Patients sickened by a Clostridium difficile infection (CDI) are prone to recurring episodes, but data from the MODIFY I and II clinical trials showed that bezlotoxumab (Zinplava—Merck) coupled with antibacterial therapy effectively lowers the odds of new infection. Administering a single I.V. infusion of 10 mg of the monoclonal antibody along with metronidazole, vancomycin, or fidaxomicin was enough to clip the 12-week recurrence rate to 22% compared with 33% in control patients. Based on the findings from the two large studies, bezlotoxumab became the first drug to win FDA approval for the purpose of preventing CDI recurrence in adults with CDI at high risk for recurrence. The therapy could be dangerous, however, for patients with a history of congestive heart failure, as the drug was correlated with higher rates of cardiac failure and death. Nausea, pyrexia, and headache also were more common among bezlotoxumab recipients than placebo patients.