A 52-year-old man, weighing 240 kg and with a BMI of 74 kg/m2, was admitted to hospital with a diagnosis of ischaemic stroke. As pathological history of interest, the patient had presented in the past with deep vein thromboembolism, for which reason he was prescribed anticoagulant therapy at home with Rivaroxaban.
The Emergency Department suggested the possibility of fibrinolytic treatment with alteplase. However, after examination, this intervention was rejected, as the patient was at the limit of the time interval, had 23 points on the NIHSS (National Institute of Health Stroke Scale) and the time of the last intake of Rivaroxaban was unknown.
After admission to the ICU for monitoring and neurological surveillance, it was decided to start treatment with enoxaparin as anticoagulant therapy. For this purpose, the Intensive Care Medicine Department contacted the Pharmacy Department to find out the most appropriate dosage given the patient's extreme obesity2 (BMI > 40 kg/m2).
For safety reasons, given the scarcity of data on the subject, it was decided to start treatment at a dose of 0.7 mg/kg/12 h subcutaneously (enoxaparin 160 mg/12 h) to avoid bleeding and as this was the maximum dose evaluated in various clinical trials3-5. 3-5 In addition, monitoring of anti-Xa factor was established to establish the final dose.

Four hours after administration of the third dose, the anti-Xa factor concentration in blood was 0.37 IU/mL. When it was between 0.35-0.49 IU/mL, the dose was increased by ≈10% (170 mg/12 h). Four hours after the next dose, the anti-Xa factor concentration was 0.59 IU/mL, and at 24 hours it was 0.48 IU/mL. In view of this result, the dose was increased, reaching 180 mg/12 h. Finally, the next determination obtained a value of 0.84 IU/mL, placing us within the therapeutic range and setting the optimal dose for our patient at 0.75 mg/kg/12 h.