A variety of pyrimidine nucleosides (both halogenated and nonhalogenated) effectively inhibit the replication of herpes simplex viruses with limited host-cell toxicity. The exact mechanism of action of these compounds appears to reflect substitution of pyrimidine for thymidine, causing defective DNA molecules. Idoxuridine is effective for the treatment of herpesvirus infection of the superficial layers of the cornea (herpesvirus keratitis) and of the skin, but is toxic when administered systemically.
Trifluridine, also an analog of deoxythymidine, is currently the agent of choice for the treatment of herpesvirus keratitis in humans. The other antiviral pyrimidine nucleosides have not been used clinically to any notable extent.
Last full review/revision March 2012 by Dawn Merton Boothe, DVM, PhD, DACVIM, DACVCP