STABLE AND BIOEQUIVALENT FORMULATION DEVELOPMENT OF HIGHLY ACID LABILE PROTON PUMP INHIBITOR: RABEPRAZOLE- A Research Article by Shivang Chaudhary & Amit Mukharya

International Journal of
Pharmaceutical Research & Innovation

STABLE AND BIOEQUIVALENT FORMULATION DEVELOPMENT OF
HIGHLY ACID LABILE PROTON PUMP INHIBITOR: RABEPRAZOLE
A. Mukharya*, S.A. Chaudhary, A. Bheda, A. Mulay,
N.Mansuri, N. Laddha, A. K. Misra
Formulation Development Department, Cadila Pharmaceuticals Limited, 1389, Trasad Road, Dholka,
Ahmedabad, Pin Code: 387 810. India.

Abstract Rabeprazole sodium is a Proton-Pump-Inhibitor (PPI), used for treatment of acidity by inhibiting
H+/K+/ATPase pump at the gastric parietal secretary cells. The main challenge in the formulation of
Rabeprazole is to prevent degradation of Active Pharmaceutical Ingredient (API) upon exposure to acidic
environment or moisture. In order to prevent acid degradation of API in Gastro Intestinal Tract (GIT),
tablets should be enteric coated to prevent its exposure to gastric acid. Coating of acid labile PPI with
enteric coating acidic material may further cause the decomposition of acid labile PPI. In order to
overcome this limitation, the core containing acid labile PPI and alkalizers was seal coated with water-
insoluble polymer and non-hygroscopic alkalizer (stabilizer) and subsequently enteric coating was done on
seal coated tablet, with a polymer to prevent its exposure to acidic environment of GIT and facilitate
absorption through intestinal fluid. The optimized formulation was packed in Alu-Alu blister and charged
for stability study at 40C/75%RH. It was observed that over 6 months the formulation was stable with
impurities in control. In vivo bio-equivalence study was performed, in which optimized formulation was
found bio-equivalent with marketed reference formulation.
Keywords: Bio-equivalence, Enteric-coating, Rabeprazole, Seal-coating, Stability.
INTRODUCTION
Amongst all Proton-Pump Inhibitors (PPIs),
Rabeprazole is the most potent acid secretion
Parietal cells of the stomach secret gastric acid
inhibitor during first day of dosing2. Rabeprazole is
in response to stimuli such as the presence of food
chemically
2-[[4-(3-methoxypropoxy)-3-methyl-
in the stomach or intestine and the taste, smell,
pyridine-2-yl] methyl sulfinyl]-1H-benzimidazole3,
sight or even thought of food. Such stimuli result
mainly used for treatment of acidity by decreasing
in the activation of histamine (H2), acetylcholine
acid secretion through inhibiting especially
(M3) or gastrin (CCK2) receptors located in the
H+/K+/ATPase enzymatic system present on the
basolateral membrane of the parietal cells, which
secretary surface of gastric parietal cells4.
initiate signal transduction pathways resulting in
Rabeprazole is a pro-drug that is converted to
activation of H+/K+/ATPase Pump (also known as
their active form in acidic environments.
Proton pump) consequentially inducing gastric
Rabeprazole is a weak base, and so specifically
acid secretion1. If this proton pump is inhibited by
concentrates in the acidic secretory canaliculi of
some means than gastric acid secretion will be
the parietal cell, where it is activated by a proton-
reduced.
catalysed process to generate a sulphenamide. As
represented in Figure 1, the sulphenamide
*Corresponding author:
interacts covalently with the sulphydryl groups of
Email: amit.mukharya@cadilapharma.co.in
cysteine residues in the extracellular domain of
the H+/K+/ATPase enzyme - in particular Cys 813 -
thereby inhibiting its acid secretary activity5.

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Fig. 1. Schematic representation of proton pump pnhibition by Rabeprazole (R= -(CH2)3OCH3 ) in
acidic secretary canaliculi of the gastric parietal cells6 .
Upon exposure
to
acidic
or
neutral
Prior art search showed, a Japanese patent
environment or upon exposure to moisture
describing a method comprising intermediately
Rabeprazole is converted to colored degradation
coating the core containing PPI with water soluble
products, as depicted in Figure 27. So, it is
polymer and then seal coated tablet was coated
recommended to formulate Rabeprazole as an
with an enteric coating polymer, but seal coating
enteric coated tablet to prevent decomposition of
with water soluble polymer could not sufficiently
the API upon exposure to gastric acid. But most of
extend the shelf-life of formulation10. An European
the enteric coating materials are acidic in nature
patent application has disclosed a composition of
(e.g. Pthalate- Pthalic acid ester or Acrylate-Acrylic
Rabeprazole sodium with potassium hydroxide,
acid
copolymers)8,
that
may
cause
the
sodium hydroxide and potassium carbonate, but
decomposition of acid labile PPI. In present
these alkalizers are hygroscopic in nature and
research work, to prevent the interaction of
leading to degradation of Rabeprazole, because it
Rabeprazole with acidic enteric coating material,
absorbs water into the formulation11. Another
core tablet is seal-coated with water-insoluble
excipient for stabilization of acid labile API is
polymer. Moreover, seal-coating provides a
Magnesium oxide (MgO). Since MgO is very
moisture barrier to core tablet9.
slightly soluble in purified water and its saturated
solution yields a pH of about 10.3, it provides
Fig. 2. Two major degradation products of Rabeprazole.

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Table 1 Formulation ingredients of Rabeprazole tablet
Category
Ingredients
Application
Intra-granular
Rabeprazole sodium
Active Pharmaceutical Ingredient
ingredients
Mannitol
Bulking agent
L HPC LH 21
Disintegrant
Sodium hydroxide
Stabilizer (alkalizer)
Absolute alcohol
Solvent
Extra-granular
Mannitol
Bulking agent
ingredients
Disodium hydrogen phosphate
Stabilizer (alkalizer)
anhydrous
L HPC LH 21
Disintegrant
Purified Talc
Anti-adherant
Magnesium stearate
Lubricant
Seal-coating
Ethyl cellulose 4 cps
Water- insoluble Polymer
ingredients
Light magnesium oxide
Stabilizer (alkalizer)
Magnesium stearate
Anti-sticking agent
Absolute alcohol
Solvent
Enteric-coating
Instacoat(R) Hydroxy Propyl Methyl
Enteric coating polymer
ingredients
Cellulose Pthalate (HPMCP)- IC EN 783
Absolute alcohol
Solvent

alkaline pH to Rabeprazole micro-environment,
Experimental Methods
which is most favorable for its stability12.
Rabeprazole is moisture sensitive API, hence all
MATERIALS AND METHODS
the processing steps including granulation,
compression and coating were carried out at
Materials
305C and 305% Relative Humidity (RH). Due
Rabeprazole sodium (Cadila Pharmaceuticals
to light sensitivity of Rabeprazole, processing was
Limited, India), Mannitol (Roquette, France), Low
carried out under the light of sodium vapor lamp.
substituted Hydroxy propyl cellulose (L-HPC,
Preparation of core tablet
Shinetsu Chemicals, Japan), Sodium hydroxide
(Cento Pharma, India), Disodium hydrogen
Intra-granular and extra-granular material as
phosphate anhydrous BP (Sujata Chemicals, India),
enlisted in Table 2 were accurately weighed and
Ethyl cellulose (Colorcon Asia pvt ltd., India), Light
sifted through 40# sieve. Intragranular material
magnesium oxide BP (SCORA, France), Purified
was mixed in the dry state in Rapid Mixer
Talc BP (Luzenac Pharma, USA), Magnesium
Granulator (RMG- Sigmagran(R)) for 10 minutes at
stearate BP (Ferro Synpro VG, Ohio), Methylene
slow speed of impeller. Weighed sodium
chloride BP (Reliance chemicals, India), Absolute
hydroxide was completely dissolved in absolute
alcohol BP (Shree Chalthan Vibhag Khand Udyog
alcohol with continuous stirring. This binding
Sahakari Mandli Ltd., India). All other reagents
solution was slowly added to pre-mixed intra-
were of analytical grade and they were used as
granular material in RMG mentioned above and
received
from
manufacturer
or
supplier.
mixed at 75 RPM of Impeller speed for 5 minutes.
Applications of the entire active ingredient as well
Then prepared wet mass was dried in Fluidized
as inactive ingredients (excipients) are mentioned
Bed Dryer (FBD-Retsch(R) TG-200) at inlet
in Table 1.
temperature of 50C-60C and outlet temperature

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Table 2 Formulations details of Rabeprazole Tablets, 20mg (core and coated tablet)
Formulations
Rab 1
Rab 2
Rab 3
Rab 4
Rab 5
Rab 6
Intra-granular Ingredients (mg)
Rabeprazole sodium
20.00
20.00
20.00
20.00
20.00
20.00
Mannitol
76.10
76.10
66.10
71.10
76.10
76.10
L-HPC
5.00
10.00
15.00
15.00
20.00
15.00
Sodium hydroxide
0.40
0.40
0.40
0.40
0.40
0.40
Absolute alcohol
0.50
0.50
0.50
0.50
0.50
0.50
Extra-granular Ingredients (mg)
Mannitol
15.00
15.00
25.00
20.00
15.00
15.00
L-HPC
20.00
15.00
10.00
10.00
5.00
10.00
Disodium hydrogen
5.00
5.00
5.00
5.00
5.00
5.00
phosphate
Purified talc
5.00
5.00
5.00
5.00
5.00
5.00
Magnesium stearate
3.00
3.00
3.00
3.00
3.00
3.00
Total weight of
150.00
150.00
150.00
150.00
150.00
150.00
core tablet
Seal-coating Ingredients (mg)
Ethyl cellulose 4cps
0.96
0.96
0.96
0.96
0.96
0.96
Light Magnesium
0.77
0.77
0.77
0.77
0.77
0.77
oxide
Magnesium stearate
0.77
0.77
0.77
0.77
0.77
0.77
Absolute alcohol
q.s.
q.s.
q.s.
q.s.
q.s.
q.s.
Total weight of Seal
152.50
152.50
152.50
152.50
152.50
152.50
coated tablet
Enteric-coating Ingredients (mg)
Instacoat(R) Hydroxy
Propyl Methyl
15.00
15.00
15.00
15.00
15.00
15.00
Cellulose Pthalate
(HPMCP)
Absolute alcohol
q.s.
q.s.
q.s.
q.s.
q.s.
q.s.
Final weight
167.50
167.50
167.50
167.50
167.50
167.50
Abbreviations: Rab No.= Rabeprazole tablet formulation number
of 40C-45C for approximately 50 minutes, until
compressed into core tablet using round shaped
LOD not more than 2.0% w/w at 105C for 4
plain standard concave die-punches set of 9/32"
minutes was achieved.
dimension in rotary tablet press (RIMEK(R), India).
Dried granules were sifted through multi-mill
Seal - coating of core tablet
(Cadmill(R), Cadmach Machinery Co. Ltd.) equipped
Seal coating serves as a separating layer to
with 1.5-5.0 mm screen at 500-600 RPM and
prevent
interaction
between
acid
labile
collected in polyethylene lined drum. The dried
Rabeprazole sodium and acidic enteric coating
milled granules were transferred to double cone
material. In addition, it also acts as a moisture
blender and extra-granular material were added
barrier to core tablet. Seal coating materials were
to it and mixed for 10 minutes in same blender.
dispensed as mentioned in Table 2 and dissolved
The prelubricated blend was ready for lubrication.
in absolute alcohol. This was stirred for 45 minutes
For lubrication magnesium stearate was added in
till homogeneous suspension was obtained that
double cone blender and mixed at 10 RPM for 5
was sifted through 60# screen. Seal coating of core
minutes. Sampling was done to check the
tablets was done in 24" auto coater (Ganson Auto
uniformity of the blend. The final blend was

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Rabeprazole is displayed in Figure 3.
Table 3 Coating parameters
In Process Quality Control (IPQC) testing of
Coating parameters
Set limits
Rabeprazole tablets
Pan speed
2-8 RPM
Enteric coated tablets of Rabeprazole were
Inlet temperature
50C 5C
subjected to IPQC tests that includes appearance,
Outlet temperature
40C 5C
dimension (diameter and thickness), hardness,
Tablet bed temperature
30C 5C
friability, disintegration time; during compression
Peristaltic pump speed
5-10 RPM
and coating as per Pharmacopoeia13. The
Compressed air
formulations were also assessed by content
2-4 kg/cm2
pressure
uniformity test and dissolution testing by USP
Atomizing air pressure
2-4 kg/cm2
Type I Basket apparatus at 50 RPM in 900 ml of
100-150
0.1 N HCl for 120 minutes and afterwards in
Spray rate
gm/minute
Phosphate buffer of pH 7.4 for 45 minutes14.

Stability study of Rabeprazole tablets
Coater(R) GAC-275, India) using the same solution
as per set parameters, as mentioned in Table 3.
Final optimized formulation was packed in Alu-
Alu blister (cold formed foil: made up of 25 micron
Enteric - coating of seal-coated tablet
OPA Film /Adhesive/45 micron Aluminium foil/
Enteric coating of the seal coated tablet was
Adhesive/60 micron PVC film) and charged for
done to prevent release of Rabeprazole into
accelerated stability study for 6 months at 402C
gastric acidic media as Rabeprazole is unstable at
and
75%5%
RH15
in
stability
chamber
gastric pH. For enteric coating, accurately weighed
(Thermolab(R), India). During stability study, Assay
HPMC Pthalate as mentioned in Table 2 was slowly
as well as % Related Substances (RS) were
added into absolute alcohol and mixed for 45
determined at 1 Month, 3 Months and 6 Months.
minutes, subsequently passed through 100#
Bio-Equivalance (BE) study
screen. Seal coated tablets were preheated in
coating pan for 10 minutes at 40C -45C. The
In vivo bioavailability study of Rabeprazole
tablets were coated in 24" auto coater (Ganson
tablets was performed for optimized stable
Auto Coater(R) GAC-275, India) to achieve 3%
formulation of Rabeprazole tablets to determine
weight gain. After enteric coating (up to 3% weight
the rate and extent of drug absorption into blood
gain), average weight gain and average thickness
from drug released from enteric coated tablets. A
was checked for 20 tablets. Enteric coated tablets
randomized, two treatment, two-period, two
were dried to achieve constant weight gain. The
sequence, single dose, two way crossover
pictorial diagram of enteric coated tablet of
bioavailability study on Rabeprazole sodium 20 mg
tablet of Cadila Pharmaceuticals Ltd., India (Test
Drug Product) compared with that of Pariet(R) 20
(Rabeprazole sodium 20 mg) tablet of Janssen
Pharmaceutica16,
Belgium
(Reference
Drug
Product) in 23 healthy, adult, male human
subjects under fasting conditions was carried out.
Rabeprazole sodium was extracted from human
plasma by a Liquid-liquid extraction by using 5 mL
Tertiary Butyl methyl ether as an extracting
solvent17. The study protocol was approved by
ethical committee and subjects were duly
informed.
The
pharmacokinetic
parameters
were
calculated for Rabeprazole sodium 20 mg Tablet
Fig. 3 Schematic representation of enteric
using WinNonlin-Pro(R) Software 4.0.1 version
coated Rabeprazole sodium tablet.
(Pharsight
Corporation,
USA)18.
Descriptive
statistics (Mean, SEM) for Rabeprazole sodium 20

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Table 4 Results of IPQC testing of all formulations of Rabeprazole tablets
IPQC
Rab 1
Rab 2
Rab 3
Rab 4
Rab 5
Rab 6
Parameters
Diameter
7.15
7.13
7.12
7.13
7.15
7.14
(mm.)
0.40
0.60
0.20
0.10
0.10
0.20
Thickness
3.62
3.63
3.63
3.66
3.65
3.65
(mm.)
0.30
0.10
0.40
0.10
0.50
0.30
Friability (%w/w)
0.21
0.13
0.31
0.36
0.42
0.09
Hardness (Kg/cm2)
7-8
9-10
8-9
8-9
9-10
9-10
Disintegration test profile
a) Coating layer
removal time
24
36
37
32
34
29
(minutes.)
b) Complete
disintegration time
57
54
46
53
53
48
(minutes)
Dissolution test profile
Percentage drug






release






a) 0.1 N HCL within
00
00
00
00
00
00
02:00 hrs






b) pH 8.0 Tris HCl






buffer after 2:00 hrs






1) 02:10
02
03
06
08
07
14
2) 02:20
24
29
32
36
34
37
3) 02:30
43
48
67
63
59
68
4) 02:40
74
79
81
79
76
91

m
g Test and Reference Tablets was calculated for
Stability study
all pharmacokinetic parameters.
Results of stability study are summarized in
RESULTS AND DISCUSSION
Table 5, the results showed that level of known
impurities was below 0.5% and are acceptable as
In Process Quality Control (IPQC) Tests
per ICH guidelines19. Furthermore, assay results of
The results of in process quality control tests,
Rabeprazole suggested that Rabeprazole remained
are listed in Table 4. Hardness of all the
stable in sealed Alu-Alu blister packing in the
formulations lies within the range of 5-8 kg /cm2,
optimized formulation for 6 months in stability
suggested that the product was firm enough to
study at 40C/75%RH.
withstand handling without breaking, chipping or
Bio-Equivalence (BE) Study
crumbling and not so hard that the disintegration
time was unduly prolonged. All the formulations
Pharmacokinetic parameters (Cmax, Tmax, Kel,
passed in friability test, because % weight loss was
t1/2, AUC0-t and AUC0-) for both test and reference
within Pharmacopoeial limit. In in vitro
drug products are summarized in Table 6. In this
disintegration test, enteric coating layer was
study, both formulations under the study (i.e. Test
remained intact in 0.1N HCl for 2 hrs. Enteric
and Reference) follow the same pattern in
coating layer of tablet started to imbibe the
absorption, metabolism and elimination phases
alkaline media of Tris-HCl buffer of pH 8.0 and
for Rabeprazole sodium 20mg tablet.
completely removed approximately at 30 minute
The relative bioavailability was assessed by
and
afterwards
tablets
were
completely
ratio of C
disintegrated within 50 minutes.
max and AUC0- values. The ratios of least
square Means of Cmax, AUC0-t and AUC0- were

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Table 5 Results of stability testing of optimized formulation at 40C/75%RH
Test
conditions
Total
Assay

Rabesulphone (%)
Rabesulphide(%)
Max. Ind. Impurity
(%)
Level of
(%)
impurity
Initial
0.26
0.07
0.06
0.47
99.40
1 Month
0.41
0.11
1.61
2.62
100.60
3 Months
0.46
0.12
1.43
2.53
99.30
6 Months
0.48
0.14
1.46
2.38
99.10

Table 6 Summary of pharmacokinetic parameters of Rabeprazole test (Cadila) and reference (Pariet) tablets
Rabeprazole sodium 20mg Tablet
Pharmacokinetic
EISSAI Pariet(R) Reference
parameters
CADILA Test Tablet
Tablet
Cmax (ng/ml)
340.279 27.319
322.689 29.877
Tmax (hr)
2.000 0.213
2.304 0.208
Kel (hr-1)
0.812 0.087
0.761 0.085
t1/2 (hrs)
1.114 0.133
1.329 0.211
AUC0-t (ng/ml/hr)
561.767 67.273
552.823 67.350
AUC0- (ng/ml/hr)
621.907 69.078
622.299 66.486
All values represent Mean SEM of twenty three subjects.

101.27%, 100.33% and 99.77% respectively for
acidic enteric coating material, seal coating was
generic Rabeprazole 20mg tablet of Cadila
done over the core tablet.
Pharmaceuticals Ltd., India compared with that of
Another challenge in the formulation of
Pariet 20mg (Rabeprazole sodium 20mg) tablet of
Rabeprazole tablets was to match rate and extent
Janssen Pharmaceutica, Belgium.
of bioavailability of test product with Reference
Since the 90% CI for AUC, Cmax ratios were
product i.e. Pariet. To achieve the same rate and
falling within the 80-125% for Rabeloc 20mg
extent of bioavailability as Pariet, formulation
(Rabeprazole sodium 20mg) tablet with Pariet
containing different ratios of intragranular and
20mg (Eisai Co. Ltd. Tokyo) tablet, it was
extragranular diluent and disintegrant were
concluded that the generic Rabeprazole 20mg
prepared as mentioned in Table 2.
tablet of Cadila Pharmaceuticals Ltd., India is
Among all six formulations, formulation VI
bioequivalent to Pariet 20mg Tablet of Janssen
passed in all IPQC parameters and it showed
Pharmaceutica, Belgium after single dose
similar disintegration and dissolution profile as
administration in healthy human volunteers.
shown by Pariet(R). Formulation VI did not release
CONCLUSION
Rabeprazole in gastric acidic pH and released 91%
of Rabeprazole in 45 minutes at intestinal alkaline
The main challenge in the formulation of
pH. During stability testing, Rabeprazole remained
Rabeprazole tablets was the degradation of
stable upto 6 Months at 40C/75%RH with
Rabeprazole upon exposure to acidic environment
which results into high impurity level. Thus, to
impurity levels within limits. In formulation VI, the
prevent exposure of Rabeprazole in gastric acidic
90% CI for AUC and Cmax ratios were falling within
environment enteric coating was done and to
the range of 80-125% for Rabeloc 20mg
(Rabeprazole sodium 20mg) tablet with Pariet(R)
prevent interaction between Rabeprazole and
20mg (Eisai Co. Ltd. Tokyo) tablet. So from above

---

data, it can be concluded that Rabeprazole 20mg
13 Indian Pharmacopoeia, Volume 1, The Indian
tablet of Cadila Pharmaceuticals Ltd., India is
Pharmacopoeia
Commission,
Ghaziabad,
stable and bioequivalent to reference product i.e.
India, pp.174-183 (2007).
Pariet(R) 20mg tablet of Janssen Pharmaceutical,
14 Indian Pharmacopoeia, Volume 3, The Indian
Belgium in terms of both rate and extent of
Pharmacopoeia
Commission,
Ghaziabad,
bioavailability after single dose administration in
India, pp.1033-1034 (2007).
healthy human volunteers.
15. http://www.ich.org/LOB/media/ accessed on
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