Gimeracil is primarily used in combination with other anticancer agents, especially in chemotherapy regimens. It plays a critical role in enhancing the efficacy and stability of certain fluoropyrimidine drugs by inhibiting their degradation. By blocking the enzyme dihydropyrimidine dehydrogenase (DPD), Gimeracil helps maintain higher plasma concentrations of active chemotherapeutic components, thereby prolonging their antitumor effects. This action allows for lower doses of the primary drug, reducing the risk of side effects while maintaining therapeutic effectiveness. It is a key component in oral fluoropyrimidine formulations used to treat cancers such as colorectal, gastric, and head and neck cancers. Its use contributes to more consistent drug exposure and improved patient compliance due to oral administration.