Direct-Acting Oral Anticoagulant Doses in Primary Care

Introduction: Direct-acting oral anticoagulants (DOACs) have seen a recent increase in numbers prescribed, due to effective prevention of strokes and embolic events in non-valvular atrial fibrillation. Despite increasing use, expansive dosing criteria and strict monitoring guidelines, inappropriate doses of DOACs are being prescribed in the community. Recent studies predicted that 15%-20% of elderly patients with AF were receiving inappropriate DOAC doses, with most underdosed. Patients are thus at risk of increased bleeding if overdosed or thrombotic events if underdosed.

Method: 85 patients requiring a review regarding potential DOAC dosing changes were identified in SystmOne at Dinnington Group GP Practice. For each patient, the following was reviewed:

• Current repeat prescription DOSE and indication

• Patient AGE

• Patient WEIGHT

• Patient SERUM CREATININE (ensuring up to date U&E)

• Patient CrCl

For AF dosing, patients must meet the CrCl threshold or TWO of the other criteria to require dose reduction. Information was compared with Rotherham CCG guidelines.

Results: 37 patients were identified as having incorrect DOAC dosing for non-valvular AF. Of these patients, over twice the number required a DOAC dose increase compared to a decrease. These patients were therefore receiving sub-optimal doses, often only meeting one dose reduction criteria. Age was the patient criteria most often met. A prescribing error was also identified, whereby a patient was receiving both treatment and maintenance dose apixaban for previous PE.

Conclusions: Patients are more often underdosed than overdosed. This should be considered when initiating or reviewing DOAC treatment. Recent weight measurements must be gathered and added to SystmOne for accurate CrCl calculation, perhaps by prompting patients when attending for blood monitoring or other appointments. Patient values are changeable so frequent monitoring of CrCl and other criteria is needed to ensure correct dose. Medication initiation and prescription reviews should therefore be an active, reasoning process rather than passive.