Adrenomimetics include drugs that are agonists of adrenergic receptors. Depending on their affinity for receptors, they are subdivided into alpha-, beta-, alpha- or beta-adrenergic agonists with the corresponding index for the subtype (alphaone-, alpha2– and etc.). Sympathomimetics (ephedrine, etc.) have an indirect effect, increasing the release of norepinephrine from the endings of the adrenergic nerves (and inhibiting its reuptake), which causes the corresponding (adrenomimetic) effects. The nucleus of most adrenomimetic drugs is beta-phenylethylamine. The presence of OH groups in the 3 and 4 positions of the benzene ring (epinephrine, norepinephrine) complicates the passage of the BBB (no effect on the central nervous system with a strong peripheral pressor effect). The action of adrenomimetics is manifested by the narrowing of most blood vessels, increased myocardial contractions, increased heart rate, increased automatism and improved conduction in the heart muscle, and bronchial expansion. The activation of adrenergic receptors leads to an increase in the intracellular concentration of calcium or cAMP. The mechanism of action of sympathomimetics is mainly determined by their ability to displace catecholamines from their neuronal depots.
The peculiarities of the chemical structure of sympathomimetics – ephedrine and amphetamine (the absence of one or two OH groups in the phenolic ring) – contribute to an increase in bioavailability after oral administration and an increase in the duration of action (COMT and MAO are not inactivated). In addition, their penetration into the central nervous system increases, which determines the central effects (the feeling of fatigue, the need for sleep decreases, and efficiency increases). In terms of peripheral action, sympathomimetic drugs are close to adrenaline. Of the side effects, they are characterized by the development of tremor, agitation, insomnia.
Special sympathomimetics deserve attention, which include the local anesthetic cocaine and tyramine, which is a product of tyrosine metabolism in the body and is found in high concentrations in some foods (cheese, wine, etc.). These drugs, administered parenterally, exhibit sympathomimetic activity (i.e., constrict blood vessels, increase blood pressure, etc.) associated with inhibition of the reuptake of norepinephrine (cocaine) or the release of stores of catecholamines from the depot (tyramine).
The main area of application of adrenergic and sympathomimetics is cardiovascular lesions (shock, including anaphylactic, collapse, cardiac arrest, hypotension) and bronchopulmonary (bronchial asthma) diseases.
Below is a list of adreno- and sympathomimetics (alpha, beta):
- Ephedrine (Ephedrinum)