F10 and deep vein thrombosis: DVT occurred despite adequate levels of prophylactic anticoagulation: the median peak anti-FXa levels 2 hours and 4 hours after dalteparin administration were 0.29 (interquartile range, 0.19 to 0.39) based on 159 observations in 101 patients, and 0.31 (interquartile range, 0.22 to 0.43) based on 153 observations in 98 patients, respectively.