Clearance of intravenous rhFIX with or without concurrent subcutaneous rhFIX prophylaxis. The peak recovery and half-life of infused rhFIX (50 IU/kg) were estimated while the tolerized dogs were on subcutaneous rhFIX therapy (▪) and after 2 months without rhFIX (•). Both appeared comparable under these 2 conditions at this dose. Error bars indicate SD.