Author: Dr. Surya Prakash Gupta
Volume: 01
First Online: 31 August 2024
Pages: 58-68
DOI:

Sympathomimetic agents, also known as adrenergic agonists, mimic the effects of endogenous catecholamines like epinephrine and norepinephrine. These agents are classified based on their mechanism of action into direct-acting, indirect-acting, and mixed-acting sympathomimetics. Direct-acting agents, such as epinephrine, norepinephrine, phenylephrine, dopamine, methyldopa, clonidine, dobutamine, isoproterenol, terbutaline, salbutamol, bitolterol, naphazoline, oxymetazoline, and xylometazoline, directly stimulate adrenergic receptors. Indirect-acting agents, like amphetamines, increase the release or inhibit the reuptake of endogenous catecholamines. Mixed-acting agents, like ephedrine, exhibit both direct and indirect actions. The mechanism of action of sympathomimetic agents involves the activation of alpha- or beta-adrenergic receptors, leading to various physiological responses such as increased heart rate, bronchodilation, vasoconstriction, and lipolysis. These agents are used to treat conditions like asthma, hypotension, cardiac arrest, and nasal congestion. The structure- activity relationship (SAR) of sympathomimetics reveals that modifications to the catecholamine structure can significantly alter receptor selectivity and potency. For example, the presence of hydroxyl groups on the benzene ring and specific side chain substitutions determines the affinity and selectivity for alpha or beta receptors.