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LEVOTEC Technilab Levothyroxine Sodium Hypothyroidism Therapy Action And Clinical Pharmacology: Levothyroxine sodium is the monosodium salt of the levorotatory isomer of thyroxin (tetraiodothyronine), the principal hormone secreted by the normal thyroid gland. Following oral administration, the absorption of levothyroxine is incomplete and variable (50 to 75%), especially when taken with food. Once absorbed, synthetic levothyroxine is indistinguishable from the endogenous hormone. Levothyroxine is nearly totally bound to serum proteins and…

LEVSIN® Rivex Pharma Hyoscyamine Sulfate Antispasmodic Action And Clinical Pharmacology: Hyoscyamine inhibits specifically the actions of acetylcholine on structures innervated by postganglionic cholinergic nerves and on smooth muscles that respond to acetylcholine but lack cholinergic innervation. These peripheral cholinergic receptors are present in the autonomic effector cells of the smooth muscle, cardiac muscle, the sinoatrial node, the atrioventricular node, and the exocrine glands. It is completely devoid of any action…

LEUCOVORIN CALCIUM INJECTION Faulding Citrovorum Factor Folic Acid Derivative Action And Clinical Pharmacology: Leucovorin is a reduced form of folic acid, which is readily converted to other reduced folic acid derivatives (e.g., tetra-hydrofolate). Because it does not require reduction by dihydrofolate reductase as does folic acid, leucovorin is not affected by blockages of this enzyme by folic acid antagonists (dihydrofolate reductase inhibitors). This allows purine and thymidine synthesis, and thus…

LEUKERAN® Glaxo Wellcome Chlorambucil Antineoplastic Agent Action And Clinical Pharmacology: Chlorambucil is an aromatic nitrogen mustard derivative which acts as a bifunctional alkylating agent. Alkylation takes place through the formation of a highly reactive ethylenimonium radical. A probable mode of action involves cross-linkage of the ethylenimonium derivative between two strands of helical DNA and subsequent interference with replication. After oral administration of carbon-14 labelled chlorambucil, maximum plasma radioactivity occurs between…

LEUSTATIN® Janssen-Ortho Cladribine Antineoplastic – Chemotherapeutic Agent Warning: Cladribine should be administered under the supervision of a qualified physician experienced in the use of antineoplastic therapy. Suppression of bone marrow function should be anticipated. This is usually reversible and appears to be dose-dependent. Significant and prolonged lymphopenia has been noted. Serious neurological toxicity (including irreversible paraparesis and quadriparesis) has been reported in patients who received cladribine injection by continuous infusion…

LEVAQUIN® Janssen-Ortho Levofloxacin Antibacterial Action And Clinical Pharmacology: Levofloxacin is a synthetic broad spectrum antibacterial agent for oral and i.v. administration. Levofloxacin is the l-isomer of the racemate, ofloxacin, a quinolone antibacterial agent. The antibacterial activity of ofloxacin resides primarily in the l-isomer. The mechanism of action of levofloxacin and other quinolone antibacterials involves inhibition of DNA gyrase (bacterial topoisomerase II), an enzyme required for DNA replication, transcription, repair and…

LEDERLE LEUCOVORIN® CALCIUM Wyeth-Ayerst Citrovorum Factor Folic Acid Derivative Action And Clinical Pharmacology: Lederle Leucovorin Calcium (calcium folinate), the calcium salt of folinic acid (citrovorum factor), is a mixture of the diastereoisomers of the 5-formyl derivative of tetrahydrofolic acid. The biologically active compound of the mixture is the (-)-L-isomer. It is a metabolite of folic acid and an essential coenzyme for nucleic acid synthesis. Leucovorin is a reduced form of…

LESCOL® Novartis Pharmaceuticals Fluvastatin Sodium Lipid Metabolism Regulator Action And Clinical Pharmacology: Fluvastatin is a fully synthetic HMG-CoA reductase inhibitor and is hydrophilic. Fluvastatin is a racemate of two erythro enantiomers of which one exerts the pharmacological activity. Fluvastatin is a competitive inhibitor of HMG-CoA reductase, which is responsible for the conversion of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) to mevalonate, a precursor of sterols, including cholesterol. The inhibition of cholesterol biosynthesis reduces…

LANVIS® Glaxo Wellcome Thioguanine Antileukemic Agent Action And Clinical Pharmacology: Thioguanine is a close relative of mercaptopurine and like the latter is an antimetabolite which blocks purine metabolism. It causes depletion of human bone marrow producing neutropenia, reticulopenia, anemia, thrombocytopenia, and prolongation of clotting time. The protracted but reversible aplasia of bone marrow closely resembles the effects of ionizing radiations. In man, thioguanine is extensively converted to 2-amino-6-methyl-mercaptopurine which is…

LARIAM® Roche Mefloquine HCl Antimalarial Agent Action And Clinical Pharmacology: Mefloquine acts on the asexual intraerythrocytic forms of the human malaria parasites: P. falciparum, P. vivax, P. malariae and P. ovale. Mefloquine is also effective against malaria parasites resistant to other antimalarials such as chloroquine, proguanil, pyrimethamine and pyrimethamine-sulfonamide combinations. Resistance to P. falciparum to mefloquine has been reported, mainly in parts of South-East Asia. Cross-resistance between mefloquine and halofantrine…