Back to the Top
Dear all
The search for the intestinal water rate constant is quite difficult.
The few papers are somehow controversial, because there is some
confound between only water reabsorption measurements with water
reabsorption measurements when sodium or carbohydrated solutions are
perfused into the human intestine.
The papers describing the ADAM model also lack values related to fluid
dynamics.
Can someone please reply with some references
Best regards
--
Nuno Elvas Silva (MSc)
Assistant
Pharmacokinetics Dept.
Faculty of Pharmacy
Lisbon University
Av. Prof. Gama Pinto
1649-003 Lisboa, Portugal
E-mail: nmens.aaa.ff.ul.pt
Site: www.ff.ul.pt
Back to the Top
The following message was posted to: PharmPK
Dear Nuno,
Here is a recent reference that should be helpful:
Sutton, Role of physiological intestinal water in oral absorption,
AAPS J. 2009 available on-line for AAPS members at:
http://www.pharmagateway.net/ThemedIssuePage.aspx?JournalID=12248&CategoryID=244
Best regards,
Walt Woltosz
Chairman & CEO
Simulations Plus, Inc. (NASDAQ: SLP)
42505 10th Street West
Lancaster, CA 93534-7059
U.S.A.
http://www.simulations-plus.com
E-mail: walt.at.simulations-plus.com
Back to the Top
The following message was posted to: PharmPK
Dear Walt
The suggested reference is one of the references with some confounding
issues, as for my understanding. In the appendix it is described from
the experimental procedure and calculations that:were assumed to be approximately 10 ml for duodenum and 39 ml for the
jejunum1 compartments. This was based on the assignment of 10%organ
volume for the small intestine. During the 5 min, 20 ml/min duodenal
infusion, 100 ml was infused into the duodenum, followed by a 40-ml
rinse. During this time, water was absorbed from the duodenum at a rate
of 2.8 ml/min. This water absorption rate was based on a 14 cm length
(default) and a water absorption rate of 12 ml/min/cm determined by
Fordtran (Gastroenterolgy. 50:263-285 (1968)). By the end of the
administration, 14ml water had been absorbed and 140 ml water had been
introduced, giving a net water volume of 126 ml.>
On my undertstanding:
10 mL (basal) + 100 mL= 110 mL. However after 5 minutes only 40 mL were
in the duodenum which means that 70 mL was absorbed. The absorption
rate, therefore must be 14 mL/min (how 2.8 mL/min was calculated?). And
based at 14 cm length for duodenum, the absorption rate for the duodenum
is 1 mL/(min*cm) and not 12 mL/min/cm (which I think the author want to
mean 12 mL/(min*cm).
I'm not able to get the Fordtran paper to check out. But there is
another paper (Gisolfi, C.V., et al., Human intestinal water absorption:
direct vs. indirect measurements. Am J Physiol, 1990. 258(2 Pt 1): p.
G216-22) and a comment from Fordtran to this paper (Fordtran, J.S.,
Measurement of intestinal water absorption. Am J Physiol, 1992. 262(2 Pt
1): p. G377-8) where it is described a net flux of water (mean; SE) of
(9.4; 1.28)mL/(h*cm) (i.e. 0.157 mL/(min*cm))
Facing this different values for small intestine water reabsorption
rate, which one (12 mL/(min*cm) or 0.157 mL/(min*cm)) is the best
estimate?
Best regards
Nuno Silva
Want to post a follow-up message on this topic?
If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Human intestinal water reabsorption rate constant" as the subject | Support PharmPK by using the |
Copyright 1995-2011 David W. A. Bourne (david@boomer.org)