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We have a patient who weighs 274kg (BMI=89; IBW=74kg), so falls WELL
outside normal dose range. The patient has been dosed for a DVT with
enoxaparin at 100mg q12h for approximately 2 weeks, and has re-
presented with multiple PEs. Prior to discharge approx 2 weeks ago,
anti-Xa levels were taken, and were found to be just sub-therapeutic
but the medical team was happy to press on with this dose.
I was wondering if anyone had any more updated info (I searched the
archives) on dosing/PK in obese patients - the product info says
100mg q12h is the highest we should go. Monitoring anti-Xa levels in
this patient is not appropriate due to extreme venous access
difficulties. Should we dose closer to the IBW .at. 1mg/kg q12h and risk
further PE/DVT or should we dose adjust and go above recommended
levels, without the option of anti-Xa monitoring?
I'd appreciate any opinions.
Cheers,
Glen Bayer
(PE ? DVT ? PK ;-) - db)
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The following message was posted to: PharmPK
Hi Glen- There is a huge amount of interpatient PK variability in
the obese, so no one dosage size will fit all. For drugs where a lot
is known, like AGS and Vanco, the intial dosage recommendations must
be followed up with serum level monitoring to acheive reasonable
outcomes.
For obese patients, these are the suggestions of our anticoagulation
clinic:
II. Dosage Adjustments in Obesity
A. Use Total Body Weight (TBW) up to 190kg.
B. If > 190kg:
1.. AntiXa level monitoring available:
a.. Use TBW and adjust dose downward if necessary based on
antiXa levels
2.. AntiXa level monitoring NOT available
a.. Use TBW and adjust dose downward if necessary if bleeding
occurs
http://www.uwmcacc.org/Enoxaparin.html#Anchor-Dosage-6296
--Larry
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The following message was posted to: PharmPK
Glen
Two articles that may help:
Green B, Duffull SB. Development of a dosing strategy for enoxaparin in
obese patients. Br J Clin Pharmacol. 2003 Jul;56(1):96-103.
Spinler SA, Inverso SM, Cohen M, Goodman SG, Stringer KA, Antman EM;
ESSENCE and TIMI 11B Investigators. Safety and efficacy of
unfractionated heparin versus enoxaparin in patients who are obese and
patients with severe renal impairment: analysis from the ESSENCE and
TIMI 11B studies.Am Heart J. 2003 Jul;146(1):33-41.
Green and Dufull recommended that obese patients are dosed 100 IU kg-1
(1 mg/kg-1) based on LBW every 8 h.
Jan-Stefan
Dr J-S van der Walt
Division of Clinical Pharmacology
University of Cape Town
K45-53 Old Main Building
Groote Schuur Hostpital
Observatory 7925 Cape Town
South Africa
Email: js.vanderwalt.-at-.uct.ac.za
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