Sympathomimetics: Direct agonists
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Sympathomimetics: Direct agonists
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
Prerequisite basic sciences
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Amphetamines p. 243
as noradrenergic drug p. 240
norepinephrine and p. 240
Cocaine p. 571
as noradrenergic drug p. 240
Depression
serotonin-norepinephrine reuptake inhibitors (SNRIs) for p. 599
Dopamine p. 243, 334
in noradrenergic drugs p. 240
Ephedrine p. 243
as noradrenergic drug p. 240
Generalized anxiety disorder (GAD) p. 585, 586
serotonin-norepinephrine reuptake inhibitors (SNRIs) for p. 599
Hypotension
norepinephrine for p. 243
Isoproterenol
norepinephrine vs p. 244
Noradrenergic drugs p. 240
Norepinephrine (NE)
adrenal medulla secretion p. 332
amphetamines and p. 240
bupropion effect on p. 600
changes with disease p. 512
circadian rhythm p. 513
direct sympathomimetic p. 243
isoproterenol vs p. 244
male sexual response p. 651
MAO inhibitor effects p. 599
in nervous system p. 237
opioid effect on p. 572
phenoxybenzamine and p. 231
pheochromocytoma secretion p. 345
REM sleep and p. 513
tramadol effects p. 572
tyrosine catabolism p. 81
vitamin B6 and p. 65
Phenoxybenzamine p. 245
norepinephrine and p. 231
Reserpine
as noradrenergic drug p. 240
Septic shock
norepinephrine for p. 243
Serotonin-norepinephrine reuptake inhibitors (SNRIs)
Shock p. 319
norepinephrine for p. 243
SNRIs (serotonin-norepinephrine reuptake inhibitors ) p. 599
Tricyclic antidepressants (TCAs) p. 599
as noradrenergic drug p. 240
Tyrosine
as noradrenergic drug p. 240
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Transcript
Content Reviewers
Alpha agonists and beta agonists are two types of adrenergic medications that stimulate their respective receptors and mimic the effect of endogenous catecholamines, like norepinephrine and epinephrine.
The nervous system is divided into the central nervous system and the peripheral nervous system.
The peripheral nervous system can be further divided into the somatic nervous system, which controls voluntary movement of our skeletal muscles; and the autonomic nervous system, which controls the involuntary movement of the smooth muscles and glands of our organs; this system is then further divided into the sympathetic and parasympathetic nervous systems.
Now, the autonomic nervous system is made up of a relay that includes two neurons.
We’ll focus on just the sympathetic nervous system.
Signals for the autonomic nervous system start in the hypothalamus, at the base of the brain.
Hypothalamic neurons have really long axons that carry signals all the way down to the thoracic and lumbar spinal cord nuclei, where they synapse with preganglionic neuron cell bodies.
From there, the signal goes from the preganglionic neurons down its relatively short axon, exits the spinal cord, and reaches the nearby sympathetic ganglion, which is made up of lots of postganglionic neuron cell bodies.
The postganglionic neurons are also called adrenergic neurons, because they release the neurotransmitter norepinephrine, which is also called noradrenalin; and to a much lesser degree, epinephrine also known as adrenaline.
Summary
Sympathomimetics are drugs that act on the sympathetic nervous system to produce their effects. They include classes of drugs like alpha agonists and beta-agonists. Both alpha agonists and beta-agonists bind to receptors in the body and activate them.
Alpha agonists activate alpha receptors, which are found primarily in the smooth muscles of the blood vessels and lungs. Alpha agonists are divided into alpha-1 agonists, like phenylephrine and midodrine; and alpha-2 agonists, like clonidine. Phenylephrine is used to treat hypotension, but it can also be used as a decongestant to treat rhinitis, or as a topical agent to cause mydriasis. Midodrine is used to treat orthostatic hypotension; while intravenous and nasal administration of clonidine causes vasoconstriction.
On the other hand, beta-agonists activate beta receptors, which are found in the heart, lungs, and other organs. Beta-agonists are subdivided into non-selective beta agonists like isoproterenol; and selective beta-2 agonists, like albuterol, salmeterol, and terbutaline. Isoprenaline is used to stimulate the heart in individuals with bradycardia or heart block, while albuterol, salmeterol, and terbutaline are used in the treatment of asthma, chronic obstructive pulmonary disease, and hyperkalemia.
Sources
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- "Rang and Dale's Pharmacology" Elsevier (2019)
- "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
- "Midodrine" Drugs & Aging (1998)
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- "Mechanism of action of agents used in attention-deficit/hyperactivity disorder" J Clin Psychiatry (2006)
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- "Nebulized Terbutaline and Ipratropium Bromide Versus Terbutaline Alone in Acute Exacerbation of Chronic Obstructive Pulmonary Disease Requiring Noninvasive Ventilation: A Randomized Double‐blind Controlled Trial" Academic Emergency Medicine (2018)
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