['To evaluate the haemostatic efficacy and safety of prophylactic oral administration of Yunan Baiyao capsules on reduction of blood loss in bimaxillary orthognathic surgery.', 'Eighty-seven patients scheduled for Le Fort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) were enrolled in the prospective, randomized, double-blind, placebo-controlled clinical study. Forty-three patients took prophylactic oral administration of Yunnan Baiyao capsules 3 days before operation, and 44 patients without Yunnan Baiyao administration served as control. The intraoperative blood loss during Le Fort I osteotomy and bilateral sagittal split ramus osteotomy was estimated and the safety of Yunnan Baiyao capsules was evaluated.', 'The total blood loss in the Yunnan Baiyao group (330.5 +/- 134.4) ml was significantly lower than that of the control group (420.3 +/- 175.9) ml. The blood loss of Le Fort I osteotomy in the Yunnan Baiyao group (154.9 +/- 84.3) ml was also significantly lower than that of the control group (203.8 +/- 98.1) ml. The mean blood loss of BSSRO in the Yunnan Baiyao group was also lower than that of the control group, but the differences was not significant. The post-operative fibrinolysis was in the same level in both groups. Thromboemblic events or other side effects were not observed in this clinical trial.'] Does [ Prophylactic administration of Yunnan Baiyao capsule reduce intra-operative blood loss in orthognathic surgery ]?