Alpha 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

A rare genetic disorder in which a person is missing the enzyme alpha1-antitrypsin, which protects the body from damage by other enzymes.

The disease mainly affects tissues in the lungs, resulting in emphysema, and the liver, causing cirrhosis.

The effects of alpha1-antitrypsin deficiency may not become apparent until after the age of 30.

There is no cure, but symptoms can be relieved by drug treatment.

In severe cases, a liver transplant may be a possibility.... alpha-antitrypsin deficiency

A protein that is produced in the liver and gastrointestinal tract of the fetus and by some abnormal tissues in adults.

Alpha-fetoprotein (AFP) can be measured in the maternal blood from the latter part of the 1st trimester of pregnancy, and its concentration rises between the 15th and 20th weeks.

Raised levels of are associated with fetal neural tube defects, such as spina bifida or anencephaly, and certain kidney abnormalities. High levels of also occur in multiple pregnancies (see pregnancy, multiple) and threatened or actual miscarriage. levels may be unusually low if the fetus has Down’s syndrome. For this reason, measurement of blood is included in blood tests, which are used to screen pregnant women for an increased risk of Down’s syndrome.

levels are commonly raised in adults with hepatoma (see liver cancer), cancerous teratoma of the testes or ovaries, or cancer of the pancreas, stomach, or lung.

For this reason, is known as a tumour marker.

(AFP) levels can be used to monitor the results of treatment of certain cancers; increasing levels after surgery or chemotherapy may indicate tumour recurrence.

However, levels are also raised in some noncancerous conditions, including viral and alcoholic hepatitis and cirrhosis.... alpha-fetoprotein

(Greek) The firstborn child; the first letter of the Greek alphabet... alpha

See “Type I error”.... alpha (i) error

A statistic commonly used to reflect the reliability of a measurement scale. See “reliability”.... alpha (i) statistic

Also called adrenoceptor-blocking agents or alpha blockers, these drugs stop the stimulation of alpha-adrenergic receptors at the nerve endings of the SYMPATHETIC NERVOUS SYSTEM by HORMONES with ADRENALINE-like characteristics. The drugs dilate the arteries, causing a fall in blood pressure, so they are used to treat HYPERTENSION and also benign enlargement of the PROSTATE GLAND. Examples of this group of drugs are doxazosin, indoramin, phentolamine and prazosin. The drugs should be used with caution as some may cause a severe drop in blood pressure when ?rst taken.... alpha adrenergic blockers

A protein produced in the gut and liver of the FETUS. Abnormality in the fetus, such as neural tube defect, may result in raised levels of alphafeto protein in the maternal blood. In DOWN’S (DOWN) SYNDROME, levels may be abnormally low. In either case, screening of the pregnancy should be carried out, including AMNIOCENTESIS to check the amount of alpha-feto protein in the amniotic ?uid. The protein may also be produced in some abnormal tissues in the adult – in patients with liver cancer, for example.... alpha-feto protein

A group of drugs used to treat hypertension (high blood pressure) and urinary symptoms due to enlargement of the prostate gland. Alpha-blockers are also used to treat urinary retention caused by an enlarged prostate gland (see prostate, enlarged). Side effects of the drugs may include dizziness and fatigue due to a sudden drop in blood pressure, nausea, dry mouth, and drowsiness.... alpha-blocker drugs

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

(alpha-adrenergic blocker) a drug that prevents the stimulation of alpha *adrenoceptors at the nerve endings of the sympathetic nervous system by noradrenaline and adrenaline: it therefore causes relaxation of smooth muscle, including widening of arteries (vasodilatation) and a drop in blood pressure. Alpha blockers include *doxazosin, *phentolamine, *phenoxybenzamine, *indoramin, *prazosin, *alfuzosin, and *tamsulosin.... alpha blocker

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

see sympathomimetic.... beta agonist

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