Despite the move towards NOACs for the prevention of thromboembolic disease, transition is not smooth for some patients and about 5% will revert back to warfarin.

This is the conclusion of a Queensland study of more than 3,000 patients in a warfarin program, which found 4.7% of patients switched back from NOACs, typically within six months

More than half (51%) did so on the recommendation of their GP but the rationale for the advice was not available to the study team.

Intolerance (23%), bleeding (9%), hospitalisation (6%), thromboembolic events (3%) and renal function (2%) were some of the specific reasons given for reverting from NOAC to warfarin.

The study found the median time to first INR within range after reverting to warfarin was six days; and time to two consecutive INRs in range was 14 days.

The vast majority of patients (96%) had at least one INR test within range within the first month of switching back.

After their experience with a NOAC, patients on warfarin required more frequent testing but a smaller dose of warfarin than before moving to a NOAC.

The study authors said the Australasian Society of Thrombosis and Haemostasis guidelines suggested that patients stable on warfarin, with time in therapeutic range (TTR) more than 65% over a three-month period, were the least suitable patients for NOACs.

“Using the TTR < 65% criteria for changing from warfarin, it could be argued that 80% of these patients were not suitable candidates for a change from warfarin,” they wrote in the Journal of Thrombosis and Thrombolysis.

“Further studies are required to identify the subset of existing warfarin patients that would particularly benefit from changing to NOACs especially in the Australian context with relatively high levels of warfarin control reported.”

Researcher Nijole Bernaitis, from Griffith University’s School of Pharmacy and Pharmacology, told the limbic the recommendations on who to switch were still up for consideration.

“It’s debatable what additional benefit patients will get, particularly if they have a high level of control.”

“However, even though the haematology guidelines are not to switch unless patients are unstable, there is data that NOACs potentially have a reduced risk, particularly of intracranial haemorrhage, so there may still be support for switching even in stable patients.”

And more research was required to help refine the transition strategy, he added, with consideration for individual clinical factors such as renal function and potential drug interactions.