(an-tag'ŏ-nĭst )

[Gr. antagōnistēs, struggler]

Something that blocks, reverses, or opposes an action.

adenosine diphosphate a.Thienopyridine.

adenosine diphosphate receptor a.Thienopyridine.

aldosterone a.Any of a class of drugs (such as spironolactone or eplerenone) that blocks mineralocorticoid receptors. These drugs are used as diuretics, e.g., in treating heart failure.

and rogen-receptor a.Any drug that blocks cellular receptors for male hormones. Spironolactone is a drug in this class.

calcitonin gene-related peptide a.

ABBR: CGRP antagonist

dihydropyridine calcium a.A calcium channel blocking drug that resembles or is based on pyridine. It is a potent relaxer of smooth muscle cells and therefore works as a peripheral vasodilator. Drugs from this class are used to treat hypertension, angina pectoris, and other conditions. Amlodipine, felodipine, and nifedipine are dihydropyridine calcium antagonists.

drug a.A drug that prevents receptor stimulation. An antagonist drug has an affinity for a cell receptor, binds to it, and prevents the cell from responding to an agonist.

endothelin-receptor a.A drug that lowers blood pressure by opposing the vasoconstricting effects of endothelins.

growth hormone receptor a.Any drug that blocks the effects of growth hormone on its cellular receptors, e.g., in treating diseases such as acromegaly.

H₂-receptor a.Any of the drugs that inhibit gastric acid secretion by blocking the effects of histamine or acetylcholine on receptors found on parietal cells. Such drugs are used to treat peptic ulcers and gastroesophageal reflux disease. SYN: H₂ blocker.

H₃-receptor antagonist Any of the drugs that block H₃ receptors in the central nervous system. Such drugs may be used to treat disorders of sleep and arousal, wakefulness, and attention.

leukotriene-receptor a.Any of several drugs (such as zafirlukast and montelukast) that block the inflammatory effects of leukotrienes and are used to treat patients with asthma. These medications help to reduce the dependence of asthmatic patients on corticosteroids and beta-agonist inhalers.

long-acting muscarinic a.

ABBR: LAMA

muscular a.A muscle that opposes the action of the prime mover and produces a smooth movement by balancing the opposite forces.

narcotic a.A drug that prevents or reverses the action of a narcotic.

SEE: nalorphine hydrochloride.

neurokinin receptor a.Any of a group of drugs, e.g., aprepitant and rolapitant, that block nausea and vomiting caused by chemotherapy. They are often used with other antiemetic drugs.

neutral a.A chemical or drug with no activity of its own except to block the effect of another agent on its cellular receptor. SYN: silent antagonist.

nondihydropyridine calcium a.Any calcium channel blocker that is not based on a pyridine molecule, e.g., verapamil and diltiazem. Compared to dihydropyridines, these agents are more negatively inotropic and are more likely to slow the conduction of the electrical activity of the heart, e.g., by prolonging the P–R interval.

platelet-activating factor a.Any drug that blocks the effects of platelet-activating factor on inflammatory or allergic diseases and conditions.

peripheral opioid receptor a.Any of a class of medications that circulate in the body but do not cross the blood-brain barrier. They block the adverse effect of opioids (such as constipation in the gastrointestinal tract) without decreasing the pain-relieving effects of opioids in the central nervous system.

serotonin a.Any of a class of drugs used to treat or prevent nausea and vomiting. Examples are ondansetron (Zofran) and granisetron (Kytril).

silent a.Neutral antagonist.

vasopressin-receptor a.Any of the drugs (such as conivaptan and tolvaptan) that block cellular receptors to antidiuretic hormone and increase the excretion of water by the kidneys. These agents are used to treat hyponatremia in patients with the syndrome of inappropriate antidiuretic hormone.

vitamin K a.

ABBR: VKA