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Sympathomimetic drugs are substances that mimic the effects of the hormone epinephrine (adrenaline) and the hormone/neurotransmitter norepinephrine (noradrenaline). They all raise blood pressure and are all weak bases. The drugs include:
- Clonidine
- Cyclopentamine
- Fenfluramine
- Isoproterenol
- Parahydroxyamphetamine
- Phenylephrine
- Tetrahydrozoline
Mechanisms of action[]
The mechanisms of sympathomimetic drugs are to act as catecholamine synthesis precursors, norepinephrine transporter blockade, adrenergic receptor agonism, inhibition of epinephrine and norepinephrine metabolism and/or cholinergic inhibition.
Synthesis precursor[]
Synthesis precursors of catecholamines stimulate the catecholamine synthesis. One example is levodopa.
Norepinephrine transporter blockade[]
Classical sympathomimetic drugs are amphetamines (including MDMA), ephedrine and cocaine, which act by blocking and reversing norepinephrine transporter (NET) activity. NET is a transport protein expressed on the surface of some cells that clears noradrenaline and adrenaline from the extracellular space and into cells, terminating the signaling effects.
Adrenergic receptor agonism[]
- Main article: Adrenergic agonist
Direct stimulation of the α- and β-adrenergic receptors can produce sympathomimetic effects. Albuterol is a very commonly used direct-acting β2-agonist.
Inhibition of epinephrine and norepinephrine metabolism[]
Inhibition of norepinephrine or epinephrine metabolism can produce sympathomimetic effects. Both are mainly metabolized by the enzyme monoamine oxidase, the monoamine oxidase inhibitor (MAOI) drugs can induce such effects. COMT inhibitors can also decrease metabolism of norepinephrine and epinephrine.
Cholinergic inhibition[]
Sympathomimetic drugs may also work by inhibiting the opposite system, i.e. the parasympathetic system. It does so by inhibiting the effects of acetylcholine, e.g. by inhibiting synaptic vesicle release, antagonize acetylcholine receptors,
- synaptic vesicle release inhibitors:
- ACh receptor inhibitors
- atropine (all muscarinic)
- scopolamine (M1 receptors)
- tubocurarine (Muscle type nicotinic
Cross-reactivity[]
Substances like cocaine also affect dopamine, and some substances like MDMA affect serotonin.
Norepinephrine is synthesized by the body into epinephrine, causing central nervous system stimulation. Thus, all sympathomimetic amines fall into the larger group of stimulants (see psychoactive drug chart). Many of these stimulants have therepeutic use and abuse potential, can induce tolerance, and possibly physical dependence.
See also[]
External links[]
- MeSH Amines,+Sympathomimetic
- Dictionary at eMedicine Sympathomimetic+amine
- Dictionary at eMedicine Sympathomimetic
Psychoanaleptics: psychostimulants, agents used for ADHD and nootropics (N06B)
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Centrally acting sympathomimetics | Amphetamine - Dexamphetamine - Dextromethamphetamine - Methylphenidate - Pemoline - Fencamfamin - Modafinil - Fenozolone - Atomoxetine - Fenetylline |
Xanthine derivatives | Caffeine - Propentofylline |
Other psychostimulants and nootropics | Racetams (Piracetam, Oxiracetam, Aniracetam, Pramiracetam) - Meclofenoxate - Pyritinol - Deanol - Fipexide - Citicoline - Pirisudanol - Linopirdine - Nizofenone - Acetylcarnitine - Idebenone - Prolintane - Pipradrol - Adrafinil - Vinpocetine |
Template:Nasal preparations
Ophthalmologicals: antiglaucoma preparations and miotics (S01E) | |
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Sympathomimetics |
Apraclonidine • Brimonidine • Clonidine • Dipivefrine • Epinephrine |
Parasympathomimetics |
Aceclidine • Acetylcholine • Carbachol • Demecarium • Echothiophate • Stigmine (Fluostigmine, Neostigmine, Physostigmine) • Paraoxon • Pilocarpine |
Carbonic anhydrase inhibitors |
Acetazolamide • Brinzolamide • Diclofenamide • Dorzolamide • Methazolamide |
Beta blocking agents |
Befunolol • Betaxolol • Carteolol • Levobunolol • Metipranolol • Timolol |
Prostaglandin analogues |
Bimatoprost • Latanoprost • Travoprost • Unoprostone |
Other agents |
Dapiprazole • Guanethidine |
Ophthalmologicals: mydriatics and cycloplegics (S01F) | |
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Anticholinergics/antimuscarinics |
Atropine - Scopolamine - Methylscopolamine - Cyclopentolate - Homatropine - Tropicamide |
Sympathomimetics |
Phenylephrine - Ephedrine - Ibopamine |
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