Arasena-A - General Information
A nucleoside antibiotic isolated from Streptomyces antibioticus. It has some antineoplastic properties and has broad spectrum activity against DNA viruses in cell cultures and significant antiviral activity against infections caused by a variety of viruses such as the herpes viruses, the vaccinia VIRUS and varicella zoster virus.
Pharmacology of Arasena-A
Arasena-A 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 Arasena-A is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts Arasena-A into Arasena-A 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, Arasena-A triphosphate stops replication of herpes viral DNA. When used as a substrate for viral DNA polymerase, Arasena-A triphosphate competitively inhibits dATP leading to the formation of 'faulty' DNA. This is where Arasena-A 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.
Arasena-A for patients
VIRA-A Ophthalmic Ointment, 3%, is contraindicated in patients who develop hypersensitivity reactions to it.
Additional information about Arasena-A
Arasena-A Indication: For treatment of chickenpox - varicella, herpes zoster and herpes simplex
Mechanism Of Action: Arasena-A 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.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Vidarabine
Synonyms: Adenine Arabinoside; Arabinofuranosyladenine Triphosphate; Arabinoside Adenine; Arabinosyl Adenine; Arabinosyladenine; Arabinosyladenine Triphosphate; Vidarabine Triphosphate; Ara Atp; Ara-A; Ara-a Triphosphate; Ara-Atp; Araadenosine; Arabinosyl-Atp; 9-beta-D-arabinofuranosyl-adenine
Drug Category: Antimetabolites; Antiviral Agents
Drug Type: Small Molecule; Approved
Other Brand Names containing Vidarabine: Arasena-A; Spongoadenosine; Vira-A; Vidarabin;
Absorption: Systemetic absorption of vidarabine should not be expected to occur following ocular administration and swallowing lacrimal secretions.
Toxicity (Overdose): Acute massive overdosage by oral ingestion of the ophthalmic ointment has not occurred. However, the rapid deamination to arabinosylhypoxanthine should preclude any difficulty. The oral LD50 for vidarabine is greater than 5020 mg/kg in mice and rats. No untoward effects should result from ingestion of the entire contents of the tube. Overdosage by ocular instillation is unlikely because any excess should be quickly expelled from the conjunctival sac.
Protein Binding: 24-38%
Biotransformation: In laboratory animals, vidarabine is rapidly deaminated in the gastrointestinal tract to Ara-Hx.
Half Life: Not Available
Dosage Forms of Arasena-A: Ointment Ophthalmic
Chemical IUPAC Name: (2R,3S,4S,5R)-2-(6-aminopurin-9-yl)-5-(hydroxymethyl)oxolane-3,4-diol hydrate
Chemical Formula: C10H15N5O5
Vidarabine on Wikipedia: http://en.wikipedia.org/wiki/Vidarabine
Organisms Affected: Human Herpes Virus