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Calculation of Parenteral Iron Dose  (Iron Deficit)

Equations:

Hemoglobin iron deficit (mg) = weight (kg)  x (14 - Hgb) x (2.145) 1
Note: Hbg (current hemoglobin level) units: (g/dL)

Alternatively: Volume of product required (mL) = [weight (kg) x (14 - Hgb) x (2.145)] / C
Where C= concentration of elemental iron (mg/ml) in the product being used:
Iron dextran: 50 mg/mL. Iron sucrose: 20 mg/mL.  Ferric gluconate: 12.5 mg/mL


Note (alternative equations)
[1 ] The Iron dextran package insert lists the following equation:
Dose (mL) = 0.0442 (Desired Hb - Observed Hb) x LBW + (0.26 x LBW)
Iron dextran calculator can be found here.

[2 ] An earlier version of the Venofer® package insert as well as the
current package insert for CosmoFer® lists the following equation:
Total iron deficit = Body weight [kg] x (Target Hb – Actual Hb) [g/l] x 2.4 + Iron stores [mg]
500 mg iron for iron stores is recommended if the body weight is above 35 kg.
A calculator using this equation can be found here.
 Patient Weight:  
Current Hemoglobin level  g/dL
Target (desired) Hemoglobin level:   g/dL

Background:

Iron deficit - equation derivation1 :
Assumptions:
   -Blood volume = 65 mL/kg
   -Hgb conc target =14.0 g/dL
   -Deficits in body stores are ignored.

Intermediate calculations:
  -Blood volume (dL) =  [65 (mL/kg) x body weight (kg)] / 100 (mL/dL)
  -Hgb deficit (g/dL) = 14.0 - patient hgb conc.
  -Hgb deficit (grams) = Hgb deficit (g/dL) x blood volume (dL)
  -Iron deficit (mg) = Hgb deficit (grams) x 3.3 (mg Fe/g Hgb) 
         [Note: 3.3 x 0.65 = 2.145]
  -Volume of parenteral iron product req'd (mL) = [Iron deficit (mg)] / C(mg/mL)

Final calculations:
  -Hgb iron deficit (mg) = weight (kg) x (14 - Hgb) x (2.145)
  -Volume of product required (mL) = [weight (kg)x (14 - Hgb) x (2.145)] / C
        Where C= concentration of elemental iron (mg/ml) in the product being used:
         Iron dextran: 50 mg/mL. Iron sucrose: 20 mg/mL.  Ferric gluconate: 12.5 mg/mL



 
Source
Venofer® (Iron Sucrose Injection, USP) package insert - (2006).
NOTE: Latest package insert does not include this information.

Calculation of dosage:
The total cumulative dose of Venofer, equivalent to the total iron deficit (mg), is determined by the haemoglobin level and body weight. The dose of Venofer must be individually determined for each patient according to the total iron deficit calculated with the following formula:

Total iron deficit [mg] = body weight [kg] x (target Hb-actual Hb) [g/dl] x 2.4* + depot iron [mg]

Below 35 kg body weight: Target Hb = 13 g/dl and depot iron = 15 mg/kg body weight
35 kg body weight and above: Target Hb = 15 g/dl and depot iron = 500 mg
* Factor 2.4 = 0.0034 x 0.07 x 10000: Iron content of hemoglobin ~ 0.34%
Blood volume ~ 7% of body weight
Conversion from g/dl to mg/l = Factor 10000
Depot iron refers to the approximately 20% of the total iron content in the body stored in ferritin and hemosiderin in cells of the recticuloendothelial system (liver, spleen, and bone marrow).
Total amount of Venofer to be administered (in ml) = Total iron deficit [mg]
20mg/ml

 



References:


Iron deficit equation (source): 
[1 ]  Schrier SL, Mentzer WC, Landaw SA. Treatment of anemia due to iron deficiency. UpToDate®. 2010;18(3). http://www.uptodate.com/ (Requires subscription). Accessed: 4/12/2011.

Alternative equation:
Total iron deficit = Body weight [kg] x (Target Hb – Actual Hb) [g/l] x 2.4 + Iron stores [mg]
500 mg iron for iron stores is recommended if the body weight is above 35 kg.

[2 ] CosmoFer® package insert and  product website: http://www.cosmofer.com/product/dose-calculation/dose-calculator.aspx





Disclaimer

All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgement. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.   Read the disclaimer
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