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Hi,
are there any kind of guidelines based on the new recommendations
published in January this year regarding the vancomycin dosing in ICU
patients who usually have unstable renal function? How do you predict
the expected through concentrations (and calculate the necessary dose
to reach the target through) if you have a morning creatinine value
(is there a formula)? Our lab gives us the Cockcroft-Gault estimate of
GFR. The problem is that patients have unstable renal function - is
there a better way to estimate it in critical patients? Vanco is given
in a short infusion (over 1 hour).
Thanks!
Kristina Nadrah(MPharm, MD)
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Hi Tina, On a practical basis for ICU patients who not only have poor
renal function but have also unstable renal function and/or unstable
blood pressure and changing blood or plasma volumes, measuring serum
vancomycin levels becomes necessary. Estimates of serum levels based
on a model, in this situation, can be inaccurate and unreliable.
Ron Floyd, PharmD, BCPS
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>The problem is that patients have unstable renal function - is there
a better way to estimate it in critical patients?
YES, Kristina, there is. Contact please, Dr. Roger Jelliffe at
http://www.lapk.org/
He has developed a well validated formula ang a PC program just for
such patients. Kind regards, Dimiter
--
Dimiter Terziivanov, MD,PhD,DSc, Professor and Head,
Clinic of Clinical Pharmacology and Pharmacokinetics,
Univ Hosp "St. Ivan Rilski", 15 Acad. Ivan Geshov st, 1431 Sofia,
Bulgaria
e-mail: dterziivanov.-a-.rilski.com; terziiv.-a-.yahoo.com
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The following message was posted to: PharmPK
Thanks!
I have one more question: do you think that if patient's hemodinamic
parameters change a lot within 24h it is reasonable to measure trough
levels before each dosing (q8 or 12h) or is this overdoing it?
Thanks,
Tina Nadrah
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Dear Tina,
As already meantioned by Dimiter, our lab (under the direction of Dr.
Jelliffe) has developed algorithms and software specifically to
address this problem of changing PK parameters. Our software will
estimate an individual's parameter values, allowing for jumps in time
to account for changing clinical circumstances, such as development or
resolution of sepsis. Once the parameters are estimated, the optimal
dosage regimen will be provided to you that will achieve whatever
target drug concentration you wish with maximal precision and accuracy.
Here is a reference:
Macdonald I, Staatz CE, Jelliffe RW, Thomson AH. Evaluation and
comparison of simple multiple model, richer data multiple model, and
sequential interacting multiple model (IMM) Bayesian analyses of
gentamicin and vancomycin data collected from patients undergoing
cardiothoracic surgery. Ther Drug Monit. 2008 Feb;30(1):67-74.
Hope that is helpful.
--
Michael Neely, MD
Assistant Professor
Division of Pediatric Infectious Diseases
1640 Marengo St., #300
Los Angeles, CA 90033
Laboratory of Applied Pharmacokinetics
2250 Alcazar St. CSC 134B
Los Angeles, CA 90033
Web: http://www.lapk.org
Email: mneely.-a-.usc.edu
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Hi Tina
Also worth noting that vanc CL (and other drug clearances) can also be
a useful biomarker of organ function, ie renal CL in this case.
Matt
Dr Matt Doogue
Clinical Pharmacologist / Endocrinologist
Flinders Medical Centre, Flinders University
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Studies have shown that the haemodynamic parameters such as Cardiac
output, Mean arterial pressure, Central venous pressure, and Pulmonary
capillary wedge pressure normally wont change much within 24 hours
from baseline, after administration of 1g of Vancomycin over a period
of 30 min. The study demonstrated that there is no correlation between
peak Vancomycin levels and release of histamine (which is considered
to be the primary cause of haemodynamic changes). Hence, according to
my view, it's not necessary to measure trough values before each dosing.
For your reference:
http://www.anesthesia-analgesia.org/cgi/content/abstract/71/4/394
Regards,
Dr.S.Gunasakaran, MBBS, MD.,
Medical Affairs
[That describes the (lack of) some pharmacological effects of
vancomycin. The concerns of the original poster was the effect of
changing pathology (i.e. renal function) on the pharmacokinetics of
vancomycin. If the patient doesn't eliminate vancomycin as expected a
dosing regimen may result in much higher or lower than epected
vancomycin concentrations after multiple doses. Blood concentration
measurements and PK analysis can be used to monitor the changed
elimination - db]
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YES, I think it will be of supportive value for evidence based
decision making about the next dosing regimen.
Regards, Dimiter
--
Dimiter Terziivanov, MD,PhD,DSc, Professor and Head,
Clinic of Clinical Pharmacology and Pharmacokinetics,
Univ Hosp "St. Ivan Rilski",
15 Acad. Ivan Geshov st, 1431 Sofia,
Bulgaria
e-mail: dterziivanov.at.rilski.com; terziiv.aaa.yahoo.com
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