VIENNA – When given in conjunction with an antibiotic, rifampicin didn’t improve treatment response or mortality in patients with Staphylococcus aureus bacteremia, either in an overall analysis or in any of 18 subgroups.
The only hints of benefit associated with the drug were decreases in treatment failure and recurrence, but the numbers needed to treat were excessive (29 and 26, respectively). They didn’t translate into any long-term survival benefit and couldn’t balance out other findings that rifampicin increased drug interactions and complicated treatment,, said at the European Conference on Clinical Microbiology and Infectious Diseases.
He presented the results of the randomized, placebo-controlled(Adjunctive Rifampicin to Reduce Early Mortality From Staphylococcus aureus bacteremia) study. ARREST was conducted at 29 sites in the United Kingdom. It enrolled 758 adults with proven S. aureus bacteremia who were already on standard antibiotic therapy and switched them to either adjunctive rifampicin or placebo for 2 weeks. Clinicians could choose rifampicin in either 600 mg or 900 mg, oral or IV formulations, once or twice daily doses.
Patients were followed with clinical assessments and blood cultures for 12 weeks and for overall mortality for 102 weeks. The primary endpoint was bacteriologically confirmed treatment failure or recurrence by week 12.
Patients were a mean of 65 years old. Most infections (64%) were community acquired, with the remainder associated with a stay in a health care facility, and 6% were methicillin resistant. Serious comorbidities were common, including cancer (17%), chronic lung disease (12%), kidney disease (18%), and diabetes (30%).
The largest portion of infections (40%) had a deep focus, including native cardiac valve or joint, prosthetic cardiac valve or implant, and deep tissue infections. Other sites of infection were indwelling lines, skin/soft tissue, surgical sites, pneumonia, and urinary tract. For 18%, no specific focus was ever established.
Rifampicin was initiated a mean of 68 hours after main antibiotic therapy. Most patients (86%) received it orally, in the 900-mg dose (78%). The mean rifampicin treatment duration was 13 days.
Treatment failure rates through week 12 were practically identical for rifampicin and placebo (17.5% vs. 18.9%) in the overall analysis. Clinical failure or recurrence through week 12 was also similar for rifampicin and placebo (21.4% vs. 22.9%). Dr. Thwaites didn’t present all 18 subgroup analyses but said the results were similar no matter how patients were divided.
There was no significant difference in 12-week mortality for rifampicin vs. placebo (15.7% vs. 14.8%). There were 112 deaths, 56 in each group. Of these, 28 were directly related to the S. aureus infection. There was no difference in long-term survival measured at 102 weeks.
When an independent endpoint review committee examined some of the composite endpoints separately, it determined that rifampicin did confer a significant advantage in both bacterial and clinical recurrence. However, 29 patients needed to be treated to avoid a bacteriologic recurrence and 26 to avoid a clinical recurrence. Two cases of rifampicin resistance developed.
One-quarter of the group experienced serious adverse events. Dr. Thwaites didn’t review these but said they were evenly distributed between the groups. He also said that rifampicin was associated with an increase in drug-drug interactions, some of which required changing the backbone antibiotic.
There was a small, but nonsignificant, increase in acute kidney injury in the rifampicin group.
The study was funded by the National Institute of Health Research in the United Kingdom. Dr. Thwaites had no financial disclosures.