sympathomimetic
A sympathomimetic is any drug that mimics the sympathetic nervous system, producing the same effects as fight-or-flight. Picture a drug that flips the body's accelerator: heart faster, vessels tighter, airways open, pupils wide. That is the sympathomimetic effect.
Drugs achieve this in two broad ways. Direct-acting sympathomimetics bind and activate adrenergic receptors themselves (for example, adrenaline at alpha and beta receptors, or salbutamol at beta-2). Indirect-acting ones work upstream, increasing the amount of norepinephrine in the synapse by promoting its release or blocking its reuptake (for example, amphetamine and ephedrine). Some agents do both.
Their uses follow their receptor profile: raising blood pressure in shock, opening airways in asthma, stopping nosebleeds and congestion, supporting a failing heart, and prolonging local anaesthesia. Because the same receptors drive the heart, the main hazards are high blood pressure, fast or irregular heartbeat, and anxiety.
Pseudoephedrine, an oral sympathomimetic decongestant, constricts swollen nasal vessels through alpha receptors to relieve a blocked nose.
A common over-the-counter decongestant.
Indirect-acting sympathomimetics depend on the body's own norepinephrine stores, so repeated doses can exhaust those stores and give progressively weaker effects, a form of tachyphylaxis.