n. a *sympathomimetic drug that stimulates alpha receptors and is used as a *vasoconstrictor to treat acute *hypotension.
adj. having the effect of stimulating the *sympathetic nervous system. The actions of sympathomimetic drugs are adrenergic: they act on alpha or beta *adrenoceptors. Alpha-adrenergic stimulants (alpha agonists) stimulate alpha receptors. They include *vasoconstrictors (e.g. *ephedrine, *phenylephrine, *metaraminol), used to treat nasal congestion and severe hypotension, and the selective ?2 agonists *apraclonidine and *brimonidine, which are used in the treatment of glaucoma. Beta-adrenergic stimulants (beta agonists) stimulate ?1 and/or ?2 adrenoceptors. ?2 agonists such as *salbutamol, *salmeterol, and *terbutaline relax bronchial smooth muscle and are used as *bronchodilators. Some ?2 agonists, including salbutamol, relax uterine muscle and are sometimes used in the treatment of premature labour (see tocolytic). ?1 agonists (e.g. *dobutamine) stimulate ?1 receptors in the heart and are therefore used for their *inotropic effects.... sympathomimetic
n. an agent that causes narrowing of the blood vessels and therefore a decrease in blood flow. Vasoconstrictor drugs are alpha agonists (see sympathomimetic): they are used to raise the blood pressure in disorders of the circulation, shock, or severe bleeding and to maintain blood pressure during surgery (e.g. *ephedrine, *metaraminol, *phenylephrine). Some vasoconstrictors (e.g. ephedrine, *xylometazoline) have a rapid effect when applied to mucous membranes and may be used to relieve nasal congestion. If the blood pressure rises too quickly headache and vomiting may occur. A vasoconstrictor is often added to local anaesthetic solutions used in dentistry to prolong their effectiveness.... vasoconstrictor
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