Catecholamines and Sympathomimetic Drugs
Most of the actions of catecholamines and sympathomimetic agents can be classified into seven broad types:
A peripheral excitatory action on certain types of smooth muscle, such as those in blood vessels supplying skin, kidney, and mucous membranes; and on gland cells, such as those in salivary and sweat glands.
A peripheral inhibitory action on certain other types of smooth muscle, such as those in the wall of the gut, in the bronchial tree, and in blood vessels supplying skeletal muscle.
A cardiac excitatory action that increases heart rate and force of contraction.
Metabolic actions, such as an increase in the rate of glycogenolysis in liver and muscle and liberation of free fatty acids from adipose tissue.
Endocrine actions, such as modulation (increasing or decreasing) of the secretion of insulin, renin, and pituitary hormones.
Actions in the central nervous system (CNS), such as respiratory stimulation, an increase in wakefulness and psychomotor activity, and a reduction in appetite.
Prejunctional actions that either inhibit or facilitate the release of neurotransmitters, the inhibitory action being physiologically more important.
Many of these actions and the receptors that mediate them are summarized in Tables 8–1 and 8–8. Not all sympathomimetic drugs show each of the above types of action to the same degree; however, many of the differences in their effects are only quantitative. The pharmacological properties of these drugs as a class are described in detail for the prototypical agent, epinephrine.
Appreciation of the pharmacological properties of the drugs described in this chapter depends on an understanding of the classification, distribution, and mechanism of action of α and β adrenergic receptors (Chapter 8).
CLASSIFICATION OF SYMPATHOMIMETIC DRUGS
Catecholamines and sympathomimetic drugs are classified as direct-acting, indirect-acting, or mixed-acting sympathomimetics (Figure 12–1). Direct-acting sympathomimetic drugs act directly on one or more of the adrenergic receptors. These agents may exhibit considerable selectivity for a specific receptor subtype (e.g., phenylephrine for α1, terbutaline for β2) or may have no or minimal selectivity and act on several receptor types (e.g., epinephrine for α1, α2, β1, β2, and β3 receptors; norepinephrine for α1, α2, and β1 receptors). Indirect-acting drugs increase the availability of norepinephrine (NE) or epinephrine to stimulate adrenergic receptors. This can be accomplished in several ways:
Classification of adrenergic receptor agonists (sympathomimetic amines) or drugs that produce sympathomimetic-like effects. For each category, a prototypical drug is shown. (*Not actually sympathetic drugs but produce sympathomimetic-like effects.)
by releasing or displacing NE from sympathetic nerve varicosities
by blocking the transport of NE into sympathetic neurons (e.g., cocaine)
by blocking the metabolizing enzymes, monoamine ...
Log In to View More
If you don't have a subscription, please view our individual subscription options below to find out how you can gain access to this content.
Want remote access to your institution's subscription?
Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.
If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
AccessAnesthesiology Full Site: One-Year Subscription
Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more
Pay Per View: Timed Access to all of AccessAnesthesiology
24 Hour Subscription $34.95
48 Hour Subscription $54.95
Pop-up div Successfully Displayed
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.