U.S. Department of Health & Human Services Divider Arrow National Institutes of Health Divider Arrow NCATS

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Showing 111 - 120 of 12124 results

Nevirapine is a non-nucleoside reverse transcriptase inhibitor (nNRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). HIV-2 RT and eukaryotic DNA polymerases (such as human DNA polymerases alpha, beta, or sigma) are not inhibited by nevirapine. Nevirapine is, in general, only prescribed after the immune system has declined and infections have become evident. It is always taken with at least one other HIV medication such as Retrovir or Videx. The virus can develop resistance to nevirapine if the drug is taken alone, although even if used properly, nevirapine is effective for only a limited time. Nevirapine binds directly to reverse transcriptase (RT) and blocks the RNA-dependent and DNA-dependent DNA polymerase activities by causing a disruption of the enzyme's catalytic site. The activity of nevirapine does not compete with template or nucleoside triphosphates. Nevirapine is used for use in combination with other antiretroviral drugs in the ongoing treatment of HIV-1 infection.
Topotecan, a semi-synthetic derivative of camptothecin (a plant alkaloid obtained from the Camptotheca acuminata tree), is an anti-tumor drug with topoisomerase I-inhibitory activity similar to irinotecan. DNA topoisomerases are enzymes in the cell nucleus that regulate DNA topology (3-dimensional conformation) and facilitate nuclear processes such as DNA replication, recombination, and repair. During these processes, DNA topoisomerase I creates reversible single-stranded breaks in double-stranded DNA, allowing intact single DNA strands to pass through the break and relieve the topologic constraints inherent in supercoiled DNA. The 3'-DNA terminus of the broken DNA strand binds covalently with the topoisomerase enzyme to form a catalytic intermediate called a cleavable complex. After DNA is sufficiently relaxed and the strand passage reaction is complete, DNA topoisomerase reattaches the broken DNA strands to form the unaltered topoisomers that allow transcription to proceed. Topotecan interferes with the growth of cancer cells, which are eventually destroyed. Since the growth of normal cells can be affected by the medicine, other effects may also occur. Unlike irinotecan, topotecan is found predominantly in the inactive carboxylate form at neutral pH and it is not a prodrug. Topotecan has the same mechanism of action as irinotecan and is believed to exert its cytotoxic effects during the S-phase of DNA synthesis. Topoisomerase I relieves torsional strain in DNA by inducing reversible single strand breaks. Topotecan binds to the topoisomerase I-DNA complex and prevents religation of these single strand breaks. This ternary complex interferes with the moving replication fork, which leads to the induction of replication arrest and lethal double-stranded breaks in DNA. As mammalian cells cannot efficiently repair these double strand breaks, the formation of this ternary complex eventually leads to apoptosis (programmed cell death). Topotecan mimics a DNA base pair and binds at the site of DNA cleavage by intercalating between the upstream (−1) and downstream (+1) base pairs. Intercalation displaces the downstream DNA, thus preventing religation of the cleaved strand. By specifically binding to the enzyme–substrate complex, Topotecan acts as an uncompetitive inhibitor. Topotecan is used for the treatment of advanced ovarian cancer in patients with disease that has recurred or progressed following therapy with platinum-based regimens. Also used as a second-line therapy for treatment-sensitive small cell lung cancer, as well as in combination with cisplatin for the treatment of stage IV-B, recurrent, or persistent cervical cancer not amenable to curative treatment with surgery and/or radiation therapy. Topotecan is sold under the trade name Hycamtin.
Ritonavir is a protease inhibitor with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Ritonavir binds to the protease active site and inhibits the activity of the enzyme. It is FDA approved for the treatment of HIV-1 infection. In patients receiving medications metabolized by CYP3A or initiation of medications metabolized by CYP3A in patients already receiving Ritonavir, may increase plasma concentrations of medications metabolized by CYP3A. The most frequently reported adverse drug reactions among patients receiving Ritonavir alone or in combination with other antiretroviral drugs were gastrointestinal (including diarrhea, nausea, vomiting, abdominal pain (upper and lower)), neurological disturbances (including paresthesia and oral paresthesia), rash, and fatigue/asthenia.
Ibutilide is a 'pure' class III antiarrhythmic drug, used intravenously against atrial flutter and fibrillation. At a cellular level it exerts two main actions: induction of a persistent Na+ current sensitive to dihydropyridine Ca2+ channel blockers and potent inhibition of the cardiac rapid delayed rectifier K+ current, by binding within potassium channel pores. In other words, Ibutilide binds to and alters the activity of hERG potassium channels, delayed inward rectifier potassium (IKr) channels and L-type (dihydropyridine sensitive) calcium channels. Ibutilide is indicated for the rapid conversion of atrial fibrillation or atrial flutter of recent onset to sinus rhythm. Ibutilide is marketed as Corvert by Pfizer.
Glimepiride, like glyburide and glipizide, is a "second-generation" sulfonylurea agents. Glimepiride is used with diet to lower blood glucose by increasing the secretion of insulin from pancreas and increasing the sensitivity of peripheral tissues to insulin. The mechanism of action of glimepiride in lowering blood glucose appears to be dependent on stimulating the release of insulin from functioning pancreatic beta cells, and increasing sensitivity of peripheral tissues to insulin. Glimepiride likely binds to ATP-sensitive potassium channel receptors on the pancreatic cell surface, reducing potassium conductance and causing depolarization of the membrane. Membrane depolarization stimulates calcium ion influx through voltage-sensitive calcium channels. This increase in intracellular calcium ion concentration induces the secretion of insulin. Glimepiride is used for concomitant use with insulin for the treatment of noninsulin-dependent (type 2) diabetes mellitus. Glimepiride`s original trade name is Amaryl.
Amifostine is an organic thiophosphate cytoprotective agent known chemically as 2-[(3¬ aminopropyl)amino]ethanethiol dihydrogen phosphate (ester), it’s adjuvant used in cancer chemotherapy and radiotherapy involving DNA-binding chemotherapeutic agents. It is marketed under the trade name Ethyol. Amifostine is a prodrug and is dephosphorylated by alkaline phosphatase in tissues to a pharmacologically active free thiol metabolite. This metabolite is believed to be responsible for the reduction of the cumulative renal toxicity of cisplatin and for the reduction of the toxic effects of radiation on normal oral tissues. The ability of Ethyol to differentially protect normal tissues is attributed to the higher capillary alkaline phosphatase activity, higher pH and better vascularity of normal tissues relative to tumor tissue, which results in a more rapid generation of the active thiol metabolite as well as a higher rate constant for uptake into cells. The higher concentration of the thiol metabolite in normal tissues is available to bind to, and thereby detoxify, reactive metabolites of cisplatin. This thiol metabolite can also scavenge reactive oxygen species generated by exposure to either cisplatin or radiation. Healthy cells are preferentially protected because amifostine and metabolites are present in healthy cells at 100-fold greater concentrations than in tumor cells.
Sevoflurane is a general anesthetic that is FDA approved for the induction and maintenance of general anesthesia in adult and pediatric patients for inpatient and outpatient surgery. Sevoflurane induces a reduction in junctional conductance by decreasing gap junction channel opening times and increasing gap junction channel closing times. Sevoflurane also activates calcium dependent ATPase in the sarcoplasmic reticulum by increasing the fluidity of the lipid membrane. It also appears to bind the D subunit of ATP synthase and NADH dehydogenase and also binds to the GABA receptor. Common adverse reactions include cardiovascular: bradyarrhythmia, hypotension, gastrointestinal: nausea, vomiting, neurologic: somnolence, psychiatric: agitation, respiratory: cough, interrupted breathing and other: shivering.
Mycophenolic acid (MPA) possesses antibacterial, antifungal, antiviral, immunosuppressive and anticancer properties. Mycophenolic acid (MPA) is a fungal metabolite that was initially discovered by Bartolomeo Gosio in 1893 as an antibiotic against anthrax bacillus, Bacillus anthracis. It is an uncompetitive and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), and therefore inhibits the de novo pathway of guanosine nucleotide synthesis without incorporation to DNA. It was approved under the brand name Myfortic for the prophylaxis of organ rejection in adult patients receiving a kidney transplant and is indicated for the prophylaxis of organ rejection in pediatric patients 5 years of age and older who are at least 6 months post kidney transplant. Myfortic is to be used in combination with cyclosporine and corticosteroids.
Carvedilol competitively blocks β1, β2 and α1 receptors. The drug lacks sympathomimetic activity and has vasodilating properties that are exerted primarily through α1-blockade. Animal models indicate that carvedilol confers protection against myocardial necrosis, arrhythmia and cell damage caused by oxidising free radicals, and the drug has no adverse effects on plasma lipid profiles. COREG® (carvedilol) is a racemic mixture in which nonselective β-adrenoreceptor blocking activity is present in the S(-) enantiomer and α1-adrenergic blocking activity is present in both R(+) and S(-) enantiomers at equal potency. Carvedilol is the first drug of its kind to be approved for the treatment of congestive heart failure, and is now the standard of care for this devastating disease. Carvedilol is also confirmed as effective in the management of mild to moderate hypertension and ischaemic heart disease.
Nefazodone hydrochloride (trade name Serzone) is an antidepressant drug marketed by Bristol-Myers Squibb. Its sale was discontinued in 2003 in some countries, due to the small possibility of hepatic (liver) injury, which could lead to the need for a liver transplant, or even death. The incidence of severe liver damage is approximately 1 in 250,000 to 300,000 patient-years. On May 20, 2004, Bristol-Myers Squibb discontinued the sale of Serzone in the United States. Within the serotonergic system, nefazodone acts as an antagonist at type 2 serotonin (5-HT2) post-synaptic receptors and, like fluoxetine-type antidepressants, inhibits pre-synaptic serotonin (5-HT) reuptake. These mechanisms increase the amount of serotonin available to interact with 5-HT receptors. Within the noradrenergic system, nefazodone inhibits norepinephrine uptake minimally. Nefazodone also antagonizes alpha(1)-adrenergic receptors, producing sedation, muscle relaxation, and a variety of cardiovascular effects. Nefazodone's affinity for benzodiazepine, cholinergic, dopaminergic, histaminic, and beta or alpha(2)-adrenergic receptors is not significant.