Doctors find no benefit in prescribing anti-clotting medications or blood thinners to COVID-19 outpatients

A doctor talks to a patient through a laptop used for a virtual visit.

Neither aspirin nor an anti-clotting medication prevented the number of adult patients recovering from COVID-19 at home from experiencing a major adverse event, such as seeking hospital care or experiencing a heart attack or stroke. The results of this clinical trial, partially supported by the NHLBI, published in JAMA.  
As part of the adaptive study, medical researchers randomized 558 adults, ages 40-80, recovering from COVID-19 as an outpatient into one of three treatment groups or a control arm. The first group received a daily dose of aspirin. The second and third groups received either a lower or higher amount of twice-daily apixaban, the anti-clotting medication. A placebo pill was provided to patients in the control arm. All patients were followed for 45 days. Before treatment started, 22 patients (3.3% of the study) experienced an adverse event. During the treatment period, about one patient from each group, including the control, experienced an adverse event. The study started in September 2020 and stopped early in June 2021 due to a lower-than-expected number of adverse events among participants. The team found no significant differences in outcomes among patients in either treatment group or in the control arm.  
The researchers note a few reasons may help explain why the number of adverse events was lower than expected. First, as the pandemic progressed, medical care teams in hospitals could treat more patients – including those with more moderate compared to critical illness. Second, a younger wave of patients who became infected later in the pandemic didn’t have as many underlying risk factors for severe COVID-19 complications. Third, the researchers used loose estimates at the start of the study, which changed as testing became more available.