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Additionally, the heart rate and contractile force increase when SNS is activated, which may be harmful to cardiac function as it increases metabolic demand. [ 1 ] Adrenergic blocking agents treat certain diseases through blocking the adrenergic receptor , [ 2 ] [ 3 ] preventing it from being activated by noradrenaline and epinephrine .
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.
α receptors have actions in common, but also individual effects. Common (or still receptor unspecified) actions include: vasoconstriction [13] decreased flow of smooth muscle in gastrointestinal tract [14] Subtype unspecific α agonists (see actions above) can be used to treat rhinitis (they decrease mucus secretion).
Alpha-adrenergic antagonists are also used for treatment of ureteric stones, pain and panic disorders, withdrawal, and anesthesia. [18] [2] Adrenergic antagonists are used to treat acute cardiovascular toxicity (e.g. in overdose) caused by sympathomimetics, for instance caused by amphetamine, methamphetamine, cocaine, ephedrine, and other drugs ...
Medications such as clonidine and dexmedetomidine target pre-synaptic auto receptors, therefore leading to an overall decrease in norepinephrine which clinically can cause effects such as sedation, analgesia, lowering of blood pressure and bradycardia. There is also low quality evidence that they can reduce shivering post operatively.
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).
An adrenergic agonist is a drug that stimulates a response from the adrenergic receptors.The five main categories of adrenergic receptors are: α 1, α 2, β 1, β 2, and β 3, although there are more subtypes, and agonists vary in specificity between these receptors, and may be classified respectively.