Australian and New Zealand Registry of Anticoagulation in the Obese
ISTH Academy. McCaughan G. Jul 10, 2019; 274005; OC 73.5 Topic: DOACs
Georgia McCaughan
Georgia McCaughan
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OC 73.5

Australian and New Zealand Registry of Anticoagulation in the Obese

G. McCaughan1,2, H. Crowther3,4, V. Chen2,5, S. Chunilal6, M.S. Lim6, E. Merriman7, P. Rebeiro3, L. Pasalic1,2,4, F. Tahir2,5, L. Hall2,5, J. Curnow1,4
1Westmead Hospital, Department of Haematology, Sydney, Australia, 2University of Sydney, Sydney Medical School, Sydney, Australia, 3Blacktown Hospital, Department of Haematology, Sydney, Australia, 4Sydney Centres for Thrombosis and Haemostasis, Sydney, Australia, 5Concord Repatriation General Hospital, Department of Haematology, Sydney, Australia, 6Monash Medical Centre, Department of Haematology, Melbourne, Australia, 7North Shore Hospital, Department of Haematology, Auckland, New Zealand

Main Topic: Venous Thromboembolism
Category: DOACs

Background: There is limited data to guide prescribing of anticoagulants in the obese, in particular in those weighing > 150kg or with a BMI > 40kg/m2.
Aims: To examine anticoagulant prescribing in the obese in Australia and New Zealand; determine an appropriate LMWH dosing strategy; evaluate whether obese patients achieve appropriate DOAC levels and evaluate the efficacy and safety of anticoagulation in the obese.
Methods: We have prospectively registered patients with a BMI >35kg/m2 or weight >120kg receiving anticoagulants at sites in Australia and New Zealand from August 2017. 3 years of follow-up is planned.
Results: Currently 91 patients have been recruited across 6 sites with a further 3 sites awaiting approval. Cross-over between agents occurred during the follow-up period.

Drug Number of Patients Age (median, range) Weight (kg) (median, range) BMI (kg/m2) (median, range) Indication
Apixaban 25 49 (27-85) 124 (76-184) 44.4 (35.3-70.0) DVT (14), PE (12).
Dabigatran 2 40 (41-42) 113 (108-118) 36.8 (35.2-38.3) AF (1), PE (1)
Rivaroxaban 37 55 (27-81) 120 (90-171) 38.5 (35-51.6) DVT (26), PE (10), other (1)
Enoxaparin 22 51 (29-78) 130 (90-290) 45.1 (35.2-87.5) DVT (6), PE (15), other (1)
Warfarin 18 55 (33-79) 153 (110-229) 49.5 (36.3-74.5) DVT (6), PE (12)
[Table 1: Demographics]

Anticoagulant Dose Median peak (ng/ml) (range) Median trough (ng/ml) (range)
Rivaroxaban 20mg daily 281 (165-561) (n=17) 31 (<10-122) (n = 17)
  15mg BD 338 (n=1) 37 (25-55) (n=3)
Apixaban 5mg BD 122 (55-241) (n=11) 40 (<25-115) (n=9)
  2.5mg BD 85 (61-130) (n=3) 55 (33-63) (n=3)
[Table 2: DOAC Levels]

Interpretation of DOAC levels varies depending on which of the published 'on therapy' ranges are used. According to one publication, 5/17 peak rivaroxaban, 3/11 peak apixaban and 5/9 trough apixaban levels fell outside range; while using another published range all apixaban levels were within the expected ranges. Median enoxaparin dose to achieve therapeutic Anti-Xa (0.5-1.2U/ml) (n=12) was 0.88mg/kg (range 0.52-1.01), all patients (n=5) weighing ³200kg achieved therapeutic Anti-Xa on 150mg BD (0.52-0.75mg/kg). A confirmed recurrence occurred on therapeutic warfarin and on apixaban (suspected non-compliance), an equivocal recurrence occurred on enoxaparin and 1 DVT occurred on dabigatran for a cardiac indication. 3 patients were changed from rivaroxaban due to low drug levels (peak 165 and troughs < 25ng/ml), no patient ceased apixaban for this reason.
Conclusions: Interpretation of DOAC levels is difficult due to a lack of well validated therapeutic ranges with clinical correlates. Further data regarding the clinical utility of DOAC levels, appropriate dosing strategy for enoxaparin, and clinical outcomes in this population is required. Our registry adds to recently published data by providing data on drug levels and how this may influence prescribing.

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