Beta agonist Health Dictionary

(1) A muscle which contracts and causes a movement. Contraction of an agonist is complemented by relaxation of its antagonist (see below).

(2) A drug that acts through receptors on the surface of the cell or within the cell and provokes a biological response. As the body contains natural agonists that combine with cell receptors, any ‘occupation’ of these cell receptors by drug molecules will have a pharmacological e?ect on the individual. The intensity of that pharmacological e?ect is believed to be directly proportional to the number of receptors on the cell that combine with the drug molecule. For example, the natural agonist noradrenaline contracts the smooth muscle of blood vessels; the drug agonist phenylnephrine has a similar e?ect.

Antagonists are drugs which will combine with the receptor site to prevent another agent from producing its greatest e?ect. If the drug has no e?cacy of its own, but simply prevents the agonist from acting at the receptor site, it is called a full antagonist. A partial antagonist is a drug that provokes some activity at the receptor site. An example of an antagonist is prazosin, which acts against the natural agonist noradrenaline at the receptor site of the cells of blood-vessel muscle and prevents the vascular muscle from contracting.... agonist

Drugs used to slow the response to epinephrine (released by the adrenal medulla), usually to attempt controlling high blood pressure... beta blockers

See “Type II error”.... beta (i) error

See ADRENERGIC RECEPTORS.... beta adrenoceptor

Antibiotics with a beta-lactam ring in their molecular structure, including the penicillins and the cephalosporins. Act on penicillin binding proteins in the mucopeptides of the bacterial cell wall. Can be destroyed bybacterial beta-lactamases.... beta lactams

Linn. subsp. cicla (L.) Moq.

Synonym: B. vulgaris auct. non L.

Family: Chenopodiacae.

Habitat: Native to Mediterranean region; cultivated in North India, Maharashtra and South India.

English: Beet Root, Garden Beet, Chard.

Ayurvedic: Palanki.

Folk: Chukandar.

Action: Leaf—used in burns and bruises, also for diseases of spleen and liver. Tuber and seed— expectorant. Leaf and seed— diuretic. Leaf, tuber and seed— anti-inflammatory. Seed oil— analgesic.

Beet roots are eaten raw as salad or cooked. The leaves are nutritionally superior to roots and are a good source of vitamins and minerals.

The plant contains alkaloids ofwhich betaine is a mild diuretic and emme- nagogue.

In research, using rats, chard increased regeneration of beta cells in pancreas. Maximum reduction of blood glucose was after 42 days of administration. (J Ethnopharmacol, 2000, 73: 251-259.)

Beets are used orally as a supportive therapy in the treatment of liver diseases and fatty liver (possibly due to betaine). Ingestion of large quantities might worsen kidney disease. (Natural Medicines Comprehensive Database, 2007.)... beta vulgaris

Precursor of Vitamin A. Increases resistance against infection. Antioxidant. Together with Vitamins C and E form a vital line of defence in protection of strands of DNA, the genetic code, from cancerous mutation. Immune booster. Increases lymphocytes and T cells, part of the defence system.

Deficiency. Sun sensitivity; exposure inducing itching, burning and swelling of the skin. Kidney, bladder, and gut infections. Severe earache in young children. Strokes, heart attacks.

It is claimed that those who eat a diet rich in beta-carotene are less likely to develop certain types of cancer.

Smokers usually have low levels of beta-carotene in the blood. Statistics suggest that people who eat a lot of beta-carotene foods are less likely to develop lung, mouth or stomach cancer. In existing cases a slow-down of the disease is possible.

Daily dose. Up to 300mg. Excess may manifest as yellow discoloration of the skin, giving appearance of sun-tan.

Sources. Mature ripe carrots of good colour. A Finland study suggests that four small carrots contain sufficient beta-carotene to satisfy the recommended daily amount of Vitamin A. Orange and dark green fruits and vegetables. Broccoli, Brussels sprouts, spinach, pumpkin, apricots, peaches, oranges, tomatoes. Harvard Medical School study. Among 333 subjects with a history of heart disease, those who received beta-carotene supplements of 50 milligrams every other day suffered half as many heart attacks as those taking placebos. (Dr Charles Hennekens, Harvard Medical School) ... beta-carotene

A group of drugs, also known as 5HT1 agonists, used to treat acute attacks of migraine.

They work on the same receptors in the brain as 5 hydroxytryptamine (5HT), a neurotransmitter and vasodilator.

Common serotonin agonists include naratriptan and sumatriptan.

These drugs can cause chest pain, particularly in people with heart disease.

They should be used with caution in those at increased risk of coronary artery disease.

Other side effects include flushing, tingling, and nausea.... serotonin agonists

see sympathomimetic.... alpha agonist

see islets of Langerhans.... beta cells

one of a group of drugs that includes the *penicillins and the *cephalosporins. All have a four-membered beta-lactam ring as part of their molecular structure. Beta-lactam antibiotics function by interfering with the growth of the cell walls of multiplying bacteria. Bacteria become resistant to these antibiotics by producing beta-lactamases, enzymes (such as *penicillinase) that disrupt the beta-lactam ring. To counteract this, beta-lactamase inhibitors (e.g. *clavulanic acid) may be added to beta-lactam antibiotics. For example, co-amoxiclav is a mixture of *amoxicillin and clavulanic acid.... beta-lactam antibiotic

Also called beta blockers, these drugs interrupt the transmission of neuronal messages via the body’s adrenergic receptor sites. In the HEART these are called beta1 (cardioselective) receptors. Another type – beta2 (non-cardioselective) receptors – is sited in the airways, blood vessels, and organs such as the eye, liver and pancreas. Cardioselective beta blockers act primarily on beta1 receptors, whereas non-cardioselective drugs act on both varieties, beta1 and beta2. (The neurotransmissions interrupted at the beta-receptor sites through the body by the beta blockers are initiated in the ADRENAL GLANDS: this is why these drugs are sometimes described as beta-adrenergic-blocking agents.)

They work by blocking the stimulation of beta adrenergic receptors by the neurotransmitters adrenaline and noradrenaline, which are produced at the nerve endings of that part of the SYMPATHETIC NERVOUS SYSTEM – the autonomous (involuntary) network

– which facilitates the body’s reaction to anxiety, stress and exercise – the ‘fear and ?ight’ response.

Beta1 blockers reduce the frequency and force of the heartbeat; beta2 blockers prevent vasodilation (increase in the diameter of blood vessels), thus in?uencing the patient’s blood pressure. Beta1 blockers also affect blood pressure, but the mechanism of their action is unclear. They can reduce to normal an abnormally fast heart rate so the power of the heart can be concomitantly controlled: this reduces the oxygen requirements of the heart with an advantageous knock-on e?ect on the respiratory system. These are valuable therapeutic effects in patients with ANGINA or who have had a myocardial infarction (heart attack – see HEART, DISEASES OF), or who suffer from HYPERTENSION. Beta2 blockers reduce tremors in muscles elsewhere in the body which are a feature of anxiety or the result of thyrotoxicosis (an overactive thyroid gland – see under THYROID GLAND, DISEASES OF). Noncardioselective blockers also reduce the abnormal pressure caused by the increase in the ?uid in the eyeball that characterises GLAUCOMA.

Many beta-blocking drugs are now available; minor therapeutic di?erences between them may in?uence the choice of a drug for a particular patient. Among the common drugs are:

Primarily cardioselective	Non-cardioselective
Acebutolol	Labetalol
Atenolol	Nadolol
Betaxolol	Oxprenolol
Celiprolol	Propanolol
Metoprolol	Timolol

These powerful drugs have various side-effects and should be prescribed and monitored with care. In particular, people who suffer from asthma, bronchitis or other respiratory problems may develop breathing diffculties. Long-term treatment with beta blockers should not be suddenly stopped, as this may precipitate a severe recurrence of the patient’s symptoms – including, possibly, a sharp rise in blood pressure. Gradual withdrawal of medication should mitigate untoward effects.... beta-adrenoceptor-blocking drugs

A group of drugs, also known as beta-adrenergic blocking agents, prescribed principally to treat heart and circulatory disorders such as angina and hypertension. Beta-blockers block the effects of the sympathetic nervous system, which releases adrenaline (epinephrine) and noradrenaline (norepinephrine) at nerve endings that are known as beta receptors.

There are 2 types of beta receptor: beta 1 and beta 2. Beta 1 receptors are present in the heart and blood vessels, and beta 2 in the lungs. Some betablockers (such as acebutolol, atenolol, and metoprolol) are termed cardioselective and, because they act mostly on beta 1 receptors, are used mainly to treat heart disease such as angina, hypertension, and cardiac arrhythmia. The drugs are sometimes given after a myocardial infarction (heart attack) to reduce the likelihood of further damage to the heart muscle.

Other types of beta-blocker, such as oxprenolol, propranolol, and timolol, may be given to prevent migraine attacks by acting on blood vessels in the head; reduce the physical symptoms of anxiety; or control the symptoms of thyrotoxicosis. Beta-blocker drugs such as timolol are sometimes given in the

form of eye drops to treat glaucoma and work by lowering the fluid pressure in the eyeball.

Beta-blockers may reduce an individual’s capacity for strenuous exercise. The drugs may worsen the symptoms of asthma, bronchitis, or other forms of lung disease. They may also reduce the flow of blood to the limbs, causing cold hands and feet. In addition, sleep disturbance and depression can be side effects of beta-blockers.... beta-blocker drugs

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

(beta-adrenergic receptor blocker) a drug that prevents stimulation of the beta *adrenoceptors at the nerve endings of the sympathetic nervous system. Blockade of ?1 receptors causes a decrease in heart rate and force; blockade of ?2 receptors causes constriction of the airways and the arteries. Beta blockers include *acebutolol, *atenolol, *bisoprolol, *oxprenolol, *propranolol, and *sotalol; they are used to control abnormal heart rhythms, to treat angina, and to reduce high blood pressure (although they are no longer regarded by some experts as the first choice of drug for treating hypertension in the absence of heart disease, being less effective than newer antihypertensive drugs). Beta blockers that block both ?1 and ?2 receptor sites cause constriction of air passages in the lungs, and these drugs should not be used in patients with asthma and bronchospasm. Other beta blockers are relatively selective for the heart (cardioselective) and are less likely to constrict the airways. Some beta blockers (e.g. *carteolol, *levobunolol, and *timolol) reduce the production of aqueous humour and therefore the pressure inside the eye; they are taken as eye drops in the treatment of *glaucoma.... beta blocker