- On 5 Jun 2006 at 11:38:56, "Bozik, Kara" (KBozik.-a-.unch.unc.edu) sent the message
The following message was posted to: PharmPK
Hi-
Currently we have a pediatric patient with renal dysfunction,
estimated GFR
~30ml/min/1.73m2 per Schwartz formula, and are trying to dose adjust
foscarnet. Her dry weight ~16kg, currently 19kg.
Foscarnet provides dosage recommendations in terms of ml/min/kg. I'm
assuming this is based on a 70kg man.
How does one interpret or convert between the types of clearance
units? For
a pediatric patient? Thanks in advance for any help you can offer!
~Kara
Kara M. Bozik, Pharm.D., BCPS
Clinical Specialist, Pediatrics
University of North Carolina Healthcare
Chapel Hill, NC
kbozik.at.unch.unc.edu
phone: 919-966-6679
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- On 5 Jun 2006 at 13:38:00, "Samuel A. Roiko" (roik0002.-a-.umn.edu) sent the message
The following message was posted to: PharmPK
Kara,
Here is a citation that may be helpful:
John D. Current: A Linear Equation For Estimating The Body Surface
Area In Infants And Children. The Internet Journal of Anesthesiology.
1998. Volume 2 Number 2
I believe it is available on the web if you google it (author/title).
-Sam
Sam Roiko
Graduate Student
Dept of Pharmacology
University of Minnesota
Minneapolis, MN
roik0002.aaa.umn.edu
(612)-347-6847
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- On 5 Jun 2006 at 13:38:00, "Samuel A. Roiko" (roik0002.aaa.umn.edu) sent the message
The following message was posted to: PharmPK
Kara,
Here is a citation that may be helpful:
John D. Current: A Linear Equation For Estimating The Body Surface
Area In Infants And Children. The Internet Journal of Anesthesiology.
1998. Volume 2 Number 2
I believe it is available on the web if you google it (author/title).
-Sam
Sam Roiko
Graduate Student
Dept of Pharmacology
University of Minnesota
Minneapolis, MN
roik0002.aaa.umn.edu
(612)-347-6847
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- On 5 Jun 2006 at 13:27:12, "Jones, Michael" (Michael.Jones.-at-.uch.edu) sent the message
The following message was posted to: PharmPK
One approach is to convert mL/min/1.73m2 to mL/min using the patient's
BSA; and then dividing by the patient's weight in kg to get mL/min/kg.
Thanks,
Mike
Michael A. Jones, Pharm.D.
Pharmacy Informatics
Pharmacy Care Team A027
University of Colorado Hospital
Phone: 303-372-8214
michael.jones.at.uch.edu
www.uch.edu
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- On 6 Jun 2006 at 08:48:18, Alan Boddy (alan.boddy.at.ncl.ac.uk) sent the message
The following message was posted to: PharmPK
An alternative way to calculate BSA from body weight is given in this
paper:
Body surface area estimation in children using weight
alone: application in paediatric oncology
I Sharkey, AV Boddy, H Wallace, J Mycroft, R Hollis and S Picton
British Journal of Cancer (2001) 85(1), 23\0xAD28
Alan
--
Senior Lecturer
Northern Institute for Cancer Research
Medical School
University of Newcastle
Newcastle upon Tyne
NE2 4HH
Tel 44 191 246 4412
Fax 44 191 246 4301
WWW.ncl.ac.uk/nicr
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- On 6 Jun 2006 at 16:27:28, "Dowling, Thomas" (tdowling.aaa.rx.umaryland.edu) sent the message
The following message was posted to: PharmPK
Kara - the literature regarding unit conversions for GFR is vague at
best, especially in pediatrics. Unfortunately, units such as mL/min and
mL/min/1.73m2 are often used interchangeably (which is OK as long as all
of your patients are 1.73m2!). Obviously the goal is to get all units
the same, i.e. compare apples-to-apples. For example see website below
which gives 3 separate equations/results for pediatric GFR:
http://www.globalrph.com/specialpop.htm (note the wrong units used for
Schwartz!)
Regarding your case, you will need to use some clinical judgment to
determine the degree of renal insufficiency for your pediatric patient
(appears that this patient may have CKD stage 3 vs. acute renal
failure?), and the aggressiveness of dosing based on indication. I agree
that the dosing recommendations for foscarnet, given in unconventional
units (mL/min/kg), are confusing and not likely validated in pediatrics,
which requires back-calculation based on your patient's renal function
and weight. There are a few approaches you might consider, ranging from
aggressive (higher dose) to conservative (lower dose):
1. An aggressive approach would be to determine your patient's BSA [BSA
(m2) = 0.024265 * height(exp 0.3964) * mass (exp 0.5378)], determine
creatinine clearance in mL/min, then divide by weight. For example, if
your pediatric patient has BSA of 0.8 m2, then Clcr would be
30*(0.8/1.73) = 13.9 mL/min. If your patient weighs 16 kg, then Clcr
would be 13.9/16 = 0.87 mL/min/kg, with dose reduction based on package
insert and indication.
2. A more conservative approach would be to interpret your patient's
renal function (30 mL/min/1.73m2) in the context of a 70kg adult with
BSA of 1.73m2. Here, creatinine clearance would be calculated as 30
mL/min/70 kg or 0.43 ml/min/kg, with dose adjusted accordingly.
3. Another approach would be to conduct therapeutic drug monitoring,
depending on your lab capabilities. However, I am not familiar with
association between PK/PD or toxicity with this drug.
Hope this helps,
Tom
--
Thomas C. Dowling, PharmD, PhD
Associate Professor
University of Maryland
410-706-0884
tdowling.-a-.rx.umaryland.edu
http://www.pharmacy.umaryland.edu/faculty/tdowling/
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