Atrial fibrillation is characterised by a rapid, irregular heart-rate and affects an estimated 2.7-6.1 million in the US. The new research paper examined 14,865 patients who were taking blood-thinning treatments apixaban, dabigatran or rivaroxaban between October 2010 to September 2015. Of this number, it was found that 16% were given a dose which did not match the recommendations provided by the FDA’s labelling.

"Dosing errors of these blood-thinning medications in patients with atrial fibrillation are common and have concerning adverse outcomes," explained Xiaoxi Yao, lead author of the paper. "The number of patients using these drugs has quickly increased since the introduction of this new class of drugs in 2010."

The principle implication in these findings is that, as 10% of those suffering from atrial fibrillation also have severe kidney disease, an erroneous dose of such medication could lead a heightened risk of serious bleeding. Furthermore, the data indicates that as much as 40% of these patients are on a higher dose than recommended. 43% of this group were administered with the standard dosage, which could result in a lethal overdose. Conversely, it is estimated that 13% of those without kidney disease are underdosed, which is associated with less efficacy in stroke prevention.

"Overdosing is a fairly straightforward problem and can be avoided by regularly monitoring kidney function," added Dr Peter Noseworthy, a senior author on the paper. "However, underdosing is more complex. These medications need to strike a balance between stroke reduction and risk of bleeding. I think physicians often choose to reduce the dose when they anticipate their patients are at a particularly high bleeding risk ─ independent of kidney function.

"We conducted this study to highlight the prevalence of inappropriate dosing in routine clinical practice and the associated adverse outcomes," Noseworthy continued. "This study underscores the importance for physicians to be vigilant of kidney function when selecting or adjusting dose."