Dear Group,Back to the Top
I have got problem in keeping rat alive in my experiments, I use
pentobarbital to have the animal anaesthesized, but it is dead after
1 hour. I need to keep it alive 2h or more. any suggestions will be
Thanks in advance
[A smaller loading dose with additional small doses after a brief
period may help, no more details since it has been a little since I
used pentobarb, any better anesthetics?, ask your Animal Use Committee
for advice - db]
Dilute the 50 mg/ml to 25 mg with saline, if a rat weighs 250 mg useBack to the Top
0.3 ml and give 0.1 ml when animals gets "light". Dose initially via
the I.P. route, cannulate jugular vein for further use.
Dear PravinBack to the Top
You may use Propofol inj in small doses
Dear Parvin,Back to the Top
It is not very clear whether your experimental
protocol involves any surgery in rats.However in my
experience, Ketamine at the dose of 60 mg/kg,i.p in
combination with Xylazine at 7.5 mg/kg, i.p produces
an anesthetic effect for not less than 1 hr and
undoubtfully you can recover the animals without any
S Syed Mustafa,
Drug Metabolism & Pharmacokinetics,
Dr Reddy's Research Foundation,
Bollaram Road, Miyapur,
Dr Parvin,Back to the Top
I have not followed the complete string on your question and study
Nevertheless, keep in mind that the anesthetic used may alter the
pharmacokinetic profile obtained; thus, selection of an anesthetic that
does not alter the normal body functions is important (or at least its
clearance/biodistribution effects are minimal and well
understood/documented). If the proposed study is part of a series, I
would recommend that you use the same anesthetic used before to avoid "odd"
data or lengthy explanations and/or repeating studies.
There are several articles that compare different commonly used
anesthetics and how these affect drug PK profiles in the same animal model.
Regards and best of luck,
Dr Alfredo R. Sancho,
To that effect it is likely preferable to use anesthetic that are notBack to the Top
metabolized by the liver and are excreted unchanged, secondly
anesthetic affecting blood pressure and blood flow might also affect Pk
profile. Isoflurane is a good anesthetic agent that is poorly
metabolized and excreted unchanged. Assuming you have a decent
ventilation system for the users, it can be used as for ether with an
open system with saturated gauzes applied close to animal's nose
altough the ultimate system would be a standard anesthesia system (Bain
circulation sytem) adapted to rodents.
Biopharmacopae Design International
Dr Moreau,Back to the Top
More food for thought...
In the selection of an anesthetic for an animal study, one should
consider various issues, including the route/s of elimination of the drug being
studied (i.e., renal, respiratory, and/or fecal) as well as the
appropriateness of the animal model itself.
For instance, if the drug is mainly eliminated via renal function and
the selected anesthetic gravely reduces the renal function, this will
affect the calculated PK parameters. These calculated values may lead to incorrect conclusions and/or misguided decisions for future studies.
If all anesthetics available have an effect on the physiological
processes and/or the pahtophysiology being studied, then the anesthetic best
understood and which has the least effect on key processes should be
selected. Moreover, this anesthetic should be used consistently in all
the animal studies for that drug development. Additionally, one may end up
doing comparative small/pilot studies to demonstrate the anesthetic's
effect and/or clarify any inconsistencies in the obtained parameters.
Documentation of why a particular anesthetic was selected and how it's
effects were addressed may be necessary, particularly if the initial
human pk results are very different than those from animals.
Dr Alfredo R. Sancho,
Hello Dr. Parvin-Back to the Top
Sorry to hear about your difficulties with pentobarbital. I used it
quite a bit as a grad student and often we were able to maintain
anesthesia for up to 4 hours (although the validity of our data after
such a long anesthetic protocol is another issue!). We used sodium
pentobarbital 50 mg/kg (of the commercial solution whose name escapes
me right now) as a single intraperitoneal injection and the rats would
stay under for well over an hour. Occasionally when rats did not
respond as we anticipated, we would supplement with a small dose of
10-20 mg/kg. A significant issue you need to consider is that if doses
via the intraperitoneal route and you are not careful, you can actually
dose the drug into the bowel. This then appears as if you did not dose
enough initially, and there is a temptation to give more drug. What you
may observe, however, is drug being absorbed from the bowel and a rat
"overdosing" due to additional pentobarbital given following the
Also, if you are investigating drug metabolism or PK, beware that
pentobarbital induces CYP-mediated metabolism, but it will take many
hours to days before you see a significant change.
You may consider a different anesthetic. We use a 1:1:1 (v:v:v) mixture
of ketamine 100 mg/mL, xylazine 20 mg/mL, and acepromazine 10 mg/mL at
a 1 mL/kg dose. We dose rats with a 1 mL/kg volume via the
intramuscular route and the rats are generally in surgical-plane
anesthesia for 45-60 minutes. They recover more rapidly than following
pentobarbital as well.
Lane J. Brunner, Ph.D.
College of Pharmacy
The University of Texas at Austin
1 University Station, A1920 (USPS)
2409 West University Street (courier)
Austin, TX 78712-0126
Tel: (512) 471-0942
Fax: (512) 471-7474
Parvin:Back to the Top
The issue is not only to keep the rat alive, but to maintain it under
conditions that whatever you are trying to measure is meaningful. Thus,
if you shut down renal excretion, and the rat dies as a consequence,
whatever data on biodistribution, clearance etc that you may have
collected while the rat was "alive" have no real signficance and can
not be used except for understanding the behavior of a living system
under terminal conditions.
The following paper, from my laboratory, illustrates the problem and
addresses some of the issues that need to be taken into account when
using an anesthetic in animals:
The Effect of Anesthesia on the Biodistribution of Drugs in Rats: a
Carboplatin Study. Alfredo R. Sancho, James A. Dowell and Walter Wolf.
Cancer Chemotherapy and Pharmacology, 40: 521-525, 1997.
Professor Walter Wolf, Ph.D. President, Correlative Imaging Council,
Society of Nuclear Medicine
Distinguished Professor of Pharmaceutical Sciences
Director, Pharmacokinetic Imaging Program
Department of Pharmaceutical Sciences, School of Pharmacy
University of Southern California 1985 Zonal Ave., Los Angeles, CA
Dear Parvin,Back to the Top
If you are using any surgery involving opening of peritoneal region or
any thing else, its better to use Ketamine 50 mg/kg + Xylazine 10
mg/kg.b.wt as IM injection .at. 1 ml/kg.b.wt so that anaesthetic effect
could stay for 45-60 minutes.
KANTHI KIRAN V.S. VARANASI, M.Pharm, MBA
Sr. Research Scientist,
Drug Metabolism and Pharmacokinetics Department,
Glenmark Pharmaceuticals LTD.
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