Biowaiver monographs for immediate release solid oral dosage forms based on biopharmaceutics classification system (bcs) literature data: verapamil hydrochloride, propranolol hydrochloride, and atenolol
Biowaiver Monographs for Immediate Release Solid OralDosage Forms Based on Biopharmaceutics ClassificationSystem (BCS) Literature Data: Verapamil Hydrochloride,Propranolol Hydrochloride, and Atenolol
H. VOGELPOEL,1* J. WELINK,2* G.L. AMIDON,3 H.E. JUNGINGER,4 K.K. MIDHA,5 H. MO
1RIVM—National Institute for Public Health and the Environment, Center for Quality of Chemical-Pharmaceutical Products,P.O. Box 1, 3720 BA Bilthoven, The Netherlands
2Medicines Evaluation Board in the Netherlands, P.O. Box 16229, 2500 BE The Hague, The Netherlands
3College of Pharmacy, University of Michigan, Ann Arbor, Michigan
4Leiden/Amsterdam Center for Drug Research, Leiden University, Division of Pharmaceutical Technology,P.O. Box 9502, 2300 RA Leiden, The Netherlands
5University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 5C9
6Zentrallaboratorium Deutscher Apotheker, Carl-Manich-Strasse 20, 65760 Eschborn, Germany
7Center of Drug Evaluation and Research, U.S. Food and Drug Administration, Rockville, Maryland
Received 11 June 2003; revised 23 October 2003; accepted 1 January 2004
Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jps.20131
ABSTRACT: Literature data related to the Biopharmaceutics Classification System(BCS) are presented on verapamil hydrochloride, propranolol hydrochloride, andatenolol in the form of BCS-monographs. Data on the qualitative composition ofimmediate release (IR) tablets containing these active substances with a MarketingAuthorization (MA) in the Netherlands (NL) are also provided; in view of these MA’s theassumption was made that these tablets were bioequivalent to the innovator product. Thedevelopment of a database with BCS-related data is announced by the InternationalPharmaceutical Federation (FIP). ß 2004 Wiley-Liss, Inc. and the American PharmacistsAssociation J Pharm Sci 93:1945–1956, 2004Keywords:
BCS; biowaiver; verapamil; propranolol; atenolol
met considerable interest. A biowaiver impliesthat bioequivalence (BE) assessment studies are
In recent years the necessity to provide a scientific
waived for marketing authorizations (MA) by
basis for biowaivers for individual substances has
Health Authorities for a new tablet or capsule,or a new formulation of an existing immediate
*This article reflects the scientific opinion of the authors
release (IR) dosage form, and hence the product is
and not the policies of regulating agencies.
considered bioequivalent to its reference product,
Correspondence to: Dirk M. Barends (Tel: þ31 30 2744209;
without carrying out a BE study. In this case the
Fax: þ31 30 2744462; E-mail: [email protected])
comparative in vitro study assures BE of the test
Journal of Pharmaceutical Sciences, Vol. 93, 1945–1956 (2004)ß 2004 Wiley-Liss, Inc. and the American Pharmacists Association
product. The scientific basis for this work was
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
developed by Amidon et al.1 and is known as the
The present article summarizes and discusses
Biopharmaceutics Classification System (BCS).
the main features obtained from the literature
The BCS states that three major factors govern
the rate and extent of drug absorption of IR solidoral dosage forms: dissolution rate, solubility, andintestinal permeability. For IR dosage forms
containing active pharmaceutical ingredients(APIs) showing high solubility, high intestinal
A literature search was performed in electroni-
permeability, and rapid dissolution a waiver from
cally available databases. The search performed
performing BE studies (biowaiver) can be scien-
included information from the Merck Index, the
Dictionary of Substances and their Effects, the
In the regulatory domain this is adopted by both
Hazardous Substances Data Bank, Medline, Tox-
line and Embase. Only literature published in the
Guidance for Industry: Waiver of In Vivo Bioavail-
last 10 years and written in English or German
ability (BA) and BE Studies for Immediate-Release
was included. When searching for dissolution and
Solid Oral Dosage Forms Based on a BCS,2 and the
solubility data, two problems occurred. The
Note for Guidance on the Investigation of BA and
search resulted in a large number of hits so that
BE,3 respectively, together referred to as the
a detailed study of all references on relevant data
Guidances. In particular the FDA document
was considered to be too time consuming, and
describes in detail the data that are necessary for
secondly almost all literature was related to
a successful application for a biowaiver.
modified release dosage forms. Therefore, the
When a set of BCS-data for an API is established
decision was made to use, in general, only data
and could be made publicly available in the form
obtained form standard reference books like the
of a monograph, this monograph could be referred
United States Pharmacopeia (USP) and European
to by subsequent applicants for biowaivers of
other IR oral dosage forms with the same API
For data on permeability the literature search
without the need for reestablishing the data. Such
was performed in the same way as described above,
a publicly available BCS-monograph is also of
limiting the keywords to permeability and related
interest for Official Medicines Control Labora-
to permeability, and the drug substance name. The
tories (OMCL’s), which want to translate their
outcome of the search was satisfactory and
dissolution test data into terms of the BA of the
sufficient. Relevant literature on all three sub-
To explore the scope and the possibilities of
It is known that dissolution and permeability of
gathering BCS related data from scientific litera-
an API can be influenced by excipients in the solid
ture, and in order to set up such BCS-monographs,
oral dosage forms. In order to gather insight of
a literature search was carried out on verapamil
possible excipient interactions tablet compositions
hydrochloride, propranolol hydrochloride, and
of generic formulations registered in NL were
examined. The qualitative composition of the IRtablets containing one of the three active sub-stances was obtained from the publicly available
Summary of Product Characteristics (SmPC). TheSmPC’s can be obtained from the website of
Both chemical–pharmaceutical and pharmacoki-
the Medicines Evaluation Board in NL at www.
netic BCS-related information on three sub-
cbg-meb.nl. Only the excipients used in the tablet
stances, verapamil hydrochloride, propranolol
cores were considered since we made the assump-
hydrochloride, and atenolol, was obtained by
tion that the tablet coating for an IR tablet will be
means of a literature search. The following data-
of very limited influence on the dissolution proper-
fields were defined in order to standardize the
dataset: indication, solubility, dissolution, poly-
The International Pharmaceutical Federation
morphism, partition coefficient, pKa, available
(FIP) will post these monographs on its website at
dose, permeability, stereospecificity, pharmacoki-
www.fip.org. Additional information will be pub-
netic properties. In addition, the qualitative
lished and discussed in the form of Addenda to
composition of IR tablets having an MA in the
these monographs. The corresponding author of
this article can be contacted for any contribution.
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
BIOWAIVER MONOGRAPHS FOR VERAPAMIL, PROPRANOLOL, AND ATENOLOL
Dr. C.A.M. Versantvoort on their comments on
a of 8.6,8 and a range 8.6 – 8.9, respectively,
The BCS-monographs of each of the three sub-
stances are presented and discussed separately.
Strengths currently having an MA in NL: 40, 80,
Verapamil hydrochloride is a well-known calciumantagonist. It is used in the treatment of angina
The permeability data found for verapamil are
After oral administration of a mixture of R- and S-
verapamil, plasma concentrations of the R-isomer
were substantially higher than those of the S-
The Analytical profiles of drug substances,
isomer, suggesting stereospecific first-pass meta-
(Volume 17)7 contain a profile for verapamil
hydrochloride. The solubility of verapamil hydro-chloride as a function of the pH is shown in Table 1.
Oral absorption of labeled 14C-verapamil in man
No reference to polymorphic forms was found.
averaged over 90%. The absolute BA is 10–20%,indicating extensive first-pass metabolism.4,16
Peak plasma concentrations are reached within1–2 h after administration of a single dose.17,18
Kasim et al.8 calculated n-octanol/water partition
Pharmacokinetics shows a large inter-individual
coefficients using different fragmentation meth-
ods that were based on atomic contributions to
Food intake prolonged the time to peak concen-
lipophilicity; for uncharged verapamil, log p
values of 4.47 and 5.69 were reported.
area under the curve (AUC) of both isomers.20
The apparent volume of distribution of verapamilis about 2.5 L/kg. Protein binding is moderate
(90%),4 not concentration dependent over the
range of 10–2000 ng/mL16 and similar for both
enantiomers.21 Verapamil binding to red blood
Verapamil is extensively metabolized in the liver,
primarily by N-dealkylation and O-demethyla-
tion. Nor-verapamil is the only active metabolite
formed. Further metabolism results in the form-
ing of several metabolites that are excreted as
inactive conjugates. There is a wide interpatient
A 0.1 N NaOH solution and a 0.1 N HCl solution were used
variation in verapamil metabolism consistent
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
a95% confidence interval; concentrations are concentrations of the racemate.
with the fact that verapamil undergoes extensive
dissolved in 30 min in 900 mL 0.01 N HCl, using
first-pass extraction. Urinary and fecal excretion
account for about 70 and 15%, respectively, ofverapamil over 5 days. An average of 3% of theparent drug is recovered unchanged in the urine.
The elimination half-life is about 4–5 h, and issimilar for the R- and S-isomer.23
The solubility values observed are critical at a pHat or above 6.76. When the current solubility
A number of different excipients are used in the
criteria of the Guidances for the highest dose
manufacturing of IR verapamil hydrochloride
strength (120 mg) in 250 mL or less of aqueous
tablets. The excipients used in the formulation
media over the pH range of 1–7.52 or 8.0,3 are
of the core of the IR tablets having an MA in NL
strictly applied, verapamil hydrochloride fails to
meet these criteria. At pH 7.32 the solubility isabout equivalent to the minimally required
solubility of 0.48 mg/mL (120 mg/250 mL). Athigher pH values the solubility will be below
The USP 26 specification for verapamil hydro-
the minimal limit of 0.48 mg/mL. However, since
chloride tablets is not less than (NLT) 75% (Q)
the major fraction of the drug substance will beabsorbed in the upper part of the gastrointestinal
(GI) tract where the pH value will normally be
below 7.3 the limited solubility at high pH values
is considered to be of no concern. This is also
supported by a recent proposal to narrow the
required pH range for sufficient solubility from
Croscarmellose sodiumFurcelleranaGelatine
Lactose anhydrate/monohydrateMagnesium stearate
The requirements of the USP 26 differ from the
stricter and more extensive requirements of the
Guidances. They serve however a different pur-
pose. The criteria defined by the Guidances aim to
assure BE with a reference product, in the context
of a regulatory decision, while the USP criteria
define the attributes for an acceptable article. In
the preface of the USP 2426 the goal of the method
aFurcelleran is also known as Danish Agar or Danagar.
was described, which was essentially: to set
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
BIOWAIVER MONOGRAPHS FOR VERAPAMIL, PROPRANOLOL, AND ATENOLOL
standards for ‘‘clinically acceptable articles’’
The observed high permeability of verapamil is
by defining a dissolution method that is suffi-
in line with the reported oral absorption of about
ciently discriminating so that both BA and quality
90%. The presence of an absorption window cannot
control is covered. This paragraph was deleted
be ruled out from the literature data reviewed here
starting with the USP 25, but it seems safe to
but the postulated mechanism of the permeability
assume that the USP 26 still aims at clinically
of verapamil, being passive transport, makes such
sufficient BA, which is less strict than bioequiva-
lent towards a reference product. For verapamil
In the IR verapamil hydrochloride tables which
hydrochloride tablets the USP 26 prescribes
have an MA in NL, and hence are assumed to be
900 mL of 0.01 N HCl as dissolution medium.
bioequivalent to the innovator’s product, a wide
Given the limited solubility at higher pH values of
range of excipients are used (see Table 3). This
this API, testing at a pH of 6.8–7.5 seems more
provides evidence that for the usual pharmaceu-
discriminative. However, the solubility of this API
tical excipients no effect on the extent (and rate) of
will not be the limiting factor at this pH-range.
absorption is to be expected. However, it should be
The decisive factor for the BA of an IR solid
kept in mind that this holds only for excipient
dosage form with this API will be the dissolution
amounts which are normally used in IR tablet
rate. This parameter is suitably controlled by the
formulations. In addition, for highly soluble and
USP 26 method, which makes it highly likely
highly permeable drug substances, formulated
that an insufficient dissolution from the for-
into IR tablets with known excipients, it has been
mulation will be detected. So, the practice to
reported that no excipient interaction in the rate
carry out the batch to batch dissolution testing
and extent of absorption is to be expected.2
according to USP 26 once a formulation has been
In conclusion, when the criteria of the Gui-
shown to be bioequivalent to the reference
dances are strictly applied, verapamil hydrochlor-
formulation by a BE study or by comparative
ide is a BCS Class II substance and this API can not
dissolution studies is supported by the BCS-
be considered a candidate for granting a biowaiver.
However, this API is clearly on the borderline, theonly problematic area is the insufficient solubilitybetween pH 7.3 and 8.0. In vivo the limited
solubility in this pH interval will not be proble-
In the Guidances the term ‘‘highly permeable’’ is
matic. This means that the solubility boundaries
used for substances whose absorption in humans
for this API should be redefined to for instance
from an orally administered dose is 90% or more.
1.0–6.8, as is recently suggested in general.25 In a
The work of Amidon et al.1 has demonstrated that
provisional classification of the WHO Essential
the limit for absorption of >90% corresponded
Drugs, verapamil was classified to be BCS Class I.8
with a permeability >2.10À4 cm/s (Attachment A
So, from a scientific point of view, verapamil
hydrochloride is a candidate for granting a bio-
On the basis of the data presented in Table 2
waiver when the IR tablets are formulated with
verapamil can be considered as a highly permeable
well-known excipients, show rapid in vitro dis-
solution, and meet the dissolution profile compar-
Verapamil is passively transported and is a
ison criteria as defined in the Guidances, but with
substrate for P-gp. The effect of P-gp on verapamil
a redefined upper boundary for the pH of 6.8. The
absorption is low, due to the high permeability of
USP 26 criteria and method are suitable to assure
the drug. At high doses the efflux-mediated
mechanism by P-gp becomes saturated and there-fore effective permeability (Peff) increases.11 Nodifference in Peff is observed between R- and S-
Permeability values obtained in vivo by the
intestinal perfusion technique were comparablewith the Peff obtained by Caco-2 cell line studies.
Propranolol hydrochloride is a well-known non-
Permeability values of verapamil, obtained from a
selective b-blocker, which is used in the manage-
correlation of partition coefficients versus intest-
ment of angina pectoris, hypertension myocardial
inal permeability, also suggest a high permability
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
The presence of an absorption window cannot be
ruled out from the data reviewed here but the
Soluble (1 g dissolves in 10–30 mL) in water.5,6
postulated mechanism of the permeability of pro-pranolol: passive transport driven by the strong
lipophilic nature of the substance, makes the
Propranolol hydrochloride is known to have two
existence of such an absorption window unlikely.
Propranolol is rather rapidly distributed over
Kasim et al.8 calculated n-octanol/water partition
tissues. It is highly lipophilic and moderately
coefficients using different fragmentation meth-
bound to plasma proteins (80–95%), mainly to a-1
ods that were based on atomic contributions to
acid glycoprotein. The distribution volume is
lipophilicity; for uncharged propranolol, log p
about 4 L/kg. Studies in animals showed that
values of 2.75 and 2.65 were reported.
propranolol is distributed into the lungs, liver,kidneys, brain, and the heart.37–39
A pKa range of 9.03–9.09 was reported.9
Propranolol is almost completely metabolized in
the liver. Only a small portion of the administereddose is excreted unchanged in urine and feces (1–
Strengths currently having a MA in NL: 10, 40,
4%). The main metabolites are naphtoxyl acetic
acid (42%), 4-hydroxypropranolol (41%), andpropranolol-O-glucuronide (17%). 4-hydroxy-pro-
pranolol is pharmacologically active and is equi-
The permeability data found for propranolol are
potent to the parent drug. However, due to rapid
conjugation, the contribution to the pharmacolo-gical effect is low. The main metabolites are
metabolized by cytochrome P450. Propranololand its metabolites are mainly excreted in
urine (>90%). The elimination half-life is about
Propranolol is almost completely absorbed after
oral administration (>90%). Peak plasma concen-trations are reached within 1–2 h after adminis-
tration of a single dose. The absolute BA variesbetween 5 and 50%, due to a high pre-systemic
The excipients used in the formulation of the core
metabolism. As a result, the BA and plasma levels
show a large inter-individual variability.36–38
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
BIOWAIVER MONOGRAPHS FOR VERAPAMIL, PROPRANOLOL, AND ATENOLOL
Using the Caco-2 cell lines, comparable perme-
ability values were found (see Table 4). At a pH of
Carboxymethylcellulose sodiumCellulose (microcrystalline)
5.4 permeability decreases at the apical (i.e., the
luminal) site,41 but still takes place although the
unionized fraction is very small (this is also
the case at a pH of 7.2). This is probably due to
the fact that the paracellular route represents a
relatively small fraction of accessible area of the
cell monolayer. Beside this, propranolol is lipo-
philic enough to take advantage of the large sur-
face area for transcellular permeation.31 Using a
different cell line, TC-7 (which is a clone of Caco-2,
displaying increased tauro-cholic acid transport)
Adding plasma to the basolateral chamber does
not influence the Peff of propranolol, due to its highlipophilicity. However, propranolol is avidly boundto plasma protein, and this resulted in a significant
decrease of the exsorption (from basolateral toapical) of propranolol.33
The USP 26 specification for dissolution of
Permeability values obtained in vivo by the
propranolol hydrochloride tablets is NLT 75%
intestinal perfusion technique were about 10–20-
(Q) dissolved in 30 min in 1000 mL of dilute HCl
fold higher than obtained by Caco-2. This differ-
using the basket method operated at 100 rpm.
ence is less than observed for atenolol (see further,up to 500-fold). As propranolol is a highly lipophilicdrug, and transported transcellularly, factors
influencing permeability in vitro versus in vivowill be less pronounced or even lacking.
The high permeability of propranolol is in line
The pKa value of propranolol is about 9.05. At a
with the reported high oral absorption of more
pH of 7.2, it is reported that propranolol is highly
soluble. Therefore, solubility will not be the rate-
Given the high permeability of propranolol, it is
limiting step in the absorption process of propra-
considered unlikely that excipients should have an
effect on the permeability and hence have aninfluence on the rate and extent of absorption,provided that rapid and complete dissolution over
the physiological pH-range has been demon-
The differences in purpose between the dissolu-
strated. This is substantiated for the excipients
tion tests of the Guidances and the USP were
of the IR tablets which have an MA in NL as listed
discussed under ‘‘verapamil hydrochloride.’’ For
propranolol hydrochloride solubility within the
In conclusion, according to the criteria of the
physiological pH is not critical, so the dissolution
Guidances, propranolol hydrochloride is a BCS
rate of the formulation will be the decisive factor
Class I substance. In a provisional classification of
for BA of this API. The USP 26 dissolution
the WHO Essential Drugs, this API was also
method, using dilute HCl as dissolution medium,
classified to be BCS Class I.8 So, from a scientific
can be expected to control insufficient dissolution
point of view this API is a candidate for granting a
from the formulation. So, the practice to carry out
biowaiver when the IR tablets are formulated with
the batch to batch dissolution testing according to
well-known excipients, show rapid in vitro dis-
USP 26 once a formulation has been shown to be
solution, and meet the dissolution profile compar-
bioequivalent to the reference formulation by a
ison criteria as defined in the Guidances. The USP
BE study or by comparative dissolution studies is
26 criteria and method are suitable to assure batch
supported by the BCS-characteristics of this API.
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
The permeability data found for atenolol are
Atenolol is a cardio selective b-blocker, widelyused in the management of hypertension, angina
pectoris, cardiac arrhythmia’s, and myocardial
Following oral administration about 46–62% of aradio-labeled dose is absorbed.4 Peak plasma con-
centrations are reached within 2–4 h after admin-
Sparingly5 (1 g dissolves in 3–100 mL) to
istration of a single dose.4 Atenolol plasma
slightly6,42 (1 g dissolves in 100–1000 mL) soluble
concentrations increase proportionally to the dose.
In BA studies in healthy subjects in which the AUC
after orally and intravenously administration of
pH ¼ 1.243 and 2.48 g/100 mL in 0.2 M KH
atenolol was compared, an absolute BA of 40–60%
was reported. Since only 10% of an intravenousdose, but about 50% of an oral dose is excreted in thefeces, biliary excretion appears to be minimal and
the limited BA is thus probably due to incomplete
No reference to polymorphic forms was found.
absorption.51–54 Stereoselective oral BA has beenindicated, as it has been observed that the amount
excreted unchanged in the urine, the AUC and thepeak concentrations differed between the enantio-
Partition coefficients of 0.008 at pH 7.0 and 0.052
mers.55 Food intake significantly shortened the
at pH 8.0 (n-octanol/phosphate buffer (0.16 M))
time to peak concentration and also caused a
were reported.6,42 Kasim et al.8 calculated n-
significant reduction in the AUC values (about
octanol/water partition coefficients using differ-
20%), while the elimination half-life remained
ent fragmentation methods that were based on
atomic contributions to lipophilicity; log p valuesof À0.11 and 0.50 were reported.
Atenolol is relatively widely distributed, with an
apparent volume of distribution of 50–75 L.
Protein binding is low and in the range of 6–
Strengths currently having an MA in NL: 25, 50,
Atenolol is mainly excreted unchanged in urine in
man.4 Small amounts of the glucuronide metabo-
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
BIOWAIVER MONOGRAPHS FOR VERAPAMIL, PROPRANOLOL, AND ATENOLOL
according to the Guidance for Industry2 is defined
as the highest dose dissolvable in 250 mL or less. Based on the limited information available with
regard to atenolol solubility at different pH’s, the
Cellulose (microcrystalline)Colloidal anhydrous silica
solubility of atenolol is not expected to be the rate-
limiting step in the absorption of atenolol from the
HypromelloseLactose anhydrate/monohydrate
The differences in purpose between the dissolu-
tion tests of the Guidances and the USP were
discussed under ‘‘verapamil hydrochloride.’’ For
atenolol solubility within the physiological pH
range is not critical, so the dissolution rate of the
Pregelatinized (maize) starchSodium lauryl sulfate
formulation will be the decisive factor for BA of
this API. The USP 26 dissolution method, using
900 mL acetate buffer pH 4.6 as dissolution
medium, can be expected control insufficientdissolution from the formulation. So, the practiceto carry out the batch to batch dissolution testingaccording to USP 26 once a formulation has been
lite (ca. 2%) and of the non-conjugated hydro-
shown to be bioequivalent to the reference
xylated metabolite (2–3% of the 14C-labeled dose
formulation by a BE study or by comparative
after oral administration and 5.8% after i.v.
dissolution studies is supported by the BCS-
administration) have been reported in the urine
Excretion is essentially complete after 48 h after
administration of a single dose.56 The total bodyclearance of atenolol is about 100 mL/min/1.73 m2
On the basis of the data in Table 6, in accordance
and the elimination half-life is 6–9 h.57
with the definition of permeability in the Gui-dances, atenolol can be considered as a lowpermeable drug substance.
The Caco-2 cell drug transport studies showed
The excipients used in the formulation of the core
comparable permeability values. A value of about
of generic IR atenolol tablets marketed in NL are
3.7 Â 10À6 cm/s was found by Rubas et al.47 that
was significantly higher than those values re-ported by the other groups. The cause of this highpermeability value is not clear from the report.
Permeability values obtained in vivo by the
The USP 26 specification for dissolution of
intestinal perfusion technique were up to 500-fold
atenolol tablets is NLT 80% (Q) dissolved in 30
higher than those obtained by Caco-2. Factors that
min in 900 mL acetate buffer pH 4.6, using the
may explain the observed difference are: firstly,
atenolol is a hydrophilic drug that is transportedvia the paracellular route through tight junctions. A higher permeability observed in the intestinalperfusion technique may be due to a lower
paracellular transport and/or a larger area avail-able for absorption in vivo in humans, as it is
assumed that the absorption of hydrophilic com-
Atenolol with a pKa value of 9.6 is expected to be
pounds is so slow that a larger surface area of the
sufficiently soluble under physiological condi-
intervillous space is exposed.48,49 Secondly, the
tions. The highest tablet strength dissolves in
intestine has mucus producing goblet cells, which
about 25 mL of water at pH 7.4. ‘‘Highly soluble’’
influence the tight junctions. When Caco-2 cells
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 93, NO. 8, AUGUST 2004
are mixed with mucus producing cells (HT29-
MTX), permeability of atenolol increased.30 Whenmucus-producing cells were used instead of Caco-
1. Amidon GL, Lennerna¨s H, Shah VP, Crison JR.
2, permeability increased up to 30-fold.45 Thirdly,
1995. A theoretical basis for a Biopharmaceutics
differences in extracellular Caþþ-concentrations
Drug Classification: The correlation of in vitro drug
can lead to a change in the integrity of the cell
product dissolution and in vivo bioavailability.
structures, thereby causing a change in the
paracellular permeability of atenolol. It has been
2. U.S. Department of Health and Human Services
reported that by lowering the (free) extracellular
Food and Drug Administration Center for Drug
Caþþ-concentration, the permeability of atenolol
Evaluation and Research (CDER). 2000. Guidance
increased about 7-fold.27 Finally, cell tissue of
for industry: Waiver of in vivo bioavailability and
intestine has a transepithelial electrical resistance
bioequivalence studies for immediate-release solid
(TEER) of 50–100 OÁcm2.46 Caco-2 cell lines have a
oral dosage forms based on a Biopharmaceutics
TEER of >200–300 OÁcm2. Atenolol, having a low
3. Committee for Proprietary Medicinal Products
permeability and being paracellularly trans-
(CPMP). 2001. Note for guidance on the investiga-
ported, the higher TEER of Caco-2 cells may
tion of bioavailability and bioequivalence.
contribute to the lower permeability when com-
4. Martindale. The extra pharmacopoeia, 31st edn.
Royal Pharmaceutical Society, London, UK: Royal
The data obtained with the intestinal perfusion
technique are in reasonable agreement. On the
5. European Directorate for the Quality of Medicines.
average, a value of 2.10À5 cm/s is found, demon-
European pharmacopoeia, 4th edn. Strasbourg,
strating that the permeability of atenolol is low.
France: European Directorate for the Quality of
The low permeability of atenolol is in line with
Medicines, Council of Europe, Strasbourg, France.
the reported moderate oral absorption of about
6. Merck Index CD-ROM version 12:1, Merck & Co.
7. Chang ZL. In: Florey—Analytical profiles of drug
In the IR atenolol tables which have an MA in
substances, Vol. 17. London, UK: Academic Press.
NL, and hence are bioequivalent to the innovator’s
8. Kasim NA, Whitehouse M, Ramachandran C,
product, a wide range of excipients is used (see
Bermejo M, Lennerna¨s H, Hussain AS, Junginger
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Visit by New Zealand Track II Delegation for Inaugural India-New Zealand New Zealand Delegation Dr Richard Grant, Executive Director, Asia New Zealand Foundation (Leader of Mr Brian Lynch, Director, New Zealand Institute of International Affairs (mob. +64 27 445 2958) (arrive on 5 Dec in Delhi, overnight at Hotel Pooja Palace,15A/11 WEA Puja Park,Karol Bagh. Tel 2574 5275(76) Professor Xiaomi
VOLUNTARY SECTOR Introduction Voluntarism is an integral part of Indian society and dates back to ancient times when it operated in the fields of education, medicine, cultural promotion, and in crises such as droughts and famines. Modern indigenous forms of voluntary organisations began to appear in the colonial period. According to the World Development Report (World Bank, 1993),"