Arixtra (fondaparinux) Dosing For Adults
Marshall Pierce, PharmD

Use the tab key to navigate the form. Required data entry fields are teal in color. Other fields are output only. 
Enter Age (years)
Enter Height in
Enter Actual Weight in
Select Sex  
Enter Most Recent Serum Creatinine (mg/dl)
Enter Previous Serum Creatinine (mg/dl)
Use the same value twice if renal function is stable.

Enter time between serum creatinines (hours). Use 24 if renal function is stable. Creatinines should be > 1 T1/2 apart to accurately determine creatinine clearance when renal function is changing.

There is no antidote for Arixtra; protamine does not reverse its anticoagulant effects. The manufacturer recommends fresh frozen plasma and factor VIIa. Arixtra continues to be active until it is excreted from the body and is not consumed during inactivation of factor Xa. Arixtra is renally eliminated unchanged and is not metabolized. Arixtra's half-life is dependent on renal function. Arixtra's anticoagulant effect, inhibition of thrombin generation, is directly related to serum levels. Excessive peak levels are to be avoided. This dosing tool adjust the dose based on patient's dosing weight (lean body weight or actual weight, which ever is less) and renal function. Goal mid point levels are 1 mcg/ml for DVT/PE treatment and 0.33 mcg/ml for VTE prophylaxis in orthopedic and abdominal surgery. The tool predicts serum levels at the mid point of the dosing interval and minimizes peak to trough fluctuations. As renal function declines smaller doses are given to obtain the same mid point level, while the peak decreases and the trough increases. Mid point levels are dependent on drug clearance and are independent of volume of distribution. Mid point levels also decrease serum level sampling error, due to timing of drug administration and blood level drawing, which is inherent in peak serum levels. When ordering levels please order a mid point level. Steady state or non steady state levels may be fit. Non steady state fitting assumes all doses are the same before the level.

Dosing for Treatment of DVT/PE or Prophylaxis for abdominal or orthopedic surgery.
Select Drug
Calculated Lean Body Weight (kg)
Calculated Drug Dosing Weight (kg)
Calculated Creatinine Clearance (ml/min)
Calculated T1/2 for CREATININE (hours)
Calculated Drug K (hours-1)
Calculated Drug T1/2 (hours)
Calculated Drug Vd (liters)
Calculated Drug Clearance (liters/hour)
Calculated Loading Dose (mg)
For  peak level of 1.5 mcg/ml based on Dosing Weight assuming no drug on board, only for PE/DVT Treatment. 
Calculated Daily Dose (mg)
For mid point level of 1 mcg/ml for Treatment of DVT/PE or 0.33 mcg/ml for VTE Prophylaxis for Abdominal and Orthopedic Surgery
Enter Rounded Dose (mg)
Select Dosage Interval 
Daily dosing is recommended to minimize peaks and reduce peak to trough fluctuations.
A therapeutic level for DVT/PE treatment at the mid point of the dosing interval is 1 mcg/ml. This is based on the level obtained by a 75 kg patient with a creatinine clearnance of 120 ml/min receiving 7.5 mg per day.  The usual mid point level for VTE Prophylaxis for orthopedic and abdominal surgery is 0.33 mcg/ml and is based on the level obtained by a 75 kg patient with a creatinine clearance of 120 ml/min receiving 2.5 mg per day.

Calculated Steady StatePeak (mcg/ml)

Calculated Steady State Trough (mcq/ml)

AUC mg/hour/liter
Calculated Steady State Mid Point Level (mcg/ml)
  Treatment of DVT/PE: 1 mcg/ml, (0.8-1.2 mcg/ml)   
  VTE Prophylaxis: Orthopedic or Abdominal Surgery 0.33 mcg/ml, (0.26-0.4 mcg/ml)

Calculated Steady State Mid Point Anti Xa Level (units/ml)
  Treatment of DVT/PE: 0.666 units/ml, (0.53-0.799 units/ml)   
  VTE Prophylaxis: Orthopedic or Abdominal Surgery 0.22 units/ml, (0.177-0.266 units/ml)  

Serum level analysis: Please complete the input boxes below if you have an actual fondaparinux anti-Xa level and the time is was drawn. Levels at the mid point of the dosage interval are recommended. These values along with the entered dosage history will be used to calculated the patient's elimination rate constant (K) and clearance.
Enter the Number of Doses given before the level was drawn or enter 99 if the level was drawn at steady state. Steady state is achieved when 5 half-lives have passed from the start of the regimen. Non steady state levels may be fit if the number of doses administered is known.
Enter Actual Measured Fondaparinux Level in mcg/ml. Note 1 mcg/ml of fondaparinux equals 0.666 anti Xa units/ml.
Steady State Mid Point levels are recommended. 
Enter the time in hours that the level was drawn after the PREVIOUS DOSE. 
K (hours-1) Fit (Fit using level, time of level,  dosage form, and entered dosage history.)
Thanks for using the program. If you have any comments, suggestions or questions please contact the author..

Copyright Marshall A. Pierce PharmD, all rights reserved, no warranties expressed or implied.