Antagonist

antagonist /an·tag·o·nist/ (an-tag´o-nist)

1. a substance that tends to nullify the action of another, as a drug that binds to a cell receptor without eliciting a biological response, blocking binding of substances that could elicit such responses.antagonis´tic

2. antagonistic muscle.

Antagonist. The triceps brachii extends the forearm at the elbow while the biceps brachii, its antagonist, flexes the elbow.

3. a tooth in one jaw that articulates with one in the other jaw.

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a-adrenergic antagonist  alpha-adrenergic blocking agent; see adrenergic blocking agent.

ß-adrenergic antagonist  beta-adrenergic blocking agent; see adrenergic blocking agent.

folic acid antagonist  an antimetabolite, e.g., methotrexate, that interferes with DNA replication and cell division by inhibiting the enzyme dihydrofolate reductase; used in cancer chemotherapy.

H1 receptor antagonist  any of a large number of agents that block the action of histamine by competitive binding to the H1 receptor; they also have sedative, anticholinergic, and antiemetic effects and are used for the relief of allergic symptoms, as antiemetics, as antivertigo agents, and as antidyskinetics in parkinsonism.

H2 receptor antagonist  an agent that blocks the action of histamine by competitive binding to the H2 receptor; used to inhibit acid secretion in the treatment of peptic ulcer.

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an·tag·o·nist (n-tg-nst)

n.

Something, such as a muscle, disease, or physiological process, that neutralizes or impedes the action or effect of another.

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Antagonist

A substance that tends to nullify the action of another.

Mentioned in: Withdrawal Syndromes

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antagonist,

n 1. a drug that counteracts, blocks, or abolishes the action of another drug.
n 2. a muscle that acts in opposition to the action of another muscle (e.g., flexor vs. extensor).
n 3. a tooth in one jaw that occludes with a tooth in the other jaw.

antagonist, narcotic,

n a narcotic drug that acts specifically to reverse depression of the central nervous system.

antagonists, insulin,

n.pl the circulating hormonal and nonhormonal substances that stimulate glyconeogenesis (e.g., 11-oxysteroids and S hormones).

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antagonist

1. a muscle that counteracts the action of another muscle, its agonist.

2. a drug that binds to a cellular receptor for a hormone, neurotransmitter, or another drug blocking the action of that substance without producing any physiological effect itself.

3. a tooth in one jaw that articulates with one in the other jaw. See also antagonism.