8.1. preparation of solid snedds...
TRANSCRIPT
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 168
8.1. Preparation of Solid SNEDDS (S-SNEDDS)
The acceptability of prepared liquid SNEDDS was enhanced by solidification
of the liquid SNEDDS into S-SNEDDS by adsorption method. An advantage of the
adsorption technique is uniformity of content and high drug loading is possible
compared to other techniques67. The S-SNEDDS offers better stability on long storage
and advantages of a solid dosage form (e.g. low production cost, convenience of
process control, high stability, reproducibility and better patient compliance).
The ideal solid matrix excipients for preparation of S-SNEDDS should have
high adsorption capacity, which could hold a larger liquid SNEDDS163 and facilitate
the preparation of tablets28. Thus the adsorbents used in the study, to load SNEDDS,
are Aerosil 200, Porous polystyrene beads (PPB) and Accurel MP 1000, which have
high surface area, can hold high amount of liquid on it. Adsorption efficiency of any
carrier is dependent on its porosity, surface area and hydrogen bonding capacity160.
All powders were dry and free flowing. The lipid formulation would be
retained either partially or completely within intraparticular pores of the adsorbent.
Further, addition of SNEDDS, resulted in a sudden formation of paste or single
agglomerate, which may corresponds to a pendular state in stepwise growing
behavior103.
The Porous carriers are characterized by stable uniform porous structures, high
surface areas, tunable pore sizes with narrow distributions, and well-defined surface
properties, thus allowing them to adsorb and release the drugs in a more reproducible
and predicable manner164.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 169
Aerosil 200 has the mean particle size of 12nm and specific surface area
(BET) of 380 ± 30 m2/g. Because of its high specific surface area and oil adsorbing
capacity, loading efficiency of SNEDDS was higher than PPB and Accurel (Table
8.1). The PPB are inert, stable over a wide pH range and to extreme conditions of
temperature and humidity. PPB essentially consists of hydrocarbon backbone with
benzene rings and are devoid of any functional groups and has particle size of 0.3-
1µm. The loading efficiency of SNEDDS was relatively less in PPB than aerosil 200.
The porous structures in the Accurel act like tiny sponges which absorb the
liquid through capillary forces and keep them inside. It has particle size of 0.2 µm
which provide large surface area for adsorption. The loading efficiency was higher
than PPB, but lesser than aerosil 200. By considering the high loading capacity and
better flow property, The SNEDDS loaded with adsorbent were selected for
preparation of tablets103.
Table 8.1: Flow rate and Loading efficiency of SNEDDS loaded in different
adsorbents
SNEDDS Adsorbent Angle of repose*
°
Loading efficiency*
%
Efavirenz
Aerosil 18.7±0.15 138.15±2.89
PPB 23.2±0.25 112.64±1.76
Accurel 22.6±0.17 120.86±2.1
Atorvastatin Calcium
Aerosil 19±0.37 132.74±2.28
PPB 23.7±0.29 118.31±2.79
Accurel 22±0.19 126.59±1.21
Rosuvastatin Calcium
Aerosil 19.1±0.12 135.43±1.56
PPB 23.5±0.26 121.62±2.37
Accurel 22.3±0.18 124.47±1.82
* Mean±Standard deviation, n=3
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 170
Scanning electron microscopy (SEM)
The scanning electron micrographs of Accurel, Porous polystyrene beads,
Aerosil and SNEDDS loaded with the adsorbents are shown in Figure 8.1- 8.3.
The surface topography of accurel clearly shows highly porous structure with
pores of almost similar size arranged as a network. The morphology of SNEDDS
loaded with accurel (Figure 8.1) showed relatively rough surface, suggesting that drug
might be attached and dispersed onto the surface of the solid carrier at either
molecular level or as precipitates165. The Accurel microporous structures on surface
and in the matrix will form channels for water to infiltrate, which could eases the
microemulsion formation and dispersion.
Figure 8.1: Scanning electron micrographs of Accurel (A, B) and Accurel loaded
SNEDDS (C, D)
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 171
Figure 8.2: Scanning electron micrographs of Porous polystyrene beads (A, B)
and Porous polystyrene beads loaded SNEDDS (C, D)
The Scanning electron micrographs of the SNEDDS loaded with PPB showed
the separate, uniform and spherical particles with small pits on surfaces (Figure 8.2).
Upon SNEDDS loading, these pits filled up, accommodating SNEDDS within the
micropores.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 172
Figure 8.3: Scanning electron micrographs of Aerosil 200 (A) and Aerosil 200
loaded SNEDDS (B, C and D)
The SEM photographs of Aerosil 200 and S-SNEDDS are shown in Figure
8.3. Aerosil 200 (Figure 8.3, A) appeared as fine particles with rough-surface.
However, The SNEDDS loaded with aerosil (Figure 8.3 B, C and D) appeared as
rough surfaces granular particles, indicating that the liquid SNEDDS was absorbed or
coated on aerosil. No distinct crystals were seen on the surface of the particles.126
Such molecular dispersion of the drug on the solid carrier may account for the
enhanced drug release158.
Differential Scanning Calorimetry
The DSC thermogram showed pronounced endothermic peak at 137.5°C for
efavirenz, that corresponding to its melting point. Accurel loaded SNEDDS showed
the peak at 162.2°C, that corresponding to the melting point of Accurel. The peak at
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 173
82.05°C in PPB loaded SNEDDS, which corresponds to the melting point of PPB.
The DSC thermogram of aerosil loaded SNEDDS did not show the peak at the entire
temperature range. The absence of drug peak in SNEDDS loaded adsorbents was due
to presence of drug in molecularly dissolved state in the lipid excipients. The DSC
thermograms of efavirenz and efavirenz SNEDDS loaded in adsorbents are shown in
the Figure 8.4.
Figure 8.4: Differential scanning calorimetric thermogram: (A) Efavirenz (B)
Accurel loaded Efavirenz SNEDDS (C) PPB loaded Efavirenz SNEDDS (D)
Aerosil loaded Efavirenz SNEDDS.
The DSC thermogram showed pronounced endothermic peak at 149.9°C for
atorvastatin calcium, that corresponding to its melting point. The SNEDDS loaded in
Accurel, PPB and Aerosil, did not show peak at the entire temperature range. The
absence of drug peak in SNEDDS loaded adsorbents was due to presence of drug in
molecularly dissolved state in the lipid excipients. The DSC thermograms of
atorvastatin calcium and atorvastatin calcium SNEDDS loaded with adsorbents are
shown in the Figure 8.5.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 174
Figure 8.5: Differential scanning calorimetric thermogram: (A) Atorvastatin
calcium (B) Accurel loaded Atorvastatin calcium SNEDDS (C) PPB loaded
Atorvastatin calcium SNEDDS (D) Aerosil loaded Atorvastatin calcium
SNEDDS.
The DSC thermogram showed pronounced endothermic peak at 128.6°C for
rosuvastatin calcium, that corresponding to its melting point. The SNEDDS loaded in
Accurel, PPB and Aerosil, did not show peak at the entire temperature range. The
absence of drug peak in SNEDDS loaded adsorbents was due to presence of drug in
molecularly dissolved state in the lipid excipients. The DSC thermograms of
rosuvastatin calcium and rosuvastatin calcium SNEDDS loaded with adsorbents are
shown in the Figure 8.6.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 175
Figure 8.6: Differential scanning calorimetric thermogram: (A) Rosuvastatin
calcium (B) Accurel loaded Rosuvastatin calcium SNEDDS (C) PPB loaded
Rosuvastatin calcium SNEDDS (D) Aerosil loaded Rosuvastatin calcium
SNEDDS.
X-ray diffraction studies (XRD)
Efavirenz
X-ray diffractogram showed multiple peaks for efavirenz, indicating
crystalline nature of drug (Figure 8.7 (A)). However, X-ray diffractogram of
SNEDDS (B) showed diffused spectra without any characteristic peaks of efavirenz.
The crystalline peaks of efavirenz were absent in S-SNEDDS indicating that the drug
was not in crystalline form. The results correlate with the DSC studies.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 176
Figure 8.7: X-ray diffraction patterns of Efavirenz (A) and S-SNEDDS (B)
Atorvastatin calcium
X-ray diffractogram showed multiple peaks for Atorvastatin calcium,
indicating crystalline nature of drug (Figure 8.8 (A)). However, X-ray diffractogram
of SNEDDS (B) showed diffused spectra without any characteristic peaks of
Atorvastatin calcium. The crystalline peaks of Atorvastatin calcium were absent in
S-SNEDDS indicating that the drug was not in crystalline form. The results correlate
with the DSC studies.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 177
Figure 8.8: X-ray diffraction patterns of Atorvastatin calcium (A) and
S-SNEDDS (B)
Rosuvastatin calcium
X-ray diffractogram showed multiple peaks for rosuvastatin calcium,
indicating crystalline nature of drug (Figure 8.9 (A)). However, X-ray diffractogram
of SNEDDS (B) showed diffused spectra without any characteristic peaks of
rosuvastatin calcium.
The crystalline peaks of rosuvastatin calcium were absent in S-SNEDDS
indicating that the drug was not in crystalline form. The results correlate with the
DSC studies.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 178
Figure 8.9: X-ray diffraction patterns of Rosuvastatin calcium (A) and
S-SNEDDS (B)
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 179
8.2. EFAVIRENZ
8.2.1. Preparation of Efavirenz loaded SNEDDS tablet
The tablets were prepared by direct compression technique, direct
compression (DC) is most effective, fastest and simplest method in the manufacturing
of tablet. The method also secures the drug from moisture and heat. Furthermore, the
tablet characteristics such as stability, dissolution, and bioavailability of the active
drugs were reported to be improved using the DC method166. In the process of
compaction, the material is metamorphose from loose powder form into a solid
compact. The composition of granules/powders and the parameters of the
compression process determine the strength of tablets167.
Micro crystalline cellulose (MCC), poly vinyl pyrollidone (PVP) and sodium
starch glycolate (SSG) were used as directly compressible diluent, binder and super
disintegrating agent.
The microcrystalline cellulose PH 101 (MCC) is an excellent filler/flow-aid
for direct compression with an average particle size of 50µm that attributes to the
excellent batch flowability and compressibility properties168. Due to its high surface
area and enormous internal porosity it is capable to absorb and retain a large quantity
of liquid and also absorbs the any squeezing of lipid occurs while punching of
tablets169.
PVP K 30 is used as binder because of its directly compressible property.
Sodium starch glycolate (SSG) is added in the formulations as it belongs to category
of directly compressible super disintegrants which swell upto 5-10 times in less than
30s. The inclusion of disintegrants improved the general redispersion of all the
formulations28.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 180
Analysing the effect of multiple excipients in various ratio by trial and error
or changing one separate factor at a time (COST) ways are usually ineffective, as the
output obtained through these trials do not accredit the recognition of interaction
effects with the formulation ingredients170.
Design of experiments (DOE) is a scientific approach applied to understand
the processes in a larger way and to resolve how the inputs influence the
response(s)171, 172. In the current research work, 23 factorial design was applied to
study the effect of variable on the selected responses.
Every excipient is included to suit the needs of product use and processibility.
The major types of adjuvants used are diluents, binders, disintegranting agents and
lubricants which are nearly present in all tablet preparations173, 174.
By conducting a group of preliminary trials by varying the relative ratio of the
selected three components i.e. MCC, PVP, SSG and on the previous related
experiences, the upper and the lower limits of each variable were defined (Table 8.2).
If all of the possible combination for the excipients in the initial formulation system is
to be evaluated, a full factorial DOE could requires 8 studies, as shown in Table 8.3
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 181
Table 8.2: Variables in 23 factorial designs
Independent variable Levels
Low(mg) High(mg)
A: MCC 200.00 300.00
B: PVP 12.00 20.00
C: SSG 8.00 16.00
Dependent variable
Y1 Hardness (kg)
Y2 Disintegration Time (sec)
Y3 % Cumulative drug release (%)
Table 8.3: Matrix of 23 factorial designs for Efavirenz loaded SNEDDS tablet
Run
Factor 1 Factor 2 Factor 3
A:MCC
mg
B:PVP
mg
C:SSG
mg
1 300 12 8
2 300 20 16
3 200 12 8
4 200 12 16
5 200 20 16
6 300 20 8
7 200 20 8
8 300 12 16
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 182
Table 8.3 reports the corresponding 8 runs of experimental design in which the
mixture component compositions are indicated. The test mixtures were prepared
according to this experimental design and analysed for their physical characteristics.
It was observed that adding lactose into MCC, improved the compactibility.
Efavirenz SNEDDS tablets, showed faster release of drug due to water soluble lactose
used as solid matrixing agent.
8.2.2. Micromeritic properties of powder blend
The results of bulk density, tapped density, angle of repose, Carrs index and
Hausners ratio are given in the Table 8.4. The angle of repose, Carrs index and
Hauseners ratio confirms the good flow property.
Table 8.4: Micromeritic properties
Run Bulk
Density
(g/cc) *
Tapped
Density
(g/cc) *
Angle of
repose*
°
Carrs index
%*
Hausners
ratio*
1 0.310±0.001 0.422±0.002 29.06±0.531 26.54±0.494 1.361±0.004
2 0.327±0.001 0.437±0.003 27.11±0.478 25.17±0.592 1.336±0.002
3 0.324±0.002 0.435±0.003 28.45±0.287 25.51±0.448 1.342±0.002
4 0.319±0.002 0.429±0.001 28.72±0.421 25.64±0.293 1.344±0.005
5 0.321±0.003 0.432±0.002 28.94±0.610 25.69±0.503 1.345±0.005
6 0.322±0.001 0.434±0.002 29.13±0.477 25.8±0.391 1.347±0.003
7 0.317±0.002 0.430±0.001 28.93±0.639 26.27±0.491 1.356±0.001
8 0.311±0.001 0.428±0.002 29.21±0.224 27.33±0.5 1.377±0.002
* Mean±Standard deviation, n=3
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 183
8.2.3. Experimental design.
Table 8.5: Observed Response in 23 Factorial Design for Efavirenz loaded
SNEDDS tablet
Std
Run
Factor
1
Factor
2
Factor
3
Response
1
Response
2
Response
3
A:MCC
mg
B:PVP
mg
C:SSG
mg
Hardness
kg
Disintegration
Time (Sec)
%
Cumulative
drug release
2 1 300 12 8 5.9 125 76.4
8 2 300 20 16 4.6 98 87.3
1 3 200 12 8 5.2 112 82.6
5 4 200 12 16 3.4 72 99.2
7 5 200 20 16 4.3 92 90.6
4 6 300 20 8 7.1 152 68.5
3 7 200 20 8 6.3 138 71.2
6 8 300 12 16 4 85 95.4
The result depicts (Table 8.5) that variables chosen have strong influence on
the selected responses, as hardness, disintegration time and percentage cumulative
drug release values were in the range of 3.4-7.1 kg, 72-152s and 68.5-99.2%
respectively.
The application of factorial design yielded the following regression equations.
Hardness = +4.775+6.0E-003 * MCC+0.118 * PVP-0.256* SSG
Disintegration Time= +105.0+0.115* MCC+2.68 * PVP-5.62 * SSG
% Cumulative drug release = +84.22-0.04 * MCC-1.12 * PVP+2.30 * SSG
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 184
Where negative values indicate a negative effect of a specific variable on the
response factors and positive values indicate a positive effect of a specific variable on
the response factors. The polynomial regression results were expressed using 3-D graphs
and contour plots (Figure 8.10-8.11)
Hardness
Low concentration of PVP has positive effect on the hardness of the tablet the
hardness was between 3.4-5.9kg (Table 8.5). With increase in concentration of PVP,
the hardness was increased upto 7.1 kg. MCC and SSG have slight effect on the
hardness.The increase in hardness of tablet with increase in concentration of MCC in
some formulations is attributed to large free hydroxyl groups and hence the interaction
forces (hydrogen bonding) in a contact point might be stronger175.
Disintegration Time (DT)
SSG has negative effect on the disintegration time, with increase in the
concentration of SSG in tablets, the disintegration time was decreased. At the low
concentration, the disintegration time was between 112-152 sec, as the concentration
of SSG increased,the disintegration time decreased to 72-98 sec. The decrease in DT
with increase in the concentration of SSG was due to its rapid swelling property.
In certain runs (1 and 6), MCC increased the DT as it may indirectly increase
the hardness of the tablet. MCC accelerates water penetration into tablets, due to
wicking action, that can cause enormous swelling of SSG, and this revealed the
superdisintegrant property of SSG136.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 185
Percentage Cumulative drug release
The extent of drug release, however, is dependent on the reversible attraction
and surface adsorption of efavirenz and the oily formulation onto the adsorbents.
Therefore, physical properties of the ingredients used to prepare the solid compacts
have a profound effect on the emulsion release rate. This relationship between the
formulation ingredients (independent variables) and emulsion release rates (dependent
variables) was elucidated using 3D graphs (Figure 8.10).
Figure 8.10: Three-dimensional response surface plot depicting the impact of
MCC:PVP, MCC:SSG and SSG:PVP on hardness, disintegration time and %
drug release respectively
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 186
Figure 8.11: Counter Plot Showing impact of MCC:PVP, MCC:SSG and
SSG:PVP on hardness, disintegration time and % drug release respectively
There is no significant contribution by eliminated terms from the equation on
the prediction of Cumulative percentage drug release. Results of regression analysis
showed coefficients of MCC and PVP bearing a negative sign, i.e., with increase in
the concentration of these factors show negative effect on percentage cumulative drug
release. This is due to, with increase in the concentration of MCC and PVP, the
hardness of tablet increase which leads to delay in tablet disintegration and thus
hindered the drug release. Whereas SSG showed positive effect, with increase in the
concentration of SSG, the DT significantly decrease which attributes the faster release
of drug.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 187
The Response surface plots and contour plots exhibits, as the concentration of
PVP increases, the hardness of the tablets increases due to the increased bonding
between the particles.
8.2.4. Evaluation of tablets
Slight deviation associated with the tablet weight could be due to variation in
the bulk density of the formulations. Tablet thickness was in the range of 3.00-3.2mm
and was constant for all the formulations. Percentage weight variation and thickness
suggested that there is low probability of any variability corrolated with the tablet
machine or the method of preparation of tablets.
Friability of all the prepared tablets shows in the range of 0.61-0.92%, which
is well within the limit i.e >1% that confirms the good mechanical resistance. Drug
content was 98-102% which complied to the pharmacopeial limits (Table 8.6).
Table 8.6: Evaluation of Efavirenz tablets
Run Thickness
(mm) *
Friability*
%
% Weight
variation*
Drug
content
(%)*
1 3.2±0.070 0.81±0.021 0.149±0.004 99.12±1.41
2 3.1±0.141 0.73±0.035 0.049±0.006 98.43±2.82
3 3.2±0.141 0.89±0.028 0.249±0.003 101.07±0.70
4 3.1±0.070 0.92±0.141 0.049±0.004 98.62±1.21
5 3.0±0.212 0.74±0.036 0.149±0.002 102.17±1.62
6 3.2±0.070 0.61±0.042 0.049±0.005 100.28±0.86
7 3.1±0.070 0.68±0.031 0.149±0.006 102.15±1.21
8 3.2±0.212 0.78±0.025 0.049±0.003 99.37±0.92
* Mean±Standard deviation, n=3
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 188
From the experimental results (Table 8.5), the effects of all studied variables
and the variable interactions were graphically and statistically interpreted for all
responses. The results of ANOVA indicated that all models were significant (p <
0.05) for all response parameters investigated. Model simplification was carried out
by eliminating non-significant terms (p > 0.05) in polynomial equations. Values of
"Prob > F" less than 0.0500 in all the cases indicates model terms are significant. The
Pred R-Squared is in reasonable agreement with the Adj R-Squared. The signal to
noise ratio is measured by Adeq Precision and ratio greater than 4 is desirable. The
value shows much higher than 4 confirms an adequate signal (Table 8.7).
Table 8.7: Summary of results of regression analysis for responses
Value F-value p-value
Hardness
R-Square 0.9865
97.16
0.0003 Adj R-Squared 0.9763
Pred R-Squared 0.9458
Adeq Precision 26.291
Disintegration Time
R-Square 0.9867
99.08
0.0003 Adj R-Squared 0.9768
Pred R-Squared 0.9469
Adeq Precision 26.275
% Cumulative Drug Release
R-Square 0.9950
266.61
< 0.0001 Adj R-Squared 0.9913
Pred R-Squared 0.9801
Adeq Precision 42.528
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 189
8.2.5. Optimisation
To obtain the optimized tablet, the required limits of the response values were
clearly defined (hardness of 4, disintegration time of less than 80 sec and percentage
cumulative drug release of more than 95%) (Table 8.8). The combinations of
variables which resulted in tablets meeting the required specifications were calculated
using the design expert software. The overlapping of the obtained result over the
predicted values confirms the practicability and validation of the model.
Table 8.8: Optimisation of final efavirenz tablet
Value MCC
(mg)
PVP
(mg)
SSG
(mg)
Hardness
(kg)
Disintegration
Time(sec)
% Cumulative
drug release (%)
Predicted 278.75 12 15.88 4 79.9 96.1
Actual 278.75 12 15.88 4 78 97
Relative
error (%) 0 2.37 0.9
8.2.6. Reconstitution properties of optimized S-SNEDDS tablets
The globule size and polydispersity index of the solid and liquid SNEDDS are
presented in Table 8.9. The globule size of both systems was less than 150 nm. The
droplet size of the nanoemulsion formed from the S-SNEDDS was slightly increased,
but the difference is not statistically significant compared to the liquid SNEDDS. The
SNEDDS loaded tablet emulsifies fast and robust to dilution.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 190
Table 8.9: Globule size with polydispersity index of the reconstituted
nanoemulsions
Formulation Globule size (nm) Polydispersity index (PDI)
Liquid SNEDDS 142.8 0.581
Solid SNEDDS 145 0.725
Figure 8.12: Globule size distribution
8.2.7. Comparative in vitro drug release studies and Release kinetics
The comparative dissolution profiles of optimized Efavirenz SNEDDS loaded
tablet formulation and marketed preparation (Sustiva) was carried out in 0.1M HCl.
The dissolution profile shows that the optimized Efavirenz SNEDDS loaded tablet
exhibited faster drug release (97.6% at 40 min) whereas market preparation showed
22.27% at 40 min (Figure 8.13). Thus the optimized Efavirenz SNEDDS loaded tablet
showed a 4-5 fold increase in dissolution rate. Diffusion, swelling and erosion are the
most important drug release mechanisms. The drug release from the Efavirenz
SNEDDS loaded tablet tends to follow nearly zero-order kinetics (R2=0.9821)
followed by non-Fickian kinetics (n value 0.74), owing to interplay of diffusion and
convection mechanisms.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 191
Figure 8.13: In-vitro drug release profiles of Efavirenz SNEDDS tablets and
market formulation
8.2.8. Pharmacokinetics studies
The chromatograms of rat plasma spiked with Efavirenz and after oral
administration of S-SNEDDS are shown in Figure 8.14-8.15.
Figure 8.14: Typical chromatogram of rat plasma spiked with Efavirenz
0
20
40
60
80
100
120
0 10 20 30 40 50
SNEDDS Tablet
Marketed formulation
% C
umul
ativ
edr
ug r
elea
se
Time (min)
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 192
Figure 8.15: Representative chromatogram of plasma sample after oral
administration of efavirenz SNEDDS tablets to rats
Pharmacokinetic parameters
The pharmacokinetic parameters of efavirenz absorption are summarized in
Table 8.10. The Figure 8.16 depicts the mean plasma concentration profile as a
function of time obtained by the pharmacokinetic studies carried out in rats for
SNEDDS tablets and pure drug. The plasma level profiles were significantly
increased for SNEDDS tablets compared to pure drug.
Table 8.10: Pharmacokinetic parameters
Product Cmax
(mcg/ml) *
Tmax
(h) *
Kel
(h-1) *
T1/2
(h) *
(AUC)0t
(mcg/ml×h)*
Efavirenz 10.46±2.27 3.7±0.62 0.1776±0.02 3.9±0.28 95.39±6.23
Efavirenz SNEDDS tablets
42.6±3.79 1.1±0.37 0.2038±0.05 3.4±0.16 388.49±12.7
* Mean±Standard deviation, n=3
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 193
The results showed that Cmax of SNEDDS tablets was 4.1 times higher than
that of pure drug. Additionally, Tmax of the SNEDDS tablets was all shorter than
that of the pure drug, suggesting that self emulsifying technique could improve drug
release and absorption in GIT. It indicated that the absorption of efavirenz was
evidently improved after it was dispersed in solid SNEDDS formulations. There were
no significant differences between the half-life and elimination rate constant of
efavirenz and SNEDDS tablets.
Many factors could be involved in the improvement of efavirenz
bioavailability. Due to relatively high lipophilicity, efavirenz could have a good
permeability through epithelia cells of gastrointestinal (GI) tract. However, the poor
aqueous solubility efavirenz limited its dissolution and resulted in a low
bioavailability. After oral administration of SNEDDS tablets, the emulsion readily
dispersed, and no dissolution of efavirenz was required since the drug was dissolved
in the oil phase of the emulsion. In addition, Labrafac PG, a medium chain
triglyceride, could induce the activation of the “ideal brake mechanism” which slowed
down GI transit time; moreover, it was reported that medium chain triglyceride like
Labrafac PG had an enhanced effect on the intestinal cells to allow the lipid particles
through the cell layer 27.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 194
Figure 8.16: Plasma drug level profiles of optimized SNEDDS tablets and pure
drug.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 195
8.3. Atorvastatin calcium (AC)
8.3.1. Preparation of Atorvastatin calcium loaded SNEDDS tablet
In the present study, the design of experiment (23 factorial design) was
employed to systematically evaluate the effect of varying the amount of MCC, PVP
and SSG on the hardness, disintegration time, percentage cumulative drug release.
Every excipient is included to suit the needs of product use and processibility. The
major types of adjuvants used are diluents, binders, disintegranting agents and
lubricants which are nearly present in all tablet preparations176 .
The microcrystalline cellulose PH 101 (MCC) which is an excellent
filler/flow-aid for direct compression. PVP K 30 is used because of its directly
compressible property that acts as binder. Sodium starch glycolate (SSG) are added in
the formulations as it belongs to directly compressible super disintegrants which swell
upto 5-10 times in less than 30s.
By conducting a group of preliminary trials by varying the relative ratio of the
selected three components i.e. MCC, PVP, SSG and on the previous related
experiences, the upper and the lower limits for each variable were defined
(Table 8.11).
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 196
Table 8.11: Variables in 23 factorial design
Independent variable Levels
Low(mg) High(mg)
A: MCC 250 350
B: PVP 8.75 15.75
C: SSG 5 14
Dependent variable
Y1 Hardness (kg)
Y2 Disintegration Time (sec)
Y3 % Cumulative drug release (%)
Table 8.12: Matrix of 23 Factorial Design for AC loaded SNEDDS tablet
Std
Run
Factor 1 Factor 2 Factor 3
A:MCC
mg
B:PVP
mg
C:SSG
mg
1 1 250 8.75 5
4 2 350 15.75 5
6 3 350 8.75 14
2 4 350 8.75 5
8 5 350 15.75 14
7 6 250 15.75 14
5 7 250 8.75 14
3 8 250 15.75 5
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 197
Table 8.12 reports the corresponding 8 runs of experimental design in which
the mixture component compositions are indicated. The test mixtures were prepared
according to this experimental design and analysed for their physical characteristics.
It was observed that adding lactose into MCC, improved the compactibility.
AC SNEDDS tablets, showed faster release of drug due to water soluble lactose used
as solid matrixing agent.
8.3.2. Micromeritic properties of powder blend
The results of bulk density, tapped density, angle of repose, carrs index and
Hausners ratio are given in the Table 8.13. The angle of repose, Carrs index and
Hausners ratio indicates that powder blends have good flow property.
Table 8.13: Micromeritic properties
Run Bulk
Density
(g/cc) *
Tapped
Density
(g/cc) *
Angle of
repose*
°
Carrs
index
%*
Hausners
ratio*
1 0.335±0.002 0.463±0.003 24.32±0.01 27.6±0.21 1.382±0.003
2 0.380±0.003 0.512±0.003 23.14±0.03 25.78±0.09 1.347±0.005
3 0.374±0.006 0.505±0.005 23.26±0.02 25.94±0.18 1.350±0.002
4 0.379±0.008 0.510±0.006 23.02±0.01 25.68±0.16 1.345±0.004
5 0.382±0.004 0.516±0.005 23.78±0.03 25.97±0.2 1.350±0.006
6 0.343±0.006 0.473±0.003 24.13±0.02 27.48±0.08 1.379±0.004
7 0.339±0.004 0.471±0.004 24.95±0.03 28.02±0.19 1.389±0.004
8 0.347±0.002 0.477±0.003 24.19±0.01 27.25±0.15 1.374±0.005
* Mean±Standard deviation, n=3
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 198
8.3.3. Experimental design.
The summary of result data obtained of various responses is presented in Table
8.14.
Table 8.14: Observed Response in 23 Factorial Design for AC loaded
SNEDDS tablet
Std
Run
Factor
1
Factor
2
Factor
3
Response
1
Response
2
Response
3
A:MCC
mg
B:PVP
mg
C:SSG
mg
Hardness
Kg
Disintegration
time Sec
% cumulative
drug release
1 1 250.00 8.75 5.00 3.8 99 97.5
4 2 350.00 15.75 5.00 7.1 184 76.4
6 3 350.00 8.75 14.00 5.2 117 96.8
2 4 350.00 8.75 5.00 4.9 121 92.1
8 5 350.00 15.75 14.00 6.8 176 79.8
7 6 250.00 15.75 14.00 6.4 144 87.9
5 7 250.00 8.75 14.00 4.1 91 99.1
3 8 250.00 15.75 5.00 5.9 154 83.4
The results depicits (Table 8.14) that variables chosen have strong influence
on the selected responses, as hardness, disintegration time and percentage cumulative
drug release values were in the range of 3.8-7.1 kg, 91-184s and 76.4-99.1%
respectively.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 199
The application of factorial design yielded the following regression equations.
Hardness =-1.12361+9.50000E-003 * MCC+0.29286 * PVP+0.022222* SSG
Disintegration time =-39.45833+0.27500 * MCC+8.21429 * PVP-0.83333 * SSG
% Cumulative drug release =+127.85278-0.057000 * MCC-2.07143* PVP+
0.39444 * SSG
Where negative values indicate a negative effect of a specific variable on the
response factor and positive value indicates positive effect of a specific variable. The
polynomial regression results were expressed using 3-D graphs and contour plots (Figure
8.17-8.18)
The ANOVA studies indicated that all models were significant (p < 0.05) for
all response parameters scrutinized. Model simplification was done by removing non-
significant terms (p > 0.05) in polynomial equations.
Hardness
The regression equation depcits that PVP has a strong effect on the hardness
of the tablet. As the concentration of PVP increased there is significant increase in the
hardness of tablet. MCC and SSG has slight effect on the hardness. The increase in
hardness with increase in concentration of MCC in few formulations observed,
attributed to large free hydroxyl groups which makes the interaction forces (hydrogen
bond) in a contact point might be stronger.
Disintegration time
SSG has negative effect on the disintegration time of the tablets. With increase
in the concentration of SSG, disintegration time decreases, due to its rapid swelling
property. At the low concentration, the disintegration time was between 97-184 sec,
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 200
as the concentration of SSG increased,the disintegration time decreased to 91-176 sec.
The decrease in DT with increase in the concentration of SSG was due to its rapid
swelling property.
In certain runs (2 and 5), MCC increased the DT as it may indirectly increase
the hardness of the tablet. MCC accelerates water penetration into tablets, due to
wicking action, that can cause enormous swelling of SSG, and this revealed
superdisintegrant property of SSG136.
Percentage cumulative drug release
The Response surface plots and contour plots exhibits, as the concentration of
SSG increased, the percentage cumulative drug release increased from 76.4-99.1%.
The SSG makes the tablet to disintegrate and exposes them to large dissolution
medium leading to greater release. There is no significant contribution by eliminated
terms from the equation on the prediction of Cumulative percentage drug release.
Microcrystalline cellulose being insoluble has negative influence on the
dissolution when used at very high concentration. However this did not warrant
attention, as the drug release was in some cases it acts as disintegrant which ensured
faster and complete dissolution rate176, 177.
MCC and PVP have negative effect on the cumulative drug release. This may
be due to contribution of these factors in increase in the hardness178. The Response
surface plots and contour plots exhibits, as the concentration of SSG increases,.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 201
Figure 8.17: Three-dimensional response surface plot depicting the impact of MCC:PVP, MCC:SSG and MCC:SSG on hardness, disitegration time and %
drug release respectively.
Figure 8.18: Counter Plot Showing impact of MCC:PVP, MCC:SSG and
SSG:PVP on hardness, disintegration time and % drug release respectively
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 202
8.3.4. Evaluation of tablets
Tablet weight showed very low variability as was expected from the excellent
flow of the direct compression excipients used. The thickness of the prepared tablet
also show low variability related to the good flow and consistency of compression
force. The friability value was found to be less than 1% that confirms the good
mechanical resistance of the tablets. Drug content was 97-102% which complied with
pharmacopeial limits. The result of thickness, friability, % weight variation and drug
content are given in the Table 8.15.
Table 8.15: Evaluation of AC tablets
Run Thickness
(mm) *
Friability*
%
% Weight
variation*
Drug content
(%)*
1 3.16±0.057 0.73±0.03 0.075±0.002 97.33±0.577
2 3.06±0.057 0.65±0.04 0.322±0.007 98.66±1.154
3 3.1±0.1 0.82±0.02 0.123±0.003 102±1.011
4 3.13±0.057 0.76±0.03 0.275±0.002 101.66±0.577
5 3.3±0.057 0.67±0.03 0.322±0.004 100.66±1.527
6 3.2±0.173 0.78±0.02 0.075±0.002 101±1.73
7 3.26±0.057 0.74±0.02 0.275±0.003 99.66±2.08
8 3.1±0.173 0.63±0.03 0.075±0.004 98.33±0.577
* Mean±Standard deviation, n=3
From the experimental results, the effects of all studied variables and the
variable interactions were graphically and statistically interpreted for all responses.
The results of ANOVA indicated that all models were significant (p < 0.05) for all
response parameters investigated. Model simplification was carried out by eliminating
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 203
non-significant terms (p > 0.05) in polynomial equations. Values of "Prob > F" less
than 0.0500 in all the cases indicates model terms are significant. The Pred R-Squared
is in reasonable agreement with the Adj R-Squared. The signal to noise ratio is
measured by Adeq Precision and ratio greater than 4 is desirable. The value shows
much higher than 4 confirms an adequate signal (Table 8.16). This model can be used
to navigate the design space.
The high values of r2 shown by the polynomial relationships assure high
statistical validityof polynomial models for fitting to the experimental data. The
linearity of the correlation plots between predicted and observed responses confirms
high prognostic ability of the postulated model.
Table 8.16: Summary of results of regression analysis for responses
Value F-value p-value
Hardness
R-Square 0.9786
60.98
0.0009 Adj R-Squared
Pred R-Squared
Adeq Precision
0.9626 0.9144 19.081
Disintegration Time
R-Square 0.9958
323.04
< 0.0001
Adj R-Squared 0.9928
Pred R-Squared 0.9835
Adeq Precision 44.8690
% Cumulative Drug Release
R-Square 0.9810
68.99
0.0007
Adj R-Squared 0.9668
Pred R-Squared 0.9242
Adeq Precision 21.382
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 204
8.3.5. Optimisation
To obtain the optimized tablet, the required limits of the response values were
clearly defined (hardness of 4.5kg, disintegration time of 100 sec and % cumulative
release of more than 98%) (Table 8.17). The combinations of variables which resulted
in tablets meeting the required specifications were calculated using the design expert
software. The overlapping of the obtained result over the predicted values confirms
the practicability and validation of the model.
Table 8.17: Optimisation of final AC tablet
Value MCC
(mg)
PVP
(mg)
SSG
(mg)
Hardness
(Kg)
Disintegration
Time(sec)
% Cumulative
drug release(%)
Predicted 250.02 10.08 13.37 4.5 100 98.00
Actual 250.02 10.08 13.37 4.5 98 97.5
Relative
error 0 2.0 0.51
8.3.6. Reconstitution properties of optimized S-SNEDDS tablets
The z-average diameter and polydispersity index of the solid and liquid
SNEDDS are presented in Table 8.18. As shown in the table, the z-average droplet
sizes of both systems were less than 50 nm. The droplet size of the nanoemulsion
from the solid SNEDDS was slightly increased, but the difference is not statistically
significant. S-SNEDDS formulation disperse quickly and completely when subjected
to aqueous environment under mild agitation and showed robustness to high dilutions.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 205
Table 8.18: Globule size with polydispersity index of the reconstituted
nanoemulsions
Formulation z-Average diameter (nm) Polydispersity index (PDI)
Liquid SNEDDS 42.21 0.184
Solid SNEDDS 49.4 0.262
Figure 8.19: Globule size distribution
8.3.7. Comparative in vitro drug release studies and Release kinetics
The comparative dissolution profiles of optimized AC SNEDDS loaded tablet
and market preparation (Astin) was carried out in 0.1M HCl. The dissolution profile
showed that the optimized AC SNEDDS loaded tablet exhibited faster drug release
(97.5% at 40 min) whereas marketed preparation shows 32.7% at 40 min. Thus the
optimized AC SNEDDS loaded tablet showed almost 3 fold increase in dissolution
rate. Diffusion, swelling and erosion are the most important drug release mechanisms.
The drug release from the AC SNEDDS loaded tablet tends to follow nearly zero-
order kinetics followed by non-Fickian kinetics, owing to interplay of diffusion and
convection mechanisms.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 206
Figure 8.20: In-vitro drug release profiles of AC SNEDDS tablets and market
formulation
8.3.8. Pharmacokinetics studies12
The Pharmacokinetic study shows that the OPT AC SNEDDS tablets showed
significant improvement of Cmax and AUC of the drug while compared to its pure
form. The chromatograms of rat plasma spiked with AC and after oral administration
of SNEDDS tablets are shown in Figure 8.21-8.22.
Figure 8.21: Typical chromatogram of rat plasma spiked with AC
0
20
40
60
80
100
120
0 10 20 30 40 50
AC SNEDDS Tablets
Market Formulation
Time(min)
% C
umul
ativ
edr
ug r
elea
se
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 207
Figure 8.22: Representative chromatogram of plasma sample after oral
administration of AC SNEDDS tablets to rats
Table 8.19: Pharmacokinetic parameters
Product Cmax
(mcg/ml) *
Tmax
(h) *
Kel
(h-1) *
T1/2
(h) *
(AUC)0t
(mcg/ml×hr) *
AC 6.92±1.76 2.5±0.25 0.031±0.002 22.35±1.22 73.56±8.52
AC SNEDDS tablets
48.02±5.98 1.2±0.18 0.035±0.033 19.8±1.73 386.2±15.69
* Mean±Standard deviation, n=3
The results showed that Cmax of AC SNEDDS tablets were 6.93 times higher
than that of pure drug. Additionally, Tmax of the AC SNEDDS tablets was all shorter
than that of the pure drug, suggesting that self emulsifying technique could improve
drug release and absorption in GIT. It indicated that the absorption of AC was
evidently improved after it was dispersed in solid SNEDDS formulations (Figure
8.23).
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 208
The increase in Cmax and AUC is because, after oral administration of AC
SNEDDS tablets, the emulsion readily dispersed, and no dissolution of atorvastatin
calcium was required since the drug was in the dissolved form in the oil phase of the
emulsion. In addition, Capmul, a medium chain triglyceride and surfactants could
improve the permeation of drug. There were no significant differences between the
half-life and elimination rate constant of AC and AC SNEDDS tablets.
Figure 8.23: Plasma drug level profiles of optimized SNEDDS tablets and pure
drug.
0
10
20
30
40
50
60
0 4 8 12 16 20 24
Plas
ma
drug
conc
entr
atio
n (m
cg/m
l)
Time(h)
Pure drug
SNEDDS tablets
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 209
8.4. Rosuvastatin calcium (RC)
8.4.1. Preparation of RC loaded SNEDDS tablet
The tablets were prepared by direct compression technique, direct
compression (DC) is most effective, fastest and simplest method in the manufacturing
of tablet. The method also secures the drug from moisture and heat.
Micro crystalline cellulose (MCC), poly vinyl pyrollidone (PVP) and sodium
starch glycolate (SSG) were used as directly compressible diluent, binder and super
disintegrating agent.
The microcrystalline cellulose PH 101 (MCC) is an excellent filler/flow-aid
for direct compression with an average particle size of 50µm that attributes to the
excellent batch flowability and compressibility properties173. Due to its high surface
area and enormous internal porosity it is capable to absorb and retain a large quantity
of liquid and also absorbs the any squeezing of lipid occurs while punching of
tablets169.
PVP K 30 is used as binder because of its directly compressible property.
Sodium starch glycolate (SSG) is added in the formulations as it belongs to category
of directly compressible super disintegrants which swell upto 5-10 times in less than
30s. The inclusion of disintegrants improved the general redispersion of all the
formulations28.
Every excipient is included to suit the needs of product use and processibility.
To identify the most important factors among all the factors screening is done at
beginning of the experimental procedure.
By conducting a group of preliminary trials by varying the relative ratio of the
selected three components i.e. MCC, PVP, SSG and on the previous related
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 210
experiences, the upper and the lower limits of each variable were defined (Table
8.20). If all of the possible combination for the excipients in the initial formulation
system is to be evaluated, a full factorial DOE could requires 8 studies, as shown in
Table 8.20
Table 8.20: Variables in 23 factorial design
Independent variable Levels
Low(mg) High(mg)
A: MCC 250 350
B: PVP 8.75 15.75
C: SSG 5 14
Dependent variable
Y1 Hardness (kg)
Y2 Disintegration Time (sec)
Y3 % Cumulative drug release (%)
Table 8.21: 23 Factorial Design for RC loaded SNEDDS tablet
Std
Run
Factor 1 Factor 2 Factor 3
A:MCC
mg
B:PVP
mg
C:SSG
mg
1 1 250 8.75 5
4 2 350 15.75 5
6 3 350 8.75 14
2 4 350 8.75 5
8 5 350 15.75 14
7 6 250 15.75 14
5 7 250 8.75 14
3 8 250 15.75 5
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 211
8.4.2. Micromeritic properties of powder blend
The results of bulk density, tapped density, angle of repose, Carrs index and
Hausners ratio are given in the Table 8.22. The angle of repose, Carrs index and
Hausners ratio confirms the good flow property.
Table 8.22: Micromeritic properties
Run Bulk
Density
(g/cc) *
True
Density
(g/cc) *
Angle of
repose*
°
Carrs index
(%)*
Hausners
ratio*
1 0.339±0.001 0.467±0.003 24.73±0.04 27.41±0.18 1.377±0.04
2 0.382±0.003 0.518±0.002 24.26±0.04 26.25±0.11 1.356±0.002
3 0.371±0.002 0.502±0.003 24.37±0.02 26.09±0.06 1.352±0.005
4 0.385±0.002 0.511±0.004 23.94±0.03 24.65±0.21 1.327±0.004
5 0.389±0.004 0.521±0.002 24.11±0.04 25.33±0.15 1.339±0.003
6 0.340±0.002 0.478±0.003 25.62±0.02 28.84±0.19 1.405±0.003
7 0.344±0.002 0.473±0.004 25.93±0.02 27.27±0.12 1.375±0.002
8 0.352±0.003 0.482±0.004 24.91±0.03 26.97±0.09 1.369±0.005
* Mean±Standard deviation, n=3
8.4.3. Experimental design.
In the present study, the design of experiment methodology was employed to
systematically evaluate the effect of varying the amount of MCC, PVP and SSG on
the Hardness, Disintegration time, percentage cumulative drug release. The summary
of result data obtained of various responses is presented in Table 8.23.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 212
Table 8.23: Observed Response in 23 Factorial Design for RC loaded SNEDDS
tablet
Std
Run
Factor
1
Factor
2
Factor
3
Response
1
Response
2
Response
3
A:MCC
mg
B:PVP
mg
C:SSG
mg
Hardness
Kg
Disintegration
time Sec
% cumulative
drug release
1 1 250 8.75 5 3.4 105 97.9
4 2 350 15.75 5 7.5 192 76
6 3 350 8.75 14 5.4 123 97.6
2 4 350 8.75 5 5.1 130 92.7
8 5 350 15.75 14 7.1 169 82.1
7 6 250 15.75 14 6.2 139 88.5
5 7 250 8.75 14 3.9 88 99.3
3 8 250 15.75 5 6 160 81.6
The result depicts (Table 8.23) that variables chosen have strong influence on
the selected responses, as hardness, disintegration time and percentage cumulative
drug release values were in the range of 3.4-7.1kg, 88-192s and 76-99.3%
respectively.
The hardness of the tablets were in the range of 3.4-7.5kg. The disintegration
time of the prepared tablets were in the range of 88-192 sec. The drug release at the
end of 40 min was between 76-99.3%.
The application of factorial design yielded the following regression equations.
Hardness =-2.72083+0.014000 * MCC+0.32143 * PVP+0.016667 * SSG
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 213
Disintegration time =-28.93056+0.30500 * MCC+7.64286 * PVP-1.88889 *
SSG
% Cumulative drug release = +124.48819-0.047250 * MCC-2.11786 * PVP +
0.53611* SSG
Where negative values indicate a negative effect of a specific variable on the
response factors and positive values indicate a positive effect of a specific variable on
the response factors. The polynomial regression results were expressed using 3-D graphs
and contour plots (Figure 8.24-8.25). The contour plots depict the concentration of the
factors at which the particular response produced.
Hardness
PVP has a significant effect on the hardness of the tablet whereas MCC and
SSG have a slight effect. Hence the concentration of PVP was the main factor
affecting the hardness. The PVP has a positive effect on the hardness of the tablet, at
low concentration the hardness was between 3.4-5.4 kg. With increase in
concentration of PVP, the hardness of the tablet increased to 7.5kg (Table 8.23). The
increase in hardness with increase in concentration of MCC, attributed to large free
hydroxyl groups which make the interaction forces (hydrogen bond) in a contact point
might be stronger.
Disintegration time
As it can be seen from the plot (Figure 8.25), concentration of SSG has
significant effect on the disintegration time. The model equation relating
Disintegration time showed SSG has negative effect on the DT. MCC and PVP
showed positive effect, with increase in the concentration of MCC and PVP, the DT
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 214
increased due to the contribution of these factors in increase in hardness. SSG has
negative effect on the disintegration time.
Low concentration of SSG showed the disintegration time of 105-192 sec. As
the concentration was increased, the disintegration time decreased to 88 sec. The
formulation containing the higher concentration of SSG, shows faster disintegration
followed by higher dissolution rate. As soon as the glycolate comes in contact with
water, it rapidly absorbs which causes enormous swelling that leads to the rapid
disintegration. There is no significant contribution by eliminated terms from the
equation on the prediction of disintegration time.179
Percentage cumulative drug release
Results of regression analysis showed coefficients of MCC and PVP bearing a
negative sign, i.e., with increase in the concentration of these factors show negative
effect on percentage cumulative drug release. This is due to, with increase in the
concentration of MCC and PVP, the hardness of tablet increase which leads to delay
in tablet disintegration and thus hindered the drug release. The SSG has positive effect
on percentage cumulative drug release, due to the swelling property of SSG which
increase the disintegration. The drug release at the end of 40 min was between in the
range of 76-99.3%.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 215
Figure 8.24: Three-dimensional response surface plot depicting the impact of
MCC:PVP, PVP:SSG and SSG: PVP on hardness, disitegration time and %
cumulative drug release respectively
Figure 8.25: Counter Plot Showing impact of MCC:PVP, MCC:SSG and
SSG:PVP on hardness, disintegration time and percentage drug release
respectively
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 216
8.4.4. Evaluation of tablets
Tablet thickness was in the range of 3.1-3.26 mm and was considered constant
for all the formulations (Table 8.24). Percentage weight variation and thickness
suggested that there is a low possibility of any variability associated with the tablet
press or the method of preparation of tablets. Friability of less than 1% in all the
prepared formulations confirms mechanical strength of the tablets. Drug content was
in the range of 98.7-101.2%, which complied with pharmacopeial limits.
Table 8.24: Evaluation of RC tablets
Run Thickness
(mm) *
Friability*
%
% Weight
variation*
Drug content
(%)*
1 3.16±0.057 0.65±0.02 0.254±0.004 99.1±0.909
2 3.06±0.057 0.77±0.02 0.453±0.003 98.9±1.262
3 3.1±0.1 0.86±0.03 0.143±0.004 99.6±1.614
4 3.13±0.057 0.59±0.05 0.055±0.005 100.6±0.98
5 3.3±0.057 0.63±0.04 0.254±0.003 98.7±1.861
6 3.2±0.173 0.71±0.03 0.342±0.002 101.2±1.334
7 3.26±0.057 0.82±0.03 0.541±0.004 99.8±1.758
8 3.1±0.173 0.66±0.02 0.254±0.002 100.3±0.891
* Mean±Standard deviation, n=3
From the experimental results, the effects of all studied variables and the
variable interactions were graphically and statistically interpreted for all responses.
The results of ANOVA indicated that all models were significant (p < 0.05) for all
response parameters investigated. Model simplification was carried out by eliminating
non-significant terms (p > 0.05) in polynomial equations. Values of "Prob > F" less
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 217
than 0.0500 in all the cases indicates model terms are significant. The Pred R-Squared
is in reasonable agreement with the Adj R-Squared.
The signal to noise ratio is measured by Adeq Precision and ratio greater than
4 is desirable. The value shows much higher than 4 confirms an adequate signal
(Table 8.25). This model can be used to navigate the design space.
The high values of r2 shown by the polynomial relationships assure high
statistical validityof polynomial models for fitting to the experimental data. The
linearity of the correlation plots between predicted and observed responses confirms
high prognostic ability of the postulated model.
Table 8.25: Summary of results of regression analysis for responses
Value F-value p-value
Hardness
R-Square 0.9788
61.60 0.0008 Adj R-Squared 0.9629
Pred R-Squared 0.9152
Adeq Precision 19.462
Disintegration Time
R-Square 0.9907
142.27 0.0002 Adj R-Squared 0.9838
Pred R-Squared 0.9629
Adeq Precision 32.661
% Cumulative Drug Release
R-Square 0.9777
58.56 0.0009 Adj R-Squared 0.9610
Pred R-Squared 0.9110
Adeq Precision 19.832
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 218
8.4.5. Optimisation
To obtain the optimized tablet, the required limits of the response values were
clearly defined (hardness of 4.5, disintegration time of less than 103 sec and
percentage cumulative drug release of more than 98%) (Table 8.26). The
combinations of variables which resulted in tablets meeting the required specifications
were calculated using the design expert software. The overlapping of the obtained
result over the predicted values confirms the practicability and validation of the
model.
Table 8.26: Optimisation of RC final tablet
Value MCC PVP SSG Hardness (Kg)
Disintegration Time (sec)
% Cumulative drug release (%)
Predicted 267.73 10.08 14 4.5 103 98.00
Actual 267.73 10.08 14 4.5 106 97.1
Realtive
error(%)
2.91 0.91
8.4.6. Reconstitution properties of optimized S-SNEDDS tablets
The z-average diameter and polydispersity index of the solid and liquid
SNEDDS are presented in Table 8.27. As shown in the table, the z-average droplet
sizes of both systems were less than 41nm. The droplet size of the nanoemulsion from
the S-SNEDDS was slightly increased, but is not statistically significant. SNEDDS
emulsifies as soon as it comes in contact with the dissolution media and also it is
robust to higher dilutions.
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 219
Table 8.27: Droplet size with polydispersity index of the reconstituted
nanoemulsions
Formulation z-Average diameter (nm) Polydispersity index (PDI)
Liquid SNEDDS 35.27 0.172
Solid SNEDDS 40.1 0.194
Figure 8.26: Globule size distribution
8.4.7. Comparative in vitro drug release studies and Release kinetics
The comparative dissolution profiles of optimized RC SNEDDS loaded tablet
formulation and market preparation (Rosavel10mg) was carried out in 0.1M HCl. The
dissolution profile showed that the optimized RC SNEDDS loaded tablet exhibited
faster drug release (97.1% at 40 min) whereas market preparation shows 36.9% at 40
min. Thus the optimized RC SNEDDS loaded tablet showed almost 3 fold increase in
dissolution rate. Diffusion, swelling and erosion are the most important drug release
mechanisms. The drug release from the RC SNEDDS loaded tablet tends to follow
nearly zero-order kinetics followed by non-Fickian kinetics, owing to interplay of
diffusion and convection mechanisms
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 220
Figure 8.27: In-vitro drug release profiles of RC SNEDDS tablets and market
formulation
8.4.8. Pharmacokinetics studies13
The Pharmacokinetic study shows that the optimised RC SNEDDS tablets
shows significant improvement of Cmax and bioavailability of the drug compared to
the pure drug. The chromatograms of rat plasma spiked with RC and after oral
administration of SNEDDS tablets are shown in Figure 8.28-8.29.
Figure 8.28.: Typical chromatogram of rat plasma spiked with RC
0
20
40
60
80
100
120
0 10 20 30 40 50
% C
umul
ativ
e dr
ug re
leas
e
Time (min)
RC SNEDDS Tablets
Market Formulation
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 221
Figure 8.29. Representative chromatogram of plasma sample after oral
administration of RC SNEDDS tablets to rats
The pharmacokinetic parameters of RC absorption are summarized in Table
8.28. The Figure 8.30 depicts the mean plasma concentration profile as a function of
time obtained by the pharmacokinetic studies carried out in rats for SNEDDS tablets
and pure drug. The plasma level profiles were significantly increased for SNEDDS
tablets compared to pure drug.
Table 8.28: Pharmacokinetic parameters
Product Cmax
(mcg/ml) *
Tmax
(h) *
Kel
(h-1) *
T1/2
(h) *
(AUC)0t
(mcg/ml×hr) *
RC 7.92±1.81 5±0.79 0.042±0.005 16.4±1.83 52.9±6.89
RC S-SNEDDS 57.4±3.05 1.9±0.24 0.048±0.002 14.2±1.21 418.6±14.95
* Mean±Standard deviation, n=3
The results showed that Cmax of SNEDDS tablets was 7.24 times higher than
that of pure drug. Additionally, Tmax of the SNEDDS tablets was all shorter than
that of the pure drug, suggesting that self emulsifying technique could improve drug
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 222
release and absorption in GIT. It indicated that the absorption of RC was evidently
improved after it was dispersed in solid SNEDDS formulations. There were no
significant differences between the half-life and elimination rate constant of RC and
SNEDDS tablets.
Figure 8.30: Plasma drug level profiles of optimized SNEDDS tablets and pure
drug.
9. Stability testing
The results of the stability study (Table 8.29) of prepared formulations stored
at 40°C and 75% relative humidity for 6 month with accordance with ICH
guidelines139. The drug content and dissolution behaviour of prepared formulations
remain unchanged during storage. FT-IR studies confirm the no interaction of drug
and excipient occurs during the storage.
0
10
20
30
40
50
60
0 4 8 12 16 20 24
Plas
ma
drug
con
cent
ratio
n (m
cg/m
l)
Time(Hrs)
Pure drug
SNEDDS tablets
Result and Discussion
Dept of Pharmaceutics, JSSCP, Mysore 223
Table 8.29: Stability study data of optimized formulations
Sample name: Efavirenz Loaded SNEDDS tablets
Storage condition: 40°C /75% RH
Testing interval FT-IR Study Drug content
(%)
% cumulative
drug release
Initial Complies 98.72±0.47 97.89±0.89
1 month Complies 97.67±0.29 96.72±0.74
2 month Complies 96.28±0.6 96.02±0.28
3 month Complies 95.45±0.19 95.18±0.13
6 month Complies 95.02±0.22 95.01±0.30
Sample name: AC Loaded SNEDDS tablets
Storage condition: 40°C /75% RH
Initial Complies 99.14±0.58 98.79±0.74
1 month Complies 98.34±0.64 98.22±0.62
2 month Complies 98.02±0.28 97.68±0.86
3 month Complies 97.28±0.46 97.10±0.37
6 month Complies 96.33±0.19 96.45±0.29
Sample name: RC Loaded SNEDDS tablets
Storage condition: 40°C /75% RH
Initial Complies 99.27±0.79 98.23±0.91
1 month Complies 98.43±0.83 97.98±0.85
2 month Complies 98.09±0.26 97.24±0.47
3 month Complies 97.67±0.28 96.62±0.64
6 month Complies 97.14±0.17 96.15±0.57
* Mean±Standard deviation, n=3