Enoxaparin dosing in Noonan syndrome: a case report

Background Noonan syndrome is a genetic condition that typically includes heart abnormalities and characteristic facial features. Various bleeding disorders have been associated with Noonan syndrome. Some affected individuals have excessive bruising, nosebleeds or prolonged bleeding following injury or surgery. This paper describes anti‐Factor Xa levels following excessive enoxaparin dosing in a male patient with Noonan syndrome. Clinical details A 24‐year‐old male (weighing 53 kg) presented under Orthopaedics for his elective three‐stage scoliosis surgery for kyphoscoliosis. The patient was usually on warfarin for a mechanical valve replacement. Bridging enoxaparin was prescribed (initially 1.5 mg/kg, SC, daily), but failure to reach therapeutic anti‐Factor Xa levels (highest level 0.44 units/mL) resulted in escalating enoxaparin doses (90 mg, SC, twice daily). Outcomes Despite a doses of up to 1.7 mg/kg enoxaparin twice daily, the patient did not reach therapeutic anti‐Factor Xa levels according to recommended reference ranges. The patient’s regular warfarin dose was restarted and the enoxaparin was ceased once his International Normalised Ratio was within the therapeutic range. The patient was transferred to a a rehabilitation facility 10 days after surgery. Conclusion Medication assay ranges may not always be an accurate point of reference, particularly when patients present with unusual comorbidities. As health care moves towards patient‐centred care, it is essential that individual patient parameters are considered when monitoring medication treatment plans.