In ICU patients, low molecular weight heparins (LMWH) were recommended for thromboprophylaxis but frequently failed to achieve adequate peak anti-Xa activity. For a study, researchers compared the pharmacokinetic profiles of LMWH administered via intravenous (IV) versus subcutaneous (SC). This was a randomized, prospective, monocentric trial. Patients were randomly assigned to either the IV or SC route of administration with a 4-hour infusion of nadroparin of 3,800 IU. The randomization was stratified based on whether or not a vasopressor was required. Anti-Xa activity was measured at baseline and 1, 2, 4, 6, 8, 12, and 24 hours after the administration began. About 60 patients were included in the study, with 30 assigned to the IV route and 30 assigned to the SC route. The pharmacokinetic profiles were noticeably different. The mean peak anti-Xa activity in the IV group was 0.38 IU/ml compared to 0.20 IU/ml in the SC group (P<0.001). Trough values and AUC (0-24 h) were comparable between groups. Whether patients were given vasopressors or not, their pharmacokinetic profiles were similar. However, the IV route with a 4-h infusion resulted in significantly higher peak anti-Xa activity without affecting trough value or AUC (0-24 h). More research was needed to determine whether IV administration of LMWH improved the efficacy of thromboprophylaxis.