Dihydrofolate Reductase Inhibitor: From 1 Different Sources
any of various drugs that interfere with the conversion of folate to its active form in the body. They include *pyrimethamine, *trimethoprim, and *methotrexate. When such drugs are necessary, folate deficiency is treated with *folinic acid rather than folic acid.
A drug that curbs the action of an ENZYME in the blood controlling the production of carbonic acid or bicarbonate from CARBON DIOXIDE (CO2). Called carbonic anhydrase, the enzyme is present in ERYTHROCYTES and it has a key part in maintaining the acid-base balance in the blood. Inhibiting drugs include ACETAZOLAMIDE and DORZOLAMIDE, and these are used as weak DIURETICS to reduce the increased intraocular pressure in ocular hypertension or open-angle GLAUCOMA (see EYE, DISORDERS OF).... carbonic anhydrase inhibitor
These are drugs that inhibit the production of acid in the stomach by blocking a key enzyme system, known as the PROTON PUMP, of the parietal cells of the stomach. The drugs include omeprazole, lansoprazole and pantoprazole, and they are the treatment of choice for oesophagitis (erosion and stricture – see under OESOPHAGUS, DISEASES OF); for the short-term treatment for gastric ulcer (see under STOMACH, DISEASES OF) and DUODENAL ULCER; and, in combination with ANTIBIOTICS, for the eradication of Helicobacter pylori.... proton-pump inhibitors
See ANGIOTENSIN-CONVERTING ENZYME (ACE) INHIBITORS.... ace inhibitors
The ENZYME that converts angiotensin I to angiotensin II (see ANGIOTENSIN) is called angiotensin-converting enzyme. Angiotensin II controls the blood pressure and is the most potent endogenous pressor substance produced in the body; angiotensin I has no such pressor activity. Inhibition of the enzyme that converts angiotensin I to angiotensin II will thus have marked effects on lowering the blood pressure, and ACE inhibitors have a valuable role in treating heart failure when thiazides and beta blockers cannot be used or fail to work, especially after myocardial infarction (see HEART, DISEASES OF). Captopril was the ?rst ACE inhibitor to be synthesised: it reduces peripheral resistance by causing arteriolar dilatation and thus lowers blood pressure. Other drugs such as enalapril, lisinopril, cilazapril, quinapril and ramipril have since been developed. Some kidney disorders increase the production of angiotensin II and so cause HYPERTENSION.... angiotensin-convertingenzyme (ace) inhibitors
A group of drugs that stop the action of the ENZYME, aromatase. This enzyme converts androgens (see ANDROGEN) to OESTROGENS. If this conversion is inhibited, the concentrations of oestrogens in the body are reduced – so these drugs operate against tumours, such as breast cancer, that depend on oestrogen for their growth. Aromatase inhibitors include anastrazole and formestane, and they are usually prescribed as second-line treatment after TAMOXIFEN, the prime drug treatment for breast cancer.... aromatase inhibitors
This stands for cyclo-oxygenase 2 inhibitors – a class of drugs used in treating ARTHRITIS – of which the most well-used is celecoxib. Their main claim is that they are less likely to cause gastrointestinal disturbance than NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS). In 2001, the National Institute for Clinical Excellence (NICE) recommended that they should not be used routinely in rheumatoid arthritis or osteoarthritis but only in patients with a history of peptic ulcer or gastrointestinal bleeding. They should also be considered in persons over the age of 65 taking other drugs which could cause gastrointestinal bleeding, those who are very debilitated, and those who are taking maximum doses of NSAIDs. In 2005, rofecoxib was withdrawn because of concerns about cardiac side-effects.... cox-2 inhibitors
See COX-2 INHIBITORS.... cyclo-oxygenase-2 selective inhibitors
See REVERSE TRANSCRIPTASE INHIBITOR.... nucleoside reverse transcriptase inhibitor
Exogenously, a PGE inhibitor like aspirin, and usually intended to lessen joint inflammation and uterine spasms.... pg inhibitor
A new group of drugs which, in combination with antiviral agents, are used to treat AIDS (see AIDS/HIV). They inhibit the activity of PROTEASE, an enzyme produced by HIV, and which breaks down proteins. The drugs have recently been introduced: those in use are indinavir, nel?navir, ritonavir and saquinavir.... protease inhibitors
An agent that prevents the action of the viral ENZYME, REVERSE TRANSCRIPTASE, so disrupting the virus’s colonisation of its target host. The reverse transcriptase inhibitor ZIDOVUDINE is used (in combination with other agents) to treat HIV infection.... reverse transcriptase inhibitor
These ANTIDEPRESSANT DRUGS have few antimuscarinic effects (see ANTIMUSCARINE), but do have adverse effects of their own – predominantly gastrointestinal. They are, however, much safer in overdose than the tricyclic antidepressants, which is a major advantage in patients who are potentially suicidal. Examples are citalopram, used to treat panic disorders, as well as depressive illness; FLUOXETINE; and PAROXETINE. (See also MENTAL ILLNESS.)... selective serotonin-reuptake inhibitors (ssris)
A group of vasodilator drugs used to treat heart failure, hypertension, and diabetic nephropathy. (angiotensin converting enzyme) inhibitors are often prescribed with other drugs such as diuretic drugs or betablocker drugs. Possible side effects include nausea, loss of taste, headache, dizziness, and dry cough.... ace inhibitor drugs
A group of non-steroidal anti-inflammatory drugs (NSAIDs) that cause less stomach irritation as a side effect than other NSAIDs. Examples of -2 inhibitors include celecoxib and rofecoxib.... cox-2 inhibitor drugs
A class of drugs used in the treatment of diseases, including HIV infection, that are caused by retroviruses. The drugs affect the ability of the virus to reproduce by blocking reverse transcriptase, a key enzyme. Drugs include lamivudine, zidovudine (AZT), efavirenz, and stavudine.... reverse transcriptase inhibitors
angiotensin-converting enzyme inhibitor: any one of a group of drugs used in the treatment of raised blood pressure and heart failure. ACE inhibitors act by interfering with the action of the enzyme that converts the inactive *angiotensin I to the powerful artery constrictor angiotensin II. The absence of this substance allows arteries to widen and the blood pressure to drop. Possible side-effects include weakness, dizziness, loss of appetite, and skin rashes.... ace inhibitor
any member of a group of *oral hypoglycaemic drugs, including acarbose (Glucobay), used for treating type 2 *diabetes mellitus. They reduce the breakdown and absorption of carbohydrates in the intestine by blocking the action of an important enzyme (?-glucosidase) in this process. Side-effects include flatulence and diarrhoea.... alpha-glucosidase inhibitor
an agent that prevents the development of new blood vessels (*angiogenesis) by inhibiting the action of *vascular endothelial growth factor (it is also known as anti-VEGF). Angiogenesis inhibitors are used as anticancer drugs, since growing cancers have a greater need for blood supply than normal tissue and must develop new blood vessels before progressing beyond a very small size. They include *aflibercept, *bevacizumab, and *thalidomide. Because of their action, some of these drugs are used in the treatment of wet age-related *macular degeneration.... angiogenesis inhibitor
any one of a class of drugs used in the treatment of early and advanced oestrogen-dependent breast cancer in postmenopausal women. These drugs act by inhibiting the action of aromatase, an enzyme that promotes the conversion of testosterone to oestradiol. They therefore reduce oestrogen levels, which can be helpful in the control of oestrogen-dependent tumours. Aromatase inhibitors include anastrazole, exemestane, and letrozole. Side-effects include symptoms of oestrogen deficiency (e.g. hot flushes), nausea and vomiting, and headache.... aromatase inhibitor
any one of a class of drugs that block the action of acetylcholinesterase (see cholinesterase), an enzyme that quickly breaks down the neurotransmitter acetylcholine. This neurotransmitter is central to the functional interconnection between nerve cells in the outer layer (cortex) of the brain; the early impairment of cognitive function found in Alzheimer’s disease is associated with a reduction in acetylcholine levels. By inhibiting acetylcholine breakdown, acetylcholinesterase inhibitors have been found helpful in slowing down the rate of cognitive decline in mild to moderate dementia; they do not halt the progress of the disease. The group includes donepezil, galantamine, and rivastigmine... acetylcholinesterase inhibitor
drugs that act by inhibiting the calcium-dependent protein *phosphatase calcineurin, an enzyme that initiates a sequence of events that bring about activation of T *lymphocytes. The group includes *ciclosporin and *tacrolimus, which are major maintenance immunosuppressants used in transplantation. Topical calcineurin inhibitors (e.g. tacrolimus, pimecrolimus [Elidel]) are used in the treatment of eczema when topical steroids have failed or are contraindicated. Stinging is a common transient side-effect, and reactivation of infections may occur.... calcineurin inhibitors
any one of a group of anti-inflammatory drugs (see NSAID) that selectively block the action of the enzyme cyclo-oxygenase 2 (COX-2), which mediates the production of *prostaglandin at sites of inflammation, especially in joints; they are less likely to inhibit COX-1, which controls the production of prostaglandin in the stomach (where it is involved in the production of protective mucus), and therefore less likely than nonselective NSAIDs to cause peptic bleeding or ulceration. COX-2 inhibitors are used in the treatment of arthritis, acute gout, and moderate or severe pain. They include *celecoxib and etoricoxib. However, because their use is associated with an increased incidence of heart attack and stroke, COX-2 inhibitors should be taken only by those who are not at risk of developing these conditions and who have a high risk of developing peptic ulceration. Other side-effects include fluid retention (oedema), intestinal upset, dizziness, insomnia, and sore throat.... cox-2 inhibitor
(cytokine modulator) any one of a group of agents that inhibit the activity of cytokines, especially *tumour necrosis factor alpha (TNF-?). They include *infliximab, *etanercept, and *adalimumab, known as anti-TNF drugs, which are used as *disease-modifying antirheumatic drugs and to treat inflammatory bowel disease.... cytokine inhibitor
any one of a class of antiviral drugs that inhibit the action of DNA polymerase enzymes, which are used by viruses to form their own DNA. These drugs prevent, to a varying degree, the reproduction of viruses. They include *aciclovir, *foscarnet, *ganciclovir, and *valaciclovir.... dna polymerase inhibitor
a group of *oral hypoglycaemic drugs used in the treatment of type 2 diabetes mellitus. Through inhibiting the enzyme dipeptidyl peptidase-IV they enhance the action of *glucagon-like peptide-1. Five drugs in this group are currently licensed for use in the UK: sitagliptin, vildagliptin, saxagliptin, linagliptin, and alogliptin.... dpp-iv inhibitors
hydroxymethylglutaryl coenzyme A reductase: the key rate-limiting enzyme that is involved in the production of cholesterol in the liver. Inhibition of its action is the mechanism by which the *statin group of lipid-lowering agents work.... hmg coa reductase
n. a substance that prevents the occurrence of a given process or reaction. See also MAO inhibitor.... inhibitor
a drug that blocks the action of the PARP enzyme, which is required for *DNA repair in cancer cells with faulty *BRCA1 and BRCA2 genes. These drugs are used in the treatment of cancer in patients with BRCA1 or BRCA2 mutations. They are also undergoing trials to see if they are useful in the treatment of other cancers.... parp inhibitor
a drug that reduces gastric acid secretion by blocking the *proton pump. Proton-pump inhibitors include esomeprazole, lansoprazole, *omeprazole, pantoprazole, and rabeprazole sodium; they are used for treating gastro-oesophageal reflux disease, peptic ulcer, and acid hypersecretion associated with *gastrinoma.... proton-pump inhibitor
receptor activator of nuclear factor kappa B ligand inhibitor: an agent that works by inhibiting the development of *osteoclasts and bone resorption, thus minimizing bone loss and the potential for fractures in those with postmenopausal osteoporosis and bone metastases.... rankl inhibitor
see SNRI.... selective serotonin and noradrenaline reuptake inhibitor
see calcineurin inhibitors.... topical calcineurin inhibitors
(MAOI) a drug that prevents the activity of the enzyme *monoamine oxidase (MAO). MAO inhibitors include phenelzine, isocarboxazid, and tranylcypromine. These drugs are irreversible inhibitors of monoamine oxidase A, whose use as antidepressants is now restricted because of the severity of their side-effects. These include interactions with other drugs (e.g. ephedrine, phenylephrine) and with foods or drinks containing *tyramine (e.g. cheese or red wine) to produce a sudden and dangerous increase in blood pressure. *Moclobemide is a reversible inhibitor of monoamine oxidase A (RIMA), with less severe side-effects. See also selegiline.... mao inhibitor
any one of a class of drugs used in the treatment of HIV infection and *AIDS. Used in combination with other *antiretroviral drugs, they act by inhibiting the action of protease, an enzyme produced by HIV that cleaves two precursor proteins into smaller fragments. These fragments are required for viral growth, infectivity, and replication. Protease inhibitors include atazanavir, indinavir, lopinavir and ritonavir (which are used in combination), saquinavir, and tipranavir. Side-effects include nausea, vomiting, diarrhoea, and rashes; these drugs are also associated with hyperglycaemia and *lipodystrophy. See also boceprevir.... protease inhibitor
any one of a class of *cytotoxic drugs that work by blocking the action of topoisomerase enzymes, which promote the uncoiling of the DNA double helix, a necessary preliminary to replication. Topoisomerase I inhibitors include irinotecan, used for treating advanced colorectal cancer (especially in combination with *fluorouracil); and topotecan, given for treating advanced ovarian cancer, relapsed small-cell lung cancer, and recurrent cervical cancer. Side-effects include delayed but severe diarrhoea and reduction in blood-cell production by the bone marrow. Topoisomerase II inhibitors include *etoposide and *doxorubicin.... topoisomerase inhibitor
any one of a class of drugs that interfere with cell growth in a variety of different ways by inhibiting the action of tyrosine kinases. This family of enzymes, which occur both within cells and as components of cell-membrane receptor sites, have an important role in cell division and cell growth. Many tumour cells have been shown to have both intracellular enzymes and extracellular receptor sites, and a variety of anticancer agents have been developed to inhibit enzyme activity at these sites. Among these drugs are *imatinib, dasatinib, and nilotinib, used for treating chronic myeloid leukaemia; *sunitinib, for treating renal cell carcinoma; and erlotinib, for treating pancreatic cancer and non-small-cell lung cancer. See also epidermal growth factor receptor.... tyrosine kinase inhibitor
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