Oestrogen-receptor antagonist Health Dictionary

(1) A muscle the contraction of which opposes that of another muscle called the AGONIST. When the agonist contracts, the antagonist relaxes.

(2) The action of one drug in opposing the action of another.... antagonist

(1) Organs, which may consist of one cell or a small group of cells, that respond to di?erent forms of external or internal stimuli by conveying impulses down nerves to the CENTRAL NERVOUS SYSTEM, alerting it to changes in the internal or external environment.

(2) A small, discrete area on the cell membrane or within the cell with which molecules or molecular complexes (e.g. hormones, drugs, and other chemical messengers) interact. When this interaction takes place it initiates a change in the working of the cell.... receptor

A site on the membrane surrounding a cell (see CELLS) that binds to the hormone OESTROGENS. This activates the cell’s reaction to the hormone. Anti-oestrogen drugs such as TAMOXIFEN used to treat breast cancer (see BREASTS, DISEASES OF) prevent the oestrogen from binding to these receptors.... oestrogen receptor

n. one of a group of steroid hormones (including oestriol, oestrone, and oestradiol) that control female sexual development, promoting the growth and function of the female sex organs (see menstrual cycle) and female secondary sexual characteristics (such as breast development). Oestrogens are synthesized mainly by the ovary; small amounts are also produced by the adrenal cortex, testes, and placenta. In men excessive production of oestrogen gives rise to *feminization.

Naturally occurring and synthetic oestrogens are used to treat *amenorrhoea and menopausal symptoms (see hormone replacement therapy), as well as androgen-dependent cancers (e.g. cancer of the prostate). Synthetic oestrogens are a major constituent of *oral contraceptives. Side-effects of oestrogen therapy may include nausea and vomiting, headache and dizziness, irregular vaginal bleeding, fluid and salt retention, and feminization in men. Oestrogens should not be used in patients with a history of cancer of the breast, uterus, or genital tract. —oestrogenic adj.... oestrogen

These are drugs that block the action of HISTAMINE at the H2 receptor (which mediates the gastric and some of the cardiovascular effects of histamine). By reducing the production of acid by the stomach, these drugs – chie?y cimetidine, ranitidine, famotidine and nizatidine – are valuable in the treatment of peptic ulcers (healing when used in high dose; preventing relapse when used as maintenance therapy in reduced dose), re?ux oesophagitis (see OESOPHAGUS, DISEASES OF), and the ZOLLINGERELLISON SYNDROME. These drugs are now being supplanted by PROTON-PUMP INHIBITORS and HELICOBACTER PYLORI eradication therapy. (See also DUODENAL ULCER.)... h2 receptor antagonists

A group of drugs used in the treatment of hypertension (high blood pressure). They have a similar action to ACE inhibitors but do not cause a dry cough. Examples are losartan and valsartan.... angiotensin ii antagonists

See H-receptor antagonists.... histamine-receptor antagonists

A drug that blocks the action of a hormone.... hormone antagonist

A group of antiallergy drugs, such as montelukast and zafirlukast, used to prevent symptoms of mild to moderate asthma. The drugs work by blocking the effects of leukotrienes – naturally occurring substances released in the lungs during an allergic reaction.

Because they are not bronchodilator drugs, and will not relieve an existing attack, they are usually used with bronchodilators and inhaled corticosteroids to reduce the frequency of attacks.

Side effects include gastrointestinal disturbances and headache.

Skin and hypersensitivity reactions may also occur.... leukotriene receptor antagonists

A group of synthetically produced drugs that are used in oral contraceptives and to supplement or replace the body’s own oestrogen hormones.

Oestrogen drugs are often used together with progestogen drugs.

Oestrogens suppress the production of gonadotrophin hormones, which stimulate cell activity in the ovaries. High doses are used in postcoital contraception to prevent conception (see contraception, emergency). They are also used to treat, or sometimes prevent, menopausal symptoms and disorders. Oestrogens may be used to treat certain forms of infertility, female hypogonadism, abnormal menstrual bleeding, prostatic cancer (see prostate, cancer of), and certain types of breast cancer.

Oestrogens may cause breast tenderness and enlargement, bloating, weight gain, nausea, reduced sex drive, depression, migraine, and bleeding between periods. Side effects often subside after 2 or 3 months. The drugs can increase the risk of abnormal blood clotting and susceptibility to high blood pressure (see hypertension). Oestrogen drugs should not be taken in pregnancy as they may adversely affect the fetus.... oestrogen drugs

A group of hormones that are essential for normal female sexual development and healthy functioning of the reproductive system.

In women, they are produced mainly in the ovaries and also in the placenta in pregnancy.

Small amounts are produced in the adrenal glands in both men and women, but oestrogens have no known specific function in men.

When levels are low, oestrogen hormones can be replaced with oestrogen drugs.... oestrogen hormones

A group of drugs used to treat the nausea and vomiting caused by radiotherapy and anticancer drugs. They are also used to control nausea and vomiting following surgery. Common serotonin antagonists include granisetron and ondansetron.... serotonin antagonists

any one of a class of drugs that block the action of the hormone *angiotensin II, which constricts blood vessels; they are therefore useful in treating *hypertension. These drugs include candesartan, irbesartan, losartan, telmisartan, and valsartan. Side-effects are usually mild.... angiotensin ii antagonist

(oestrogen-receptor antagonist) n. one of a group of drugs that oppose the action of oestrogen by binding to *oestrogen receptors in the body’s tissues. The most important of these drugs is currently *tamoxifen, which is used in the treatment of breast cancers dependent on oestrogen. Because they stimulate the production of pituitary *gonadotrophins, some anti-oestrogens (e.g. *clomifene, tamoxifen) are used to induce or stimulate ovulation in infertility treatment. Side-effects of anti-oestrogens include hot flushes, itching of the vulva, nausea, vomiting, fluid retention, and sometimes vaginal bleeding.... anti-oestrogen

(EGFR) a protein on the surface of cells (see receptor) that binds with epidermal *growth factor and is therefore involved in cell division. EGFR is expressed at increased levels in numerous tumours, particularly of the head and neck, and in colorectal cancer, in which it can be a target for antibody therapy with *cetuximab. *Tyrosine kinase inhibitors acting specifically on the EGFR include gefitinib and erlotinib in lung and pancreatic cancer.... epidermal growth factor receptor

a group of drugs used in the treatment of type 2 diabetes. They mimic the actions of *glucagon-like peptide-1 in regulating the rise in blood glucose levels after eating and they also enhance satiety (see incretin). As these drugs respond to a falling blood glucose level there is a reduced tendency to *hypoglycaemia compared with *sulphonylurea drugs and insulin therapy itself. They are given by subcutaneous injection and three of them are licensed for use in the UK: exenatide (Byetta; twice daily dosing), liraglutide (Victoza; once daily dosing), and lixisenatide (Lyxumia; once daily dosing).... glp-1 receptor agonists

one of a class of drugs that prevent the action of *leukotrienes by blocking their receptors on cell membranes, such as those in the airways. These drugs are used in the management of asthma for their effects in relaxing the smooth muscle of the airways and in reducing inflammation in the bronchial linings. Examples are montelukast and zafirlukast; side-effects may include headache and abdominal pain or gastrointestinal upsets.... leukotriene receptor antagonist

a receptor on synapses that binds the *neurotransmitter glutamate and also binds its *agonist NMDA (N-methyl-D-aspartate). This receptor is involved in learning, memory, mood, and cognition; its overactivity is associated with chronic pain. NMDA-receptor antibodies are associated with an *encephalitis preceded by psychiatric symptoms, often in patients with ovarian malignancy (teratoma). NMDA-receptor antagonists (e.g. *amantadine, *memantine hydrochloride, *riluzole) are used in the treatment of (among other conditions) epilepsy, Alzheimer’s disease, and chronic pain syndromes.... nmda receptor

(PRRT) a type of radiotherapy used to treat neuroendocrine tumours (NETs; see neuroendocrine system). A *radionuclide is combined with a relevant *peptide to create a so-called radiopeptide, which is injected into the patient’s bloodstream. Because NETs have an overexpression of peptide receptors, the radiopeptide binds to the tumour, delivering a high dose of radiation directly to the cancer cells. The chief merit of PRRT is this ability to target delivery of radionuclides for highly localized treatment. A similar technique, using a gamma emitter as the radionuclide, can be used for locating and imaging NETs.... peptide receptor radionuclide therapy

a cell or group of cells found between muscle fibres that responds to stretching of the muscle by transmitting impulses to the central nervous system through the sensory nerves. Stretch receptors are part of the *proprioceptor system necessary for the performance of coordinated muscular activity.... stretch receptor

autoantibodies targeted against the *thyroid-stimulating hormone (TSH) receptor of the thyroid cells. They can activate the TSH receptor, leading to the hyperthyroidism of *Graves’ disease, or they can block the TSH receptor, causing *hypothyroidism.... tsh receptor antibodies