DOAC prescribing and body weight
This is the third in a series of DOAC blogs
Key messages
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Anticoagulation prescribing is a complex and high risk area of practice. Direct oral anticoagulant (DOAC) dosing depends on a number of factors such as indication, actual body weight, renal/hepatic function, age, past medical history and concomitant medication.
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In patients weighing less than 120kg, apixaban is the DOAC of choice for the treatment of venous thromboembolism (VTE) and edoxaban is the DOAC of choice for stroke prevention secondary to non-valvular atrial fibrillation (AF) in NHSGGC.
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For patients weighing 120-150kg, apixaban is the DOAC of choice in NHSGGC for treatment of VTE and for stroke prevention secondary to non-valvular AF.
Body weight is an important factor to be considered when prescribing a DOAC. Dose adjustments are recommended in some circumstances when patients are 60kg or less. Refer to the Summary of Product Characteristics (SPC) via emc or BNF via Medicines Complete for each DOAC for full prescribing information.
For patients weighing more than 120kg, there has been historically a degree of caution surrounding the use of DOACs due to concerns of sub therapeutic effect. Evidence is now available to support the use of apixaban and rivaroxaban at standard doses in patients weighing more than 120kg as recommended by the International Society of Thrombosis and Haemostasis (ISTH). There is no need for DOAC therapeutic monitoring checks.
The evidence published by ISTH is specific to treatment of VTE however cardiologists across NHSGGC have agreed to follow the same advice for patients receiving a DOAC for non-valvular AF. This is a pragmatic approach based on pharmacokinetic data and rates of major bleeds and strokes in obese patients enrolled in clinical trials comparing DOACs against warfarin as summarised by the European Heart Rhythm Association in 2021.
If a decision has been made to start a patient weighing 120-150kg on a DOAC for treatment of VTE or for stroke prevention secondary to non-valvular AF, NHSGGC consensus is to prescribe apixaban on the basis of familiarity acquired over the years by clinicians in the use of this particular DOAC.
Current evidence does not specify a maximum body weight for when apixaban may become sub therapeutic. Consensus across NHSGGC is that this advice applies to patients up to 150kg. In patients over 150kg, a decision needs to be taken based on individual circumstances.
In all cases, it is best practice to discuss with the patient which form of oral anticoagulant should be prescribed (DOAC vs warfarin) and be informed by their preference.
For VTE or non-valvular AF patients being considered for a switch from warfarin to a DOAC please follow the advice available here: GGC Medicines - Conversion from Warfarin to DOAC.
Refer to other blogs in the DOAC series:
Safe Prescribing of Direct Oral Anticoagulants (DOACs)
Updated Guidance: Use of DOACs in Patients with Venous Thrombosis and Malignant Disease
Published 19/04/2023. Amended 09/06/23. Medicines Update blogs are correct at the time of publication.
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