Antimetabolites are a class of drugs that interfere with the normal metabolism of cells, particularly during the process of cell division. They mimic the structure of natural substances in the body, which allows them to disrupt the synthesis of DNA and RNA. This makes them particularly useful in treating certain types of cancer, as rapidly dividing cancer cells are more affected by these drugs. Common examples of antimetabolites include methotrexate and 5-fluorouracil. These medications are often used in chemotherapy regimens to slow down or stop the growth of tumors. While effective, antimetabolites can also affect healthy cells, leading to side effects such as nausea and fatigue.