Association Between First-Time Neurologic Events and Metronidazole Treatment: A Case-Time Control Study

Purpose Metronidazole, a widely used antimicrobial medication, has been linked to neurologic adverse drug reactions. This study investigates the association between metronidazole use and first-time neurologic events. Methods We conducted a case-time-control study using data from the Danish National Patient Register and the National Prescription Register in years 2013 to 2021. Patients with a first-time diagnosis of encephalopathy, cerebellar dysfunction, or peripheral neuropathy were included. Conditional logistic regression analyses were performed to estimate the risk of neurologic events associated with metronidazole use. Findings Out of 476,066 first-time metronidazole prescriptions, the 100-day cumulative incidence of peripheral neuropathy was 0.016%, and 0.002% for cerebellar dysfunction or encephalopathy. In the case-time control study, we identified 17,667 persons with a first-time neurologic event and were included for the analysis. The estimated odds ratio for the combined neurologic events was 0.98 (95% CI, 0.59–1.64, P = 0.95) with no statistically significant association across different subgroups and time windows. Implications Our findings suggest that metronidazole-induced neurologic events may be rarer than previously described, and we did not find any consistent or statistically significant association between metronidazole exposure. Nonetheless, clinicians should remain vigilant to potential neurologic risks in patients receiving metronidazole, to ensure its safe and effective use.