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VITAMIN B1 General Monograph Thiamine Vitamin Pharmacology: Vitamin B1 is a water soluble B complex vitamin. In vivo, vitamin B1 combines with adenosine triphosphate (ATP) to form thiamine pyrophosphate, also known as cocarboxylase, a coenzyme. Its role in carbohydrate metabolism is the decarboxylation of pyruvic acid and alpha-ketoacids to acetaldehyde and carbon dioxide. Increased levels of pyruvic acid in the blood indicate vitamin B1 deficiency. Vitamin B1 depletion can occur…

VITAMIN B2 General Monograph Riboflavin Vitamin Pharmacology: Vitamin B2 is a water-soluble, B complex vitamin. It is required for tissue respiration and is also indirectly involved in maintaining erythrocyte integrity. Vitamin B2 deficiency often accompanies pellagra and other B vitamin deficiency states and is also associated with conditions causing negative protein balance, such as chronic diarrhea, malabsorption syndrome, diabetes mellitus and chronic debilitating diseases. Deficiency is manifested by angular stomatitis,…

VIROPTIC® Glaxo Wellcome Trifluridine Topical Antiviral Action And Clinical Pharmacology: Trifluridine is phosphorylated by a cellular thymidine kinase to its nucleotide monophosphate. Trifluridine monophosphate is an inhibitor of thymidylate synthetase, the target enzyme for the action of monofluorinated pyrimidines. Trifluridine has been demonstrated to combine slowly and irreversibly with thymidylate synthetase in a reaction that requires ATP. Trifluridine monophosphate is further phosphorylated by cellular enzymes to the triphosphate which is…

VISKAZIDE® Novartis Pharmaceuticals Pindolol – Hydrochlorothiazide Antihypertensive Action And Clinical Pharmacology: Viskazide contains the antihypertensive activity of 2 agents: a beta-adrenergic receptor blocking agent (pindolol) and a diuretic (hydrochlorothiazide). Pindolol is a nonselective beta-adrenergic receptor blocking agent which possesses partial agonist activity (intrinsic sympathomimetic activity-ISA). The mechanism of the antihypertensive effect of beta-adrenergic receptor blocking agents has not been established. Among the factors that may be involved are: (a) competitive…

VIPRINEX® Knoll Ancrod Anticoagulant Action And Clinical Pharmacology: Ancrod, a thrombin-like enzyme obtained from the venom of the Malayan Pit Viper (Agkistrodon rhodostoma), is highly specific for fibrinogen, producing anticoagulation by defibrinogenation. Enzymatically, Ancrod cleaves fibrinogen to split off the A-fibrinopeptides (A, AY and AP), but not the B-fibrinopeptide. The resulting fibrin polymers are imperfectly formed and much smaller in size (1 to 2 m long) than the fibrin polymers…

Virazole (Lyophilized) ICN Ribavirin Antiviral Action And Clinical Pharmacology: Ribavirin is active against respiratory syncytial virus (RSV). In cell cultures, the inhibitory activity of ribavirin for RSV is selective. The mechanism(s) of action is unknown, although evidence exists that inhibition of other RNA and DNA viruses may be due to ribavirin competition with guanosine in formation of viral mRNA cap structures and/or interference with enzymes responsible for functional methylation of…

VIDEX™ Bristol Didanosine Antiretroviral Agent Action And Clinical Pharmacology: Didanosine is a synthetic, purine nucleoside analogue of deoxyadenosine, active against the Human Immunodeficiency Virus (HIV). Didanosine inhibits the in vitro replication of HIV in human primary cells cultures and in established cell lines. The active antiviral metabolite, dideoxyadenosine-triphosphate (ddATP), is formed in several steps by phosphorylation of didanosine by cellular enzymes. Inhibition of HIV reverse transcriptase by ddATP is through…

VINCRISTINE SULFATE INJECTION USP Faulding Antineoplastic Action And Clinical Pharmacology: The mode of action of vincristine has not been completely delineated. Evidence is available from in vitro studies that vincristine inhibits spindle formation and is associated with the reversible binding of vincristine to spindle proteins in the S phase. Vincristine has also been found to interfere with RNA synthesis. It has also been shown to stop cell reproduction in metaphase,…

VIAGRA® (sildenafil citrate) Tablets DESCRIPTION VIAGRA®, an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Sildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate and has the following structural formula: Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/mL in water and a molecular weight of 666.7. VIAGRA® (sildenafil citrate)…

VIASPAN™ DuPont Pharma Cold Storage Solution Indications And Clinical Uses: For the flushing and cold storage of organs including kidney, liver and pancreas at the time of their removal from the donor in preparation for storage, transportation and eventual transplantation into a recipient. After precooling the solution to approximately 2 to 6°C in ice, the cold solution is used to flush the isolated organ immediately before removal from the donor…