Researchers in the US report that concomitant diltiazem increased the risk of serious bleeds by about 20 per cent in atrial fibrillation (AF) patients receiving apixaban or rivaroxaban.

The study retrospectively followed 204,155 AF patients aged 65 years or older (mean age 76.9 years). Of these, 53,275 received diltiazem and 150,880 took metoprolol. 

During the median follow-up of 120 days, patients receiving diltiazem were 21 per cent more likely to show the primary outcome (composite of bleeding-related hospitalisation or death with recent evidence of bleeding) than those taking metoprolol: 60.3 and 49.7 per 1,000 person years respectively. 

Compared with metoprolol, the risk of bleeding-related hospitalisation was 22 per cent higher and the likelihood of death with recent evidence of bleeding increased by 19 per cent among those receiving concomitant diltiazem. 

The risk of developing the primary outcome was higher with initial diltiazem doses exceeding 120mg a day (the median dose) than with lower doses (29 and 13 per cent respectively). There were 15 additional cases of the composite outcome for every 1,000 person-years of treatment with diltiazem doses exceeding 120mg daily. The likelihood of major ischaemic or haemorrhagic events was 14 per cent higher with diltiazem doses exceeding 120mg. 

The risk of ischaemic stroke, systemic embolism or death without recent evidence of bleeding did not seem to differ in people receiving concomitant diltiazem or metoprolol.