Levmetamfetamine
# Levmetamfetamine

Levmetamfetamine is the levorotatory (L-enantiomer) form of methamphetamine. Levmetamfetamine is a sympathomimetic vasoconstrictor that is the active ingredient in some over-the-counter (OTC) nasal decongestant inhalers in the United States.

## Pharmacology

Levmetamfetamine 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 levmetamfetamine 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 levmetamfetamine is between 13.3 and 15 hours, whereas dextromethamphetamine has a half-life of about 10.5 hours.

### Selegiline

Levmetamfetamine is an active metabolite of the antiparkinson's drug selegiline. Selegiline, a selective monoamine oxidase B $(MAO_B)$ inhibitor at low doses, is also metabolized into levmetamfetamine and levoamphetamine. This has caused users to test positive for amphetamines.

Selegiline itself has neuroprotective and neuro-rescuing effects, but concern over the resulting levmetamfetamine 's neurotoxicity led to development of alternative $MAO_B$ inhibitors, such as rasagiline, that do not produce toxic metabolites.

## Side effects

When the nasal decongestant is taken in excess, levmetamfetamine has potential side effects. These would be similar to those of other decongestants.

## Non-medicinal usage

As of 2006, there were no studies demonstrating "drug liking" scores of oral levmetamfetamine 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 levmetamfetamine to dextromethamphetamine within batches of racemic meth.

## Detection in body fluids

Levmetamfetamine 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.

