A pyrimidine nucleoside analog that is used mainly in the treatment of leukemia, especially acute non-lymphoblastic leukemia. cytarabine is an antimetabolite antineoplastic agent that inhibits the synthesis of dna. Its actions are specific for the s phase of the cell cycle. It also has antiviral and immunosuppressant properties. (From Martindale, The Extra Pharmacopoeia, 30th ed, p472)