# Levomethamphetamine
**Levomethamphetamine** (levmetamfetamine; also called l-methamphetamine, l-desoxyephedrine, or R-(−)-methamphetamine) is the levorotatory (−)-isomer of methamphetamine, a central nervous system stimulant with a pharmacological profile similar to the (+)-isomer but of lower potency.[1](https://ecddrepository.org/en/levomethamphetamine) In the United States it is the active ingredient of over-the-counter nasal decongestant vapor inhalers, sold under the drug name levmetamfetamine, and the finished inhaler is an exempt preparation excluded from the [Controlled Substances Act](https://www.edgepedia.org/controlled-substances-act) even though the substance itself is a schedule II controlled substance.[2](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac) • [3](https://www.govinfo.gov/content/pkg/FR-2015-10-27/pdf/2015-27264.pdf)
| Key fact | Detail |
|---|---|
| Identity | The (−)-isomer of methamphetamine; a CNS stimulant, less potent than the (+)-isomer[1](https://ecddrepository.org/en/levomethamphetamine) |
| OTC product | Nasal decongestant vapor inhaler containing 50 mg levmetamfetamine per inhaler; each 800 mL of air delivers 0.04 to 0.150 mg[2](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac) |
| Dosing | Adults and children 12 and over: 2 inhalations in each nostril, no more often than every 2 hours; not for children under 2; do not use for more than 7 days[2](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac) |
| US legal status | Schedule II controlled substance because it is an isomer of methamphetamine; the finished OTC inhaler is an excluded nonnarcotic product, and extracting the ingredient from the inhaler negates the exclusion[3](https://www.govinfo.gov/content/pkg/FR-2015-10-27/pdf/2015-27264.pdf) |
| International control | Recommended for Schedule II of the 1971 Convention on Psychotropic Substances by the WHO Expert Committee on Drug Dependence[1](https://ecddrepository.org/en/levomethamphetamine) |
| Pharmacology | d-Methamphetamine is substantially more potent for monoamine release and dopamine-selective; l-methamphetamine acts primarily as a selective releaser of norepinephrine[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC11015966/) |
| Drug testing | Standard immunoassays do not distinguish the enantiomers; chiral LC-MS or GC-MS confirmation is required[5](https://www.sigmaaldrich.com/GB/en/technical-documents/protocol/analytical-chemistry/small-molecule-hplc/chiral-lcms-methamphetamine) |
## Chemistry and pharmacology
Methamphetamine exists as two stereoisomers, S-(+)-methamphetamine and R-(−)-methamphetamine.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) The (+)-isomer is the well-known stimulant of abuse and the pharmaceutical Desoxyn, while the (−)-isomer has been commercially available in the United States as an over-the-counter nasal decongestant since before 1994.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) The two enantiomers differ substantially in potency and transporter selectivity: d-methamphetamine shows greater overall potency for monoamine release and selectivity for dopamine, whereas l-methamphetamine acts primarily as a selective releaser of norepinephrine.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC11015966/) The World Health Organization Expert Committee on Drug Dependence describes levomethamphetamine as a CNS stimulant with a profile similar to the (+)-isomer but less potent, self-administered by rats under experimental conditions, and notes that the drug is controlled in several countries.[1](https://ecddrepository.org/en/levomethamphetamine)
## The nasal decongestant inhaler
The OTC product is a vapor inhaler whose active ingredient is 50 mg of levmetamfetamine, combined with inactive ingredients bornyl acetate, camphor, lavender oil, menthol, and methyl salicylate.[2](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac) It is indicated for temporary relief of nasal congestion due to the common cold, hay fever, or upper respiratory allergies. The label directs adults and children 12 years and over to take 2 inhalations in each nostril no more often than every 2 hours, children 6 to under 12 (with adult supervision) 1 inhalation in each nostril, and states the product should not be used for more than 7 days, since frequent or prolonged use may cause congestion to recur or worsen.[2](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac) The inhaler remains effective for a minimum of 3 months after first use.[2](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac)
**Formulation history.** Vicks Vapor Inhalers, marketed by [Procter & Gamble](https://www.edgepedia.org/procter-and-gamble), originally contained 113 mg of levmetamfetamine per inhaler, reduced to 50 mg in 2009; the 50 mg preparation delivers between 0.04 and 0.15 mg per inhalation.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) Generic versions have since become available, decreasing cost and increasing availability.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/)
## Legal status
Under the United States Controlled Substances Act, levmetamfetamine is controlled in schedule II because it is an isomer of methamphetamine.[3](https://www.govinfo.gov/content/pkg/FR-2015-10-27/pdf/2015-27264.pdf) The Attorney General may, however, exclude nonnarcotic drugs containing controlled substances that are lawfully sold over the counter, and the finished Nasal Decongestant Inhaler/Vapor Inhaler containing 50 mg levmetamfetamine is listed as an excluded nonnarcotic product.[3](https://www.govinfo.gov/content/pkg/FR-2015-10-27/pdf/2015-27264.pdf) The exclusion applies only to the finished inhaler in its exact formulation; the [Drug Enforcement Administration](https://www.edgepedia.org/drug-enforcement-administration)'s rule states that extraction or removal of the active ingredient from the inhaler negates the exclusion and results in possession of a schedule II controlled substance.[3](https://www.govinfo.gov/content/pkg/FR-2015-10-27/pdf/2015-27264.pdf) Internationally, the WHO Expert Committee concluded that levomethamphetamine met the criteria for control under the Convention on Psychotropic Substances and, on the basis of its marked chemical and pharmacological resemblance to (+)-methamphetamine, recommended placement in Schedule II of the 1971 Convention.[1](https://ecddrepository.org/en/levomethamphetamine)
## Human pharmacology
A 2023 systematic review of R-(−)-methamphetamine pharmacology in humans identified only 10 unique studies with a total of 99 participants, with administered doses ranging from 0.0168 mg to 45.4 mg across oral, intravenous, and intranasal routes.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) In a randomized, placebo-controlled crossover study, oral doses of (−)-MAMP at or below 10 mg produced no relevant changes in heart rate, blood pressure, core temperature, respiration rate, or oxygen saturation, and no differences in participant-reported subjective effects compared with placebo.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) An intravenous deuterium-labeled dose given alongside an oral dose allowed estimation of absolute bioavailability, which was close to 1, indicating complete absorption of the oral dose.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) The review concluded that available knowledge relies heavily on urine concentrations, that systematic pharmacokinetic studies are lacking, and that (−)-MAMP is not converted to (+)-MAMP in the body.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/)
## Drug testing and forensic significance
Methamphetamine immunoassays and common reverse-phase LC-MS toxicology methods do not differentiate between the legal decongestant isomer and illicit d-methamphetamine, and will report a positive finding if either is detected above cutoff concentrations.[5](https://www.sigmaaldrich.com/GB/en/technical-documents/protocol/analytical-chemistry/small-molecule-hplc/chiral-lcms-methamphetamine) Chiral chromatographic methods, such as LC-MS on a chiral HPLC column or GC-MS with a chiral derivatizing reagent, separate the enantiomers and allow confirmation of which molecule is present.[5](https://www.sigmaaldrich.com/GB/en/technical-documents/protocol/analytical-chemistry/small-molecule-hplc/chiral-lcms-methamphetamine) • [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) Early cross-reactivity work found that immunoassays with low limits of detection for (+)-MAMP, including EMIT, Toxilab, and TDx, were cross-reactive to (−)-MAMP and gave methamphetamine-positive results; in one study following the manufacturer's inhaler dosing regimen, the greatest (−)-MAMP urine concentration was 872 ng/mL, rising to 1,560 ng/mL at double the suggested dose.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/) The 2024 Medical Review Officer Guidance Manual for federal workplace drug testing notes that enantiomer identification can help determine whether a donor used an OTC l-methamphetamine product or abused an illegal drug, but that the presence of the l-isomer does not by itself rule out illegal use.[7](https://www.samhsa.gov/sites/default/files/mro-guidance-manual-2024.pdf)
## References
1. [Levomethamphetamine, WHO Expert Committee on Drug Dependence Information Repository](https://ecddrepository.org/en/levomethamphetamine)
2. [VAPOR INHALER – levmetamfetamine nasal decongestant inhalant, DailyMed drug label](https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=904b7e21-cce5-4b96-afc1-b36f532f98ac)
3. [Schedules of Controlled Substances: Table of Excluded Nonnarcotic Products, Federal Register Vol. 80 No. 207 (October 27, 2015)](https://www.govinfo.gov/content/pkg/FR-2015-10-27/pdf/2015-27264.pdf)
4. [Enantiomeric Contributions to Methamphetamine's Bidirectional Effects on Basal and Fentanyl-Depressed Respiration in Mice, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC11015966/)
5. [Chiral LC-MS Analysis of Methamphetamine in Urine on Astec CHIROBIOTIC V2, Sigma-Aldrich](https://www.sigmaaldrich.com/GB/en/technical-documents/protocol/analytical-chemistry/small-molecule-hplc/chiral-lcms-methamphetamine)
6. [Pharmacology of R-(−)-Methamphetamine in Humans: A Systematic Review of the Literature, ACS Pharmacology & Translational Science (PMC)](https://pmc.ncbi.nlm.nih.gov/articles/PMC10353062/)
7. [Medical Review Officer Guidance Manual for Federal Workplace Drug Testing Programs, SAMHSA (2024)](https://www.samhsa.gov/sites/default/files/mro-guidance-manual-2024.pdf)
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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Amines and nitrogen functional groups › Psychoactive amine substance families › Substituted amphetamine families › Methamphetamine and levomethamphetamine as chemical species*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license