A Prospective, Observational Study Evaluating the Incidence of Metallic Taste, Compliance, and Clinical Outcomes with Metronidazole Extended-release 600 mg Compared to Immediate-release Formulations (MERIT STUDY).

BACKGROUND

Metronidazole remains a cornerstone in the management of anaerobic bacterial and protozoal infections. However, its clinical utility is often limited by adverse effects such as a metallic taste (dysgeusia), which can negatively impact treatment adherence. Extended-release (ER) formulations have been developed to optimize pharmacokinetic profiles and improve tolerability.

OBJECTIVE

To evaluate the incidence of metallic taste, patient compliance, clinical outcomes, and safety of metronidazole ER 600 mg compared with immediate-release (IR) formulations.

MATERIALS AND

METHODS

This prospective, observational, multi-center study included 200 adult patients who were prescribed either metronidazole ER 600 mg (n = 102) or IR formulations [200/400 mg; (n = 98)]. The primary endpoint was the incidence of metallic taste. Secondary endpoints included patient-reported compliance, clinical outcomes, and safety. Assessments were conducted at baseline and on days 3 and 5.

RESULTS

The incidence of metallic taste was significantly lower in the ER group compared to the IR group (8.82 vs 19.39%; p = 0.0134), representing a 54% relative risk (RR) reduction. Compliance was significantly higher in the ER group (91.18 vs 80.61%; p = 0.0241). Clinical cure rates were comparable (95.10 vs 90.82%; p = 0.2377). Both formulations were well tolerated, with only mild adverse events reported.

CONCLUSION

Metronidazole ER 600 mg significantly improved tolerability and adherence while maintaining comparable efficacy and safety. It offers a clinically meaningful advantage in enhancing patient compliance for the treatment of anaerobic infections.