Brands, Medical Use, Clinical Data
Brands / Synonyms
Adenine Arabinoside; Ara Atp; Ara-A; Ara-a Triphosphate; Ara-Atp; Araadenosine; Arabinofuranosyladenine Triphosphate; Arabinoside Adenine; Arabinosyl Adenine; Arabinosyl-Atp; Arabinosyladenine; Arabinosyladenine Triphosphate; Arasena-A; Spongoadenosine; Vidarabin; Vidarabine Triphosphate; Vira-A
For treatment of chickenpox - varicella, herpes zoster and herpes simplex
Vidarabine is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). The inhibitory activity of Vidarabine is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts Vidarabine into Vidarabine monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. in vitro, Vidarabine triphosphate stops replication of herpes viral DNA. When used as a substrate for viral DNA polymerase, Vidarabine triphosphate competitively inhibits dATP leading to the formation of 'faulty' DNA. This is where Vidarabine triphosphate is incorporated into the DNA strand replacing many of the adenosine bases. This results in the prevention of DNA synthesis, as phosphodiester bridges can longer to be built, destabilizing the strand.
Mechanism of Action
Vidarabine stops replication of herpes viral DNA in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation into and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase.
Biotrnasformation / Drug Metabolism
VIRA-A Ophthalmic Ointment, 3%, is contraindicated in patients who develop hypersensitivity reactions to it.