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Adrenergic blocking agents are a class of drugs that exhibit its pharmacological action through inhibiting the action of the sympathetic nervous system [1] in the body. The sympathetic nervous system(SNS) is an autonomic nervous system that we cannot control by will.
The mechanisms of sympathomimetic drugs can be direct-acting (direct interaction between drug and receptor), such as α-adrenergic agonists, β-adrenergic agonists, and dopaminergic agonists; or indirect-acting (interaction not between drug and receptor), such as MAOIs, COMT inhibitors, release stimulants, and reuptake inhibitors that increase the levels of endogenous catecholamines.
They work by inhibiting the synthesis, release, or reuptake of the neurotransmitters or by antagonising the receptors on postsynaptic neurones. Their medical uses, mechanisms of action, adverse effects, and contraindications depend on the specific types of adrenergic blockers used, including alpha 1, alpha 2, beta 1, and beta 2.
Norepinephrine Epinephrine. A norepinephrine reuptake inhibitor (NRI, NERI) or noradrenaline reuptake inhibitor or adrenergic reuptake inhibitor (ARI), is a type of drug that acts as a reuptake inhibitor for the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline) by blocking the action of the norepinephrine transporter (NET).
A sympatholytic (sympathoplegic) drug is a medication that opposes the downstream effects of postganglionic nerve firing in effector organs innervated by the sympathetic nervous system (SNS). [1] They are indicated for various functions; for example, they may be used as antihypertensives .
Other side effects include headaches and essential tremor. Hypoglycemia was also reported due to increased secretion of insulin in the body from activation of β 2 receptors. [citation needed] In 2013, zilpaterol, a β agonist sold by Merck, was temporarily withdrawn due to signs of sickness in some cattle that were fed the drug. [8]
Many tricyclic antidepressants, tetracyclic antidepressants, antipsychotics, ergolines, and some piperazines like buspirone, trazodone, nefazodone, etoperidone, and mepiprazole antagonize α 1-adrenergic receptors as well, which contributes to their side effects such as orthostatic hypotension.
It has several general functions in common with the α 1-adrenergic receptor, but also has specific effects of its own. Agonists (activators) of the α 2-adrenergic receptor are frequently used in anaesthesia where they affect sedation, muscle relaxation and analgesia through effects on the central nervous system (CNS). [5]