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Dear All
We are involved in a study with aspirin and are keen to measure plasma
concentrations using HPLC with UV detection.
We would be interested to hear whether anyone has experience of measuring
aspirin on a regular basis as we are finding it difficult to achieve the
extraction efficiencies that are mentioned in the published literature
(90-100%) and do not wish to jeopardise valuable clinical specimens until
we have a robust assay.
Thanks in advance for any help you can give us,
Duncan Jodrell
***************************************************************
Duncan I. Jodrell DM, MSc, FRCP (Edin.),
Deputy Director, ICRF Medical Oncology Unit,
University of Edinburgh, Western General Hospital,
Edinburgh, EH4 2XU.
jodrell.at.icrf.icnet.uk
Tel: 0131 467 8447
Fax: 0131 332 8494
***************************************************************
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[A few replies - db]
From: "Melethil, Srikumaran K."
To: "'PharmPK.aaa.pharm.cpb.uokhsc.edu'"
Subject: RE: HPLC assay for aspirin
Date: Wed, 28 Apr 1999 08:04:01 -0500
MIME-Version: 1.0
Dear Duncan,
You may find this paper from our lab (J. Pharmacokinetics Biopharm. 19,
157-173,1991)useful.
Sri
Sri Melethil, Ph.D.
Professor of Pharmaceutics and Medicine
University of Missouri-KC
School of Pharmacy
Room 203-B, 5005 Rockhilll Road
Kansas City, MO 64110
816-235-1794 (fax: 816-235-5190)
---
Date: Wed, 28 Apr 1999 23:17:04 +0200
From: "Dr. Harald Mertes"
MIME-Version: 1.0
To: PharmPK.-at-.pharm.cpb.uokhsc.edu
Subject: Re: PharmPK HPLC assay for aspirin
Two hints for your problem:
1. Be aware that aspirin will be rapidly cleaved by several esterases to
salicylic acid. Thus the half life time in humans is about 15 - 20
minutes. Even the gut tissues are able to cleave aspirin.
2. The HPLC techniques I used required removement of proteins. Any
precipitation of proteins may cause losses of your drug due to the
protein precipitation. This as well as other disturbing factors will be
calculable by using an internal standard with radioactive nuclides added
to your samples prior to any further procedure, whereas 14C is better
than 3H of cause the triton (the proton analogon of 3H) may be involved
in acid base reactions.
Good luck,
--
Harald Mertes, MD
Anaesthesiologist
Rastatt/Germany
mailto:harald.-a-.mertes.inka.de
http://sites.inka.de/sites/mertes/index.html
---
[You might have a look at Ross-Lee LM, et al. [See Related Articles]
Aspirin pharmacokinetics in migraine. The effect of metoclopramide.
Eur J Clin Pharmacol. 1983;24(6):777-85. No abstract available.
PMID: 6884416; UI: 83287550.
Ross-Lee L, et al. [See Related Articles]
Aspirin treatment of migraine attacks: clinical observations.
Cephalalgia. 1982 Jun;2(2):71-6.
PMID: 7127458; UI: 83025052.
Ross-Lee L, et al. [See Related Articles]
Aspirin treatment of migraine attacks: plasma drug level data.
Cephalalgia. 1982 Mar;2(1):9-14.
PMID: 7116442; UI: 83001903.
Ross-Lee LM, et al. [See Related Articles]
Plasma levels of aspirin following effervescent and enteric coated
tablets, and their effect on platelet function.
Eur J Clin Pharmacol. 1982;23(6):545-51.
PMID: 7160424; UI: 83131841. - db]
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When I developed the method for direct analysis of salicylic acid and its
metabolites in human
plasma and urine by HPLC, I found
1). Aspirin will hydrolyzed to salicylic acid in plasma and urine matrix at
room temperature..
2). The wavelength of the maximum UV absorbance of aspirin and salicylic
acid are different.
3). The recovery of aspirin or salicylic acid will decrease dramatically if
you evaporate the sample to totally dryness after extractions.
To increase the extraction efficiency of aspirin, my suggestions are:
1) Measure the total concentrations of aspirin and salicylic acid.
2) Use PDA detector which can monitor different wavelength simultaneously, or
a detector can
switch the wavelength during the run.
3). Do not overdry the samples.
HPLC condition in our method is originally for both salicylic acid and
aspirin. The aspirin peak will
came out at about 30 min. If you are not interested in metabolites, you may
increase the percentage
of organic solvent to short the run time.
J.H. Liu and P.C Smith, J. Chromatogr. B (675) 61-77, 1996
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)