Dideoxycytosine is a nucleoside analogue that is used in the treatment of certain types of cancers and viral infections. It is commonly referred to as ddC and is similar in structure to the nucleoside cytosine found in DNA. However, ddC lacks a hydroxyl group, which prevents it from being incorporated into DNA and thereby inhibits the growth and replication of cancer or viruses. Some synonyms for dideoxycytosine include cytosine arabinoside, ara-C, and cytarabine. While these other drugs have different chemical structures and mechanisms of action, they are also used in the treatment of cancer and viral infections and offer alternative options for some patients.