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Greetings,
In a large PK study do you centifuge and separate plasma from blood samples
immediately after collection or collect a few and spin all together? What
is the common practice in a clinical setting. Do clinical trials protocols
specify very tightly the timing of when cells are spun out? Can keeping
samples longer without separation at low temperatures cause any loss of
drug or some other problems?
Any reply is very much appreciated.
Chandrani Gunaratna, Ph.D.
Senior Research Scientist
Bioanalytical Systems
2701 Kent Avenue
West Lafayette, IN 47906
Phone: (765)463-4527
E-Mail: prema.-a-.bioanalytical.com
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[A few replies for this topic too - db]
Date: Thu, 24 Feb 2000 5:18:59 PST
From: Walter Wolf
To: PharmPK.-a-.boomer.org
Cc: Multiple recipients of PharmPK - Sent by
Subject: Re: PharmPK Sample collection in clinical trials
Chandrani:
You asked:
>Can keeping samples longer without separation at low temperatures cause any
>loss of drug or some other problems?
That depends on the drug. For example, cisplatin is a drug that reacts
chemically very rapidly with proteins and other nucleophiles. Hence, to
measure free cisplatin, is is absolutely essential to process that sample
IMMEDIATELY upon collection. When we do such studies, we process the blood
sample within 5 minutes after collection.
See for example: Noninvasive Monitoring of Drug Biodistribution and
Metabolism: Studies with Intraarterial Pt-195m-Cisplatin. J. Shani, J.
Bertram, C. Russell, R. Dahalan, D.C.P. Chen, R. Parti, J. Ahmadi, R.A.
Kempf, T.K. Kawada, F.M. Muggia and W. Wolf. Cancer Research 49, 1877-1881,
1989.
======================================================================
| Professor Walter Wolf, Ph.D. E-Mail: wwolfw.-at-.hsc.usc.edu |
| Distinguished Professor of Pharmaceutical Sciences |
| Director, Pharmacokinetic Imaging Program |
| Department of Pharmaceutical Sciences, School of Pharmacy |
| University of Southern California Telephone:323-442-1405|
| 1985 Zonal Ave., Los Angeles, CA 90089-9121 Fax: 323-442-9804|
| |
|Center for Noninvasive Pharmacology, Los Angeles Oncologic Institute|
| MRI at St. Vincent Medical Center Telephone: 213-484-7235 |
| 2131 Third St., Los Angeles, CA 90057 Fax: 213-484-7447 |
======================================================================
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X-Sender: jhzwafri.aaa.merle.acns.nwu.edu (Unverified)
Date: Thu, 24 Feb 2000 10:38:36 -0600
To: PharmPK.-at-.boomer.org
From: zhao wang
Subject: Re: PharmPK Sample collection in clinical trials
It is necessary to separate the plasma and red cell and store the
plasma in freezer if your goal is to measure the plasma
concentration. The hemolysis may happen when storing the whole blood
in cold place for a long time and it will definitely happen when in
freezer. Hemolysis may cause more problems: 1) the concentration will
represent the whole blood but not the plasma only if the drug or
chemical distribute differently in both red cells and plasma; 2) the
extraction procedure may be more complicated since the cells.
zhao wang
Zhao Wang, M.D
Northwestern University
Medical School
Anesthesia Research
z-wang.at.nwu.edu
---
From: DGarg8838.aaa.aol.com
Date: Thu, 24 Feb 2000 19:51:14 EST
Subject: Re: PharmPK Sample collection in clinical trials
To: PharmPK.-a-.boomer.org
Usually the analytical laboratory does some in-vitro work to find out the
stability of the drug or the meabolites in the whole blood vs. plasma. Based
on these in-vitro studies, clinical protocols ask for processing samples
within certain time frame. Centrifugation within 30 minutes of draw is
common. It all depends on the drug one is working. For example with
nitroglycerine type drug one has to process within few minutes.
The protocols also recommend about keeping the samples in crushed ice or room
temprature before centrifugation. Sometime dry ice and acetone bath is used
to quick freeze the plasma after centrifugation. The analytical chemists are
the ones who find out the appropriate conditions and times within which
processing should take place.
Dyal Garg
Clinical Research Services, Inc.
8838 Indian River Run
Boynton Beach, FL 33437
Phone:561-737-3954
www.spclpopulationstudies.com
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Sample collection is one of the worst nightmares in clinical medicine. One
need understand the complete metabolism of the chemical to be measured: the
chemical state in which a drug can be measured, where it will appear with
statistical significance, and how to ensure that data collected is
preserved. As pointed out by others, many valid clinical measurements can
only be achieved under very rigid data collection procedures. The
analytical and physical chemists can help out a lot in setting up protocols.
Daro Gross
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)