Transcript Assesment of vinblastine intestinal absorption and

STUDY OF THE EFFECT OF THE XCIPIENT CROSSCARMELOSE ON METFORMIN INTESTINAL
PERMEABILITY BY AN IN SITU INTESTINAL PERFUSION MODEL IN RATS
Aceituno, A. PhD1,2, Dibsi, A., Pharm D1, Gajardo, A., Pharm D.1 & Pezoa, R., PhD2
1 [Universidad de Valparaíso], 2[Instituto de Salud Pública de Chile]
This research work was funded by the University of Valparaiso Research and Development Division and the Public Health Institute of Chile
•simultaneous perfusion of the drug solution and
Crosscarmellose in a whole intestinal segment.
•Assessment of the permeability coefficients,
calculated with and without the excipient co-infusion
of the drug.
Sodium chloride
9,2 g/L
Potassium chloride
0,34 g/L
Calcium chloride
0,19 g/L
Monobasic sodium
phosphate
0,76 g/L
Solution B
Metformin permeability was dependent on the
concentration, therefore the absorption process can be
described as an apparent first order kinetic process
combined with a saturable efflux. The first order kinetics
was used to obtain the first order apparent constants.
9,2 g/L
1/5 M (3,9 mL/L)
Monoacid sodium
phosphate
1/5 M (6,1 mL/L)
Proportion of Crosscarmellose aded
METHODOLOGY
In situ infusion model
An in situ absorption model in rats was used to
evaluate the intestinal permeability of Metformin, a
provisional BCS class III drug. Three drug
concentrations were assayed to investigate on the
passive or active absorption mechanism of the drug:
50, 70 and 100 g/mL. A whole intestinal segment
was isolated in anesthetized Sprague Dawley rats,
washed with an electrolyte solution and cannulated at
both distal ends.
An isotonic buffered solution of Metformin or
metformin plus Crosscarmellose was infused into the
segment with the help of glass syringes, and the
lumen concentration measured by a validated HPLC
technique over a period of 30 minutes at 5 minutes
intervals. At the end of this period, rats were
euthanized following a previously approved protocol.
To investigate the effect of co-infusion of the drug
and Crosscarmellose, a concentration of the
disintegrant was chosen to represent the amount
normally present in conventional tablet formulations.
The effect on the drug absorption and permeability
was evaluated by statistical comparison of the
apparent permeability coefficient of Metformin
measured when infused with and without dissolved
Crosscarmellose.
The mean calculated permeability values of Metformin in
the whole rat intestinal segment showed significant
differences at lower initial drug concentrations (50 and
70 g/mL). Under the experimental conditions, the
absorption of Metformin sulfate cannot be described as a
passive process at these concentrations.
Shown in the next tables are the volumes of
Crosscarmellose added to the Metformin solution
perfunded, keeping in all cases the drug/excipient ratio
close to the one found in conventional formulations of
the drug:
50
70
100
Added volume (mL) of a
0,1 mg/mL
Croscarmellose solution)
0,3
0,4
0,6
The apparent absorption rate constant (Eq. 1) was
calculated by fitting the lumen drug concentration left
versus time data to a first order kinetics process after
correcting the concentration for the passive water
reabsorption. The intestinal permeability values were
calculated considering the relation between ka and Peff
(Eq. 2) where R is the radius of the perfused intestinal
segment.
Ac  A0  e
 ka  t
ka  R
Peff 
2
Equation 1
solucion
50 mcg/mL
50 µg/mLmetformina
metformin solution
solucion metformina 50 mcg/mL + croscarmelosa
50 µg/mL metformin solution + Crosscarmellose
10
5
10
15
20
25
30
Tiempo
time
Figure 1: Average Metformin concentrations in the
luminal intestinal content versus time after
perfusion (50 g/mL)
Metformin solution added with
Crosscarmellose (50 mL total volume)
Metformin concentration
(g/mL)
Concentracion de metformina remanente
en lumen intestinal de rata
100
Log concentration
Log concentracion
(mcg/mL)
•an in situ intestinal perfusion model in rats (close
loop).
Solution A
RESULTS
Concentracion de metformina remanente
en lumen intestinal de rata
100
Log concentration
Log concentracion
(mcg/mL)
To investigate on the permeability BCS classification
of the drug Metformin and to study the effect of the
potential ionic interaction between the excipient
sodium Crosscarmellose (a common tablet
disintegrant) and Metformin in pharmaceutical
formulations by:
The isolated segment was first washed with 30 mL of a
pH 7,4 solution (solution A) with the purpose to
eliminate the remnant intestinal content and 30 mL
solution B, in order to condition the intestinal mucosa
prior to experiments:
Figure 4: theoretical ionic interaction between Metformin
and Crosscarmellose
Metformin predicted and experimental concentrations
at different initial drug concentrations are depicted
(Figs. 1, 2, 3). The determination coefficients of the
first order regression was always higher than 0,95.
Results showed that there was a statistical difference
between the values of Metformin permeability
coefficients when the drug was perfused with or
without Croscarmellose. In the presence of
Croscarmellose, there was a statistically significant
decrease in intestinal permeability at a concentration
of 50 and 70 g/mL (5.4 x 10-5 versus 1.9 x 10-5
cm/sec and 2.0 x 10-5 versus 1.5 x 10-5 cm/sec at 70,
respectively). No difference in permeability coefficients
was found at a concentration of 100 g/mL (table
below). Likewise, there was dependence between the
concentration of perfused Metformin and the
permeability coefficients measured.
Permeability coefficient
(cm/seg) (mean + SD)
Metformin
Metformin +
Crosscarmellose
50
5,4 * 10-5
(3,2 * 10-5)
1,9 * 10-5
(8,7 * 10-6)
 = 0,05
p < 0,05
70
2,0 * 10-5
(1,1 * 10-6)
1,5 * 10-5
(4,9 * 10-6)
 = 0,05
p < 0,05
100
2,4 * 10-5
(7,0 * 10-6)
1,4 * 10-5
(1,0* 10-5)
 = 0,05
p >0,05
Concentratio
n (g/mL)
de metformina
70 solucion
µg/mL metformin
solution 70 mcg/mL
de metformina
mcg/mL + croscarmelosa
70 solucion
µg/mL metformin
solution 70
+ Crosscarmellose
10
5
10
15
20
25
30
Tiempo
time
100
Figure 2: Average Metformin concentrations in the
luminal
intestinal content
versus time
after
Concentracion
de metformina
remanente
perfusion (70en
g/mL)
lumen intestinal de rata
LogLog
concentracion
(mcg/mL)
concentration
PURPOSE
CONCLUSIONS
1.
The rat in situ (close loop) absorption model proved to be
useful to predict potential interactions between drug and
excipients commonly used in tablet formulation
2.
The simultaneous presence of Croscarmellose and
Metformin in a formulation might decrease its absorbed
fraction and probably the bioavailability of poorly
permeable ionic drug.
3.
Crosscarmellose produced a concentration dependant
effect on Metformin intestinal permeability that is
obscured by the concentration dependant permeability of
the drug itself.
solucion
metformina
100 mcg/mL
100
µg/mLde
metformin
soluton
solucion
metformina
100+mcg/mL
+ croscarmelosa
100
µg/mLde
metformin
solution
Crosscarmellose
Equation 2
10
5
10
15
20
25
30
Tiempo
time
Figure 3: Average Metformin concentrations in the
luminal intestinal content versus time after
perfusion (100 g/mL)