Bioavailability of griseofulvin plain tablets in stomach-emptying controlled rabbits and the correlation with bioavailability in humans


Aoyagi, N.; Ogata, H.; Kaniwa, N.; Ejima, A.

Journal of Pharmacobio-Dynamics 7(9): 630-640

1984


Bioavailability after giving oral doses of 62.5 mg griseofulvin tablets having different dissolution rates to stomach-emptying controlled rabbits, was estimated and compared with that in humans receiving 125 mg dose of the same griseofulvin preparations. The relative differences in Cmax and AUC infinity between the product with the highest availability and others tended to be greater in rabbits than in humans. The in vivo parameters correlated well between the two species. However, power analysis indicated a larger variability of Cmax in rabbits than in other species (dogs, minipigs and humans). Water volume (5 and 50 ml) coadministered with the drug did not significantly influence the bioavailability. The rabbits which were not given food after oral dosing with griseofulvin exhibited a lower Cmax than those which were fed immediately after dosing. The bioavailability of an ultramicronized formulation in rabbits was higher after the postprandial dose than after the preprandial dose. Food intake just after the drug administration seems to be an important factor for controlling the passage rate of the drug through the gastrointestinal tract in stomach-emptying controlled rabbits.

J.Pharm.Dyn.,
7,
630
—640
(1984)
BIOAVAILABILITY
OF
GRISEOFULVIN
PLAIN
TABLETS
IN
STOMACH
-EMPTYING
CONTROLLED
RABBITS
AND
THE
CORRELATION
WITH
BIOAVAILABILITY
IN
HUMANS
NOBUO
AOYAGI,
HIROYASU
OGATA,
NAHOKO
KANIWA
AND
AKIRA
EJIMA
National
Institute
of
Hygienic
Sciences,
Kamiyoga
1-18-1,
Setagaya-ku,
Tokyo,
158,
Japan
(Received
February
15,
1984)
Bioavailability
after
giving
oral
doses
of
62.5
mg
griseofulvin
tablets
having
dif-
ferent
dissolution
rates
to
stomach
-emptying
controlled
rabbits,
was
estimated
and
com-
pared
with
that
in
humans
receiving
125
mg
dose
of
the
same
griseofulvin
preparations.
The
relative
differences
in
Cmax
and
A
UC
c
,
between
the
product
with
the
highest
availability
and
others
tended
to
be
greater
in
rabbits
than
in
humans.
The
in
vivo
parameters
correlated
well
between
the
two
species.
However,
power
analysis
indicated
a
larger
variability
of
C
max
in
rabbits
than
in
other
species
(dogs,
minipigs
and
humans).
Water
volume
(5
and
50
ml)
coadministered
with
the
drug
did
not
significantly
influence
the
bioavailability.
The
rabbits
which
were
not
given
food
after
oral
dosing
with
griseofulvin
exhibited
a
lower
C
max
than
those
which
were
fed
immediately
after
dosing.
The
bioavailability
of
an
ultramicronized
formulation
in
rabbits
was
higher
after
the
postprandial
dose
than
after
the
preprandial
dose.
Food
intake
just
after
the
drug
administration
seems
to
be
an
important
factor
for
con-
trolling
the
passage
rate
of
the
drug
through
the
gastrointestinal
tract
in
stomach
-emptying
controlled
rabbits.
Keywords
—rabbit;
stomach
emptying
rate;
human;
griseofulvin;
bioavailabili-
ty;
fl
uid
volume
effect;
food
effect;
correlation
In
principle,
drug
bioavailability
should
be
es-
timated
in
humans.
However,
frequent
use
of
humans
is
not
only
very
difficult,
but
also
should
be
restricted
particularly
in
the
development
of
new
drugs
and
dosage
forms,
in
order
to
avoid
unpredictable
responses
in
human
volunteers.
This
requires
an
adequate
model
animal
for
bioa-
vailability
studies.
There
have
been,
however,
only
a
few
studies
comparing
drug
bioavailabili-
ty
between
humans
and
model
animals,
which
make
it
difficult
to
estimate
drug
bioavailability
using
animals.
Our
previous
studies
investigated
the
rela-
tions
of
the
bioavailability
of
griseofulvin
in
humans
with
that
in
beagle
dogs'
)
and
in
Gott-
ingen
minipigs
(minipigs
G),
2)
using
the
same
four
kinds
of
commercial
plain
tablets.
The
cor-
relation
of
bioavailability
between
humans
and
dogs
was
poor
due
to
a
relatively
higher
availa-
bility
of
an
ultramicrosize
product
in
dogs
than
in
humans.'
)
On
the
other
hand,
the
correlation
between
humans
and
minipigs
G
was
high,
but
the
relative
differences
in
C
max
and
A
UC
be-
tween
the
product
with
the
highest
availability
and
others
were
smaller
in
pigs
than
in
humans
and,
in
addition,
the
bioavailability
parameters
in
the
pigs,
as
well
as
in
dogs,
were
more
variable
than
in
humans.
2)
This
indicates
that
the
bioa-
vailability
differences
among
products
were
less
detectable
in
minipigs
G.
These
unsatisfactory
results
necessitated
further
investigation
on
other
model
animals.
Recently,
the
usefulness
of
rabbits
for
bioa-
vailability
studies
by
controlling
stomach
-
emptying
has
been
described
by
Maeda
et
al.
3
'
4)
The
present
work
was
undertaken
to
investigate
the
relation
of
bioavailability
between
humans
and
the
rabbits
with
four
types
of
griseofulvin
ta-
blets
which
were
previously
employed
in
the
studies
using
humans,
5)
dogs'
)
and
pigs.2)
Bioavailability
of
Griseofulvin
631
METHODS
Formulations
—Four
brands
of
125
mg
gri-
seofulvin
tablets
employed
in
the
human,"
beagle
dog'
)
and
minipig
G
studies
2)
were
used.
One
of
them
was
an
ultramicrosize
griseofulvin
tablet
(A)
formulated
with
the
drug
dispersed
in
polyethyleneglycol
6000.
6)
The
others
were
microsize
griseofulvin
tablets
(B,
C
and
D)
marketed
in
Japan.
The
drug
contents
for
tablets
A,
B,
C
and
D
determined
by
a
spectrophoto-
metrical
method
7)
were
123,
122,
125
and
128
mg
per
tablet,
respectively.
Table
I
shows
the
dissolution
rates
of
four
gri-
seofulvin
tablets
which
were
expressed
as
the
time
required
for
50%
of
the
drug
to
dissolve.
5)
The
dissolution
rates
by
a
beaker
method
were
determined
in
18
1
of
pH
7.2
sodium
phosphate
buffer
(0.01
M)
contained
in
a
20
1
flat
-bottom
beaker
(29.0
cm
i.d.)
equipped
with
a
three
bladed
screw
type
impeller
(5
cm
diameter)
rotating
at
512
rpm.
In
method
I,
a
tablet
was
gently
shaken
in
1
ml
of
water
in
a
100
ml
round
bottle
fl
ask
for
1
min.
After
standing
for
5
min,
20
g
of
plastic
beads
(8
mm
diameter)
were
added
to
the
bottle.
The
bottle,
fixed
at
an
angle
of
5°,
was
then
rotated
at
3.8
rpm
in
a
water
bath
(37°C)
for
15
min.
The
contents
were
subsequently
poured
into
18
1
of
the
pH
7.2
medium
contained
in
the
20
1
beaker
along
with
100
ml
of
water
used
for
washing.
The
dissolution
rate
was
then
deter-
mined
according
to
the
beaker
method
proce-
dure
outlined
above.
In
method
II,
a
tablet
was
gently
shaken
in
20
ml
of
water
in
a 50
ml
round
bottle
flask
for
5
min
and
then
27
g
of
plastic
beads
were
added.
The
bottle
was
rotated
for
15
min
as
described
in
method
I
and
subsequent
procedures
were
the
same
as
method
I.
Animals
—Forty-two
male
albino
rabbits
(2.5-3.5
kg)
were
used
in
this
study,
eight
of
which
were
for
the
study
of
bioavailabilities
of
four
griseofulvin
tablets,
three
for
the
dose-
bioavailability,
eleven
for
the
effect
of
water
volume
study
and
twenty
for
the
food
effect.
Stomach
-emptying
controlled
rabbits
were
pre-
pared
according
to
the
cangue
method.
8)
Gastric
lavage
was
carried
out
two
days
before
drug
ad-
ministration
with
a
No.
13
Nelaton
catheter
(32
cm
in
length
and
7
mm
in
external
diameter).
A
soft
diet
given
to
rabbits
was
prepared
by
adding
3
parts
water
to
2
parts
special
solid
diet
(CR-S,
Nihon
Clea
Co.
Ltd.,
Tokyo).
3)
Bioavailability
—A
tablet
of
griseofulvin
was
cut
in
a
half
and
the
halved
product
in
the
range
of
50±5%
of
a
tablet
weight
was
used
for
the
in
vivo
study.
A
halved
tablet
was
orally
given
to
eight
rabbits
having
fasted
overnight
in
a
cangue,
together
with
20
ml
of
water,
which
was
immediately
followed
by
feeding
of
50
g
soft
diet
to
the
rabbits.
The
animals
not
consuming
this
amount
of
diet
within
10
min
were
consid-
ered
to
be
in
bad
health
and
excluded
from
the
study.
3)
No
other
food
except
the
soft
diet
was
given
to
the
rabbits
until
24
h
after
drug
admin-
istration,
at
which
time
100
g
of
special
solid
diet
(CR-S)
was
fed.
Oral
administration
was
carried
out
as
follows.
The
tip
(about
1
-cm)
of
a
No.
13
Nelaton
catheter
was
cut
off,
to
which
a
rubber
tube
(3
cm
in
length
and
5
mm
in
internal
diameter)
was
attached.
A
test
product
was
in
-
TABLE
I.
Time
(min)
Required
for
50
%
of
the
Drug
to
Dissolve
Tablet
Method
A
B
C
D
Beaker
14.1
6.5
80.6
157.5
Method
I
6.1
2.5
26.7
4.6
Method
II
2.1
3.2
17.3
6.4
632
N.
Aoyagi,
et
aL
serted
into
the
tube,
which
was
introduced
into
the
stomach
of
rabbits.
The
drug
was
pushed
out
by
means
of
a
smaller
diameter
(3
mm)
teflon
tube.
Water
was
also
given
using
the
same
cathe-
ter.
Blood
samples
were
taken
from
the
ear
vein
at
1,
2,
3,
5,
7,
10,
24
and
31
h
after
dosing,
and
serum
samples
were
stored
frozen
(-20°C)
until
assay.
The
experiments
were
repeated
every
two
weeks
according
to
a
randomized
block
design.
The
serum
drug
levels
were
normalized
for
62.5
mg
dose
of
griseofulvin
with
the
weights
of
the
halved
products.
The
bioavailability
of
each
pro-
duct
was
evaluated
from
the
observed
maximum
plasma
concentration
of
griseofulvin
(
C
max
),
time
to
C
max
(
T
max
),
mean
residence
time
(MR
T)
9,1°)
and
the
area
under
serum
drug
con-
centration
-time
curve
from
zero
to
31
h
(A
UC
31
)
and
zero
to
infinite
time
(AUG
()
)
which
were
calculated
using
the
trapezoidal
rule
and
accord-
ing
to
the
method
of
Wagner,"
)
respectively.
Assay
The
concentration
of
griseofulvin
in
serum
was
determined
by
gas
chromatography
with
a
electron
capture
detector
as
previously
described.
5)
To
0.2
ml
of
serum
were
added
0.2
ml
of
saturated
sodium
chloride
solution
and
5
ml
of
ether.
After
shaking
for
10
min,
4
ml
of
the
ether
layer
was
evaporated
to
dryness
at
about
40°C
under
nitrogen
gas
stream.
The
residue
was
dissolved
in
0.1-1
ml
of
benzene
containing
1.1
µg/ml
clothiapine
as
an
external
standard
and
5
Al
of
the
solution
was
used
for
gas
-liquid
chro-
matography
(GLC)
assay.
The
GLC
condition
was
the
same
as
previously
described.
5)
The
de-
tection
limit
for
griseofulvin
(two
or
three
times
the
noise
level)
was
about
10
ng/ml
of
the
assay
solution.
Dose-Bioavailability
Relation
—Three
stomach
-emptying
controlled
rabbits,
having
fasted
overnight,
were
orally
given
one
or
a
half
tablet
of
product
B,
corresponding
to
125
or
62.5
mg
of
griseofulvin,
respectively,
which
were
then
followed
by
ingestion
of
50
g
of
the
soft
diet.
The
drug
was
administered
at
two
week
intervals
according
to
a
cross
-over
design.
The
other
procedures
were
the
same
as
described
for
the
bioavailability
test.
Effect
of
Volume
of
Water
Coadministered
—A
group
of
six
and
a
group
of
five
stomach
emptying
controlled
rabbits
having
fasted
over-
night
were
used
for
the
tests
of
tablet
A
and
tablet
B,
respectively.
A
half
tablet
of
the
test
product
was
orally
administered
to
a
rabbit
with
5
or
50
ml
of
water
according
to
a
randomized
block
design.
The
rabbits
were
immediately
given
50
g
of
the
soft
diet.
The
drug
was
admins-
tered
every
two
weeks
according
to
a
dosage
schedule.
The
other
procedures
were
the
same
as
described
for
the
bioavailability
test.
Food
Effect
—First,
the
bioavailabilities
after
oral
doses
of
griseofulvin,
with
and
without
food,
were
investigated
using
seven
rabbits.
Ac-
cording
to
a
randomized
block
design,
a
half
tablet
of
product
B
was
orally
administered
along
with
20
ml
of
water
to
a
rabbit
after
having
fasted
overnight.
The
animals
were
im-
mediately
given
50
g
of
the
soft
diet
or
kept
in
a
fasting
state
for
24
h.
The
other
procedures
and
the
time
interval
between
experiments
were
the
same
as
described
for
the
bioavailability
test.
Secondly,
the
bioavailabilities
of
griseofulvin
ad-
ministered
after
food
ingestion
were
investigaed.
A
group
of
seven
and
a
group
of
six
rabbits
were
TABLE
II.
Relations
of
Griseofulvin
Dose
with
Cmax
and
A
UC
c
Dose
62.5
mg
125
mg
Ratio
C.(/uglml)
0.730±0.075
1.501
±0.443
2.05
AUC„,(h
j
ug/m1)
7.097
±1.092
13.835
±1.291
1.95
a)
Means
SE
(n=3).
Bioavailability
of
Griseofulvin
633
used
for
the
in
vivo
studies
of
products
A
and
B,
and
products
B,
C
and
D,
respectively.
A
half
tablet
of
the
test
product
was
orally
administered
to
the
rabbits
having
fasted
overnight
with
20
ml
of
water
30
min
after
ingestion
of
50
g
of
the
soft
diet.
The
experiments
were
repeated
every
two
weeks
according
to
a
randomized
block
design.
The
other
procedures
were
the
same
as
described
for
the
bioavailability
test.
RESULTS
Dose-Bioavailability
Relation
The
relations
of
griseofulvin
dose
with
C
max
and
A
UC
co
were
investigated
using
tablet
B.
The
mean
C
max
and
A
UC
increased
in
propor-
tion
to
the
dose
of
griseofulvin
orally
adminis-
tered
(Table
II),
which
indicates
that
linear
phar-
macokinetics
can
be
applied
to
the
serum
levels
of
griseofulvin
within
the
dose
range
studied.
A
62.5
mg
dose
of
griseofulvin
was
employed
for
the
bioavailability
study
to
avoid
over
-doses
in
the
rabbits°
and
to
compare
with
the
griseoful-
vin
results
reported
by
Maeda
et
al.
who
used
a
62.5
mg
dose.°
Bioavailability
Fig.
1
shows
the
mean
serum
levels
of
griseo-
fulvin
after
oral
administration
of
four
tablets
to
stomach
-emptying
controlled
rabbits
and
Table
III
summarizes
the
in
vivo
parameters.
The
mean
peak
concentration,
A
UC
31
and
A
UC
co
after
ad-
ministration
of
the
griseofulvin
products
were
0.8
0.6
E
0.4
0.2
0
10
20
30
Time
(h)
FIG.
1.
Mean
Serum
Levels
of
Griseofulvin
after
Oral
Administration
of
Four
62.5
mg
Griseofulvin
Tablets
to
Stomach
-Emptying
Controlled
Rabbits
(n=8)
Tablet
A
(•),
tablet
B
(
),
tablet
C
(
A),
tablet
D
(0
).
The
vertical
lines
show
the
standard
errors.
TABLE
III.
Mean
C
max
,
T
max
,
MRT
and
A
UC
after
Oral
Administration
of
Four
Griseofulvin
Tablets
(62.5
mg)
to
Stomach
-Emptying
Controlled
Rabbits
(n=8)
Tablet
Tukey's
A
B
C
D
ANOVA
test
Cm.
(I
-temp
0.599
a)
0.853
0.406
0.530
p
<0.1
(0.108)
(0.164)
(0.089)
(0.101)
T
ma
.
(h)
8.1
4.5
4.1
9.1
NS
b
)
(3.4)
(0.8)
(0.8)
(4.1)
MRT
(h)
11.4
9.0
13.8
13.0
NS
(2.4) (0.9)
(1.8)
(3.0)
AUC
31
(h
µg/ml)
5.139
7.688
3.716
4.826
p
<11.001
B
>A
>D>C
(0.779)
(1.032)
(0.761)
(0.687)
AUC„
(h
mg/m1)
5.276
7.690
4.119
5.461
p
<0.01
B
>D
>A
>C
(0.760)
(1.028) (0.810)
(0.857)
a)
The
figures
in
the
parentheses
indicate
the
standard
errors.
b)
NS:
not
significant
at
p
<
0.1.
c)
Formulations
underlined
by
a
common
line
did
not
differ
significantly
(p
<
0.05).
634
N.
Aoyagi,
etal.
almost
in
proportion
to
their
dissolution
rates
determined
by
method
I.
The
rank
orders
in
C
max
and
AUC
31
among
the
products
were
B
>A
>D
>C
and
that
in
AUG
B
>D
>A
>C,
which
were
similar
to
the
rank
orders
in
C
max
and
AUC
47
.
5
in
humans
(B
>D
>A
>0.
5)
The
mean
peak
concentration,
A
UC
H
and
AUC
„,
after
administration
of
the
product
with
the
highest
bioavailability
(tablet
B)
were
approxi-
mately
twice
as
high
as
those
of
the
product
with
the
lowest
bioavailability
(tablet
C).
Tukey's
multiple
range
test
showed
statistically
significant
difference
in
A
UC
H
between
tablets
B
and
C
and
between
B
and
D,
and
in
AUC
be-
tween
tablets
B
and
C.
Due
to
the
difficulty
of
collecting
the
serum
sample
with
a
constant
time
interval
throughout
the
experiment,
Tmax
is
apt
to
more
vary
depending
on
the
sampling
time
interval
than
C
max
and
AUC.
Assuming
that
the
disposition
and
eliminaton
parameters
do
not
change
in
an
individual,
MRT
as
well
as
T
max
reflects
the
rate
of
drug
absorption
when
evaluating
the
different
oral
dosage
formulations.
12)
MRT
is
preferable
to
T
max
,
because
MRT
is
considered
to
be
less
dependent
on
the
sampling
time
than
that
of
T
max
.
Thus,
MRT
was
also
used
as
the
in
vivo
parameters
to
estimate
the
rate
of
bioavailability
as
T
max
was
employed.
The
rank
order
in
MRT
was
well
agreed
with
that
in
C.
but
the
dif-
ferences
in
MRT
among
the
products
were
not
statistically
significant.
Power
analysis'
3,14)
was
employed
to
estimate
the
total
number
of
rabbits
required
for
a
20%
dif-
ference
in
C
max
,
T
max
and
A
UC
to
be
significant
(a=0.05,
1—/3=0.8)
in
a
randomized
block
design.
These
were
compared
with
the
numbers
of
humans,
dogs
and
Gottingen
minipigs
pre-
viously
studied
2)
(Table
IV),
which
also
showed
the
numbers
required
for
randomized
block
designs.
Compared
with
humans
and
other
ani-
mals,
the
rabbit
study
required
far
more
animals,
about
seventy,
for
a
20%
difference
in
C
max
to
be
significant
due
to
the
large
variabili-
ty.
The
power
analysis
also
indicated
that
the
parameter
of
Tmax
was
more
variable
than
C
max
or
AUC.
Relation
between
Humans
and
Rabbits
The
correlation
of
mean
C
max
,
T
max
and
AUC
from
zero
to
final
sampling
time
between
humans
and
stomach
-emptying
controlled
rab-
bits,
were
investigated.
As
Fig.
2
shows,
the
C
max
in
the
rabbits
was
significantly
correlated
with
that
in
humans.
The
correlation
of
Tmax
between
the
two
species
was
lower
than
that
of
C.
or
AUC.
In
order
to
compare
the
differences
in
C
max
and
AUC
among
products
in
rabbits
with
those
in
humans,
the
ratio
of
mean
C
max
and
A
UC
of
each
product
to
those
of
tablet
B
was
plotted
(Fig.
3).
The
differences
in
the
ratios
of
C
max
and
AUC
co
(conveniently
called
as
the
relative
differences)
between
the
product
with
the
highest
bioavailability
(tablet
B)
and
the
others
tended
to
be
larger
in
the
rabbits.
A
con-
siderably
lower
A
UC
co
in
rabbits
when
using
slow
dissolving
products
as
compared
with
humans
seems
to
indicate
that
the
drug
passed
through
the
absorption
site
without
being
corn
-
TABLE
IV.
Total
Number
of
Animals
Required
for
20%
Difference
to
be
Significant
(
a
=0.05,
1-0=0.8)
Tmax
C
max
AUC
Human
212
18
10
Dog
136
40
60
Minipig
G
60
42
38
Rabbit
334
72
32
a)
AUC
from
zero
to
final
sampling
time;
A
UC47
.
5
for
humans,
A
UC
24
for
dogs,
AUC
32
1br
minipigs
G
and
A
UC
3
i
for
rabbits.
Bioavailability
of
Griseofulvin
C
rna
.
T
max
A
UC
r
=0.964
a
)
10
r
=
0.636
8
r
=
0.853
0.8
D•
8
A
6
0.6
6
D
4
c
4
0.4
0.4
0.6
4
µg/m1
human
6
8
h
635
10
h
µg/m1
12
FIG.
2.
Correlations
of
Cmax,
T„,„
and
A
UC
between
Humans
and
Stomach
-Emptying
Controlled
Rabbits
A
UC
3
,
in
rabbits
and
A
UC
47.5
in
humans
were
employed
for
the
correlation
estimation.
The
solid
lines
show
the
regression
lines.
a)
p<
0.05.
0
C
max
AUC.,
human
rabbit
human
rabbit
1.0
-
B
_
_
0.5
D
B
A
C
B
FIG.
3.
Relative
Differences
in
C
max
and
A UC„„
among
Four
Tablets
in
Humans
and
Stomach
-
Emptying
Controlled
Rabbits
The
ratios
of
C
max
and
AUG
°
of
each
tablet
were
determined
against
those
of
tablet
B.
pletely
dissolved,
which
suggested
a
shorter
length
of
the
absorption
site
for
griseofulvin
and/or
a
faster
rate
of
passage
of
the
drug
in
rab-
bits.
Effect
of
Water
Volume
Coadminitered
The
bioavailability
of
slightly
soluble
drugs,
such
as
erythromycin
stearate
and
amoxicillin,
was
shown
to
be
enhanced
by
administration
together
with
a
large
volume
of
water.
15)
The
effect
of
water
volume
on
the
bioavailability
of
griseofulvin
tablets
A
and
B
in
rabbits
was
inves-
tigated
using
5
and
50
ml
of
water.
As
shown
in
Tables
V
and
VI,
fl
uid
volume
did
not
signifi-
cantly
influence
the
bioavailabilities
after
inges-
tion
of
either
product,
as
was
previouly
shown
in
studies
of
dogs'
)
and
minipigs
G.
2)
Food
Effect
According
to
the
dosing
method
by
Maeda
et
al.,
3)
stomach
-emptying
controlled
rabbits
were
given
drugs
followed
by
immediate
intake
of
a
636
N.
Aoyagi,
et
aL
soft
diet,
the
consumption
of
which
was
used
as
an
index
of
the
rabbit's
state
of
health.
Bioavail-
abilities
were
often
influenced
by
food,'
6)
and
that
of
griseofulvin
was
shown
to
be
increased
due
to
food
intake.'
7
'
18)
Table
VII
lists
the
in
vivo
parameters
measured
after
administration
of
product
B
to
rabbits
with
and
without
food.
Cmax
and
A
UC
after
oral
doses
of
the
drug
which
was
followed
by
food
intake,
were
44
and
26%
higher
than
those
without
food,
respective-
ly.
T
max
and
MRT
did
not
differ
significantly
either
with
or
without
food.
Bioavalability
in
rabbits
when
orally
given
griseofulvin
tablets
30
min
after
being
fed
50
g
TABLE
V.
Mean
Cmax,
T
max
,
MRT
and
AUC
0
after
Oral
Administration
of
Tablet
A
(62.5
mg)
to
Stomach
-Emptying
Controlled
Rabbits
(n=
6)
with
5
and
50
ml
of
Water
Water
volume
Paired
5
ml
50
ml
t
-test
Cmax
(µg/ml)
0.903
±0.115
0.820
±0.077
NS
b
)
T
max
(h)
4.4
±0.6
2.7
±0.1
NS
MRT
(h)
7.7
±1.9
6.0
±1.0
NS
AUG,
(h
µg/m1)
4.763
±0.483
4.197
±0.335
NS
a)
Means
SE.
b)
NS:
not
significant
at
p
<
0.1
by
one
-tailed
test.
TABLE
VI.
Mean
Cmax,
T
max
,
MRT
and
AUC
oo
after
Oral
Administration
of
Tablet
B
(62.5
mg)
to
Stomach
-Emptying
Controlled
Rabbits
(n=5)
with
5
and
50
ml
of
Water
Water
volume
Paired
5
ml
50
ml
t
-test
Cmax
(µg/ml)
0.524
±0.059
0.412
±0.057
NS
b
)
Tmax
(h)
2.0
±0.1
3.2
±0.4
NS
MRT
(h)
4.3
±0.5
5.7
±1.5
NS
A
UC
co
(h
µg/ml)
2.381
±0.293
2.145
±0.239
NS
a)
Means
±
SE.
b)
NS:
not
significant
at
p
<
0.1
by
one
-tailed
test.
TABLE
VII.
Mean
C
max
,
Tmax,
MRT
and
A
UC
after
Oral
Administration
of
Tablet
B
(62.5
mg)
to
Rabbits
(n=7)
with
and
without
Food
Treatment
Paired°
With
fooda
)
Without
food
t
-test
Cmax
(µg/ml)
0.920
±0.173
0.637
-
±0.078
p
<0.1
Tmax
(h)
4.1
±0.8
5.4
±3.1
NS
d)
MRT
(h)
9.1
±1.0
9.6
±1.4
NS
AUC31
(h
µg/m1)
8.227
±1.016
6.536
±1.417
p
<0.1
AUG,
(h
µg/ml)
8.232
±1.014
6.580
±1.450
p
<0.1
a)
50
g
of
soft
diet
was
given
just
after
dosing.
b)
one
tailed
significance
level.
c)
Means
±
SE.
d)
NS:
not
significant
at
p
<
0.1.
Bioavailability
of
Griseofulvin
of
the
soft
diet,
was
investigated.
Figs.
4
and
5
compare
the
mean
serum
drug
levels
between
tablets
A
and
B,
and
B,
C
and
D,
repsectively.
Oral
administration
of
slow
dissolving
products,
C
and
D,
gave
rise
to
an
abnormal
rise
of
the
serum
levels
in
some
rabbits
at
31
h
after
dosing,
probably
due
to
the
effect
of
food
given
24
h
after
dosing.
Tables
VIII
and
IX
list
the
in
vivo
parameters.
Contrary
to
the
in
vivo
results
after
preprandial
dose
(Table
III,
Fig.
1),
the
serum
1.0
4
0.5
E
cu
E
2
10
20
Time
(h)
30
FIG.
4.
Mean
Serum
Levels
after
Oral
Administra-
tion
of
Griseofulvin
Tablets
A
(•)
and
B
( 0
)
to
Rabbits
(n=7)
30
min
after
Food
Ingestion
The
vertical
lines
show
the
standard
errors.
637
levels
at
earlier
time
and
the
C
max
after
a
post-
prandial
dose
of
tablet
A
were
higher
than
those
of
tablet
B,
although
the
differences
were
not
statistically
significant
due
to
the
large
variabili-
ty.
However,
the
postprandial
bioavailabiliy
re-
sults
of
the
other
products
were
similar
to
those
of
the
preprandial
doses,
and
the
ranking,
ac-
cording
to
C
max
and
A
UC
31
,
B
>D
>C.
DISCUSSION
Previous
studies
investigated
the
usefulness
of
beagle
dogs
and
Gottingen
minipigs
as
model
animals
for
bioavailability
studies,
using
griseo-
fulvin
as
the
test
drug.
Since
it
is
a
poorly
water
soluble
compound
and
because
of
its
long
resi-
dence
time
in
the
gastrointestinal
tract,
its
in
vivo
0.6
4
0.4
g
0.2
0
10
20
Time
(h)
30
FIG.
5.
Mean
Serum
Levels
after
Oral
Administra-
tion
of
Griseofulvin
Tablets
B
(O
),
C
(
A
),
and
D
(1=1)
to
Rabbits
(n=6)
30
min
after
Food
In-
gestion
The
vertical
lines
show
the
standard
errors.
TABLE
VIII.
Mean
C
max
,
Tmax
and
A
UC
31
after
Oral
Administration
of
Griseofulvin
Tablets
A
and
B
(62.5
mg)
to
Rabbits
(n=7)
after
Food
Ingestion
Tablet
A
B
ANOVA
C
max
(µg/ml)
1.067
±0.250
0.646
±0.130
NS
b
)
T
max
(h)
6.7
±4.2
7.5
±4.0
NS
AUC
3
,
(h
µg/ml)
6.399
±0.727
5.359±1.572
NS
a)
Means
±
SE.
b)
NS:
not
significant
at
p
<
0.1.
638
N.
Aoyagi,
et
al.
TABLE
IX.
Mean
T„
and
AUC
31
after
Oral
Administration
of
Griseofulvin
Tablets
B,
C
and
D
(62.5
mg)
to
Rabbits
(n=6)
after
Food
Ingestion
Tablet
B
C
D
ANOVA
Cmax
(µg/ml)
0.721
±0.115
a)
0.490
±0.146
0.601
±0.225
NS
b
)
T
ma
(h)
8.2
±4.3
13.2
±5.3
9.5
±4.2
NS
AUC
31
(h
µg/m1)
5.800
-1.772
4.558
±0.943
5.091
±1.151
NS
a)
Means
±
SE.
b)
NS:
not
significant
at
p
<
0.1.
dissolution
and
absorption
is
considered
to
be
in-
fl
uenced
to
a
greater
extent
by
the
physiological
conditions
existing
in
the
gastrointestinal
tracts
of
humans
and
animals
than
are
the
more
soluble
drugs.
In
addition,
the
chemically
neutral
charac-
ter
of
the
drug
can
eliminate
pH
influence
on
its
in
vivo
dissolution,
which
simplifies
dissolution
behavior
in
the
gastrointestinal
tract
and
make
it
easier
to
investigate
the
physiological
factors
af-
fecting
dissolution
except
for
pHs.
The
previous
studies,
however,
did
not
pro-
vide
satisfactory
results.
The
correlations
of
the
in
vivo
parameters
between
humans
and
dogs
were
poor
(
r
=0.388
for
C
max
and
r
=0.306
for
A
UC)
due
to
a
relatively
higher
availability
of
the
ultramicronized
formulation
in
dogs
than
in
humans.
1)
On
the
other
hand,
the
correlation
be-
tween
humans
and
pigs
was
high
(r
=0.934
for
C
max
and
r
=0.937
for
AUC),
but
the
relative
differences
in
C
max
and
AUC
between
the
pro-
duct
with
the
highest
availability
and
the
others
tended
to
be
smaller
in
pigs
than
in
humans,
and
the
variability
of
G
ina)
,
and
A
UC
in
pigs,
as
well
as
in
dogs,
was
larger
than
that
in
humans.
2)
This
indicates
more
difficulty
in
detecting
bioavaila-
bility
difference
between
products
in
minipigs
G
than
in
humans.
Those
unsatisfactory
results
necessitate
further
study
on
other
model
animals.
Rabbits
have
not
been
considered
to
be
useful
for
bioavailability
studies
because
of
slow
gastric
emptying
times.'
9)
For
example,
the
rabbits
after
an
oral
dose
of
griseofulvin
exhibited
a
pro-
longed
plateau
in
the
plasma
concentration
-time
curves
in
a
fasting
state.
20)
However,
Maeda
et
al.
has
developed
a
new
technique
for
promot-
ing
the
stomach
emptying
rate
of
rabbits,
which
is
promising
to
be
useful
for
drug
absorption
studies.
3,4)
In
his
study,
there
was
a
high
correla-
tion
in
the
mean
plasma
levels
from
three
experi-
mental
griseofulvin
tablets
prepared
in
their
laboratory
between
humans
and
rabbits.
4)
In
the
procedure
by
Maeda
et
al.,
drug
administraton
is
designed
to
be
followed
by
feeding.
Food,
how-
ever,
influences
the
in
vivo
dissolution
and
ab-
sorption
of
drugs
in
various
manner."
)
Thus,
the
effect
of
food
in
stomach
-emptying
controlled
rabbits
was
investigated.
The
bioavailability
of
griseofulvin
adminis-
tered
with
food
tended
to
be
higher
than
that
without
food
(Table
VII),
which
suggested
that
food
increased
the
in
vivo
dissolution
and
ab-
sorption
of
griseofulvin
in
the
rabbits
as
pre-
viously
shown
in
humans.
17,18)
The
drug
level
in
the
serum
rose
abnormally
at
31
h
in
some
ani-
mals,
when
the
slow
dissolving
products
were
administered
after
feeding
(Fig.
5).
The
drug
given
after
feeding
will
have
a
tendency
to
remain
in
the
digestive
tract
longer
than
that
given
prior
to
feeding,
and
dissolution
and
ab-
sorption
of
the
remaining
drug
will
be
again
en-
hanced
by
food
given
at
24
h
after
dosing.
While,
the
drug
given
immediately
prior
to
feed-
ing,
according
to
the
dosing
method
of
Maeda
et
al.,
3)
might
move
together
with
the
food
through
the
gastrointestinal
tract,
and
thus,
the
food
seemed
to
control
the
transition
rate
of
the
drug
through
the
tract
of
the
stomach
-emptying
controlled
rabbits.
Bioavailability
of
Griseofulvin
639
The
bioavailability
of
an
ultramicrosize
gri-
seofulvin
tablet
(A)
was
relatively
higher
than
that
of
tablet
B
when
the
drug
was
administered
after
feeding
(Table
VIII)
but
lower
when
ad-
ministered
prior
to
feeding
(Table
III).
The
dif-
ferences
in
C
ma
„,
and
A
UC
31
of
the
ultramicro-
size
product
between
pre-
and
post
-prandial
doses
were
significant
by
Student's
t
-test
at
p
<0.1
and
p
<0.05,
respectively.
In
vitro,
tablet
A
had
tendency
to
form
a
paste
-like
agglomerate
in
the
presence
of
small
quantity
of
water
which
did
not
disperse
well
in
the
dissolution
medium
and
led
to
its
relatively
slow
dissolution
rate
(method
I).
Food
given
prior
to
the
drug
admin-
istration
probably
promoted
the
disintegration
and
dissolution
of
the
ultramicrosize
product
but
not
that
given
after
the
drug.
The
promoting
effect
of
food
on
the
disintegration
of
tablets
was
also
observed
in
a
chloramphenicol
study
in-
volving
humans.
21)
The
correlations
of
C
max
and
A
UC
between
humans
and
stomach
-emptying
controlled
rab-
bits
were
high
(Fig.
2)
and
the
relative
dif-
ferences
in
C
max
and
AUC
between
the
product
with
the
highest
availability
and
the
others
tended
to
be
larger
in
rabbits
than
in
humans
(Fig.
3).
However,
the
variability
of
the
in
vivo
parameters
in
the
rabbits,
as
well
as
in
other
ani-
mals,
especially
that
of
Cmax,
was
larger
than
those
in
humans
(Table
IV).
This
suggests
that
even
though
the
relative
differences
of
A
UC
and
C
ma
„,
between
products
were
larger
in
rab-
bits
than
in
humans,
the
difference
in
rabbits
may
not
be
statistically
significant
unless
many
rabbits
were
used
—more
than
three
times
the
number
of
human
subjects.
The
great
variation
of
C
max
in
stomach
emptying
controlled
rabbits
might
be
due
to
the
variation
of
their
gastric
emptying
rate,
namely,
even
if
the
gastric
emptying
of
rabbits
was
artificially
improved
by
the
procedure
of
gastric
lavage
and
using
a
cangue,
their
gastric
emptying
rate
might
not
be
completely
controlled,
which
seems
to
be
more
variable
than
that
of
humans,
dogs
and
minipigs.
Also,
the
increase
of
the
body
weight
of
rabbits
during
the
experiment
might
contribute
to
the
variation
of
the
parameters.
The
variabilities
of
the
in
vivo
parameters
in
rabbits
will
be,
howev-
er,
able
to
be
decreased
by
improvement
of
the
experimental
conditions,
since,
in
the
rabbit
study,
a
skill
of
gastric
lavage
of
rabbits
and
a
stress
which
would
be
given
to
rabbits
due
to
the
forced
drug
administration
must
affect
the
gas-
tric
emptying
and
the
in
vivo
absorption
of
the
drug,
which
leads
to
the
variation
of
the
in
vivo
parameters.
The
successive
studies
on
the
relation
of
gri-
seofulvin
bioavailability
between
humans
and
animals
lead
to
the
following
conclusion.
Mini
-
pigs
G
and
stomach
-emptying
controlled
rabbits
may
be
useful
to
predict
relative
bioavailabilities
of
an
ultramicrosize
griseofulvin
tablet
and
microsize
ones
in
humans,
judging
from
the
high
correlation
in
the
bioavailability
between
humans
and
those
animals
for
the
four
products.
While
the
use
of
beagle
dogs
may
be
restricted
to
microsize
formulations
only.
Furthermore,
those
animals
including
rabbits
have
a
disadvan-
tage
for
bioequivalence
testing
from
the
view
of
a
sample
size,
because
at
least
two
to
six
-fold
number
of
the
animals
than
that
of
humans
are
required
to
attain
the
same
statistical
power
for
C
max
or
A
UC.
Acknowledgment
We
are
grateful
to
Dr.
T.
Maeda,
Sumitomo
Chemical
Co.
Ltd.
for
technical
instruction
to
prepare
stomach
-
emptying
controlled
rabbits
and
to
Dorsey
Labo-
ratories,
Division
of
Sandoz
Inc.,
for
kindly
donating
PEG
ultramicrosize
griseofulvin
tablet®.
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