Mericitabine is primarily used in the treatment of chronic hepatitis C virus (HCV) infections. It functions as a nucleoside analog inhibitor, targeting the viral RNA polymerase to inhibit replication of the HCV genome. This makes it a key component in antiviral therapy, particularly for patients who have not responded well to other treatments. It is often used in combination with other antiviral agents, such as ribavirin and interferon, to enhance its efficacy and reduce the likelihood of viral resistance. Its role in combination therapies has been significant in improving sustained virological response rates in HCV patients.