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The following message was posted to: PharmPK
Dear readers,
If rat's cannulated jugular vein is used both for iv-bolus drug
administration and for sampling after quick catheter wash-out with
rat's own blood and a small volume of saline, can reliable data be
still obtained?
Thank you for any comments.
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[Two replies - db]
From: "Sharp, Dale"
Date: Wed, 19 Dec 2001 11:31:03 -0500
To: david.at.boomer.org
Subject: RE: PharmPK
The following message was posted to: PharmPK
In my experience it can be done, but it requires a relatively large flush
volume or one's early timpoints tend to be above the theoretical C0. I
recommend changing the needle hub (or whatever sampling apparatus one is
attaching to the cannula) after the injection as well as a 1 or 2 mL flush.
No "quick washout" will do the trick. Of course the compounds I was working
with were relatively water insoluble, it may be easier with water soluble
compounds.
Dale
---
From: "Manish Issar"
Date: Wed, 19 Dec 2001 14:18:09 -0500
To: david.aaa.boomer.org
Subject: RE: PharmPK Injection and sampling at the same site
The following message was posted to: PharmPK
hi
i guess it may or may not work in certain cases. for drugs which show poor
aqueous solubility and are formulated by addition of cosolvents, may
precipitate on the inner walls of the cannula when flushed with saline. thus
one may experience abnormally high and fluctuating levels in the sampled
volume of blood/plasma. however, an easier way is to deliver the drug via
femoral vein cannulation or blind injection in the femoral vein. some people
have also tried injecting formulation through the caudal vein(tail
vein)which works very well sometimes if the formulaton is not very viscous,
other wise there are possibilities that the formulation being viscous forms
a depot at the site of injection.
drugs that are injected in high concentrations could also experience similar
behaviour during the initial time points.
i would suggest that it would be safe game to play if dosing and sampling
sites are separate.
with best wishes
manish issar
manish69.-at-.ufl.edu
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Two replies on this topic - db]
From: "Thomas A Torda"
Date: Thu, 20 Dec 2001 13:20:10 +1100
To: david.-a-.boomer.org
Subject: Re: PharmPK Re: Injection and sampling at the same site
Status: R
The following message was posted to: PharmPK
I think there may be a significant problem with drugs which are protein
bound and stick to the plastic of the cannulation device. These may come
back in blood but not be effectively removed by saline wash.
Tom Torda
---
From: bangarurk.-at-.drreddys.com
Date: Thu, 20 Dec 2001 09:23:34 +0530
To: david.aaa.boomer.org
Subject: Re: PharmPK Injection and sampling at the same site
Status: R
The following message was posted to: PharmPK
Yes it is possible. I suggest a T-joint for collection and injection
should facilitate error free sampling. the volume retained in the catheter
say about 10-20 microliters can be discarded(one drop).
regards,
Ramakrishna Bangaru
Biopharmaceutics research
Dr. Reddy's Laboratories Ltd, generics
email: bangarurk.-at-.drreddys.com
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The following message was posted to: PharmPK
Dear Panteha and others,
First a happy new year.
Based on previous experience with midazolam and using silicon cannulas I
would suggest not to use the same cannula for administration and sampling,
or at least verify if it will be an issue by doing a simple in vitro
experiment. We found that using the same cannula overestimated the drug
concentrations. Flushing did not avoid the problem:
Kotegawa et al. Use of one cannula for both blood sampling and drug
administration: a potential cause of overestimation of drug concentration.
Pharm. Pharmacol. Commun. 1998, 4:283-5.
Good luck,
Bart Laurijssens
Modelling and Simulation
New Product Development CPEM
GSK R&D
Greenford Road
Greenford
UB6 0HE
United Kingdom
tel: +44 (0)20 8966 3814
fax: +44 (0)20 8966 2123
bart.laurijssens.aaa.gsk.com
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