Ephedrine is a central nervous system stimulant used to treat breathing problems (as a bronchodilator), nasal congestion (as a decongestant), low blood pressure problems (orthostatic hypotension), or myasthenia gravis.
Ephedrine is a sympathomimetic amine, the principal mechanism of its action relies on its direct and indirect actions on the adrenergic receptor system, which is part of the sympathetic nervous system or SNS. Central nervous system or CNS involvement is present, but the predominant clinical effects are caused by involvement with the sympathetic segment of the peripheral nervous system because while ephedrine does cross the blood-brain barrier, it doesn\'t do this very efficiently (efficient crossers with similar modes of action would include amphetamine and methamphetamine).
Ephedrine increases post-synaptic noradrenergic receptor activity by (weakly) directly activating post-synaptic α-receptors and β-receptors, but the bulk of its effect comes from the pre-synaptic neuron being unable to distinguish between real adrenaline or noradrenaline from ephedrine. The ephedrine, mixed with noradrenaline, is transported through the noradrenaline reuptake complex and packaged (along with real noradrenaline) into vesicles that reside at the terminal button of a nerve cell.
As an alkaloid, having some small amount of ephedrine within a noradrenaline vesicle increases the overall pH of the vesicle. This has the effect of increasing likelihood that the affected vesicle will be released during any subsequent action potential the nerve cell experiences. The nerve cells in question generally fire at some regular baseline rate; the effect of adding ephedrine is to increase the number of vesicles released during each action potential and possibly to extend the time during which noradrenaline has an opportunity to have an effect on the post-synaptic neuron by virtue of the fact that the reuptake complex has to process both noradrenaline AND ephedrine, presumably a longer process.
Ephedrine\'s mechanism of action on neurotransmission in the brain is wide. Its action as an agonist at most major noradrenaline receptors and its ability to increase the release of both dopamine and to a lesser extent, serotonin by the same mechanism as explained above for norepinephrine, is presumed to have a major role in its mechanism of action.
Because of ephedrine\'s ability to potentiate dopamine neurotransmission it is thought to have addictive properties by some researchers[who?]. The ability to potentiate serotonin and noradrenergic activity is clinically relevant, but is not thought to contribute to the potential for abuse.
While ephedrine\'s role in the serotonin system is less understood there is preliminary documentation of clinically significant agonism at excitory serotonin receptors, perhaps as a downstream response to the large release of norepinephrine in the nucleus accumbens (commonly referred to as the \"pleasure center\" of the brain). In mice, stereotypical behaviour was both easily induced by administration of ephedrine and its primary alkaloids and reversed when serotonin antagonists were administered.
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Nervousness, anxiety, dizziness, headache, nausea, loss of appetite, or trouble sleeping may occur. If any of these effects persist or worsen, notify your doctor promptly. Tell your doctor immediately if any of these serious side effects occur: chest pain, unusually fast or irregular heartbeat, vomiting, tremor/shakiness, sweating, severe weight loss, difficult or painful urination, stomach pain. Tell your doctor immediately if any of these unlikely but serious side effects occur: severe mental/mood changes, fever, trouble breathing, one-sided weakness, confusion, vision problems, slurred speech. If you notice other effects not listed above, contact your doctor or pharmacist.
Take this medication by mouth usually every 4 hours as needed; or as directed by your doctor. The dosage is based on your medical condition and response to therapy. For prescription ephedrine, do not exceed 150 mg per day in adults or 75 mg per day in children. Do not combine prescription ephedrine with ephedrine/ephedra/ma huang from dietary supplement products, since they are the same medicine. Use this medication exactly as prescribed. Do not increase your dose, take it more frequently, or use it for a longer period of time than prescribed because this drug can be habit-forming and you may increase for your risk for serious side effects. When used for an extended period, this medication may not work as well and may require different dosing. Talk with your doctor if this medication stops working well. Your doctor may recommend "drug holidays" where your medication is stopped temporarily. Doing so may help this medication work more effectively.