Idoxuridinehydrate (5-Iodo-2′-deoxyuridine, 5-IUdR, IdUrd) is a competitive inhibitor of phosphorylases. As an iodinated thymidine analogue, it effectively inhibits DNA polymerase and hinders viral replication, making it useful in the treatment of viral eye infections such as herpes simplex keratitis. Against feline herpesvirus, Idoxuridine has been found to have an IC50 value of 4.3 μM [1].