Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent low blood pressure during anesthesia.

[11] Common side effects include trouble sleeping, anxiety, headache, hallucinations, high blood pressure, fast heart rate, loss of appetite, and urinary retention.

[11][18] Over-the-counter dietary supplements containing ephedrine are illegal in the United States,[11] with the exception of those used in traditional Chinese medicine, where its presence is noted by má huáng.

[11][18] Ephedrine is a non-catecholamine sympathomimetic with cardiovascular effects similar to those of adrenaline/epinephrine: increased blood pressure, heart rate, and contractility.

[21][22] Ephedrine is also found to have quick and long-lasting responsiveness in congenital myasthenic syndrome in early childhood and also even in adults with a novel COLQ mutation.

Redosing usually requires increased doses to offset the development of tachyphylaxis, which is attributed to the depletion of catecholamine stores.

[29][30] Ephedrine should not be used in conjunction with certain antidepressants, namely norepinephrine-dopamine reuptake inhibitors (NDRIs), as this increases the risk of symptoms due to excessive serum levels of norepinephrine.

Ephedrine should be used with caution in patients with inadequate fluid replacement, impaired adrenal function, hypoxia, hypercapnia, acidosis, hypertension, hyperthyroidism, prostatic hypertrophy, diabetes mellitus, cardiovascular disease, during delivery if maternal blood pressure is >130/80 mmHg, and during lactation.

[31] Contraindications for the use of ephedrine include: closed-angle glaucoma, phaeochromocytoma, asymmetric septal hypertrophy (idiopathic hypertrophic subaortic stenosis), concomitant or recent (previous 14 days) monoamine oxidase inhibitor (MAOI) therapy, general anaesthesia with halogenated hydrocarbons (particularly halothane), tachyarrhythmias or ventricular fibrillation, or hypersensitivity to ephedrine or other stimulants.

[citation needed] Ephedrine should not be used at any time during pregnancy unless specifically indicated by a qualified physician and only when other options are unavailable.

[31] Ephedrine is a potentially dangerous natural compound; as of 2004[update] the US Food and Drug Administration had received over 18,000 reports of adverse effects in people using it.

[citation needed] Ephedrine with monoamine oxidase inhibitors (MAOIs) like phenelzine and tranylcypromine can result in hypertensive crisis.

[citation needed] Ephedrine, a sympathomimetic amine, acts on part of the sympathetic nervous system (SNS).

[41][20][42][43] L-ephedrine, and particularly its stereoisomer norpseudoephedrine (which is also present in Catha edulis) has indirect sympathomimetic effects and due to its ability to cross the blood–brain barrier, it is a CNS stimulant similar to amphetamines, but less pronounced, as it releases norepinephrine and dopamine in the brain.

[6][10] About 8 to 20% of an oral dose of ephedrine is demethylated into norephedrine, about 4 to 13% is oxidatively deaminated into benzoic acid, and a small fraction is converted into 1,2-dihydroxy-1-phenylpropane.

[59] In the outdated D/L system (+)-ephedrine is also referred to as D-ephedrine and (−)-ephedrine as L-ephedrine (in which case, in the Fisher projection, the phenyl ring is drawn at the bottom).

Ephedrine may be quantified in blood, plasma, or urine to monitor possible abuse by athletes, confirm a diagnosis of poisoning, or assist in a medicolegal death investigation.

Blood or plasma ephedrine concentrations are typically in the 20–200 μg/L range in persons taking the drug therapeutically, 300–3000 μg/L in abusers or poisoned patients, and 3–20 mg/L in cases of acute fatal overdosage.

[61][62][63][64] Ephedrine in its natural form, known as máhuáng (麻黄) in traditional Chinese medicine, has been documented in China since the Han dynasty (206 BC – 220 AD) as an antiasthmatic and stimulant.

[32] It was introduced in 1948 in Vicks Vatronol nose drops (now discontinued) which contained ephedrine sulfate as the active ingredient for rapid nasal decongestion.

The most popular method for reducing ephedrine to methamphetamine is similar to the Birch reduction, in that it uses anhydrous ammonia and lithium metal in the reaction.

As such, ephedrine is listed as a table-I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.

"[79] In 2004, the FDA created a ban on ephedrine alkaloids marketed for reasons other than asthma, colds, allergies, other disease, or traditional Asian use.

[80] On April 14, 2005, the U.S. District Court for the District of Utah ruled the FDA did not have proper evidence that low dosages of ephedrine alkaloids are actually unsafe,[81] but on August 17, 2006, the U.S. Court of Appeals for the Tenth Circuit in Denver upheld the FDA's final rule declaring all dietary supplements containing ephedrine alkaloids adulterated, and therefore illegal for marketing in the United States.

Signed into law by President George W. Bush on March 6, 2006, the act amended the US Code (21 USC 830) concerning the sale of products containing ephedrine and the closely related drug pseudoephedrine.

Both substances are used as precursors in the illicit production of methamphetamine, and to discourage that use the federal statute included the following requirements for merchants who sell these products: The law gives similar regulations to mail-order purchases, except the monthly sales limit is 7.5 g. As a pure herb or tea, má huáng, containing ephedrine, is still sold legally in the US.

Pills containing ephedrine up to 30 mg per tablet in combination with other medications are still available OTC, schedule 1 and 2, for sinus, head colds, and influenza.

Raw materials for the manufacture of ephedrine and traditional Chinese medicines are produced in China on a large scale.

As of 2007, companies produced for export US$13 million worth of ephedrine from 30,000 tons of ephedra annually, or about ten times the amount used in traditional Chinese medicine.

[86] Most of the l-ephedrine produced today for official medical use is made synthetically as the extraction and isolation process from E. sinica is tedious and no longer cost-effective.