It is a nucleoside analogue, a modified form of deoxyuridine, similar enough to be incorporated into viral DNA replication, but the iodine atom added to the uracil component blocks base pairing.

[1] Initially developed as an anticancer drug, idoxuridine became the first antiviral agent in 1962.

[4] Idoxuridine is ineffective against herpes simplex virus type 2 and varicella-zoster.

[3] Common side effects of the eye drops include irritation, blurred vision and photophobia.

[3] Therapy is continued for 3–4 days after healing is complete, as demonstrated by fluorescein staining.