Methamphetamine[note 1] (contracted from N-methylamphetamine) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational or performance-enhancing drug and less commonly as a second-line treatment for attention deficit hyperactivity disorder (ADHD).[23] It has also been researched as a potential treatment for traumatic brain injury.[7] Methamphetamine was discovered in 1893 and exists as two enantiomers: levo-methamphetamine and dextro-methamphetamine.[note 2]Methamphetamine properly refers to a specific chemical substance, the racemicfree base, which is an equal mixture of levomethamphetamine and dextromethamphetamine in their pure amine forms, but the hydrochloride salt, commonly called crystal meth, is widely used. Methamphetamine is rarely prescribed over concerns involving its potential for recreational use as an aphrodisiac and euphoriant, among other concerns, as well as the availability of safer substitute drugs with comparable treatment efficacy such as Adderall and Vyvanse.[23] While pharmaceutical formulations of methamphetamine in the United States are labeled as methamphetamine hydrochloride, they contain dextromethamphetamine as the active ingredient.[23][note 3] Dextromethamphetamine is a stronger CNS stimulant than levomethamphetamine.[23]
Both racemic methamphetamine and dextromethamphetamine are illicitly trafficked and sold owing to their potential for recreational use. The highest prevalence of illegal methamphetamine use occurs in parts of Asia and Oceania, and in the United States, where racemic methamphetamine and dextromethamphetamine are classified as Schedule II controlled substances. Levomethamphetamine is available as an over-the-counter (OTC) drug for use as an inhaled nasal decongestant in the United States.[note 4] Internationally, the production, distribution, sale, and possession of methamphetamine is restricted or banned in many countries, owing to its placement in schedule II of the United Nations Convention on Psychotropic Substances treaty. While dextromethamphetamine is a more potent drug, racemic methamphetamine is illicitly produced more often, owing to the relative ease of synthesis and regulatory limits of chemical precursor availability.
In low to moderate doses, methamphetamine can elevate mood, increase alertness, concentration and energy in fatigued individuals, reduce appetite, and promote weight loss. At very high doses, it can induce psychosis, breakdown of skeletal muscle, seizures, and bleeding in the brain. Chronic high-dose use can precipitate unpredictable and rapid mood swings, stimulant psychosis (e.g., paranoia, hallucinations, delirium, and delusions), and violent behavior. Recreationally, methamphetamine's ability to increase energy has been reported to lift mood and increase sexual desire to such an extent that users are able to engage in sexual activity continuously for several days while binging the drug.[28] Methamphetamine is known to possess a high addiction liability (i.e., a high likelihood that long-term or high dose use will lead to compulsive drug use) and high dependence liability (i.e., a high likelihood that withdrawal symptoms will occur when methamphetamine use ceases). Discontinuing methamphetamine after heavy use may lead to a post-acute-withdrawal syndrome, which can persist for months beyond the typical withdrawal period. At high doses, methamphetamine is neurotoxic to human midbraindopaminergicneurons and, to a lesser extent, serotonergic neurons.[29][30] Methamphetamine neurotoxicity causes adverse changes in brain structure and function, such as reductions in grey matter volume in several brain regions, as well as adverse changes in markers of metabolic integrity.[30]
^"Methamphetamine: Toxicity". PubChem Compound. National Center for Biotechnology Information. Archived from the original on 4 January 2015. Retrieved 4 January 2015.
^ ab"Methamphetamine". Drug profiles. European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). 8 January 2015. Archived from the original on 15 April 2016. Retrieved 27 November 2018. The term metamfetamine (the International Non-Proprietary Name: INN) strictly relates to the specific enantiomer (S)-N,α-dimethylbenzeneethanamine.
^ abcdMoszczynska A, Callan SP (September 2017). "Molecular, Behavioral, and Physiological Consequences of Methamphetamine Neurotoxicity: Implications for Treatment". The Journal of Pharmacology and Experimental Therapeutics. 362 (3): 474–488. doi:10.1124/jpet.116.238501. PMC11047030. PMID28630283. METH is a schedule II drug, which can only be prescribed for attention deficit hyperactivity disorder (ADHD), extreme obesity, or narcolepsy (as Desoxyn; Recordati Rare Diseases LLC, Lebanon, NJ), with amphetamine being prescribed more often for these conditions due to amphetamine having lower reinforcing potential than METH (Lile et al., 2013). ... As discussed earlier, the d-enantiomer has stronger CNS effects but is metabolized more quickly than the l-enantiomer, which is longer lasting due to the slower breakdown. ... l-METH, a vasoconstrictor, is the active constituent of the Vicks Inhaler decongestant (Proctor & Gamble, Cincinnati, OH), an over-the-counter product containing about 50 mg of the drug (Smith et al., 2014). Desoxyn, which is d-METH, is rarely medically prescribed due to its strong reinforcing properties. Therapeutic doses of Desoxyn are 20–25 mg daily, taken every 12 hours, with dosing not exceeding 60 mg/day
^"Levomethamphetamine". Pubchem Compound. National Center for Biotechnology Information. Archived from the original on 6 October 2014. Retrieved 27 November 2018.
^Cite error: The named reference Desoxyn FDA label was invoked but never defined (see the help page).
^ abCite error: The named reference pmid19328213 was invoked but never defined (see the help page).
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