Pharmacodynamic testing and new validated HPLC method to assess the interchangeability between multi-source orlistat capsules

Article abstract of DOI:10.2147/DDDT.S138926

Background: Orlistat is an irreversible inhibitor of the lipase enzyme that prevents trigylcerides from being digested, thereby inhibiting triglyceride hydrolysis and absorption. The resultant reduced calorie uptake enables a positive effect on weight con

Full text of DOI:10.2147/DDDT.S138926

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O r i g i n a l r e s e a r c h
Pharmacodynamic testing and new validated
hPlc method to assess the interchangeability
between multi-source orlistat capsules
This article was published in the following Dove Press journal:
Drug Design, Development andTherapy
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abdel naser Zaid1
nihal Zohud1
Background: Orlistat is an irreversible inhibitor of the lipase enzyme that prevents trigylcerides
from being digested, thereby inhibiting triglyceride hydrolysis and absorption. The resultant
reduced calorie uptake enables a positive effect on weight control. Systemic absorption of the
drug is, therefore, not necessary for its mode of action. An alternative in vitro study (pharma-
codynamic) has been introduced for this drug, as in vivo bioavailability studies are irrelevant
with regard to the achievement of the product’s intended purposes.
Bushra e’layan1
Tasneem aburadi1
nidal Jaradat1
iyad ali2
Objectives: To develop a new validated high-performance liquid chromatography (HPLC)
method for the analysis of orlistat and to assess the potency and equivalence of three orlistat
formulations using the pharmacodynamic method as a surrogate indicator of pharmaceutical
interchangeability.
Fatima hussein1
Mashhour ghanem3
aiman Qaddomi3
Yara abu Zaaror4
Methods: A new HPLC method was developed for the analysis and for the dissolution
studies of orlistat in capsules. Pancreatic lipase activity was measured for three different
capsule products: Orlislim®, Slimcare®, and Xenical®, G1, G2, and the brand, respectively.
Porcine pancreatic lipase and p-nitrophenyl butyrate (PNPB) were placed in a pH 7.4
reaction buffer at 37°C, and substrate hydrolysis was monitored by measuring absorbance
changes at 410 nm; this was repeated on six capsules of each product. The inhibition was
expressed by the concentration of product, which inhibited 50% of the activity of pancreatic
lipase (IC50).
1Department of Pharmacy,
2Department of Biomedical
sciences, Faculty of Medicine and
health sciences, an-najah national
University, nablus, 3Department
of regulatory, Pharmacare Plc,
4Department of research and
Development Pharmacare Plc,
ramallah, Palestine
Results: The new analytical method was suitable for orlistat analysis. Values of IC50 from
regression lines and equations were 6.14, 8.43, and 7.80 µg/mL for Orlislim®, Xenical®, and
Slimcare®, respectively.
Conclusion: Pharmacodynamic studies of lipase inhibition could be used to support in vitro
dissolution, which demonstrates interchangeability between generic and branded orlistat
capsules. Moreover, it could be suggested as an alternative tool to bioequivalence studies for
orlistat oral products.
Keywords: Orlistat, therapeutic equivalence, validation, pancreatic lipase
Introduction
Obesity is a chronic condition that is associated with significant morbidity and
mortality. Globally, over 300 million individuals are obese, and an additional
800 million are overweight.1 In the United States, Eastern Mediterranean, and Pacific
Islands, this prevalence ranges from approximately 30% to over 70%.2
Obesity has reached epidemic proportions and is becoming a public health concern
of the first order.3 It affects approximately 23% of teenagers of southern European
countries and is continuously increasing in many developing countries.4,5
correspondence: abdel naser Zaid
head of Pharmacy Department, Faculty
of Medicine and health sciences,
an-najah national University, nablus,
PO Box 7, Palestine
Tel +972 9 234 5113
Fax +972 9 234 5982
email anzaid@najah.edu
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hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission
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The essence of obesity management is based on specific glycerides and free fatty acids. This action can be measured
behavioral therapies, aiming to change eating habits and raise using a 24-hour fecal fat excretion as a representative phar-
energy expenditure. Nutritional counseling aimed at lowering macodynamic parameter. It exerts its effect within the gas-
the intake of calories, particularly fat, with increased, daily, trointestinal tract (GIT). At therapeutic doses (120 mg three
physical activities is highly recommended. Pharmacological times daily with main meals) administered in conjunction
management is seen as an additional tool to this basic with a well-balanced diet, the inhibition of fat absorption
therapy.6 Therapeutic treatment is indicated when the body (approximately 30% of ingested dietary fat) leads to an
mass index (BMI) is over 30 kg/m2, when morbidities are additional caloric deficit of roughly 200 calories.13
associated with being overweight (BMI over 25 kg/m2), when
behavioral changes such as dieting and physical activities commonly used practical measure of the safety and effective-
have been confirmed and proven to be ineffective.7,8
ness of any new drug. With regard to the new generic product,
The in vivo bioavailability studies of drugs are the most
Orlistat belongs to a group of anti-obesity agents known bioequivalence (BE) studies are the standard approved tool
as lipase inhibitors, which are designed for the long-term for proving a drug’s safety and effectiveness. BE studies are
management of obesity and related comorbidities. Orlistat usually done by comparing the drug’s pharmacokinetic param-
decreases the absorption of dietary fat as it has independent eters with the original brand under the same study conditions.17
pharmacological lipid-lowering effects.9 It also improves However, these studies may be considered unnecessary for
insulin sensitivity10 and reduces body fat11 and serum leptin drugs that have been classified under classes I and III of the
levels.12 Orlistat is a semisynthetic derivative of lipstatin, biopharmaceutical classification system (BCS).18 In certain
it is a potent and selective natural inhibitor of gastric and circumstances, BE studies may not be demonstrable using
pancreatic lipases, which play an important role in the drug concentrations, especially when the drug acts locally and
digestion of dietary fat.13 Chemically, orlistat is (S)-2- has very limited intestinal absorption. Therefore, pharmacody-
formylamino-4-methyl-pentanoic acid (S)-1-[[(2S, 3S)-3- namic or clinical endpoints may be required as an alternative
hexyl-4-oxo-2-oxetanyl] methyl]-dodecyl ester (Figure 1). tool to improve its interchangeability with the original brand.19
It is highly lipophilic and practically insoluble in water In this circumstance, orlistat is intended for local action in the
with no pKa value within a physiological pH range.14 The GIT, its absorption is negligible at the recommended thera-
oral absorption of orlistat is very low, less than 1% of the peutic schedule, and its metabolite is not detectable in plasma
administered dose, with no evidence of accumulation after (Zhi et al15). Accordingly, BE studies based on a comparison of
long-term administration and it is rapidly eliminated and pharmacokinetic parameters become insignificant. Therefore,
excreted primarily in the feces.15 Excretion via bile produces the demonstration of efficacy and safety of a new generic
two metabolites. These metabolites, M1 and M3, have 2- and orlistat formulation is becoming a true challenge for both phar-
3-hour half-lives, respectively, and they do not have any maceutical firms as well as regulatory bodies. The US Food
pharmacological effects.16
and Drug Administration (FDA) reported a special guidance
When administered along with fat-containing foods, based on the pharmacodynamic estimation of orlistat. These
orlistat partially inhibits hydrolysis of triglycerides. There- guidelines involve the estimation of the percentage of fecal
fore, it decreases the subsequent absorption of monoacyl fat excretion over a 24-hour period.20 In this study, recruiting
volunteers with a consistent diet, accurate fecal collection,
and adequate fecal sample measurement represent a serious
+
obstacle for the conduct of this test. Therefore, this guidance
2
1
2
is nonbinding and only reflects the current thinking of the
FDA on this topic, leaving an open door toward the use of
alternative approaches, on condition that these approaches
satisfy the requirements of the registration of an Abbreviated
New Drug Application (ANDA).20
+
2
2
2
Accordingly, simpler and suitably designed relevant
in vitro tests might be a reasonable way forward to establish
BE for multisource orlistat formulations.
Therefore, in vitro testing based on similarity (f2) and
non-similarity (f1) factors may be suggested as a surrogate for
Figure 1 chemical structure of orlistat.
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Pharmacodynamic assessment of multi-source orlistat capsule
BE studies. However, this kind of study requires that f2 and of 0.1% orthophosphoric acid and 90 volumes of acetonitrile.
f1 factors must be conducted at three different pHs as per the The mobile phase was filtered using 0.45 µm microporous fil-
International Council for Harmonization (ICH) guidelines, and ter and was degassed by sonication prior to use. A wavelength
the results must be higher than 50 and less than 15, respec- of 205 nm was selected and a flow rate of 1.0 mL/minute was
tively. This study aimed to investigate the effectiveness of f2 used, with an injection volume of 25 µL. The peak quantifica-
and f1,as a surrogate for the BE studies of orlistat capsules.
tion was obtained by comparing sample and standard peak
area ratios as a function of concentration.
Materials and methods
Materials
analytical validation
Three orlistat capsule formulations – one branded and two The method was validated in accordance with the ICH
generic – were available in the Palestinian market and guidelines.21 Parameters such as system suitability, selec-
were purchased from a community pharmacy. The generic tivity, linearity, range, accuracy (recovery), and precision
Orlislim® (G1; 120 mg/capsule) was produced by Birzeit (repeatability) were all validated. The method was found to
Pharmaceuticals (Ramallah-Palestine). The brand Xenical® be valid, as shown from the results in Table 1. Validation of
(120 mg/capsule) was manufactured by Roche. The second this analytical procedure was done using three trials of the
generic Slimcare® (G2; 120 mg/capsule) was manufactured by product and one trial of the placebo product, all of which were
Pharmacare PLC (Ramallah-Palestine). Dimethyl sulfoxide prepared in the same laboratory, under the same conditions,
acetonitrile, p-nitrophenyl butyrate (PNPB), and Tris–HCl and using the same excipients (microcrystalline cellulose
buffer were purchased from Sigma-Aldrich labrchemikalien pH 101, sodium starch glycolate, polyplasdone, sodium lauryl
GmbH, (Germany) whereas porcine pancreatic lipase type II sulfate, talc, and polyvinylpyrrolidone K-30). The purpose of
was obtained from Sigma (USA).
this study was to establish confidence that the orlistat capsule
assay method used was effective and reproducible according
to the validation parameters that have been mentioned earlier.
instruments
Study instruments included a water-bath shaker, Radwag The dissolution test method for the orlistat capsule, based on
electrical balance, Jenway 7315 spectrophotometer (Bibby the assay test method, was also validated.
Scientific Ltd., Stone, UK), and an MRC ultrasonic cleaner
(model: DC-200H).
standard solution
To obtain a solution with a concentration of 0.12 mg/mL,
12 mg USP orlistat reference standard (RS) was placed in
a 100 mL volumetric flask to which 80 mL methanol was
Methods
assay and chromatographic conditions
The amount of orlistat in the obtained capsule was assessed added; the mixture was stirred and sonicated to dissolve the
using the HPLC analytical method according to a new vali- drug, and the solution was diluted to volume using methanol.
dated analytical method reported in the validation section. The (The solution would be stable for 1 week at 4°C.)
HPLC experimental conditions were optimized on the HPLC
instrument, provided with octadecyl silane C18 chemically sample preparation
bonded column (150×3.9 mm i.d., 5 µm particles). The For sample preparation, 5 mL of the reconstituted suspension
optimum mobile phase was prepared by mixing 10 volumes was transferred to a 100 mL volumetric flask, to which 75 mL
Table 1 summary results of the validation of assay of orlistat capsule
Parameter
Statistical measurement
Results
Limits
Specificity
not applied
no interference between
the orlistat peak and any
other peaks was observed
99.5
no interference between
the active material peak
and any other peaks
98.00–102.00
accuracy
For 60%
For 100%
98.8
For 140%
98.9
linearity
Precision
Correlation coefficient
Coefficient of variation (RSD)
0.9992
0.39
Minimum 0.9950
Maximum 2.00%
Abbreviation: rsD, relative standard deviation.
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diluent was then added. The mixture was shaken and sonicated Related substances
for 30 minutes. The solution thus obtained was adjusted to vol-
Preparation of the test solution
umeusingthesamediluent. Thereafter, 5mLofthesupernatant
were transferred to a 50 mL volumetric flask and diluted to the
final volume using the mobile phase. A portion of this solution
was filtered using a nylon filter with porosity equal to or less
than 0.45 µm. The first 10 mL were rejected and the remaining
portion of the filtrate was used for assay preparation.
Using ultrasound, the combined content of 20 capsules
containing 120 mg orlistat was mixed, 80 mL methanol
was added, and the mixture was sonicated for 15 minutes.
After cooling, sufficient methanol was added to produce
100 mL final volume, which was filtered through a 0.45 µm
membrane filter; 5.0 mL of the filtrate was transferred to a
50 mL volumetric flask, and the volume was adjusted to the
mark using methanol.
For the test solution, 100 mg crushed orlistat pellets were
accurately weighed and transferred to a 50 mL volumetric
flask, dissolved in the mobile phase, and diluted to the desired
mark with the same mobile phase.
Preparation of the reference solution
For the reference solution, 1.0 mL test solution was accu-
rately transferred into a 10 mL volumetric flask, diluted to
the volume using the mobile phase, and mixed well to ensure
homogenization.
chromatographic procedure
The mobile phase was composed of a mixture of 85 volumes
of methanol and 15 volumes of water. The stationary phase
was composed of a stainless steel column (125×4.0 mm)
packed with octylsilane chemically bonded to porous silica
particles for chromatography (5 µm). The flow rate was set
at 1 mL/minute and the wavelength was set at 210 nm.
To assess the related substances, 20 µL reference solution
and test solution were injected and the related substances
were calculated using the following formula:
system suitability
Test parameters were determined by injecting 25.0 µL orlistat
standard solution six times, with a final concentration of
120.0 µg/mL orlistat. According to the chromatograms,
parameters such as injection precision for standard solution,
tailing factor for standard solution, and theoretical plates for
standard solution were calculated, as reported in Table 2.
For any individual impurity = Ai ×Cst ×100%
Dissolution study
A = Csa
For total impurities = At ×Cst ×100%
A = Csa
An in vitro dissolution study was conducted according to
the reported FDA dissolution method for orlistat capsule.22
To carry out this test, a dissolution apparatus, USP (type II)
at a paddle speed of 75 rounds per minute, was used.
The dissolution medium was 900 mL 3% sodium lauryl
sulfate in 0.5% sodium chloride at pH 6.0±0.05. This dis-
solution apparatus was kept at 37°C for the entire study
duration. One capsule was placed in each paddle. Samples
(10 mL) were taken at the desired time, and placed in the
same volume of the blank.
where, Ai stands for individual impurity peak area of test
solution, At stands for total impurities peak area of test solu-
tion, A stands for the major peak area of the reference solu-
tion, Cst means concentration of orlistat in the standard
preparation (mg/mL), and Csa stands for concentration of
orlistat in the sample preparation (mg/mL).
Pharmacodynamic study
Preparation of test (T) and reference (R)
Table 2 Orlistat release profile from Orlislim® (G1), Slimcare®
(G2), and the RLD (Xenical®) at pH 6.0
working stock solutions
Time
(minutes)
Brand
average %
release ±SD
G2
G1
It is worth mentioning that all samples, including test and
placebo, were treated under the same conditions. In fact, both
test and reference products were kept in the same conditions
and treated in the same way in all steps of the experiment.
Precisely, six stock test solutions (1 mg/mL) of each prod-
uct (G1, G2, and the brand) were prepared by dispersing
the content of each capsule in a 100 mL volumetric flask.
Thereafter, the dispersions were shaken for 1 hour, and then
average %
release ±SD
average %
release ±SD
0
5
0
0
0
52.85±1.68
96.37±2.33
105.60±1.49
108.78±1.46
103.95±0.92
63.82±1.80
94.55±1.62
102.72±0.83
102.83±1.42
101.20±0.75
72.37±3.88
98.50±1.10
100.35±1.28
101.12±1.97
100.72±1.63
15
25
35
45
Abbreviation: rlD, reference listed drug.
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Pharmacodynamic assessment of multi-source orlistat capsule
Table 3 Degree of inhibition (%) ±sD of the Orlislim® (G1),
slimcare® (G2), and the RLD (Xenical®))
sonicated to ensure homogeneity and complete dissolution
of the granules in the solvent. Then, nine serial dilutions
(10, 20, 30, 50, 80, 100, 200, 300, and 500 µg/mL) were
prepared using the same buffer. Further, a 1 mg/mL stock
solution of porcine pancreatic lipase enzyme was prepared
immediately before use in 10% DMSO solution, followed
by the addition of 5 mL Tris–HCl stock solution and 0.5 mL
pancreatic lipase. A test tube containing 5 mL Tris–HCl and
0.5 mL pancreatic lipase enzyme without inhibitor was used
as a blank. This procedure was repeated for each of the six
capsules for each drug product. Then, nine test tubes with
the blank were incubated at 37°C for 15 minutes. To all
tubes (including the blank), 0.5 mL p-nitrophenyl butyrate
(PNPB; which was prepared by dissolving 20.9 mg in
2 mL acetonitrile) was added and incubated for 30 minutes.
The effect of all prepared solutions of test and reference
products on porcine pancreatic lipase activity were evaluated.
Theoretical
Test products
concentration µg/mL
Degree of inhibition (%) ±SD
G1
RLD
G2
0
0
0
0
10
20
30
50
64.29±3.3
74.36±0.21
75.00±3.72
80.00±3.30
86.49±0.41
87.65±0.48
89.13±0.21
89.90±0.31
92.59±0.26
73.03±1.08
78.57±1.06
83.13±0.42
85.97±0.78
87.56±0.60
88.54±0.32
89.13±0.18
89.83±0.34
91.85±0.29
66.67±4.39
73.68±2.17
78.72±1.46
81.48±1.46
84.85±1.41
86.84±0.60
87.95±0.61
89.01±0.26
89.47±0.19
80
100
200
300
500
Abbreviation: rlD, reference listed drug.
S



% of enzyme inhibition = 1−
⋅100%



B
where, S refers to the absorbance of the sample; B refers to
the blank absorbance.
Measurement of pancreatic lipase activity
In this study, to investigate pancreatic lipase activity, a
known procedure was adopted that utilizes p-nitrophenyl
esters, such as PNPB, as reported in Figure 2. The release of
p-nitrophenol is measured spectrophotometrically at 410 nm
wavelength so that absorbance of each test tube for the six
capsules of the studied products (generic and brand) was
measured using an ultraviolet-visible spectrophotometer.23
After detecting absorbance, the average of six capsules ±
standard deviation (SD) has been considered for each drug
product at each concentration to produce a single reliable
absorbance value, as reported in Table 3.
The IC50 of the test samples were obtained from the least-
squares regression line of the plots of the logarithm of the
sample concentration versus the pancreatic lipase inhibition
(%), and the SDs of each trial were taken in consideration,
which gives a clue as to how the data were distributed
(Figure 3; Table 3).
calculating pancreatic lipase inhibition
Pancreatic lipase inhibition is indicated by the hydrolysis of
PNBP to p-nitrophenol. The extent of lipase inhibition has
a negative impact on the amount of p-nitrophenol released.
In order to detect the amount of p-nitrophenol released, and
accordingly the impact of the inhibitor, the blank absorption
has to be subtracted (some p-nitrophenol may be released
due to acidic media) from the total value according to the
equation below, used for calculating the pure inhibitory
activity.24
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Figure 3 The pancreatic lipase inhibitory effect of both the Orlislim® (G1), Slimcare®
(G2), and the RLD (Xenical®).
3ꢀQLWURSKHQ\OꢁEXW\UDWH
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Figure 2 Hydrolysis of p-nitrophenyl butyrate (PNPB) with and without orlistat.
Abbreviation: rlD, reference listed drug.
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Results
results of analytical validation
The analytical method used in this study was found to be
valid for the assay and dissolution of orlistat in the capsules
because all validation parameters were within acceptable
levels, as reported in Table 1. Moreover, parameters of sys-
tem suitability were assessed, and were found to be within the
accepted criteria because the injection precision and tailing
factors for standard solution were less than 2%, as summa-
rized in Table 4. The related substances test was carried out
according to the validated method of analysis.25 Metabolites
of orlistat was not detected in vitro. All results were within
the acceptable limit, as reported in Tables 1 and 4.
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Figure 4 Orlistat in vitro release profile from Orlislim® (G1), Slimcare® (G2), and
the RLD (Xenical®).
Abbreviation: rlD, reference listed drug.
As shown in Figure 4, the dissolution of orlistat capsules
of both generic products showed a dissolution profile
comparable with that of the original branded drug.
and the SDs were calculated, which showed how the data
were distributed.
The IC50 value represents the concentration of the inhibi-
tor at which 50% of the enzyme is inhibited, and it is generally
used to express the effectiveness of enzyme inhibitors. It can
be assessed by least-square regression of the linear segment
of theoretical concentration versus the percentage of inhibi-
tion curves.26 We used the values of IC50 from the regression
lines and equations, which were 6.14, 8.43, and 7.80 µg/mL
for Xenical®, Slimcare®, and Orlislim®, respectively. These
values are considered similar, and this is clear as the values
of degree of inhibition are very close to each other (Table 3).
Statistical analysis (using IBM SPSS 19) of these results
have revealed that there is no significant difference between
the three regression equations of all test products (p.0.1).
In fact, despite the slower initial release of orlistat from the
branded product, compared with G1 and G2 as shown in the
release study, a faster inhibitory action at low concentration
was shown by the branded product as compared with that
of G1 and G2 (Figure 3).
results of dissolution under FDa
conditions
With regard to the in vitro dissolution, both generic products
showed dissolution profiles strongly comparable with the
original brand when tested at the recommended pH media
parameters (FDA conditions). In fact, all products released
more than 85% of their active ingredient within 15 minutes,
as shown in Table 2 and Figure 4. Thus, there was no need
for the calculation of similarity and dissimilarity factors
as indicated by the ICH guidelines. On the other hand, the
dissolution of orlistat from all mentioned products was less
than 6%, and close to 1% when conducted at pH 6.8, 4.5,
and acidic pH (0.1 N HCl solution).
results of enzymatic inhibition
Concerning pharmacodynamic analyses, all orlistat products
available in the Palestinian pharmaceutical market were
subjected to this study. The inhibitory effect of orlistat in the
test and reference was dose dependent. Different solutions of
the test and reference products were prepared in escalating
doses, as shown in Table 3.
Discussion
To assess the assay and to conduct a dissolution study on
orlistat capsules, a validated HPLC method was developed
according to the ICH guidelines by testing several validation
parameters, such as: detection of wavelength, composition
of mobile phase, optimum pH, and the effect of slight varia-
tion of these parameters on the qualitative and quantitative
analysis of orlistat. In fact, the method demonstrated excellent
accuracy within the desired concentration range. The results
clearly demonstrate the ruggedness of the developed method,
and the results indicate that the testing of the sample on
different days by different analysts do not affect the assay
The values of IC50 for both products were calculated, and
the degree of lipase inhibition was plotted (Figure 3). The
degree of similarity with the studied product was estimated,
Table 4 summary of system suitability for orlistat analysis
Parameter
Data
Limit
injection precision for standard solution
Tailing factor for standard solution
Theoretical plates for standard solution
0.14
1.03
4,370
,2.0%
,2.0
.2,000
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Pharmacodynamic assessment of multi-source orlistat capsule
and its ability to accurately and precisely detect/quantify the G2, and RLD products. Recently, a pharmacodynamic study
active ingredients. based on lipase inhibition emerged as a BE surrogate to prove
With regard to in vitro-in vivo correlation (IVIVC), it clinical interchangeability between product formulations.23
is used to predict similarity between generic and reference However, in this study six orlistat capsules were simulta-
listed drug (RLD), which confirms generic interchangeability neously dispersed in the buffer media, which revealed a
and therapeutic equivalence as well as safety, efficacy, and significant difference between products but could not explore
good quality.27 In vivo studies, in spite of being essential, any variation with regard to enzyme inhibition. Six stock
may consume unnecessary time, money, and effort in addi- solutions of each product were prepared by using six capsules
tion to involving critical and sensitive ethical considerations of both generic and brand products for ensuring both reli-
(World Health Organization 2006).
ability and to assess any intravariation in the same product
Biowaiver, an alternative in vitro tool to predict drug- (reference again).
product interchangeability, can be granted in some cases, as
As summarized in Table 3 and Figure 3, all products
permitted by the FDA. In fact, the FDA allowed some prod- showed a comparable inhibitory effect at concentrations
ucts to be biowaived, which means that in vivo procedures equal to or higher than 80 µg/mL orlistat (p-value higher
are not an obligatory requirement such as for classes I and than 0.05). This initial and non-significant discrepancy may
III drugs according to BCS. In addition, BE studies can be be due to differences in the grade or ratios of excipients used
waived when the API does not produce measurable concen- in the various manufactured capsules (branded and generic)
trations in an accessible biological fluid. Comparative clinical that may encourage the use of the pharmacodynamic test to
trials, as well as comparative pharmacodynamic studies, are support the conventional drug-release study as the in vitro
further alternative tools to document equivalence in such tool for drug quality testing. In fact, this pharmacodynamic
circumstances.28
Orlistat is a semisynthetic drug that was been approved ability between generics and RLD.23
study was used as surrogate indicator of clinical interchange-
in 1999 by the FDA. It is a hydrogenated form of a natural
Accordingly, the in vitro dissolutions study, as recom-
lipase inhibitor produced by Streptomyces toxytricini.16 mended by the FDA, and pharmacodynamic testing could
Systemic absorption, after oral administration, of orlistat is support each other by using them as a surrogate for orlistat
less than 1%.16 As orlistat acts locally and systemic absorp- BE studies.
tion is unnoticeable,15 in vivo tests are extremely difficult to
conduct because neither the drug nor its metabolite can be Conclusion
detected in the plasma. Therefore, stool analysis to assess the The HPLC analytical method used was suitable for the
percentage of unabsorbed fat is the only in vivo method to qualitative and quantitative analysis of orlistat. The vali-
evaluate the efficacy of the generic orlistat product.20
dation parameters were within the limits specified by the
To the best of our knowledge, it would be very difficult ICH guidelines. The generic products are interchangeable
to find a clinical research center that is suitable to conduct with the branded product, according to the FDA dissolu-
in vivo studies. Accordingly, many regulatory bodies tions method and the pharmacodynamic testing used. Both
including the Palestinian regulation body accept the in vitro in vitro and enzyme inhibition tests support each other as a
analysis of this product. These studies include dissolution surrogate for orlistat BE studies, and even should be used in
comparison between the generic and RLD, conducted in routine analysis to demonstrate the quality of these products.
three different pH media (1.2, 4.5, and 6.8). Our in vitro However, a comparison between in vitro pharmacodynamic
release studies demonstrated the complete release of orlistat studies and in vivo clinical or pharmacodynamic studies are
from the two generic and RLD products when conducted in lacking, which represents a limitation against the use of this
FDA-recommended pH media, which contain 0.5% sodium important in vitro tool. Accordingly, future studies such as
lauryl sulfate. Unfortunately, these results were not sufficient in vitro–in vivo correlation may be conducted to assess the
to support interchangeability because release in media of effectiveness of this test.
other pH, such as acidic and phosphate buffers, was almost
negligible. In fact, these media do not contain sodium lauryl Acknowledgment
sulfate, which is a strong wetting and dissolving agent. The authors thank Linda Isa for technical support during
Accordingly, these results may need further in vivo inves- this project, and Saja Darwish for assistance with language
tigational studies to ensure interchangeability between G1, editing.
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Zaid et al
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15. Zhi J, Melia AT, Eggers H, Joly R, Patel IH. Review of limited systemic
absorption of orlistat, a lipase inhibitor, in healthy human volunteers.
J Clin Pharmacol. 1995;35(11):1103–1108.
16. Al-Suwailem K, Al-Tamimi AS, Al-Omar MA, Al-Suhibani MS. Safety
and mechanism of action of orlistat (tetrahydrolipstatin) as the first local
antiobesity drug. J Appl Sci Res. 2006;2(4):205–208.
Disclosure
Aiman Qaddomi and Yara Abu Zaaror are employees of
Pharmacare PLC, the other authors have no conflicts of
interest in this work.
17. Chen ML, Shah V, Patnaik R, et al. Bioavailability and bioequivalence:
an FDA regulatory overview. Pharml Res. 2001;18(12):1645–1650.
18. Gupta E, Barends DM, Yamashita E, et al. Review of global regulations
concerning biowaivers for immediate release solid oral dosage forms.
Eur J Pharm Sci. 2006;29(3–4):315–324.
19. European Medicines Agency. Committee for medicinal products for
human use (CHMP) 2010. Available from: http://www.ema.europa.
eu/docs/en_GB/document_library/Scientific_guideline/2010/01/
WC500070039.pdf. Accessed December 3, 2016.
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