R E S E A R C H A R T I C L E
Mucoadhesive microsphere based suppository containing
granisetron hydrochloride for management of emesis
in chemotherapy
N. H. Salunkhe   • N. R. Jadhav   • K. K. Mali   • R. J. Dias   •
V. S. Ghorpade   • A. V. Yadav
Received: 18 December 2013/ Accepted: 22 February 2014
 The Korean Society of Pharmaceutical Sciences and Technology 2014
Abstract   The purpose of present work was to develop
suppositories containing mucoadhesive microspheres of 
granisetron hydrochloride (GH) using combination of 
xanthan gum and sodium alginate. Twelve different bat-
ches of microspheres containing GH were prepared by
simple emulsification method and evaluated for surface
morphology, particle size, equilibrium swelling degree,
drug content, in vitro mucoadhesion, and in vitro drug
release. The suppositories containing optimized batch of 
microspheres (C2) were formulated by fusion method using
hydrophilic and lipophilic polymer base. The suppositories
were evaluated for weight variation, hardness, macro-
melting range, drug content, drug release, morphology of 
rectal tissues, and in vivo suppository localization. Results
show that, all microsphere batches were spherical and had
size range 23.56–36.76 lm. The % drug encapsulation was
found in the range 61.67–92.30 %, and showed satisfactory
mucoadhesion. Especially, C2 batch had 83.67 % mu-
coadhesion and 92.30 % drug encapsulation and showed
release retardation for 4 h. The results of all suppositories
were within the pharmacopoeial standard limits. Drug
content of all the suppositories was in the range
93.20–98.40 %. The suppository batch (P2M) was
considered best on the basis of optimum retardation up to
5 h, high drug content, optimum mechanical strength and
zero order release (r2 =  0.9860). The suppository of batch
P2M showed no morphological changes in rectal tissues
indicating its safety. In vivo localization revealed satis-
factory mucoadhesion of microspheres. Hence, it can be
concluded that, delivery of GH in suppository form can
avoid its presystemic metabolism, thus, may be an efficient
alternative to its oral dosage form and conventional
suppository.
Introduction
Microsphere delivery systems have been used for localized
drug delivery to reduce side effects as well as to improve
the therapeutic response at the local site (Baker   1987;
Burgess and Hickey   2005). Granisetron hydrochloride
(GH), a potent and selective 5-HT-3 receptor antagonist
with antiemetic activity incorporated in the microspheres
has been indicated for the prevention of nausea and vom-
iting associated with cytotoxic chemotherapy, radiotherapy
and post operative vomiting (Tripathi 2003). It is 10–15
times more potent than ondansetron hydrochloride and
probably more effective during the repeat cycle of che-
motherapy (Tripathi   2003). But, it undergoes extensive
presystemic metabolism (34–59 %) and has got short bio-
logical half life (3–4 h) (Dollary 1999; Swamy et al. 2010).
Tablets and intra venous (i.v.) injections of GH are avail-
able in the market. However, oral administration of antie-
metic drugs have disadvantages associated with its
N. H. Salunkhe (&)    N. R. Jadhav
Department of Pharmaceutics, Bharati Vidyapeeth College of 
Pharmacy, Kolhapur 416013, Maharashtra, India
e-mail: nsalunkhe7500@gmail.com
Department of Pharmaceutics, YSPM College of Pharmacy,
Wadhe, Satara 415011, Maharashtra, India
A. V. Yadav
Limb, Satara 415015, Maharashtra, India
 1 3
from severe nausea and vomiting. The patients suffering
from head and neck cancer also find it difficult to swallow
the oral dosage forms. I.v. administration can only be
performed under medical supervision and causes signifi-
cant patient discomfort. Problems are pronounced in
pediatric patients. Thus, rectal administration of GH may
prove to be an efficient alternative to the oral and intra-
venous route (Peter et al.  2006).
Suppositories are preferred over i.v. injection or oral
preparations in patients experiencing nausea and vomiting
due to cancer chemotherapy (Yahagi et al.  2000). Unlike
orals, they do not have gastrointestinal irritation, dis-
agreeable taste, first pass effect and undesirable effects of 
meals on drug absorption (Tarlmcl and Ermis 1997). Even,
the use of conventional suppositories is often associated
with problems like absorption irregularity, patient dis-
comfort and acceptability and first pass metabolism if 
suppository reaches to the colon (Pongjanyakul and Put-
tipipatkhachorn  2007). To overcome the drawbacks men-
tioned above, it has been thought to design novel
suppository containing mucoadhesive microspheres loaded
with GH, which will adhere to rectal mucosa and drug will
be absorbed form the lower rectum and may lead to
improved bioavailability (Uzunkaya and Bergis 2003).
The present investigation aims to avoid first pass
metabolism of GH by formulating mucoadhesive micro-
spheres using combination of xanthan gum (XG) and
sodium alginate (SA) for rectal administration. The effect
of different concentrations of XG on encapsulation effi-
ciency, surface morphology, particle size, equilibrium
swelling degree, mucoadhesion and in vitro drug release
has been studied by its comparison with sodium alginate
microspheres. The release of GH from the suppositories
containing XG–SA microspheres was evaluated by in vitro
dissolution test and in vivo evaluations involved morpho-
logical study of rectal tissues and suppository localization
in the rectum.
Materials and methods
Materials
GH was a kind gift sample from Cipla, Mumbai, India. SA,
XG, polyethylene glycol (PEG 1500, PEG 4000, and PEG
6000) base, hydroxypropyl methyl cellulose (HPMC) and
span 80 were purchased from Loba Chemie (Mumbai,
India). Cocoa butter (CB) was purchased from Rajesh
Chemicals Pvt Ltd. (Mumbai, India) and Mayol W-45
(M) was gifted by Subhash Chemical Industries (Pune,
India). All other chemicals were of analytical grade.
Methods
Twelve different batches of GH loaded microspheres were
prepared by simple emulsification method followed by
cross-linking with calcium chloride as shown in Table 1.
Core material, GH (100 mg) was dispersed in aqueous
solution (50 ml) of 5 % w/v SA:HPMC (9:1), containing
varying concentration of XG from 0.1 to 0.3 %. The
resultant aqueous phase was dispersed in hexane solution
containing 2 % v/v Span 80 using a mechanical stirrer
(Remi Motors, India) at 1,600 rpm for 30 min. After
complete emulsification, different concentrations of aque-
ous solution of calcium chloride (7, 9 and 11 %) were
added slowly to the emulsion and dispersion was stirred for
another 10 min. Microspheres were collected by filtration,
washed three times with isopropyl alcohol and finally dried
at room temperature (Rajnikanth et al.  2003).
Fourier transform-infra red (FT-IR) spectroscopy   FTIR
spectra of GH, SA, XG, GH–SA physical mixture, GH–
SA–XG physical mixture, calcium alginate blank micro-
spheres, GH loaded calcium alginate microspheres and GH
loaded XG–SA microspheres were recorded using FTIR
spectrophotometer (PERKIN ELMER 79720S).
Particle size of the microspheres   The particle size of the
microspheres was determined using optical microscope.
The average particle size was determined by using Ed-
mondson’s equation,
Dmean ¼ X
n   ð1Þ
where n  is number of microspheres observed and d is mean
size range (Uzunkaya and Bergis  2003).
Surface topography   Scanning electron microscopy (JSM-
6360; JEOL Ltd., Tokyo, Japan) was used to evaluate the
shape and surface topography of the microspheres.
Percentage drug encapsulation   Hundred milligrams of 
the microspheres from all the batches were accurately
weighed, added in distilled water and volume made to
50 ml and placed in an ultrasonic water bath for 30 min.
The samples were left to equilibrate for 2 days and assayed
spectrophotometrically at wavelength (kmax) 301.5 nm
(Wan et al.  1992).
degree (ESD) of microspheres ware determined by swell-
ing 50 mg of dried microspheres in distilled water, over-
night in a measuring cylinder. The ESD (ml/g) was
N. H. Salunkhe et al.
 1 3
 
expressed as the ratio of the swollen volume to the mass of 
the dried microspheres (Hamdi and Ponche l999).
 In vitro Mucoadhesion   Fifty milligrams of the micro-
spheres from all the batches were separately placed on
2 cm 2
sheep rectal mucosa and kept for 20 min in a
humidity and temperature controlled cabinet (REMI CH-
6S Mumbai, India) at 75 % relative humidity and tem-
perature of 25 ±  2   C to allow hydration of the micro-
spheres. This was followed by thorough washing of the
mucosal lumen with isotonic phosphate buffer (pH 6.8).
The washings were then dried at 70   C in a hot air oven
and percent mucoadhesion was determined by the ratio of 
the weight of adhered microspheres to the weight of 
applied microspheres (Rastogi et al. 2007).
 In vitro drug release from microspheres   Dissolution tests
for twelve different batches of microspheres were carried
out in USP-XXIII type dissolution apparatus using 500 ml
of phosphate buffer of pH 6.8. Rotation speed was con-
trolled at 100 rpm while temperature was maintained at
37  ±  0.5   C. Microspheres equivalent to 2 mg GH from
each batch were suspended in 500 ml of phosphate buffer
pH 6.8 with continuous stirring. A 5 ml samples were
withdrawn periodically at 30 min time intervals and the
sink condition was maintained. The samples were analyzed
spectrophotometrically at kmax 301.5 nm. The kinetics of 
GH release from the microspheres was determined using
zero-order, first-order, Higuchi equation and Korsmeyer–
Peppas equation (Korsmeyer et al.1983).
Preparation and evaluation of suppositories
The five different batches of suppositories weighing 1 g
each, containing optimized microspheres equivalent to
2 mg of GH were prepared using hydrophilic bases namely
PEG 1500, PEG 4000, PEG 6000 and lipophilic bases
namely coco butter, Mayol W-45 by fusion method
(Table  2) (Uzunkaya and Bergis   2003). The prepared
suppositories were wrapped in aluminum foil, kept in
refrigerator and were used in the further investigation. All
Suppositories were evaluated for weight variation (g),
Table 1  Composition and
process conditions for different
batches of GH microspheres
A 100 5 – 7 5
Blank – 5 0.1 7 5
Table 2  Composition of 
 M  microsphere loaded
GH (mg) equivalent
PEG 1500 (g) 1 – – – –
PEG 4000 (g) – 1 – – –
PEG 6000 (g) – – 1 – –
Cocoa butter (g) – – – 1 –
Mayol W-45 (g) – – – – 1
 1 3
macromelting range (min).
were determined by soaking individual suppository in
500 ml water for 30 min, breaking with spatula, vortexing
for 5 min further it was diluted to 50 ml with distilled
water, and placed in an ultrasonic water bath for 30 min.
The aliquots were equilibrated for 2 days. Aliquots were
filtered through a Whatmann filter and assayed spectro-
photometrically at kmax 301.5 nm. For cocoa butter/Mayol
W-45 suppositories, drug content was determined by
heating the suppository in distilled water at 50  C for
5 min, separate out the aqueous layer by separating funnel
and further it was diluted to 50 ml with distilled water and
placed in an ultrasonic water bath for 30 min. The aliquots
were equilibrated for 2 days. Aliquots were filtered through
a Whatmann filter and assayed spectrophotometrically at
kmax 301.5 nm. The determination was carried out in
triplicate (Saleem et al. 2008; Sah and Saini  2008).
 In vitro drug release from suppositories   Dissolution test
was carried out in USP-XXIII type dissolution apparatus
using 500 ml of phosphate buffer of pH 6.8. Rotation speed
was controlled at 100 rpm while temperature was main-
tained at 37  ±  0.5   C. A 5 ml samples were withdrawn
periodically at 30 min time intervals and the sink condition
was maintained. The samples were analyzed spectropho-
tometrically at   kmax 301.5 nm (Uzunkaya and Bergis
2003). The kinetics of GH release from the suppositories
was determined to fit for zero-order, first-order, Higuchi
equation and Korsmeyer–Peppas equation (Korsmeyer
et al.1983). The optimized suppository formulation was
subjected to the morphology of rectal tissues in order to
check the safety of the suppositories.
 Morphology of rectal tissues   Male albino rats weighing
250  ±  20 g were fasted for 24–36 h prior to the experiments
and allowed free access to water (protocol approved by IAEC-
CPCSEA, Satara College of Pharmacy, Satara, Approval No:
SCOP/IAEC/04/09-10). Optimized suppository batch (P2M)
was administered at 6 mg/kg into the rectum 4 cm above the
anus. At 6 h after administration, the rectum was isolated,
rinsed with a saline solution, fixed in 10 % neutral carbonate
buffered formaldehyde, embedded in paraffin using an
embedding center and cut into slices. The slices were stained
with hematoxylin-eosin and observed under a light micro-
scope (Lawrence and Mayo) (Choi et al. 2005).
Suppository localization in the rectum   Male albino rats
weighing 250  ±  20 g were fasted for 24–36 h prior to the
experiments and allowed free access to water. Suppository
containing microspheres of GH with 0.1 % blue lake was
administered at 6 mg/kg into the rectum 4 cm above the
anus. At 6 h after administration, the rectum was sectioned
and the blue color was identified in order to determine the
distance travelled by the suppository in the rectum (Choi
et al.  2005).
tion (SD). Data was analyzed by one way ANOVA fol-
lowed by Tukey’s multiple comparison tests. A ‘ p’ value
less than 0.05 was considered as statistically significant.
Results
successfully by emulsification method as shown in Table  1.
Microspheres were evaluated on the basis of sphericity,
mucoadhesion, drug entrapment, equilibrium swelling
degree and in vitro drug release study.
FTIR spectroscopic study
FTIR has proven to be a convenient technique to investigate
the drug–polymer interactions in physical mixtures in order to
evaluate any possible chemical interactions between the drug
and polymers. FTIR spectrum of GH, SA, XG and its physical
mixtures has been shown in Fig. 1. The IR spectra of pure GH
showed absorbance peaks at 3232.85, 2,939, 2449.38,
1646.97 and 1,551 cm-1, indicating stretching of N–H,
alkene, protonated tertiary amine, C=O and bending of N–H
(Fig.  1a).The IR spectra of sodiumalginate exhibited peaks at
3423.65 cm-1 (O–H stretching), 1611.44 cm-1 (–COO– asym-
metric stretching), 1415.75 cm-1 (–COO–symmetricstretch-
ing) and 1030.33 cm-1 (C–O–C stretching). The IR spectra of 
physical mixtures (Fig. 1d, e) showed presence of all the
characteristic peaks of GH. The O–H stretching peak of cal-
cium alginate blank microspheres at 3396.35 cm -1 (Fig.  1f)
showed narrowing on incorporation of GH (Fig.  1g). The
peaks of GH corresponding to stretching of N–H, protonated
tertiary amine, C=O and bending of N–H disappeared in the
spectra of GH loaded microspheres (Fig.  1g). The incorpo-
ration of XG into microspheres shifted the peak of O–H
stretching at 3422.35 cm -1 and peak of –COO– asymmetric
stretching at 1627.61 cm-1 to lower wave number respec-
tively (Fig.  1g, h).
Particle size of the microspheres
The mean size of the microspheres was found in the range
of 23.56–36.76  lm. It was observed that size of the
N. H. Salunkhe et al.
 1 3
concentration (A1, A2, B1, B2, C1 and C2). The increase
in the crosslinking agent (CaCl2) concentration and cross-
linking time also increased the size of the microspheres in
batches D1, D2, E1 and E2 respectively.
Surface topography
The SEM analysis revealed that microspheres were discrete
and spherical in shape (Fig.  2). Batches B1, B2, C1 and C2
showed smoother surface as compared to other batches (A,
A1, A2, D1, D2, E1 and E2).
Percentage drug encapsulation
The increase in concentration of SA in batches B1 and B2
showed insignificant ( p[0.05) increase in the encapsula-
tion efficiency 81.49 and 83.22 % as shown in Table 3.
However, increase in the concentration of XG in batch C1
(0.2 %) and batch C2 (0.3 %) showed a significant increase
( p\ 0.05) in entrapment of 90.6 and 92.3 % respectively.
Equilibrium swelling degree
The blank microspheres showed highest ESD (4.1 ml/g) as
compared to other batches as shown in Table  3. Increase in
the polymer concentration (SA and XG) increased ESD
whereas decrease in ESD was observed on increase in
concentration of GH. The concentration of crosslinking
agent and crosslinking time was found to be inversely
proportional to ESD of microspheres.
 In vitro mucoadhesion
concentration decreased the mucoadhesion whereas
increase in the polymer concentration increased the mu-
coadhesion (Table  3). The increase in the concentration of 
XG added to the mucoadhesive property of microspheres.
Batch C2 showed highest mucoadhesion of 83.67 %. The
concentration of crosslinking agent and crosslinking time
was inversely affected the bioadhesive property of micro-
spheres. Batch D2 showed least mucoadhesion (58.25 %).
 Drug release from microspheres
Drug release profile of all batches of microspheres has been
shown in Fig.  3. An initial burst release was observed for all
the formulations followed by moderate release. Batches A,
A1 and A2 showed more than 50 % release of GH within
30 min. As the amount of drug was increased, the rate and
extent of release was found to be increased. The micro-
spheres from batches B1, B2, C1 and C2 showed 50 % drug
release within 60, 90, 120 and 150 min respectively. The
increase in concentration of SA and XG decreased the drug
release. Batches D1, D2, E1 and E2 showed 50 % GH
release within 90 min. The kinetics of GH release from
microspheres is shown in Table 4. Batches C1, C2 and D2
showed best fit to Korsmeyer–Peppas equation whereas
other batches showed best fit to Higuchi equation. The
values of n were in the range of 0.2789–0.7107.
Evaluation of suppositories
of all suppositories were found to be as per
Fig. 1   FTIR spectrum of drug, polymer and microspheres. Pure GH
(a) , S A (b), XG (c), GH-SA physical mixture (d), GH-SA-XG
physical mixture (e), calcium alginate blank microspheres ( f ), GH
loaded calcium alginate microspheres (g) and GH loaded alginate–
xanthan microspheres (h)
 1 3
suppositories were within the permissible range
93.2–98.4 % indicating uniformity of drug dispersion in
suppositories.
 Drug release from suppositories
GH release from the suppositories has been given in Fig. 4.
PEG base suppositories containing GH loaded microspheres
Fig. 2   Scanning electron microphotograph of all batches of microspheres (magnification  93,500)
N. H. Salunkhe et al.
 1 3
having hydrophobic base showed 73.56  ±  6.04 % (CBM)
and 66.53  ±  2.13 % (MM) drug release in 5 h. The con-
ventional suppositories prepared using PEG 1500 (P1),
PEG 4000 (P2) and PEG 6000 (P3) showed complete drug
release in 1 h whereas those prepared using cocoa butter
(CB) and Mayol W-45 (M) showed complete drug release
in 90 min. The kinetics of GH release from the supposi-
tories has been shown in Table 6. The MM formulation
showed best fit to Korsmeyer–Peppas equation whereas
other formulations showed best fit to the zero order
equation.
Formulation
code
BLANK 25.23  ±  2.47 4.10 – –
Fig. 3   In vitro release profile of GH loaded microspheres
Table 4   In vitro release kinetic data for microspheres
Batch code Zero order First order Higuchi Hixson & Crowell Peppas
R k R k R k R k R k    n
A1 0.760 0.733 0.965   -0.016 0.971 7.972 0.929   -0.004 0.983 22.350 0.278
A2 0.831 0.001 0.831 – 0.989 0.007 0.831 0.000 0.987 0.012 0.388
B1 0.845 0.001 0.846 – 0.990 0.006 0.846 0.000 0.981 0.011 0.390
B2 0.939 0.001 0.939 – 0.989 0.006 0.939 0.000 0.985 0.004 0.547
C1 0.974 0.004 0.974 – 0.976 0.005 0.974 0.000 0.996 0.002 0.710
C2 0.963 0.365 0.967   -0.006 0.976 4.767 0.985   -0.002 0.994 2.277 0.662
D1 0.895 0.563 0.975   -0.011 0.995 6.544 0.978   -0.003 0.985 8.399 0.454
D2 0.939 0.461 0.969   -0.009 0.988 5.699 0.983   -0.002 0.989 4.584 0.558
E1 0.862 0.709 0.984   -0.015 0.993 7.637 0.973   -0.004 0.990 12.733 0.390
E2 0.900 0.563 0.974   -0.011 0.994 6.540 0.977   -0.003 0.983 7.897 0.466
A 0.869 0.882 0.977   -0.020 0.991 8.592 0.970   -0.005 0.986 16.104 0.358
Antiemetic suppositories containing mucoadhesive microspheres of Granisetron hydrochloride
 1 3
showed normal mucosal pattern in Fig. 5. In view of  
control rectal tissue, no evidence of acute inflammation,
edema or any other morphological damage was noted in the
section of treated rectal tissue.
Suppository localization in vivo
The blue color was observed into the rectum after 6 h of 
administration of optimized suppository batch (P2M) as
shown in Fig.  6. The distance travelled by the suppository
in the rectum was found to be 8–9 cm.
Discussion
The IR spectra of physical mixtures revealed that there was
no any physical interaction between GH, SA and XG. The
narrowing of O–H stretching peak of calcium alginate
blank microspheres on addition of GH (Fig. 1f, g) may be
due to intermolecular hydrogen bonding between GH and
SA. This may be further confirmed from disappearance of 
characteristic peaks of GH in IR spectra of GH loaded
calcium alginate microspheres (Fig. 1g). The disappear-
ance of peaks due to N–H stretching, N–H bending and
C=O stretching may be due to formation of hydrogen
bonds between ‘–CO–NH–’ group of GH and ‘–COOH’
group of alginic acid. The disappearance of peak due to
protonated tertiary amine may be attributed to its ionic
interaction with alginate. The overall FTIR spectral study
revealed the lack of any incompatibility within GH loaded
microspheres formulation.
the size of the microspheres. This may be attributed to
synergistic polymer–polymer interaction between SA and
XG. On adding XG into SA solution, self association gel
structure of XG was lost. However, due to intermolecular
hydrogen bonding between SA and XG, there was increase
in the viscosity of the SA solution (Pongjanyakul and
Puttipipatkhachorn 2007). The increase in the viscosity of 
aqueous phase droplets during emulsification might have
caused increase in the interfacial tension leading to difficult
dispersion and subdivision of droplets (Denkbas et al.
1999).
Evaluation parameter P1M P2M P3M MM CBM
Weight variation (g) 845.3  ±  2.00 861.7  ±  4.10 852.1  ±  2.80 724.3  ±  4.52 697.8  ±  4.60
Mechanical strength (kg/cm2) 2.5  ±  0.50 3  ±  1.00 4.5  ±  0.55 1.5  ±  0.16 2  ±  0.15
Disintegration (min) 14  ±  1.10 17  ±  1.53 19  ±  1.58 5  ±  2.17 4  ±  0.57
Macromelting range (min) 18  ±  2.08 22  ±  2.64 28  ±  2.01 7  ±  1.53 9  ±  3.05
Drug content (%) 97.6  ±  1.01 98.4  ±  0.35 96.7  ±  1.40 93.2  ±  1.47 95.9  ±  0.49
Values are expressed in mean  ±   standard deviation
Fig. 4   In vitro dissolution profile of suppositories
Table 6   In vitro drug release kinetic data for suppositories
Batch code Zero order First order Higuchi Hixson & Crowell Peppas
r2 K r2 K r2 K r2 K r2 K    n
P1M 0.986 0.33 0.939   -0.006 0.949 4.515 0.972   -0.001 0.981 1.462 0.739
P2M 0.986 0.287 0.891   -0.005 0.930 4.109 0.943   -0.001 0.971 1.285 0.714
P3M 0.987 0.285 0.897   -0.005 0.909 4.0367 0.941   -0.001 0.965 0.823 0.795
MM 0.986 0.295 0.950   -0.005 0.960 4.247 0.979   -0.001 0.995 1.089 0.762
CBM 0.986 0.273 0.901   -0.005 0.914 3.876 0.943   -0.001 0.966 0.959 0.759
N. H. Salunkhe et al.
 1 3
The microphotographs of batches A, A1, A2, D1, D2,
E1 and E2 revealed the presence of rough surface
(Fig.  2). This may be due to presence of surface associ-
ated drug. This can be easily predicted on comparing the
microphotograph of blank microspheres with micropho-
tographs of batches A, A1, A2, D1, D2, E1 and E2. As
the concentration of drug increased, the roughness was
found to be increased. However, increase in the concen-
tration of XG (batches C1 and C2) decreased the rough-
ness of the microsphere surface to a considerable extent.
The surface usually becomes smooth when polymer pre-
cipitates slowly with sufficient time to shrink its size and
occurs due to slow removal of organic solvent or high
solubility of solute in a particular solvent (Bain et al.
1999; Mandal et al.  2001). The increase in the polymer
concentration increases the shrinkage time by decreasing
the organic solvent removal rate and thus increasing the
smoothness of the microsphere surface. Aggregation of 
microspheres in some of the batches may be due to
incomplete removal of solvent during filtration of 
microspheres or it may be due to softening of micro-
spheres during drying.
It may be due to interaction of XG with SA leading to
increase in barrier which prevents water leakage from the
microspheres during preparation period (Peter et al. 2006).
The FTIR (compatibility study) revealed presence of 
hydrogen bonding between GH (–CO–NH– group) and XG
(–COO– group) which may also be the reason for high
encapsulation of GH in XG–SA microspheres.
SA microspheres showed high water uptake in pH 6.8
phosphate buffer because calcium ions cross-linked with
alginate rapidly exchange with sodium ions in phosphate
buffer (Ostberg et al. 1994). Incorporation of XG (0.1, 0.2
and 0.3 %) increased the water uptake capacity as XG has
high water uptake capacity than SA (Bertram and Bod-
meier 2006). The increase in concentration of crosslinking
agent and crosslinking time caused decrease in the ESD
which may be due to introduction of numerous cross-links
in the hydrogel structure (Hamdi and Ponchel 1999). As the
concentration of crosslinking agent was increased, the SA
polymer chain integration increased leading to firm asso-
ciated junction zone. This in turn increased their rubber-
like resistance to stretching (Davidovich-Pinhas and Bi-
anco-Peled 2010).
Fig. 5   Microphotographs of rat’s rectal tissues after administering suppository
Fig. 6   Distance travelled by the
suppository in the rectum
 1 3
(batch C1) to 0.3 %w/v (batch C2), the mucoadhesion also
increased than SA. This may be due to availability of more
polymer chains for entanglement with the mucin chains
along with more water uptake from mucus by XG. The
increase in the concentration of the crosslinking agent
(CaCl2) and crosslinking time decreased percent mucoad-
hesion. Increase in the concentration of crosslinking agent
and crosslinking time increased the crosslinking between
calcium ions and alginate chains, thus making less polymer
chains to entangle with mucin chains.
In vitro mucoadhesion studies revealed that as concen-
tration of SA was increased from 5 % w/v (batch A1) to
7 %w/v (batch B2), the % in vitro mucoadhesion may also
found to be increased. A further increase in mucoadhesion
was observed on increase in concentration of XG (batches
C1 and C2). This might have been due to availability of 
more polymer chains for entanglement with the mucin
chains along with more water uptake from mucus by XG.
The increase in the concentration of the crosslinking agent
(CaCl2) showed decrease in percent mucoadhesion. It was
also found that increase in crosslinking time decreased
percent mucoadhesion. Increase in the concentration of 
crosslinking agent increased the crosslinking between cal-
cium ions and alginate chains, thus making less polymer
chains to entangle with mucin chains. The increase in the
crosslinking time also resulted in decreased mucoadhesion
as it provided more time for the calcium ions to interact
with alginate chains.
indicated the initial burst release (Fig. 3); however the
extent of burst decreased on increasing the polymer con-
centration (batches B1, B2, C1 and C2). The reason for the
burst release may be the surface associated drug which was
loosely held within the polymer matrix. XG significantly
retarded ( p\ 0.05) the release of GH as compared to SA.
This may be due to increase in the density of polymer
matrix and in the diffusional path length that the drug has
to traverse. When the concentration of crosslinking agent
and crosslinking time was increased, a decrease in the rate
and extent of drug release was found. However, this
decrease was not prominent. This can be attributed to
formation of tight junction between the mannuronic acid
residues and guluronic acid residues of sodium alginate
with calcium. Calcium ions also have ability to crosslink 
XG at higher concentration (Uzunkaya and Bergis  2003).
The release of GH from microspheres was also governed
by ionic exchange between the crosslinking calcium ions in
the microspheres and the sodium ions in the buffer (Ki-
kuchi et al. 1997). The kinetics reveled that batches C1, C2
and D2 showed best fit to Korsmeyer–Peppas equation
whereas other batches showed best fit to Higuchi equation.
The batches C1 and C2 show combined diffusion and
erosion mechanism for drug release. Other batches showed
drug release which was largely governed by diffusion
through water filled pores in the matrix. As C2 batch
showed highest entrapment, satisfactory mucoadhesion and
optimum retardation of GH release (94.03 ±  1.49 % in
270 min), it was decided as an optimized microsphere
batch and was used for preparation of suppositories.
The increase in the molecular weight of PEG bases
increased the mechanical strength and macromelting range
of the suppositories. It was found that hydrophobic bases
(cocoa butter and Mayol W-45) took very less time to melt
as compared to hydrophilic bases (PEG 1500, 4000 and
6000).
was a significant decrease ( p\ 0.05) in the GH release
from microsphere loaded suppositories as compared to
conventional suppositories. This might have been due to
low water absorbing property of the microsphere matrix
and diffusional resistance. Over conventional supposito-
ries, extended release from suppositories containing GH
loaded microspheres (hydrophobic base) up to 5 h has been
an additional advantage. Due to mucoadhesion of the
microspheres, it may enhance the bioavailability of the
drug by increasing the residence time in the lower rectum
while in case of conventional suppository there might be
chances of first pass metabolism. The release kinetics data
(Table  6) revealed that GH release from P2M batch sup-
pository showed best fit to zero order equation (r2 =  0.986)
whereas Mayol W-45 suppository showed best fit to
Korsmeyer–Peppas equation. It was found that the value of 
k was high for PEG 1500 based suppositories indicating
fast release of GH whereas value of k was low for Mayol
W-45 based suppositories indicating slow release. The
suppository batch (P2M) was optimized on the basis of 
optimum retardation up to 5 h, high drug content and
having optimum mechanical strength. This batch showed
best fit to zero order. So it was decided as an optimized
batch and was used for further evaluation study.
It was clear from Fig.  5, the morphology test that the
suppositories containing GH loaded microspheres were
safe for rectal administration.
The blue color in the rectum indicated the retention of 
suppository in the lower rectum which may prevent pre-
systemic metabolism of GH. The retention may be due to
good mucoadhesive property of the microspheres.
Conclusion
efficiency, good mucoadhesion and equilibrium swelling
degree. The microspheres retarded the drug release to a
considerable extent. The suppositories containing GH
N. H. Salunkhe et al.
 1 3
drug release ( p\ 0.05) as compared to the conventional
suppositories. The histology of rectum has evidenced
suppositories containing GH loaded microspheres as safe
for rectal administration. Hence, the suppositories con-
taining GH loaded xanthan–alginate microspheres can be
suggested as a promising alternative to oral dosage forms
and conventional suppositories, because they sustain the
GH release, bypasses first pass metabolism, and can be
efficiently used in the management of emesis in cancer
chemotherapy and radiation therapy.
Acknowledgments   All authors (N. H. Salunkhe, N. R. Jadhav, K.
K. Mali, R. J. Dias, V. S. Ghorpade, A. V. Yadav) declare that they
have no conflict of interest. Authors are thankful to Cipla, Mumbai
(India) for providing the gift sample of granisetron hydrochloride and
the management of Satara College of Pharmacy, Satara for providing
the facilities to carry out the work.
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