FORMULATION AND EVALUATION OF AZITHROMYCIN SOLID
DISPERSION USING POLOXAMER
T. Raja Sekharan*, Appikatla Deepthi, R. Kannan, Ganapathi Thappatla and Kasirao Ragulakollu
Department of Pharmaceutics, Sankaralingam Bhuvaneswari College of Pharmacy,
Anaikuttam, Sivakasi, Tamil Nadu, India.
ABSTRACT
Solid dispersion technique is used to improve the dissolution/
bioavailability of poorly water soluble drug. When the drug is
incorporated with water soluble carriers the dissolution /bioavailability
can be increased. Azithromycin is a poorly water soluble drug. In this
study azithromycin solubility is increased with the help of poloxamer
188 and 407. The solid dispersion was prepared by solvent evaporation
method. The drug and the carrier compatibility study were determined
with the help of IR spectroscopy. The prepared formulations were
evaluated for percentage yield, drug content and dissolution studies.
With the help of dissolution datas the release kinetics was determined.
The formulations showed satisfied drug release.
KEYWORDS: Azithromycin, poloxamer-188 and 407, solid dispersion, solvent evaporation method.
INTRODUCTION
The oral route of drug administration is the most common and preferred method of delivery
due to convenience and ease of ingestion but it is problematic if the drug is poorly soluble or
poor membrane penetrability. [1] In 1961, Sekiguchi and Obi first proposed the utilization of solid dispersions to increase the dissolution and oral absorption of poorly water-soluble
drugs. They proposed the formation of a eutectic mixture of a poorly water-soluble drug with
a physiologically inert, easily soluble carrier.[2] In 1971 Chiou and Riegelman defined solid dispersion as “the dispersion of one or more active ingredients in an inert carrier matrix at
Volume 3, Issue 6, 879-889. Research Article ISSN 2277 – 7105
Article Received on 10 June 2014,
Revised on 05 July 2014, Accepted on 30 July 2014
*Correspondence for
Author
T. Raja Sekharan
Department of Pharmaceutics,
Sankaralingam Bhuvaneswari
College of Pharmacy,
Anaikuttam, Sivakasi, Tamil
solid-state prepared by the melting (fusion), solvent or melting-solvent method”.[2,3] The most frequent causes of low oral bioavailability are attributed to poor solubility and low
permeability.[2] Solid dispersion systems can increase dissolution rate and bioavailability of water insoluble drugs as when these are exposed to aqueous media, the carrier dissolves, and
the drug is released as very fine colloidal particles. This greatly reduces particle size and
increases surface area, which results in improved dissolution rates and per oral absorption.
Furthermore, no energy is required to break up the crystal lattice of a drug during the
dissolution process.[4] Experience with solid dispersions over the last 20-30 years indicates that this is a very fruitful approach to improving the solubility, dissolution rates and
consequently the bioavailability of poorly soluble drugs.[5] Azithromycin is used orally for the treatment of bronchitis, certain type of skin infections, sore throat (pharyngitis, tonsillitis)
and pneumonia. One of the major problems with this drug is its very poor solubility in
biological fluids that results into poor bioavailability after oral administration. It shows
erratic dissolution problem in gastric and intestinal fluid due to its poor water solubility for
such insoluble drugs are controlled by rate of dissolution in gastrointestinal fluids.[6] In this study, we attempted to improve the solubility of azithromycin by solid dispersion technique
where water soluble poloxamer 188 and poloxamer 407 were used as carriers. The solid
dispersions were prepared in 1:1 and 1:2 ratios by solvent evaporation method. The prepared
solid dispersions were tested for compatibility by FT-IR, percentage yield, drug content in
vitro release and kinetic studies were evaluated.
MATERIALS AND METHODS
Azithromycin, Poloxamer 188 and 407 was obtained as a gift sample from Lupin Bioresearch
center, Pune. Acetone, potassium dihydrogen orthophosphate and sodium hydroxide were
purchased from RFCL Limited, New Delhi. All the chemicals used are of analytical grade.
METHODS
Solid dispersion prepared by solvent evaporation method
According to the solvent method, azithromycin and poloxamer 188 and 407 were accurately
weighed and separately dissolved in a solvent acetone and the solutions were mixed with
constant stirring and the solvent was removed by evaporation. The solid dispersions were
Table-1.Formulation of azithromycin solid dispersion by solvent evaporation method. Ingredients
(mg)
Formulations
F-1 F-2 F-3 F-4
Azithromycin 500 500 500 500
Poloxamer-188 500 1000 - -
Poloxamer-407 - - 500 1000
Acetone (ml) q.s q.s q.s q.s
CALIBERATION OF STANDARD CURVE Preparation of standard solution of azithromycin
A solution of 100 mg azithromycin was prepared by dissolving in small amount of acetone in
a 100 ml standard flask then make up to 100 ml with pH 6.0. From this 10 ml was with drawn
into a separate 100 ml volumetric flask and volume was made up to 100 ml with phosphate
buffer pH 6.0 to produce concentration of 100 µg/ml.
Preparation of working solution
From the standard solution 2, 4, 6, 8, 10, 12, 14, 16, 18 ml was withdrawn into 100 ml
volumetric flask and the volume was made up to 100 ml with phosphate buffer pH 6.0 to
produce concentration of 2, 4, 6, 8, 10, 12, 14, 16, 18 µg/ml respectively. 10µg/ml
concentration sample was used to determine the λmax. The scanning was run from 200-400
nm. The maximum absorption was obtained at 262nm. The λmax graph was shown in Fig. 1.
So the solutions were analyzed by UV spectrophotometer at 262 nm and results were
recorded. The calibration graph was plotted at concentration on X-axis and absorbance on
Y-axis. The standard curve was shown in figure-2.
Figure-2.Standard curve of azithromycin
Evaluation of prepared azithromycin solid dispersion Percentage yield
Percentage practical yield was calculated to know about percent yield or efficiency of any
method, thus its help in selection of appropriate method of production. SDs were collected
and weighed to determine practical yield (PY) from the following equation[7].
Drug content
Drug content was determined by dissolving the solid dispersions equivalent to 100 mg of
azithromycin were weighed accurately and dissolved in the 10 ml of acetone and make up to
the volume with pH 6.0. The solution was filtered through Whatman filter paper No. 41.
Then the solution was diluted suitably and drug content was analyzed at 262 nm by UV
spectrophotometer. The actual drug content was calculated using the following equation as
IR spectroscopy
Infrared spectra were obtained (for drug, poloxamer-188 and 407 and for best formulation at
normal temperature and at 85°C for one day) with an infrared spectrophotometer (Shimadzu,
Kyoto, Japan). The potassium bromide discs were prepared by mixing a small amount of the
sample with potassium bromide and powder mixture was compressed to form the disc. The
potassium bromide discs were prepared by compressing the powders at a pressure of 10 tons
for 1 min in a hydraulic press. The scanning range used was 4000 to 400 cm-1 at a scan period of 1 minute.
Dissolution studies
Dissolution of azithromycin from each solid dispersion formulations were performed in USP
XXII type 2 dissolution apparatus (Disso-2000). Sample equivalent to 100 mg of
azithromycin was taken in a 900 ml phosphate buffer pH 6.0 at 37±0.5ºC and stirred at 50
rpm. Aliquot of 10 ml was withdrawn at time intervals of 10, 20, 30, 40, 50, 60, 70 and 80
min. The withdrawn volume was replaced with the same volume of dissolution medium in
order to keep the total volume constant. Withdrawn samples were immediately filtered
through a Whatman filter paper no. 41 and suitably diluted with phosphate buffer pH 6.0. The
absorbance of the samples was measured at 262 nm using pH 6.0 as a blank in UV double
beam spectrophotometer.
Release kinetics
Mechanism and kinetics of drug release was determined with the help of the results obtained
in the in vitro drug release study. The dissolution datas were fitted with various kinetic
equations like zero order (cumulative percent drug released vs. time), first order (log
cumulative percent drug retained vs. time), higuchi (cumulative percentage of drug released
vs. square root of time), hixson-crowell‟s (cubic root of percentage drug release vs. time) and
korsmeyer-peppas (log of cumulative percent drug released vs. log Time). The kinetic model
that gave higher the regression coefficient (r) values obtained as the best fit model.
Korsmeyer-peppas model used „n‟ value to characterize different release mechanisms. The
RESULTS AND DISCUSSION Percentage yield
The percentage yield for all the four prepared formulations (F-1 to F-4) was more than 90 %.
The percentage yield was more for the formulations containing poloxamer-407 when
compared to poloxamer-188. The results are given in the table-2
Table-2.Percentage yield of the prepared solid dispersion formulations.
Formulations Theoretical yield Practical yield Percentage yield
F-1 1 gm 910 mg 91.00%
F-2 1.5 gm 1.40 gm 93.33%
F-3 1 gm 945 mg 94.50 %
F-4 1.5 gm 1.46 gm 97.33%
Drug content
The drug content for all the formulations was found to be between 96.52 to 101.01%. The
drug content for formulations containing poloxamer-407 was more than the formulations
containing poloxamer-188. The results are tabulated in the table-3.
Table-3.Drug content of the prepared formulations.
Formulations Drug content (%)
F-1 96.52
F-2 99.89
F-3 98.31
F-4 101.01
IR spectroscopy
State of drug molecule with poloxamer-188 and 407 was determined using FT-IR. IR spectra
of azithromycin, poloxamer-188 and 407 and best formulation (F-4) are exactly same for both
at room temperature and at 85°C kept for one day. There is no shift of peaks after absorption
of drug onto carrier indicating that there is no change in chemical structure of drug after
preparing. The IR graph and its values for azithromycin, poloxamer-188 and 407 and for F-4
formulation at room temperature and at 85°C for one day were shown in Fig. 3 to 6 and
Figure-3.IR spectroscopy of azithromycin at initial state and at 85° C for one day
Figure-4.IR spectroscopy of poloxamer-188 at initial state and at 85° C for one day.
Figure-6.IR spectroscopy of F-4 formulation at initial state and at 85° C for one day.
Table-4.IR values for azithromycin at room temperature and at 85°C for one day Azithromycin
Functional group Room temperature 85°C for 1 day
3489.23 3502.00 N-H stretch, secondary amine
3236.55 3255.84 OH group
2980.02 2980.02 C-H stretch aliphatic
2829.57 2829.57 C-H stretching vibration
1720.50 1720.50 C=O stretching (Ketone)
1602.85 1597.06 C=O amide
1473.62 1465.90 C-N stretching (amines)
1379.10 1379.10 C-H deformation in alkane
1344.38 1344.38
C-O stretching
1282.66 1282.66
1188.15 1188.15 C-O-C ether stretching
1095.57 1095.57 Aliphatic C-O stretching
1049.28 1049.28 OH bending (alcohol)
796.60 796.60 Skeletal vibrations of aromatic ring (820-690)
731.02 731.02 Mono substituted aromatic ring
640.37 640.37 C-H deformation
Table-5.IR values for poloxamer-188 at room temperature and at 85°C for one day. Poloxamer-188
Functional group Room temperature 85°C for 1 day
2866.22 2866.22 CH stretching in CH3
1342.46 1350.17 In plane O-H bend
1251.20 1242.16 C-O stretching
Table-6.IR values for poloxamer-407 at room temperature and at 85°C for one day. Poloxamer-407
Functional group Room temperature 85°C for 1 day
3495.01 3414 OH stretching (Intra molecular hydrogen bonding)
2891.3 - CH stretching in CH3
1344.38 1350.17 In plane O-H bend
1282.66 1251.8 C-O stretching
1188.15 1188.15 C-O-C stretching
1109.07 1109.07 C-O stretching
640.37 570.93 OH stretching (Intra molecular hydrogen bonding)
Table-7.IR values for F-4 formulation at room temperature and at 85°C for one day. F-4 formulation
Functional group Peak due to
Room temperature 85°C for 1 day
3495.01 3414.00
NH stretching Azithromycin
OH stretching (Intra molecular
hydrogen bonding) Poloxamer
2891.30 - CH stretching in CH3 Poloxamer
1718.58 1718.55 C=O stretching (Ketone) Azithromycin
1473.62 1458.18 C-N stretching (amines) Azithromycin
1379.10 1386.82 C-H deformation in alkane Azithromycin
1344.38 1350.17 In plane O-H bend Poloxamer
1282.66 -
C-O stretching Azithromycin and
Poloxamer
1251.80 -
1188.15 1188.15 C-O-C stretching Azithromycin and
Poloxamer
1155.36 - C-O-C ether stretching Azithromycin
1109.07 1109.07 C-O stretching Poloxamer
1049.28 1051.20 OH bending Azithromycin
640.37 -
CH deformation;
OH stretching (Intra molecular hydrogen bonding)
Azithromycin and Poloxamer
In vitro drug release studies
The invitro drug release for the F-1 formulation was 94.52% at the end of 80 min. For F-2
formulation it was 98.05% at the end of 70 min. This indicates that when we increase the
carrier ratio the drug release was quick.
The invitro drug release for the F-3 formulation was 96.51% at the end of 80 min. For F-4
formulation it was 99.02% at the end of 70 min. This indicates that when we increase the
carrier ratio the drug release was quick. When compared to two grades of poloxamer-188 and
407 used, formulation containing poloxamer-407 showed little amount of quick release when
compared to formulation containing poloxamer-188. The comparative invitro drug release
Figure-7.Comparison of in vitro percentage drug release for all the four formulations (F-1 to F-4).
Release kinetics
When the invitro drug release readings were plotted to different kinetics models. For both the
grades of polymers the drug release follows higuchi reaction. The formulations showed a
regression co-efficient value (r2) for higuchi between 0.9824-0.9959. It showed that the drug release follows higuchi reaction. By using korsmeyer model, the mechanism of drug release
was determined. If n = < 0.45, it is fickian diffusion and if n= 0.45-0.89, it is non-fickian
diffusion transport. The results of F-1 to F-3 formulations showed that the n values are less
than 0.45. It proved that F-1 to F-3 formulations followed fickian transport mechanism. For
F-4 formulation the n value is 0.4968, it follows non-fickian diffusion transport. The release
rate kinetic data for all formulations were shown in table-8.
Table-8.Drug release kinetics for all the formulations. Formulatio
n Code
Correlation Co-efficient (r2) value Korsmeyers-Peppas Zero
order
First
order Higuchi
Hixson crowell
Slope (n)
Correlation
Co-efficient (r2) value
F-1 0.9961 0.8420 0.9827 0.9948 0.3588 0.9963
F-2 0.9659 0.8949 0.9959 0.9712 0.4023 0.9686
F-3 0.9958 0.8036 0.9824 0.9019 0.4223 0.9958
F-4 0.9659 0.8734 0.9953 0.9700 0.4968 0.9767
CONCLUSION
The present study showed that the solubility and dissolution rate of azithromycin can be
enhanced by the use of solid dispersion of azithromycin with poloxamer-188 and 407.
dissolution of azithromycin. The rate of the dissolution of azithromycin from solid dispersion
depended on the concentration of the carrier. Dissolution of drug increased with an increase
in carrier concentration. Thus our study concluded solid dispersion of azithromycin may be
prepared by using poloxamer-407 to improve the solubility there by enhancing the
dissolution/absorption.
ACKNOWLEDGEMENTS
The authors are very much thankful to the correspondent Mr. S. Sriram Ashok,
Sankaralingam Bhuvaneswari College of pharmacy, Sivakasi for providing facilities during
the present research work.
REFERENCES
1. Arun Prasad K, Narayanan N and Rajalakshmi G. Preparation and evaluation of solid
dispersion of terbinafine hydrochloride. International Journal of Pharmaceutical Sciences
Review and Research, 2010; 3(1): 130-134.
2. Sachin K. Gawai, Subhash V. Deshmane, Purohit RN and Kailash R. Biyani. in vivo-in
vitro evaluation of solid dispersion containing ibuprofen. American Journal of Advanced
Drug Delivery, 2013; 1(1): 66-72.
3. Vikas A Saharan, Vipin Kukkar, Mahesh Kataria, Manoj Gera and Pratim K Choudhury.
Dissolution enhancement of drugs. part i: technologies and effect of carriers. International
Journal of Health Research, June 2009; 2(2): 107-124.
4. Anupama Kalia and Mayur Poddar. Solid dispersions: an approach towards enhancing
dissolution rate. Int J Pharm Pharm Sci, 2011; 3(4), 9-19.
5. Debjit Bhowmik, Harish G, S.Duraivel, Pragathi Kumar B, Vinod Raghuvanshi and
Sampath Kumar KP. Solid dispersion – a approach to enhance the dissolution rate of
poorly water soluble drugs. The Pharma Innovation–Journal, 2012; 1(12): 24-38.
6. Arora SC, Sharma PK, Raghuveer Irchhaiya, Anurag Khatkar, Neeraj Singh and Jagbir
Gagoria. Development characterization and solubility study of solid dispersions of
azithromycin dehydrate by solvent evaporation method. Journal of advanced
pharmaceutical technology and research. 2010; 1(2): 221-228.
7. AppaRao B, Shivalingam MR, Kishore Reddy YV, Somesekhara Rao, Rajesh K and
Sunitha N, Formulation and evaluation of aceclofenac solid dispersions for dissolution
rate enhancement. International Journal of Pharmaceutical Sciences and Drug Research,
