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In C. difficile, metronidazole may not benefit ICU patients on vancomycin



SAN FRANCISCOIntravenous metronidazole (Flagyl) did not improve 30-day mortality when it was added to oral vancomycin in adult ICU patients with severe Clostridium difficile infections, according to a review of 101 cases at the University of Maryland.

Dr. Ana Vega

Dr. Ana Vega

Adding metronidazole is a common move in ICUs when patients start circling the drain with C. difficile, in part because delivery to the gut doesn’t depend on gut motility. “At that point, you are throwing the kitchen sink at them, but it’s” based, like much in C. difficile management, on expert opinion, not evidence, said study lead Ana Vega, PharmD, a former resident at the university’s school of pharmacy in Baltimore, and now an infectious disease pharmacist at Jackson Memorial Hospital, Miami. The investigators wanted to plug the evidence gap. Forty-seven of the 101 patients in their review – all with signs of C. difficile sepsis – had IV metronidazole added to their vancomycin regimens. Thirty-day mortality was 14.9% in the combination group versus 7.4% in the monotherapy arm, and not significantly different (P = .338). There were also no significant differences in resolution rates or normalization of white blood cell counts and temperature.

“Our data question the utility of” of adding IV metronidazole to oral vancomycin in patients with severe disease. “It’s definitely something to think twice about because metronidazole isn’t benign. It makes people feel crummy; you can induce resistance; and it increases the risk of vancomycin-resistant Enterococci colonization,” already a risk with vancomycin, Dr. Vega said at an annual scientific meeting on infectious diseases.

“When you get to the point that you are trying combination therapy based on expert opinion, I think fecal transplants are something to consider” because the success rates are so high. “That would be my suggestion,” she said, even though “it’s much easier to write an order for a drug than to get a fecal transplant.”

The issue is far from resolved, and debate will continue. A similar review of ICU patients at Wake Forest University in Winston-Salem, N.C., did find a significant mortality benefit with combination therapy, regardless of C. difficile severity (Clin Infect Dis. 2015 Sep 15. doi: 10.1093/cid/civ409).

The Maryland investigators excluded patients with toxic megacolon and other life-threatening intra-abdominal complications requiring surgery, because combination therapy is more strongly recommended in fulminant disease. They were interested in people who were not quite ready for the operating room, when what to do is more in doubt.

Subjects were admitted to the ICU from April 2016 to April 2018 with positive C. difficile nucleic acid testing and an order for oral vancomycin. The only statistically significant baseline differences were that patients who got IV metronidazole had higher median white blood cell counts (18,400 versus 13,900 cells/mL; P = .035) and were more likely to receive higher than 500-mg doses of vancomycin (36.2% versus 7.4%; P less than .0001).

The Mean Acute Physiology and Chronic Health Evaluation II (APACHE II) score in the combination group was 23 versus 19 in the monotherapy arm (P = .247). There was no difference in the probability of receiving metronidazole based on the score.

The study again found no significant 30-day mortality differences among 76 patients matched by their APACHE II scores (15.8% in the combination arm versus 9.7%; P = .480).

Severe C. difficile infection was defined as either a white cell count above 15,000 or below 4,000 cells/mL, or a serum creatinine at least 1.5 times above baseline, plus at least one other sign of severe sepsis, such as a mean arterial pressure at or below 60 mm Hg. Metronidazole was started within 72 hours of the first vancomycin dose, and subjects on combination therapy were on both for at least 72 hours.

The mean age in the study was about 60 years old, and just over half of the subjects were men.

Dr. Vega said the investigators hope to expand their sample size and see if patients with more virulent strains of C. difficile do better on combination therapy.

There was no industry funding for the work, and the investigators didn’t have any relevant disclosures.

SOURCE: Vega AD et al. ID Week 2018, Abstract 488.

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