Pathways

Vidarabine is an antiviral agent used to treat various viral infections. 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. Vidarabine stops replication of herpes viral DNA by either competitive inhibition of viral DNA polymerase, and consequently or incorporation into and termination of the growing viral DNA chain. Vidarabine is sequentially phosphorylated by kinases to the triphosphate ara-ATP, which is the active form of vidarabine that acts as both an inhibitor and a substrate of viral DNA polymerase.Ara-ATP inhibits the activity of DNA polymerase by competing with its substrate dATP. Ara-ATP also gets incorporated into viral DNA, but since it lacks the 3'-OH group which is needed to form the 5′ to 3′ phosphodiester linkage essential for DNA chain elongation, this causes DNA chain termination, preventing the growth of viral DNA.

Vidarabine is a drug that is not metabolized by the human body as determined by current research and biotransformer analysis. Vidarabine passes through the liver and is then excreted from the body mainly through the kidney.

Vilanterol is a long acting beta-2 adrenergic agonist. It can be found under the brand names Anoro, Anoro Ellipta, Breo Ellipta, and Trelegy Ellipta. It has a 24 hour activity and is used as a bronchodilator for the treatment of COPD and asthma. This drug causes the relaxation of bronchial smooth muscle through stimulation of adenylyl cyclase. The result of taking this drug is relaxation of the bronchial smooth muscles causing bronchodilaton and increased airflow. Once vilanterol is administered and it binds to the beta-2 adrenergic receptor, the G protein signalling cascade begins. The alpha and beta/gamma subunits of the G protein separate and GDP is replaced with GTP on the alpha subunit. This alpha subunit then activates adenylyl cyclase which converts ATP to cAMP. cAMP then activates protein kinase A (PKA) which in turn phosphorylates targets and inhibits MLCK through decreased calcium levels causing muscle relaxation. PKA can phosphorylate certain Gq-coupled receptors as well as phospholipase C (PLC) and thereby inhibit G protein-coupled receptor (GPCR) -PLC-mediated phosphoinositide (PI) generation, and thus calcium flux. PKA phosphorylates the inositol 1,4,5-trisphosphate (IP3) receptor to reduce its affinity for IP3 and further limit calcium mobilization. PKA phosphorylates myosin light chain kinase (MLCK) and decreases its affinity to calcium calmodulin, thus reducing activity and myosin light chain (MLC) phosphorylation. PKA also phosphorylates KCa++ channels in ASM, increasing their open-state probability (and therefore K+ efflux) and promoting hyperpolarization. Since myosine light chain kinase is not activated, Serine/threonine-protein phosphatase continues to dephosphorylate myosin LC-P, and more cannot be synthesized so myosin remains unbound from actin causing muscle relaxation. This relaxation of the smooth muscles in the lungs causes the bronchial airways to relax which causes bronchodilation, making it easier to breathe. Some side effects of taking vilanterol may include body aches, chills, cough, fever, and headache.

Vilazodone selectively inhibits serotonin reuptake in the central nervous system as well as acting as a partial agonist of 5HT-1A receptors. The exact mechanism for how these effects translate to its antidepressant effects are not known though there is an association between these effects and anti-depressive activity.

Metabolites of Vilazodone are predicted with biotransformer.