|Medical: Inhalation (nasal)|
Recreational: Oral, intravenous, insufflation, inhalation, suppository
|Elimination half-life||13 - 15 hours|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||149.23 g·mol−1|
|3D model (JSmol)|
|(what is this?)|
Levomethamphetamine[note 1] is the levorotatory (L-enantiomer) form of methamphetamine. Levomethamphetamine is a sympathomimetic vasoconstrictor that is the active ingredient in some over-the-counter (OTC) nasal decongestant inhalers in the United States.
Levomethamphetamine crosses the blood-brain-barrier and acts as a norepinephrine transporter inhibitor and TAAR1 agonist, functioning as a selective norepinephrine releasing agent (with limited effects on the release of dopamine), thus levomethamphetamine affects the central nervous system, although its effects are qualitatively distinct relative to those of dextromethamphetamine.It does not possess the same potential for euphoria or addiction that dextromethamphetamine possesses. Among its physiological effects are the vasoconstriction that makes it useful for nasal decongestion. The elimination half-life of levomethamphetamine is between 13.3 and 15 hours, whereas dextromethamphetamine has a half-life of about 10.5 hours.
Main article: Selegiline
Levomethamphetamine is an active metabolite of the antiparkinson's drug selegiline. Selegiline, a selective monoamine oxidase B (MAOB) inhibitor at low doses,[note 2] is also metabolized into levomethamphetamine and levoamphetamine. This has caused users to test positive for amphetamines.
Selegiline itself has neuroprotective and neuro-rescuing effects, but concern over the resulting levomethamphetamine's neurotoxicity led to development of alternative MAOB inhibitors, such as rasagiline, that do not produce toxic metabolites.
When the nasal decongestant is taken in excess, levomethamphetamine has potential side effects. These would be similar to those of other decongestants.
As of 2006, there were no studies demonstrating "drug liking" scores of oral levomethamphetamine that are similar to racemic methamphetamine or dextromethamphetamine in either recreational users or medicinal users.
In recent years, tighter controls in Mexico on certain methamphetamine precursors like ephedrine and pseudoephedrine has led to a greater percentage of illicit meth from Mexican drug cartels consisting of a higher ratio of levomethamphetamine to dextromethamphetamine within batches of racemic meth.
Levomethamphetamine can register on urine drug screens as either methamphetamine, amphetamine, or both, depending on the subject's metabolism and dosage. L-methamphetamine metabolizes completely into L-amphetamine after a period of time.
Topical Nasal Decongestants
Most topical nasal decongestants also carry the warning against unsupervised use with hypertension. This includes oxymetazoline (e.g., Afrin), phenylephrine (e.g., Neo-Synephrine), naphazoline (e.g., Privine), and l-desoxyephedrine/levomethamphetamine. When hypertensive patients request a nasal decongestant, the pharmacist can recommend several alternatives. Propylhexedrine (e.g., Benzedrex Inhaler) is not required to carry a warning against unsupervised use with hypertension and may be effective. Another option is the nasal strip (e.g., Breathe Right). When properly applied, the strip can open the nostrils slightly, and perhaps sufficiently to allow the patient to breathe without use of a pharmacologically active ingredient.