Microencapsulation and In vitro Characterization of Acrylate Microspheres for Controlled Release of Ambroxol Hydrochloride
Hemant H Gangurde, Nayana S Baste, Mayur A Chordiya, Chandrasekhar D Upasani
Department of Pharmaceutics, SSDJ College of Pharmacy, Nasik, Maharashtra, India
Citation: Gangurde HH, Baste NS, Chordiya MA, Upasani CD (2016) Microencapsulation and In vitro Characterization of Acrylate Microspheres for Controlled Release of Ambroxol Hydrochloride. J Pharma Pharma Sci: JPPS 113. DOI:10.29011/2574-7711/100013
1. Abstract
1. Introduction
Ambroxol is an active N-desmethyl metabolite of the mucolytic bromohexine. It is indicated for acute and chronic disorders of respiratory tract, where there is copious thick secretion or mucus production. It has biological half-life of 3-4 h. It is absorbed in throughout GIT. Its bioavailability is 70-72%. Usual initial dose of Ambroxol hydrochloride is 30 mg three times a day. Therefore, to reduce frequency of dosing as well as to increase bioavailability and enable better compliance, formulating sustained release dosage form is necessary. [1-3] In literature several sustained release formulations of Ambroxol hydrochloride have been reported that are based on tablet, capsule or sol dosage forms allowing once daily administration [4-7].
In the present study, we examine the potential for the sustained delivery of Ambroxol by forming microspheres. These multiparticulate solid dosage forms have a number of advantages such as more uniform distribution of the drug in the gastrointestinal tract, more uniform drug absorption, reduced local irritation and elimination of unwanted intestinal retention of polymeric material [8]. Microencapsulation of hydrophilic drugs have one major disadvantage of low loading efficiency. One method of ensuring high entrapment efficiency of is to use W/O emulsion solvent evaporation method which having hydrophobic processing medium [9]. Eudragit RL100 and Eudragit RS100 are hydrophobic copolymers synthesized from acrylic acid and methacrylic acid esters, with RL having higher content of functional quaternary ammonium groups than RS [10]
Ambroxol
hydrochloride microspheres were prepared by solvent evaporation technique using
Eudragit RS100 as well as Eudragit RL100 as a matrix-forming polymer. Aluminium
tristearate was used as a dispersing agent [11]. The
main objectives of this study were to formulate microspheres of Ambroxol
hydrochloride and to investigate the effect of formulation parameters such as
polymer concentration and variation of dispersing agent on microsphere
properties. Simultaneously both the polymers were compared for surface
topology, microencapsulation efficiency, and drug release. The microsphere
cross-linking mechanism and topological properties have been characterized by
FTIR, DSC, XRD, and SEM.
The
materials used were Ambroxol hydrochloride (Glen mark Pharmaceutical Ltd,
Nasik, Maharashtra, India), Eudragit RS100 and Eudragit RL100 (Rohm Pharma,
USA), aluminium tristearate (Ipca Laboratories, Mumbai, Maharashtra, India),
acetone and methanol (Fine Chemicals, Mumbai, India). All other chemicals and
solvents were of analytical grade.
Ambroxol
hydrochloride and Eudragit RS100 were dissolved in an acetone-methanol mixture.
The dispersing agent was added, and the mixture was stirred at 500 rpm in a
water bath on a magnetic stirrer at 10°C.
The mixture was then poured rapidly into liquid paraffin, previously cooled to
10°C while being stirred at a speed
of 400 rpm on remi three-blade propeller stirrer. The resulting emulsion was
stirred at 35°C for 4 h at 400 rpm,
and the organic solvent, acetone-methanol, were completely removed by
evaporation. The solidified microspheres were filtered, washed 6 times with an
aliquot of 50 ml n-hexane, then washed with water and dried under vacuum at
room temperature overnight, and stored in a desiccator [11]. Formulations
of microspheres are given in (Table 1).
2.4. Percentage Yield Value of Microspheres
The percentage yield value of microspheres was determined from the ratio of amounts of solidified total microspheres to total solid material used in the inner phase, multiplied by 100.
SPAN
= d 90- d 50 (2)
d 10
The microspheres were scanned using scanning electron microscope (Leica-Stereoscan-440). For the SEM, the microspheres were mounted directly on to the SEM sample stub using double sided sticking tape, and coated with gold film thickness of 200 mm under reduced pressure of 0.001 mm of Hg. The shape and surface characteristic of the microspheres was observed under electron micro analyzer and photographs were taken using SM 4504 camera.
were determined
after calibration with standard.
3.1 Microspheres Morphology and Drug Encapsulation
The
method showed good encapsulation efficiency. Percent drug encapsulated was
found to be in a range of 82-95% for Eudragit RS100, and 76-93% for Eudragit
RL100. From (Table 2) data it was observed that
with increase in polymer concentration drug encapsulation efficiency was
increased. Eudragit RL100 showed low encapsulation efficiency as compared to
Eudragit RS100 because it is more permeable than RS100. Drug encapsulation efficiency
was slightly increased as the aluminium tristearate concentration was increased
because dispersing agent reduces the interfacial tension between the two
immiscible phases of the emulsion and reduces the extent of collision and
coalescence between the microspheres during their solidification [15].
3.2 Effect on Particle Size
Particle
size analysis done by laser diffraction revealed that Eudragit RS100
microspheres were in the range of 26.62- 43.01 mm
with SPAN factors ranging between 1.24-1.64 whereas Eudragit RL100 microspheres
were in the range of 23.08- 44.18 mm
with SPAN factors ranging between 1.32-1.59. (Table 2)
It was found that the size of microspheres was increased as the concentration
of inner phase polymer was increased while the concentration of dispersing
agent was kept constant. Because this increased concentration of polymer
solution increases viscosity of inner phase droplets and gives difficulty in
dispersion and subdivision of droplets [14].
But the variations of the concentrations of aluminum tristearate did not affect
the particle size of microspheres. SPAN factors for all the batches ranges in
between 1.24-1.64, which indicates narrow size of distribution.
3.3 In vitro Drug Release
3.4. Release Kinetics
Similarity factor
(f2) and difference factor (f1) were calculated for optimized microspheres
considering marketed capsule as the reference standard. It was found that f1 and f2 value
for RS2 were 66.21 and 4.66 whereas for RL6, 64.56 and 4.50 respectively. This
suggested that microspheres RS2 and RL6 showed similarities of dissolution
profiles with that of marketed capsule. (Figure 5)
t70%, of RS2, RL6 and
marketed capsule was 6.32h, 6.87h, and 6.34h respectively which suggested that
microspheres RS2, RL6 showed release profiles comparable with that of marketed
capsule.
3.6 Differential Scanning Calorimetry (DSC)
3.7. Fourier Infrared
Spectroscopy (FTIR)
4.
Conclusion
In conclusion, the
attempt to microencapsulate Ambroxol hydrochloride was successful. The method
showed good encapsulation efficiency with high yield value. Aluminium
tristearate and polymer concentration were clearly effective on encapsulation
efficiency, and in vitro drug release.
Particle size was affected by only polymer concentration not aluminium
tristearate. Due to low permeability Eudragit RS100 showed more encapsulation
efficiency and slow drug release as compared to Eudragit RL100.
5. Acknowledgments
The authors are grateful to Dr. D.V. Derle, Principal NDMVP’s College of Pharmacy, Nashik for his valuable guidance and Glen mark pharmaceuticals Ltd. Nasik for providing gift sample of Ambroxol hydrochloride.
Figure 1: Scanning electron
micrograph of Optimized RS2 microspheres at 1.00 KX.
Figure 2: Scanning electron
micrograph of optimized RL6 microspheres at 1.00 KX magnifications.
Figure 3: In vitro dissolution
profile of Ambroxol hydrochloride loaded Eudragit RS100 microspheres
Figure 4: In vitro dissolution
profile of Ambroxol hydrochloride loaded Eudragit RL100 microspheres
Figure 5: Comparative in vitro dissolution profile of optimized RS2 and
RL6 microspheres with marketed capsule M1
Figure 6: X-ray diffract
grams of Ambroxol hydrochloride (A), EudragitRS100 (B), Eudragit RL100 (C),
Aluminium tristearate (D), RS100 microspheres (E), RL100 microspheres. (F)
Figure 7: DSC curves of
Ambroxol hydrochloride (A), EudragitRS100 (B), Eudragit RL100 (C), Aluminium
tristearate (D), RS100 microspheres (E), RL100 microspheres. (F)
Figure 8: FTIR spectra of
Ambroxol hydrochloride (A), EudragitRS100 (B), Eudragit RL100 (C), Aluminium
tristearate (D), RS100 microspheres (E), RL100 microspheres. (F)
Batch code
|
Variable level |
||
Polymer concentration (%) ‡ |
Dispersing agent concentration (%) ‡ |
||
RL1 |
RS1 |
10 |
3 |
RL2 |
RS2 |
15 |
3 |
RL3 |
RS3 |
20 |
3 |
RL4 |
RS4 |
10 |
2 |
RL5 |
RS5 |
15 |
2 |
RL6 |
RS6 |
20 |
2 |
RL7 |
RS7 |
10 |
1 |
RL8 |
RS8 |
15 |
1 |
RL9 |
RS9 |
20 |
1 |
|
† RS: EudragitRS100 and RL: Eudragit RL100 ‡ The concentrations of dispersing agents and polymer were calculated from dispersed inner phase volume (%w/v). Each formulation contained 1 g of Ambroxol HCl.
|
Table 1: Formulations of Ambroxol Hydrochloride Microspheres
Batch code |
YV (%) |
EE (%) |
d † |
SPAN |
RS1 |
82.26 |
82.862±0.548 |
27.67±0.127 |
1.373 |
RS2 |
92.24 |
83.461±0.403 |
26.62±0.204 |
1.555 |
RS3 |
83.55 |
86.427±1.236 |
30.48±0.089 |
1.525 |
RS4 |
87.96 |
89.758±0.619 |
38.11±0.094 |
1.246 |
RS5 |
85.72 |
90.982±0.645 |
29.32±0.249 |
1.588 |
RS6 |
92.89 |
91.407±0.528 |
32.46±0.042 |
1.642 |
RS7 |
96.25 |
92.625±0.765 |
43.01±0.346 |
1.424 |
RS8 |
90.59 |
93.827±1.380 |
35.63±0.076 |
1.566 |
RS9 |
85.03 |
95.424±0.636 |
38.33±0.418 |
1.282 |
RL1 |
86.66 |
76.16±0.509 |
28.79±0.035 |
1.518 |
RL2 |
85.00 |
78.72±0.858 |
23.08±0.287 |
1.350 |
RL3 |
84.52 |
81.75±0.502 |
32.50±0.548 |
1.498 |
RL4 |
86.91 |
82.31±0.657 |
39.20±0.426 |
1.431 |
RL5 |
98.96 |
86.70±0.799 |
29.48±0.054 |
1.324 |
RL6 |
97.4 |
88.26±0.758 |
31.84±0.016 |
1.598 |
RL7 |
89.35 |
91.42±.009 |
40.34±0.388 |
1.337 |
RL8 |
74.43 |
92.56±0.825 |
32.96±0.064 |
1.495 |
RL9 |
85.60 |
93.60±0.848 |
44.18±0.092 |
1.447 |
* YV indicates yield value; EE, encapsulation efficiency (n=3) † Values shown represent the equivalent volume diameter (µm). (n=3)
|
Table 2: Physical Properties of Microspheres.
Kinetic models |
|||||
Batch code |
Zero order |
Higuchi model |
Peppas model |
||
R2 |
K0 (%mg/h) |
R2 |
Kh (%mg/h1/2) |
n |
|
RS1 |
0.986 |
5.838 |
0.9974 |
31.793 |
0.3847 |
RS2 |
0.9882 |
5.961 |
0.9919 |
28.942 |
0.5278 |
RS3 |
0.9974 |
5.931 |
0.9828 |
27.325 |
0.5991 |
RS4 |
0.9823 |
5.142 |
0.9281 |
23.324 |
0.6431 |
RS5 |
0.9962 |
4.470 |
0.9561 |
20.882 |
0.5828 |
RS6 |
0.9971 |
3.936 |
0.9629 |
17.981 |
0.6084 |
RS7 |
0.9976 |
3.991 |
0.9722 |
16.985 |
0.7297 |
RS8 |
0.9987 |
3.246 |
0.967 |
13.452 |
0.7654 |
RS9 |
0.9899 |
3.070 |
0.9387 |
11.298 |
0.803 |
RL1 |
0.9749 |
10.135 |
0.9362 |
48.755 |
0.3812 |
RL2 |
0.9836 |
9.192 |
0.9677 |
43.688 |
0.4068 |
RL3 |
0.9909 |
7.868 |
0.9868 |
36.840 |
0.4433 |
RL4 |
0.9981 |
6.830 |
0.985 |
33.290 |
0.4586 |
RL5 |
0.9993 |
6.701 |
0.9774 |
31.569 |
0.5051 |
RL6 |
0.9901 |
5.732 |
0.9873 |
29.003 |
0.4743 |
RL7 |
0.9933 |
5.575 |
0.981 |
26.881 |
0.5675 |
RL8 |
0.9961 |
5.170 |
0.9747 |
23.503 |
0.6176 |
RL9 |
0.9962 |
4.674 |
0.9578 |
20.799 |
0.6384 |
Table 3: In vitro Release Kinetic Parameters of Ambroxol Hydrochloride Loaded Eudragit Microspheres