Isovorin, also known by its generic name leucovorin, is a medication used in various medical contexts, primarily as an antidote to folic acid antagonists, which are substances that inhibit the action of folic acid within the body. It plays a crucial role in chemotherapy regimens, particularly in combination with fluorouracil to enhance its effectiveness in the treatment of colorectal cancer. Isovorin works by helping to protect healthy cells from the toxic effects of chemotherapy drugs while allowing these drugs to target cancer cells more effectively. Additionally, it is used to treat or prevent certain types of anemia caused by a lack of folic acid in the body. Isovorin is available in both oral and injectable forms, making it versatile in its application depending on the specific needs of the patient.