vidarabine

Vidarabine is an antiviral small molecule and a nucleoside analog derived from *Streptomyces antibioticus*. It is primarily used to treat viral infections caused by herpes simplex virus types 1 and 2 (HSV-1, HSV-2), varicella-zoster virus (VZV), and vaccinia virus. Its main clinical use has been as a 3% ophthalmic ointment (Vira-A) for acute keratoconjunctivitis and recurrent superficial keratitis due to HSV-1 or HSV-2[1][4][5]. Vidarabine acts by interfering with viral DNA synthesis. After phosphorylation to its active triphosphate form (ara-ATP), it inhibits viral DNA polymerase both as an inhibitor and as a substrate—leading to the incorporation of faulty nucleotides into viral DNA strands, which disrupts further synthesis[1][2]. Additionally, its diphosphate form inhibits ribonucleotide reductase in viruses[1]. Vidarabine was the first drug available in the US for parenteral treatment of life-threatening herpes simplex infections but is now mainly used topically due to newer agents with improved safety profiles[6].

Brand names

Vira-A

Other names

vidarabineadenine arabinosideara-A