Idoxuridine hydrate (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].

Idoxuridine hydrate, at concentrations ranging between 2-10 μM over a 72-hour period, exhibits an antiviral IC50 value of 4.3 μM, as demonstrated in a Cell Proliferation Assay on Crandell-Reese feline kidney (CRFK) cells. Additionally, a Cell Cytotoxicity Assay revealed that exposure to concentrations of 5-50 μM for the same duration resulted in a relative reduction of 10.8% in CRFK cell viability.

Idoxuridine hydrate, administered through intraperitoneal injection at a dosage of 50-200 mg/kg for three times at three-hour intervals, has been shown to enhance the production of hemolysin plaque-forming cells (HPFC) against sheep red blood cells (SRBC) in both female and male C3HeB/FeJ mice as well as A/J male mice. This effect was observed across the specified dosage range.