Ephedrine (EPH) is a sympathomimetic amine commonly used as a decongestant and to treat hypotension associated with regional anaesthesia. Chemically, it is an alkaloid derived from various plants in the genus Ephedra (family Ephedraceae). The salt ephedrine hydrochloride has found various uses which utilise its sympathomimetic effect.

The traditional Chinese herb Ma Huang (Ephedra sinica) contains ephedrine as its principal active constituent. The same is true of other herbal products containing extracts from Ephedra species.

The substance called soma mentioned in old Hindu books such as the Rigveda, may have been ephedra extract.

Chemistry

Ephedrine exhibits

The isomer which is marketed is (-)-(1R,2S)-ephedrine. (Reynolds, 1988)

As with other phenylethylamines, it is also somewhat chemically similar to methamphetamine, although the methamphetamines are more potent and have additional biological effects.

Ephedrine may also be referred to as: (αR)-α-benzenemethanol, α-benzyl alcohol, or L-erythro-2-(methylamino)-1-phenylpropan-1-ol. Ephedrine hydrochloride has a melting point of 187-188°C. (Budavari, 1996)

Mode of Action

Ephedrine is a sympathomimetic amine - that is, its principal mechanism of action relies on its indirect action on the adrenergic receptor system, which is part of the sympathetic nervous system or SNS. Whilst it may have weak agonist activity at α- and β-adrenergic receptors, the principal mechanism is to displace noradrenaline from storage vesicles in presynaptic neurons. The displaced noradrenaline is released into the neuronal synapse where it is free to activate the postsynaptic adrenergic receptors.

Indications

In traditional Chinese medicine, ephedrine has been used in the treatment of asthma and bronchitis for centuries (Ford, 2001). In Western medicine ephedrine was once widely used as a topical decongestant and as a bronchodilator in the treatment for asthma. It continues to be used for these indications, though the popularity is waning due to the availability of more selective agents for these indications which exhibit fewer adverse effects (Joint Formulary Committee, 2004). The role in nasal congestion has largely been replaced by more

Ephedrine continues to be used intravenously in the reversal of hypotension from spinal/epidural anaesthesia (Joint Formulary Committee, 2004). It is also used in other hypotensive states, including overdose with ganglionic blocking agents, antiadrenergic agents, or other medications that lower blood pressure (Bicopoulous, 2002). It can be used in narcolepsy and nocturnal enuresis.

An ECA stack is a component found in thermogenic weight loss pills, composed of ephedrine, caffeine and aspirin working to speed up the metabolism and thus cause food energy to burn faster. The ECA stack (without the aspirin in most cases), is a popular supplement taken by body builders before workouts due to the increased amount of energy and alertness.

Safety issues

Ephedrine is found in many popular weight control products, in the form of Ephedra, some of which have been banned by the United States Food and Drug Administration (FDA). Some of the serious adverse effects associated with ephedrine include hypertension, stroke and myocardial infarction. However, Ephedrine is also one of the OTC drugs () currently sold in many states in the US.

Furthermore, ephedrine and pseudoephedrine (which are found in various legal over-the-counter drugs) can be manufactured into methamphetamine, a dangerous illicit drug that is growing in popularity due in part to the availability of ephedrine and pseudoephedrine. Methcathinone can also be produced from ephedrine and pseudoephedrine.

Recreational and illicit use

Anecdotal reports have suggested that ephedrine helps thinking or studying to a greater extent than caffeine. Some students and some white-collar workers have used ephedrine (or Ephedra-containing herbal supplements) for this purpose, as well as some professional athletes and weightlifters. It is common for many athletes to use stimulants while exercising. Such misuse of ephedrine has been associated with stimulant dependence, as well as deaths from heatstroke in athletes and circulatory problems such as aortic aneurysm in weightlifters.

As a phenylethylamine, ephedrine has a similar chemical structure to amphetamines. Ephedrine can be used in the synthesis of methamphetamine by chemical reduction; this has made ephedrine a highly sought-after chemical precursor in the illicit manufacture of methamphetamine. The most popular method for reducing ephedrine to methamphetamine is the birch reduction, which uses anhydrous ammonia, lithium metal, and ephedrine in the reaction. The second most popular method uses red phosphorus, iodine, and ephedrine in the reaction.

Through oxidation, ephedrine can be easily synthesized into methcathinone. Ephedrine is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.

References

• Bicopoulos, D (Ed.) (2002). AusDI. Drug Information for the Healthcare Professional (2 ed.). Castle Hill: Pharmaceutical Care Information Services
• Budavari, S (Ed.) (1996). The Merck Index. An encyclopedia of chemicals, drugs, and biologicals (12 ed.). Whitehouse Station: Merck Research Laboratories ISBN 0-91191-012-3
• Ford MD, Delaney KA, Ling LJ, Erickson T (Eds.) (2001). Clinical Toxicology. Philadelphia: WB Saunders. ISBN 0-72165-485-1
• Joint Formulary Committee (2004). British National Formulary (47 ed.). London: British Medical Association and Royal Pharmaceutical Society of Great Britain. ISBN 0-85369-854-9
• Reynolds, JEF (Ed.) (1989). Martindale. The Extra Pharmacopoeia (29 ed.). London: The Pharmaceutical Press. ISBN 0-85369-210-6

See also

• Phenethylamines
• Pseudoephedrine
• Methamphetamine
• Methcathinone
• ECA stack
• Soma

Ephedrin Efedrina Éphédrine Efedrine Efedryna Efedrina Эфедрин Efedrín Efedriini Efedrin