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The use of ex vivo platelet aggregation to confirm the in vivo alpha 2-adrenoreceptor antagonist effect of idazoxan in man. 1987

N C Muir, and J C Doxey, and M E Havler, and J M Clifford

The aggregation of human platelets induced by adrenaline has been used as a test system to investigate the in vivo effect of the alpha 2-adrenoreceptor antagonist idazoxan during initial intravenous studies with increasing doses. The inhibitory effect of idazoxan in vitro was confirmed; addition of idazoxan to platelet suspensions prior to adrenaline caused a competitive inhibition of the aggregatory response by specific antagonism of the platelet alpha 2-adrenoreceptor. Following intravenous infusions of increasing doses of idazoxan to volunteers, a dose-dependent inhibition of the ex vivo aggregatory response to adrenaline was observed in isolated platelet suspensions compared to predose values. The inhibitory effects of idazoxan in vivo declined in a biphasic manner with a more rapid fall over the first hour. This reflects the kinetics of the drug in plasma and the semilogarithmic nature of the concentration-response line observed in vitro. Intravenous doses of 100 and 300 micrograms/kg were demonstrated to be effective antagonist doses of the platelet alpha 2-adrenoreceptor in healthy volunteers.

UI MeSH Term Description Entries
D007202 Indicators and Reagents Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499) Indicator,Reagent,Reagents,Indicators,Reagents and Indicators
D007262 Infusions, Intravenous The long-term (minutes to hours) administration of a fluid into the vein through venipuncture, either by letting the fluid flow by gravity or by pumping it. Drip Infusions,Intravenous Drip,Intravenous Infusions,Drip Infusion,Drip, Intravenous,Infusion, Drip,Infusion, Intravenous,Infusions, Drip,Intravenous Infusion
D007275 Injections, Intravenous Injections made into a vein for therapeutic or experimental purposes. Intravenous Injections,Injection, Intravenous,Intravenous Injection
D008297 Male Males
D010974 Platelet Aggregation The attachment of PLATELETS to one another. This clumping together can be induced by a number of agents (e.g., THROMBIN; COLLAGEN) and is part of the mechanism leading to the formation of a THROMBUS. Aggregation, Platelet
D004146 Dioxanes Compounds that contain the structure 1,4-dioxane.
D004147 Dioxins A family of compounds that contain the 1,4-dioxin structure. Many specific dioxin derivatives are listed as CARCINOGENS; TERATOGENS; or MUTAGENS. Dioxin
D004837 Epinephrine The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS. Adrenaline,4-(1-Hydroxy-2-(methylamino)ethyl)-1,2-benzenediol,Adrenaline Acid Tartrate,Adrenaline Bitartrate,Adrenaline Hydrochloride,Epifrin,Epinephrine Acetate,Epinephrine Bitartrate,Epinephrine Hydrochloride,Epinephrine Hydrogen Tartrate,Epitrate,Lyophrin,Medihaler-Epi,Acetate, Epinephrine
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000317 Adrenergic alpha-Antagonists Drugs that bind to but do not activate alpha-adrenergic receptors thereby blocking the actions of endogenous or exogenous adrenergic agonists. Adrenergic alpha-antagonists are used in the treatment of hypertension, vasospasm, peripheral vascular disease, shock, and pheochromocytoma. Adrenergic alpha-Receptor Blockaders,alpha-Adrenergic Blocking Agents,alpha-Adrenergic Receptor Blockaders,alpha-Blockers, Adrenergic,Adrenergic alpha-Blockers,alpha-Adrenergic Antagonists,alpha-Adrenergic Blockers,Adrenergic alpha Antagonists,Adrenergic alpha Blockers,Adrenergic alpha Receptor Blockaders,Agents, alpha-Adrenergic Blocking,Antagonists, alpha-Adrenergic,Blockaders, Adrenergic alpha-Receptor,Blockaders, alpha-Adrenergic Receptor,Blockers, alpha-Adrenergic,Blocking Agents, alpha-Adrenergic,Receptor Blockaders, alpha-Adrenergic,alpha Adrenergic Antagonists,alpha Adrenergic Blockers,alpha Adrenergic Blocking Agents,alpha Adrenergic Receptor Blockaders,alpha Blockers, Adrenergic,alpha-Antagonists, Adrenergic,alpha-Receptor Blockaders, Adrenergic

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