (ID), and 5 mm column at ambient

temperature.

Solubility studies

The solubility of glimepiride was determined in oils

(Miglyol� 812, castor oil, oleic acid, cotton seed oil, and

soya bean oil), surfactants, and co-surfactants (Tween� 80,

PEG 400, propylene glycol, Cremophor� RH 40, Span� 80,

and Span� 20). An excess amount (500 mg) of drug was

added to each 1.5 ml eppendorf tubes consisting of 1 ml of

each vehicle and the contents were mixed using a vortex

mixer (REMI CM 101DX, REMI Equipment, Mumbai, India)

to facilitate uniform mixing of drug for 15 min. The

Eppendorf tubes were kept at 25 ± 1.0 �C in an orbital

shaker (CL 24, Remi Electrotech Ltd., Mumbai, India) for

48 h to reach equilibrium (Wang et al., 2009). The tubes were

centrifuged at 5000 rpm using micro centrifuge (RM 12C,

REMI Equipment, Mumbai, India) for 20 min. The super-

natant was filtered through a 0.45-mm syringe filter and an

aliquot of 0.1 ml from the filtered supernatant was collected

and diluted with methanol. The quantification of glimepiride

was performed by HPLC (Prominence HPLC, Shimadzu,

Japan) at 228 nm using a PDA detector.

Selection of oil

The selection of oil was based on solubility of glimepiride in

the oils. Higher the solubility of the drug, higher will be the

drug loading potential (Pouton, 2000, 2006). In this study, the

drug was significantly more soluble in Miglyol� 812. Thus,

the same was chosen as the oil phase for formulating the

SNEDDS system.

Selection of surfactant

The screening of surfactant was based on both the ability to

solubilize the drug in it and its ability to emulsify the selected

oil phase. The solubility of all the surfactants include Tween�

80, Span� 20, Span� 80, and Cremophor� RH 40 was

determined from solubility studies. Then to examine their

emulsification ability, 20 ml of surfactant and 20 ml of the

above selected oil phase were mixed together thoroughly in an

Eppendorf tube. From this, 25 ml of mixture was added to

25 ml of distilled water in a standard flask. The ease of

emulsification was checked by the number of inversions of

standard flask enough to produce to uniform emulsion. The

formed emulsions were allowed to stand for 2 h. Then the

transmittance was determined using a double beam UV-

visible spectrophotometer (UV-3500, Labindia, Mumbai,

India) at 638.2 nm against distilled water as the blank (Date

& Nagarsenker, 2007; Shweta et al., 2011).

Selection of co-surfactant

The screening of co-surfactants was based on both the ability

to solubilize the drug in it and their efficacy to improve the

nanoemulsification ability of the selected surfactants. The

solubility of the drug in the co-surfactants namely PEG 400,

propylene glycol was determined from the solubility studies

same as in the case of oils and surfactants. Then to screen

the efficacy of co-surfactants, 40 ml of the selected surfactant

and 20 ml of co-surfactant to be screened and 60 ml of

selected oil phase were mixed together thoroughly in

an Eppendorf tube. From this mixture, 25 ml was added to

25 ml of distilled water in a standard flask. The ease of

emulsification was checked in a similar fashion as described

above.

2 A. B. Mohd et al. Drug Deliv, Early Online: 1–10

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Construction of ternary phase diagram

For the construction of ternary phase diagrams, the screened

surfactant and co-surfactants were mixed (Smix) in three

different weight ratios (1:1, 2:1, and 3:1). These Smix ratios

were chosen to show increasing surfactant concentrations

with respect to co-surfactants. The oil phase and each Smix

ratios (a total of 51 ratios) were blended thoroughly in 17

different weight ratios from 1:9 to 9:1 (1:1, 1:2, 1:3, 1:4, 1:5,

1:6, 1:7, 1:8, 1:9, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, and 2:1).

From these each ratio, 0.1 ml of mixtures was transferred to

separate glass beakers. To these contents, 100 ml distilled

water was added gently agitated using a magnetic bar at

37 �C. The transmittance of the formed emulsions were

determined using an UV–visible double beam spectropho-

tometer (UV-3500, Labindia, Mumbai, India) at 638.2 nm

against distilled water as the blank. The resulted emulsions

were examined for clarity, phase separation, and coalescence

of oil droplets on standing for 2 h. When the oil droplets easily

spread out in water and formed a clear, transparent emulsion,

the emulsion was judged as ‘‘good’’ emulsion (% transmit-

tance 485), and when there was poor or no emulsion

formation with immediate coalescence of oil droplets, espe-

cially when stirring was stopped, the emulsion was judged as

‘‘bad’’ emulsion (% transmittance 585). The phase diagram

was constructed using Chemix school� version 3.50 software

(Arne Standnes, MN, USA) to identify the nanoemulsifying

region, using oil and Smix ratios which form ‘good’ emulsions

upon dilution with purified water. The nanoemulsion region in

the ternary phase diagram was represented as shaded area

(Figure 1).

Preparation of L-SNEDDS

Twelve L-SNEDDS of glimepiride were formulated by using

oil (5, 10, 20, and 30) and Smix in the ratios of 1:2.33, 1:4, 1:9,

and 1:19 as well as surfactant and co-surfactants in the ratios

of 1:1, 2:1, and 3:1. The drug loaded L-SNEDDS were

prepared by adding the oil phase, containing accurately

weighed quantity (20 mg) of glimepiride, drop wise into the

Smix with constant stirring for 30 min. It was equilibrated at

ambient temperature for 48 h and investigated for signs of

turbidity or phase separation. The compositions of prepared

L-SNEDDS were represented in Table 1.

Emulsion droplet size and PDI analysis

The globule size of the emulsion determines the rate and

extent of drug release (Tarr & Yalkowsky, 1989). Aliquot

(1 ml) of the optimized SNEDDS were diluted 100-fold

with purified water to assess the globule size using

Zetasizer (Zetasizer Nano ZS, Malvern Instruments,

Worcestershire, UK) at a wavelength of 635 nm with dynamic

light scattering angle of 90� at 25 �C. The Z-average diameter

was derived from cumulated analysis by the auto-measure

software.

Preparation of S-SNEDDS from L-SNEDDS

The simplest technique to convert L-SNEDDS to S-SNEDDS

is by adsorption onto the surface of carriers. In the present

study, Aerosol� 200 was used as an inert solid adsorption

Figure 1. Ternary phase diagram of theselected system (Miglyol, Tween� 80 andPEG 400) dispersed in water at 25 �C.

Table 1. Droplet size and PDI of liquid SNEDDS of glimepiride.

Formula Oil: Smix

Miglyol�

812%Tween�

80%PEG400%

Z-averagesize (d nm) PDI

F1 1:19 5.00 47.50 47.50 11 0.636F2 1:9 10.00 45.00 45.00 250 0.565F3 1:4 20.00 40.00 40.00 890 0.645F4 1:2.33 30.00 35.00 35.00 1406 0.919F5 1:19 5.00 63.33 31.66 270 0.820F6 1:9 10.00 60.00 30.00 432 0.991F7 1:4 20.00 53.33 26.66 630 0.830F8 1:2.33 30.00 46.66 23.33 1270 0.999F9 1:19 5.00 71.25 23.75 152 0.211F10 1:9 10.00 67.50 22.50 355 0.368F11 1:4 20.00 60.00 20.00 917 0.113F12 1:2.33 30.00 52.50 17.50 1126 0.688

DOI: 10.3109/10717544.2013.879753 S-SNEDDS for oral delivery of glimepiride 3

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carrier. A fixed volume of formed L-SNEDDS equivalent to

dose was transferred to a China dish, and to this, the

Aerosol� 200 was added in increments with vigorous stirring

until a free flow powder was obtained. Then the dose

equivalent free flow powder was filled in hard gelatin

capsules.

In vitro drug release studies

Pure glimepiride (2 mg), marketed tablet (2 mg dose), dose

equivalent amount of glimepiride-loaded L-SNEDDS, and

S-SNEDDS were placed in a USP-II dissolution test apparatus

(DS 8000, LABINDIA, Mumbai, India). The dissolution test

was performed using 900 ml of phosphate buffer pH 7.4 as a

dissolution medium. Temperature and speed of the paddle

were adjusted to 35 ± 0.5 �C and 100 rpm, respectively.

At predetermined time intervals (0, 5, 10, 15, 30, 45, and

60 min) an aliquot (5 ml) of the samples was collected and

filtered through a membrane filter (0.4mm) at each time 5 ml

of fresh medium was added to dissolution medium. The

concentration of drug was determined by using HPLC

(Prominence HPLC, Shimadzu, Kyoto, Japan) with a PDA

detector (SPD-M20A) at 228 nm.

Solid state characterization of optimized S-SNEDDS

Morphological analysis of S-SNEDDS (SEM)

The morphological features of solid glimepiride-loaded

S-SNEDDS, pure glimepiride, and aerosol were observed

by SEM (S-4100, Hitachi, Shiga, Japan). The analysis

was performed by placing the samples on a brass stub using

a double-sided adhesive tape and was made electric-

ally conductive by coating in vacuum (6 pas) with platinum

using an ion sputter (E-1030) at 15 mA. The micro-

photographs were taken at an excitation voltage of 10 kV.

Differential scanning calorimetry (DSC)

The thermal investigations of glimepiride S-SNEDDS, pure

glimepiride, and pure Aerosol� 200 were performed by using

a DSC (SIIO, 6300, Tokyo, Japan) by placing about 3 mg of

each separated sample in sealed standard aluminum pans

before heating under a nitrogen flow (50 ml/min) and setting

the heat flow was from 0 �C to 300 �C.

X-ray powder diffraction (XRPD)

The powder crystallinity of the S-SNEDDS formulation, pure

glimepiride, and Aerosol� 200 were assessed with an X’Pert

PRO diffractometer (PW 1729, Philips, Amsterdam, The

Netherlands) at room temperature using monochromatic Cu-

Ka radiation, over a range of 2� angles from 2� to 50�, with

an angular increment of 0.02� per second.

Stability studies

The stability studies were conducted to determine the changes

in in vitro drug release studies, drug content, emulsion droplet

size, and PDI, on storage, according to ICH guidelines at

40 �C/75 ± 5% RH (Jain et al., 2005; Girish et al., 2007;

Srinivas et al., 2011) by storing the optimized S-SNEDDS for

3 months. After 3 months, the samples were collected and

analyzed for drug content, emulsion droplet size, PDI, and

in vitro release studies.

Assessment of therapeutic efficacy in albino rabbits

This study was with a single dose design using male albino

rabbits weighing 1–1.5 kg. The study was conducted prior

approval from institution animal ethical committee, School of

Pharmacy, Anurag Group of institutions, Hyderabad, India.

The animals were kept on a standard diet and fasted

overnight. Rabbits were divided into four groups, each of

six animals. Each animal of these first group received pure

glimepiride (1 mg/kg body weight), second group received

marketed formulation, third group received S-SNEDDS, and

forth group received L-SNEDDS in an amount equivalent to

calculated dose (1 mg/kg body weight). Blood samples were

withdrawn from the marginal ear vein of the animal. Fasting

blood glucose level was assessed using Semi-Auto analyzer

(Optimas, Labindia, Mumbai, India). Blood glucose level

(BGL) was measured at different time intervals (0, 1, 2, 3, 4,

5, 6, 8, 12, 18, and 24 h) up to 24 h. Each animal served as its

own control and hence, the hypoglycemic response was

evaluated as percentage decrease in blood glucose level. The

pharmacodynamic parameter of the area under percentage

decrease in BGL versus time curve (AUC0–24h) was calculated

by adopting the trapezoidal rule (Wagner, 1975; Ammar et al.,

2006; Sandya et al., 2012).

Results and discussion

Selection of oil

The determination of solubility of glimepiride in oils,

surfactants, and co-surfactants is the most important principle

for the selection of components for SNEDDS formulation.

The equilibrium solubility of glimepiride in different oils is

shown in Table 2. Among the all selected oils (Miglyol� 812,

Oleic acid, Sunflower oil, Soya bean oil, Isopropyl Myristate)

Miglyol� 812 and Oleic acid exhibited highest and lowest

solubilization capacity for glimepiride, respectively. As

Miglyol� 812 had good solubility for glimepiride compared

to all other oils, it was selected as oil phase for SNEDDS

formulation.

Selection of surfactant

Non-ionic surfactants are usually accepted for oral ingestion

and are considered safer than the ionic surfactants. The non-

ionic surfactants used were Tween� 80, Cremophor� RH 40,

Span� 20, and Span� 80. These surfactants were screened on

the basis of its ability to emulsify the selected oil as well as its

capacity to solubilize glimepiride. Tween� 80 showed highest

solubilization capacity for glimepiride (Table 3) and had

Table 2. Solubility of glimepiride in various oils.

Oil Solubility (mg/ml)

Oleic acid 0.16 ± 0.01Sunflower oil 16.2 ± 0.36Soya oil 15.23 ± 0.40Isopropyl Myristate 0.28 ± 0.02Miglyol� 812 18.3 ± 0.26

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ability to emulsify the selected oil, i.e., Miglyol� 812. The

emulsifying abilities were determined by measuring the %

transmittance of the resultant nanoemulsion. Since the use of

Tween� 80 and Cremophor� RH 40 was found to give

transmittance above 90% and as glimepiride was found to

have considerable solubility in these surfactants, they were

chosen for further investigations.

Selection of co-surfactant

The % transmittance obtained using PEG 400 and propylene

glycol as co-surfactants in combination with the above-

selected surfactants (namely Tween� 80 and Cremophor� RH

40) and Miglyol� 812 as the oil are given in Table 4. Among

the two co-surfactants examined, PEG-400 was found to

display highest % transmittance when used in combination

with Tween� 80 as a surfactant while propylene glycol was

found to show low % transmittance when combined with

Cremophor� RH 40 as the surfactant compared to PEG 400.

The co-surfactant was finally selected based on its ability to

solubilize the glimepiride and its ability to improve the

nanoemulsification efficiency of the selected surfactant.

Accordingly, PEG-400, which afforded high solubility of

glimepiride and which showed the highest transmittance

(98.55%), was selected as the co-surfactant for further

investigations.

Ternary phase diagram

The ternary phase diagram was constructed to identify the

nano-emulsifying region and to optimize the concentration of

the selected oil, surfactant, and co-surfactants (namely

Miglyol� 812, Tween� 80, and PEG 400, respectively). For

the development of a SNEDDS formulation, optimum ratios

of excipient concentrations established by means of phase

diagram studies provided the area of the monophasic region.

It is important to determine this area in order to confirm

successful aqueous dilution without breaking the nanoemul-

sion (Setthacheewakul et al., 2010). Figure 1 shows the

ternary phase diagram of the system containing selected oil,

surfactant, and co-surfactant. It was noted that incorporation

of the co-surfactant, PEG 400, within the self-emulsifying

region increased the spontaneity of the self-emulsification

process. The efficiency of emulsification was good when the

surfactant/co-surfactant concentration was more than 75% v/v

of the SNEDDS formulation. It was observed that spontan-

eous emulsion formation was not effective with less than 50%

v/v of the surfactant in the SNEDDS. In the present system,

the formulations surrounding the good self-emulsifying

region in the phase diagram exhibited a poor emulsion

forming ability. It has been reported that the drug

incorporated in the SNEDDS may have some effect on the

self-emulsifying performance (Oh et al., 2011). However, in

our study, no significant differences were found in the self-

emulsifying performance.

Optimization of glimepiride L-SNEDDS

The amount of oil, surfactant, and co-surfactant for the final

formulation of glimepiride SNEDDS was optimized on the

basis of Z-average size and PDI. The results are shown in

Table 1. Less than 200 nm Z-average size was observed with

two SNEDDS compositions namely 5:47.5:47.5 and

5:71.25:23.75 (oil:surfactant:co-surfactant, respectively). But

if the PDI value higher than 0.8, the systems were considered

as polydisperse. Hence the results obtained for SNEDDS

with oil:surfactant:co-surfactant of 5:71.25:23.75 was the

most consistent, it was considered as optimized L-SNEDDS

(F9) and composition was represented in Table 5.

Emulsion droplet size analysis

The particle size distribution is one of the important

parameters affecting the in vivo fate of emulsions.

The droplet size of the emulsion also defines the rate and

extent of drug release (Krutika et al., 2011). The smaller the

emulsion droplet size, larger the surface area provided for the

drug absorption. The Z-average size of the resulted nanoe-

mulsion at 100 times dilution was determined to be 152 nm

and the PDI value was low (0.211), representing that the

system had narrow size distribution (Figure 2).

Characterization of optimized S-SNEDDS ofglimepiride

Morphological analysis of S-SNEDDS (SEM)

The scanning electron microscopic pictures of glimepiride

powder, Aerosol� 200, and S-SNEDDS final formulation are

presented in Figure 3. The pure glimepiride powder

(Figure 3A) appeared as smooth surfaced, irregular shaped

crystals. Aerosol� 200 (Figure 3B) appeared as a rough

surface with porous particles. However, the S-SNEDDS

(Figure 3C) appeared as smooth surfaced particles without

Table 4. Emulsification efficiency with different co-surfactants andselected surfactants.

% Transmittance (at 638.2 nm)

Co-surfactantsSolubility(mg/ml) Tween� 80 Cremophor� RH 40

PEG 400 15.34 ± 0.21 98.55 ± 1.22 95.26 ± 1.33Propylene glycol 0.06 ± 0.005 62.61 ± 2.36 59.25 ± 0.82

Table 5. Composition of S-SNEDDS.

Formula Components in S-SNEDDS Proportions in mg

F 9 Glimepiride 20Miglyol� 812 50

Tween� 80 712.5PEG 400 237.5

Aerosol� 200 750

Table 3. Solubility of glimepiride in various non-ionic surfactants andtheir emulsification efficiency.

Surfactant HLB Solubility (mg/ml)% Transmittance

(at 638.2 nm)

Tween� 80 15 19.23 ± 0.30 91.3 ± 1.98Cremophor� RH 40 13 14.3 ± 0.4 90.1 ± 1.04Span� 20 8.6 4.41 ± 0.17 55.3 ± 0.28Span� 80 4.3 2.50 ± 0.15 54.4 ± 0.34

DOI: 10.3109/10717544.2013.879753 S-SNEDDS for oral delivery of glimepiride 5

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any crystalline shape which indicates complete adsorption of

liquid NEDDS containing glimepiride inside the pores of

Aerosol� 200.

Differential scanning calorimetry (DSC)

The DSC thermograms of pure glimepiride, Aerosol� 200,

and S-SNEDDS are shown in Figure 4. Pure glimepiride

showed one sharp endothermic peak at 212.2 �C (Figure 4A),

corresponding to its melting point indicating its crystalline

nature. S-SNEDDS showed one broad endothermic peak with

reduced intensity at 153 �C (Figure 4C). It might be indicating

that the drug is present in molecularly dissolved and

amorphous state in S-SNEDDS (Nazzal et al., 2002b;

Balakrishnan et al., 2009; Wang et al., 2009; Shanmugam

et al., 2011).

X-ray powder diffraction (XRPD)

The XRPD patterns of pure glimepiride powder, Aerosol�

200, and S-SNEDDS are shown in Figure 5. XRPD was used

for further verification of the internal physical state of

glimepiride in the S-SNEDDS. Pure glimepiride powder

showed sharp peaks at the diffraction angles (2�), such as

10.9�, 12�, 16.5�, 17�, 18.8�, 21�, 23�, 28�, and 30�

(Figure 5A) indicating a typical crystalline pattern.

Aerosol� 200 showed no peaks at diffraction angles,

indicating an amorphous pattern (Figure 5B). No obvious

peaks representing crystals of glimepiride were observed for

the S-SNEDDS final formulation (Figure 5C), indicating the

absence of crystalline structure of glimepiride in the final

formulation.

In vitro drug release studies

The dissolution profiles of L-SNEDDS, S-SNEDDS, and

marketed formulation were compared with that of the pure

drug (Figure 6), using phosphate buffer pH 7 as a dissolution

medium. Both liquid and S-SNEDDS and marketed formu-

lation of glimepiride showed more than 85% drug within

15 min, whereas the pure drug showed less than 15% release

of the total amount of drug. Within 30 min, the drug is

completely released from the both solid and L-SNEDDS as a

result of the spontaneous emulsification and the resulted

nano-level droplet size. At the same time % drug release from

pure drug was found to be only 16% of overall drug release.

Figure 3. Scanning electron microscope (SEM) pictures of (A) pureglimepiride powder; (B) Aerosol� 200, and (C) S-SNEDDS formulation.

Figure 2. Z-average (nm) of liquid SNEDDSof glimepiride (F9).

6 A. B. Mohd et al. Drug Deliv, Early Online: 1–10

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Figure 5. X-ray powder diffractograms of (A) pure glimepiride, (B) Aerosol� 200, and (C) S-SNEDDS formulation.

Figure 4. Differential scanning calorimetric thermograms of (A) pureglimepiride, (B) Aerosol� 200, and (C) S-SNEDDS formulation.

Figure 6. Comparative in vitro drug release profile of pure glimepiride,optimized L-SNEDDS, S-SNEDDS, and marketed formulation. Datarepresented are cumulative % drug release versus time (min) in terms ofmean ± SD (n¼ 3).

DOI: 10.3109/10717544.2013.879753 S-SNEDDS for oral delivery of glimepiride 7

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The solid carrier used for S-SNEDDS did not interfere with

the drug release. The in vitro dissolution studies of S-

SNEDDS revealed that initial glimepiride release from porous

carriers (Aerosol� 200) was slower compared with L-

SNEDDS, This could be because of additional steps involved

during dissolution such as disintegration of solid structure of

S-SNEDDS and desorption of L-SNEDDS from the voids of

porous carriers. The S-SNEDDS when exposed to dissolution

medium leads to desorption of the L-SNEDDS from the

Aerosol� 200 surface due to stronger interaction between

Aerosol� 200 and dissolution medium than those between

Aerosol� 200 and L-SNEDDS.

Stability studies

To determine the temperature sensitivity on dissolution

release profile, emulsion droplet size, PDI, and drug content

of optimized S-SNEDDS, the stability study was performed at

40 �C and 75% ± 5% RH for 3 months. The stability samples

were evaluated for dissolution release profile, emulsion

droplet size, PDI, and drug content. Samples withdrawn

after 3 months showed no significant changes in in vitro drug

release studies, drug content, emulsion droplet size, and PDI.

The similarity factor (f2) for the optimized S-SNEDDS was

found to be 94.51 (Table 6), which indicates good similarity

of dissolution release profile, prior and after stability studies.

No significant difference (p40.05) was observed in drug

content, emulsion droplet size, and PDI data, before and after

storage.

Assessment of therapeutic efficacy in albino rabbits

Blood glucose level (BGL) was measured at different time

intervals up to 24 h. Each animal served as its own control and

hence, the hypoglycemic response was evaluated as percent-

age decrease in blood glucose level. The pharmacodynamic

parameter of the area under percentage decrease in BGL

versus time curve (AUC0–24h) was calculated adopting the

trapezoidal rule

Decrease in BGL ð%Þ ¼ BGL at t ¼ 0� BGL at t

BGL at t ¼ 0� 100

Figure 7 shows the mean percentage decrease in blood

glucose level (BGL) in normal rabbits after administration of

pure glimepiride, glimepiride S-SNEDDS, marketed formu-

lation, and L-SNEDDS. It is evident that the AUC-values for

S-SNEDDS, L-SNEDDS, and marketed formulation were

higher than the corresponding values of pure glimepiride

(Table 7). The results revealed that there was a significant

increase in the biological performance of S-SNEDDS and

L-SNEDDS than pure glimepiride, and there was no signifi-

cant difference among the S-SNEDDS, L-SNEDDS, and

marketed formulation.

Conclusion

In the present study, the optimal S-SNEDDS formulation that

showed significantly improved in vitro release of glimepiride

when compared with pure glimepiride was successfully

developed. The S-SNEDDS readily released the lipid phase

to form a fine oil-in-water nanoemulsion, with a narrow

distribution size. The solid state characterization of

S-SNEDDS by SEM, DSC, and X-ray diffraction analysis

suggested that glimepiride in the S-SNEDDS was in the

amorphous or molecular dispersion state. The in vitro dissol-

ution test showed that the S-SNEDDS had a faster in vitro

release rate than the pure glimepiride. The AUC of

glimepiride in S-SNEDDS was increased compared with the

pure glimepiride. Thus, the prepared S-SNEDDS for the

delivery of glimepiride would be a promising dosage form in

the maintaining blood glucose level.

Figure 7. The mean percentage decrease in blood glucose level onnormal rabbits.

Table 6. Results for stability studies of S-SNEDDS.

% Cumulative drug releasea

Time (min) InitialAfter storage at 40 �C/75 ± 5%

RH for 90 d

0 0.00 0.005 58.27 ± 6.51 54.31 ± 4.67

10 71.69 ± 4.54 72.18 ± 5.0715 84.04 ± 7.15 81.97 ± 3.2530 97.11 ± 4.23 92.79 ± 4.2245 100.38 ± 3.24 98.91 ± 2.5660 102.24 ± 4.75 97.60 ± 2.2390 98.78 ± 6.56 99.69 ± 4.15

120 98.96 ± 3.35 99.71 ± 3.35Physical factors Initial After storage at

40 �C/75 ± 5% RH for 90 dDroplet size 152 160PDI** 0.211 0.268Drug content** 99.7 ± 2.37 98.4 ± 1.25

**p40.05.aSimilarity factor (f2): 77.28

Table 7. Therapeutic efficacy of glimepiride pure and L-SNEDDS,S-SNEDDS, and marketed formulation.

AUC(0–24)

GlimepiridePure

OptimizedL-SNEDDS

OptimizedS-SNEDDS

Marketedformulation

Mean 128.77 248.8825 234.64 207.20± S.D 54.25 52.22 32.22 34.16

8 A. B. Mohd et al. Drug Deliv, Early Online: 1–10

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Declaration of interest

The authors report no conflicts of interest. The authors alone

are responsible for the content and writing of this article.

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