Humate-P Potency Units: Getting the Numbers Right in Clinical Practice
Humate-P’s labeling includes two potency values—one for VWF:RCo and one for Factor VIII (FVIII:C)—because it is a plasma-derived concentrate that contains both von Willebrand factor (VWF) and factor VIII.
Humate-P is a plasma-derived concentrate containing both von Willebrand factor (VWF) and factor VIII (FVIII), approved for use in von Willebrand disease (VWD) and hemophilia A.
Its labeling includes two potency values—VWF:RCo and FVIII:C—and knowing which number to use is essential to accurate dosing.
Why Two Potency Numbers Exist
- VWF:RCo (ristocetin cofactor activity)
- Measures the functional activity of VWF in promoting platelet adhesion.
- Clinically relevant for VWD, where the defect lies in VWF quantity or function.
- FVIII:C (factor VIII coagulant activity)
- Measures FVIII clotting activity.
- Relevant for hemophilia A, where FVIII is deficient or absent.
Since Humate-P contains both clotting proteins, it can be dosed for either condition—but the unit basis differs depending on the indication.
Dosing Decision: Which Number to Use
Quick rule:
- VWD? → Use VWF:RCo IU
- Hemophilia A? → Use FVIII:C IU
For mixed VWD + low FVIII, dose primarily based on VWF:RCo but monitor FVIII levels to ensure targets are met and avoid FVIII excess.
Clinical Application
| Indication | Potency Value for Dose Calculation | Why It Matters |
|---|---|---|
| VWD (all types) | VWF:RCo IU | Directly corrects the VWF defect |
| Surgical prophylaxis in VWD | VWF:RCo IU | Maintains VWF for platelet adhesion during high-risk bleeding events |
| Hemophilia A | FVIII:C IU | Direct replacement of missing FVIII |
| Mixed VWD + low FVIII | VWF:RCo IU + monitor FVIII | VWF infusion stabilizes endogenous FVIII |
Practical Pearls
- VWF infusion naturally raises FVIII levels because VWF prolongs FVIII half-life.
- FVIII:C values on the vial are typically lower than VWF:RCo values—don’t accidentally swap them.
- Over-replacement of FVIII is a risk in prolonged therapy for VWD, especially perioperatively—monitor FVIII levels during repeated dosing.
Bottom line
Humate-P’s dual potency labeling is not a redundancy—it’s a dosing roadmap. Matching the potency value to the patient’s diagnosis ensures optimal clotting factor correction and minimizes risk.
https://labeling.cslbehring.com/PI/US/Humate-P/EN/Humate-P-Prescribing-Information.pdf
