Antithrombotic doses of UHRA-10 caused less bleeding than did unfractionated heparin in a mouse tail bleeding model. (A) Bleeding times. Mice treated with 200 U/kg unfractionated heparin had significantly longer tail bleeding times than did either saline control mice or mice treated with 50 or 100 mg/kg UHRA-10. Similarly, mice treated with 1000 U/kg heparin had significantly longer bleeding times than did mice treated with 200 mg/kg UHRA-10. (B) Blood loss (quantified as milligrams of hemoglobin collected during 30 minutes). Mice treated with either 200 or 1000 U/kg heparin had significantly higher hemoglobin loss than did mice treated with saline. Mice treated with 1000 U/kg heparin had significantly more hemoglobin loss than did mice treated with 50 or 100 mg/kg UHRA-10. Mice treated with 1000 U/kg heparin had no significant difference in hemoglobin loss compared with mice treated with 200 mg/kg UHRA-10. Statistical significance was assessed by individual Student t tests. *P < .05; **P < .005; ***P < .0005.