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Return
to Pharmaceutical Sciences Transepithelial
transport of (CPT-11); In
vivo-vitro correlations; Duodenal
transfer and metabolism of [3H]tyramine; Genistin
in the isolated rat small intestine.; Interaction
with P-glycoprotein in the rat small intestine.
; Absorption
properties of drugs in isolated rat small intestine.
John Woodley, Laurence Barthe & Georges Houin Equipe: Cinétiques des Xénobiotiques, Faculté des Sciences Pharmaceutiques, 31062 Toulouse Cedex. During the development of drugs and formulations destined for oral administration, it is of considerable value to have reliable and usefully predictive in vitro methods to quantify drug transport across the intestinal epithelium. In recent years, the Caco-2 monolayer has acheived pre-eminence as such a system. There are a number of disadvantages of the Caco-2 system : it is a transformed colon cancer line and the rates of drug transport, especially of hydrophilic drugs, are very slow, and not representative of actual rates in the small intestine, which is the major site of drug absorption. It is also costly and shows considerable variation between different laboratories, making comparisons difficult. We have developed and perfected an 'improved' everted gut sac of rat small intestine, which gives excellent kinetics with very high reliability and reproducibility. Earlier uses of the technique failed because unsuitable incubation media and inappropriate handling were used. We use oxygenated tissue culture media and specific preparation techniques, which ensure high tissue viability for up to 2 hours. The technique can be used to study the transport across the intestine, and into the epithelial cells, of any type of molecule, providing sensitive detection methods are available. Radiolabelling is the most convenient. The system has been used in the past, to study the transport of macromolecules and liposomes, but recently we have concentrated on quantifying the paracellular transport of hydrophillic molecules, and the effect of potential absorption enhancers on this route of absorption. The transport of mannitol, a paracellular marker shows an apparent permeability (Papp ) of 1.5-1.7 x 10-5 cm/sec. This value is the same as that reported by other researchers for low molecular weight hydrophillic drugs in human perfusion studies. Paracellular transport can be enhanced by EGTA, caprate and some synthetic polymers, such as polycarbopols. The toxicity of potential enhancers can be monitored by the release of enzymes from the cells or by histology. Molecules that cross the epithelial barrier by a transcellular route have much higher permeabilities which can also be accurately quantified with the everted sac system. We have also used the sacs to measure absorption at differerent sites in the small intestine, and carried out preliminary experiments on absorption in the colon. The system also has potential to study the first pass metabolism of drugs in the cells of the intestinal epithelium. As an addition to the studies on absorption we also study pre-systemic metabolism, using preparations of intestinal lumen contents and tissues at different pH's. Such studies are very important when evaluating the oral bioavailability of macromolecular drugs such as peptides. We have recently demonstrated that a macromolecular drug was stable in the small intestine, but degraded by prolonged incubation with colon contents, presumably by enzymes from the colonic flora.
Active
transepithelial transport of irinotecan (CPT-1 1)
and its metabolites by human intestinal Caco-2 cells Wataru Yamamoto,1,4 Jaap Verweij, 1 Peter de Bruijn, 1 Maja JA de Jonge, 1
Hiroshi Takano, 2 Masahiko Nishiyama,2 Minoru Kurihara,3 and
Alex Sparreboom1 1Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek) and University. 2 Hospital
Rotterdam, 3008 AE Rotterdam, The Netherlands.
Department of Biochemistry and Biophysics, Research Institute for
Radiation Biology and Medicine, Hiroshima University, 734-8553 Hiroshima, Japan.
3 Department of Internal Medicine, Toyosu Hospital howa University, 135-8557 Tokyo, Japan. 'Present Department of lnternal Medicine, Toyosu Hospital, Showa University, 135-8557 Tokyo, Japan. Irinotecan
(CPT-1 1) is a camptothecin analog with low (about 10-20%) and variable oral
bioavailability in animal models. Here,
Caco-2 ceils were used to evaluate the transepithelial transport of CPT-11 and
its metabolites. Caco-2 cells
demonstrated significant expression of P-glycoprotein (Pgp), multidrug
resistance-associated protein and canalicular multispecific organic anion
transporter. Both the lactone and carboxylate forms of CPT-11 and SN-38 were
actively transported across the cell monolayers, mainly by the apical-localized
P-gp pump. Cellular permeability of CPT-11 at a concentration of 17µM converted
from active to passive diffusional transport between the 2 and 6 h exposure time
points. Anti-proliferative effects
of CPT-11 were related to permeability of the lactone form, whereas for SN-38
efficacy was dependent on lactone accumulation.
Exposure of CPT11 with cyclosporin A significantly enhanced its efficacy,
where as this was not observed with verapamil and R101933.
In contraste SN-38 efficacy decreased in the presence of P-gp inhibitors
due to active transport toward the basolaterai side, thereby reducing drug
accumulation. Hence,
multiple-active transport systems could be demonstrated to be responsable for
not only accumulation profiles but also cytotoxic efficacy of CPT-11 and SN-38
in the intestinal Caco-2 cells. It
is suggested that CPT-1 1 might act in a time-dependent manner and that
SN-38-mediated cytotoxicity relates to (dose dependent) lactone kinetics.
The results detailed in this report could contribute toward the
development of a clinically useful oral formulation of CPT-11 with improved
absorption characteristics and suggest that cyclosporin A is a suitable agent
for further research of this concept.[ 2001 Lippincott Williams &
Wilkins.] Key
words: Caco-2 cells, intestinal transport, irinotecan (CPT11), metabolism Metabolic
pathway of CPT-11
In
vitro-in vivo correlations for lipophilic, poorly water –soluble drugs Jennifer B. Dressman a, Christos Reppas b a Institute of Pharmaceutical Technology, J.W Goethe University, Frankfurt am Main, Germany
b
School of Pharmacy,
National and Kapodistriati University of Athens, Athens, Greece Although
several routes of administration can be
considered for
new drug entities, the most popular remains the oral route. To predict the
in vivo performance of a drug after oral administration from in vivo data, its
essential that the limiting factor to absorption can be modelled in vitro.
In the case of BCS class II drugs dissolution is rate-limiting to
absorption, so the use of biorelevant, dissolution tests can be, used to predict,
differences in bioavailability among different formulations and dosing
conditions. To achieve an a priori
correlation, the composition, volume and hydrodynamics of the contents in the
gastrointestinal lumen following administration. of the dosage form must be
accurately simulated. Four media have been chosen/developed to model composition
of the gastric and intestinal contents before and after meal intake.
These are SGF, milk, FASSIF and FeSSIF, which model fasted and fed state
conditions in the stomach and small intestine respectively.
Using these media, excellent correlations have been obtained with the
following poorly soluble drugs darazo, ketocorazole, atovaquone and troglitazone.
In all cases, fed vs. fasted state effects can be predicted from
dissolution data and, where several formulations were available for testing,
dissolution tests could also be used to determine which would have the best in
vivo performance. 2000
Elsevier Science B.V. All rights reserved. Keywords:
Biopharmaceutics Classification Systern (BCS); Dissolution, In vitro-in vivo
correlations (IVIVC), Lipophilic drugs
J
Pharm Sci 1994 Apr;83(4):549-52 Studies
of tyramine transfer and metabolism using an in vitro intestinal preparation.
FEBS Lett 2000 Jun 16;475(2):127-30 Absorption
and metabolism of genistin in the isolated rat small intestine.
Different
absorption behaviors among steroid hormones due to possible interaction with
P-glycoprotein in the rat small intestine.
Pharmazie 1996 Feb;51(2):101-3
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