Selegiline

Selegiline (l-deprenyl, Eldepryl® or Anipryl® veterinary) is a drug used for the treatment of early-stage Parkinson's disease and senile dementia. In normal clinical doses it is a selective irreversible MAO-B inhibitor, however in larger doses (>20 mg in a typical adult^{[citation needed]}) it loses its specificity and also inhibits MAO-A. Dietary restrictions are common for MAOI treatments, however, since selegiline is selective for MAO-B, special dietary restrictions for lower doses have been found to be unnecessary.^[1] The drug was researched by Joseph Knoll. Selegiline is most closely related to the phenylethylamines. The only difference between the two classes of drugs is the attachment of a propargyl group (three carbons with a triple bond between the second and third carbon) to the nitrogen.

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Uses

It is sometimes used off-label to treat narcolepsy and as a nootropic, as well as for its published life-extending effects among several species of mammals. It is also reported to positively affect libido, particularly in older males.^{[citation needed]} As of February 28, 2006, selegiline has also been approved by the Food and Drug Administration (FDA) to treat major depression using a transdermal patch (Emsam Patch).^[2] Selegiline is also used (at extremely high dosages relative to humans) in veterinary medicine to treat the symptoms of Cushing's disease and so-called "cognitive dysfunction" in dogs.^{[citation needed]} As of June 26, 2006, a selegiline transdermal patch is being tested for its effectiveness in treating ADHD.^{[citation needed]}

Several clinical studies are currently underway to evaluate Selegiline's effectiveness in helping people stop smoking tobacco or marijuana.^[3][4]

Mechanism of Action

Selegiline is a selective inhibitor of MAO-B; MAO-B metabolizes dopamine.^[5] Therefore to the extent that it is a DARI, it acts as a prodrug.^{[citation needed]} Selegiline exhibits little therapeutic benefit when used independently, but enhances and prolongs the anti-Parkinson effects of levodopa.^[6]

Metabolites

Desmethylselegiline

Desmethylselegiline may have neuroprotective antiapoptotic properties. A large multicenter study suggests a decrease of in the disease progression of parkinsonism but may have reflected other symptomatic response.^[7] Desmethylselegiline is metabolized by CYP2C19.^[8]

L-amphetamine and L-methamphetamine

Selegiline is partly metabolized to l-methamphetamine, a stereoisomer of methamphetamine in vivo.^[9] A characteristic metabolic pattern was noted, exemplified by a ratio of 1-methamphetamine to 1-amphetamine of about 2.8.^[10] This stereoisomer is not considered psychoactive and has little abuse potential.^[11] The stimulatory effect on locomotor activity and dopamine synthesis may be contributed to by the action of l-methamphetamine. Due to this metabolite selegiline can cause false positives for amphetamine/methamphetamine on drug tests.

Legal Issues

Possibly due to the structural similarity to illegal stimulants, selegiline has been classified as a controlled substance in Japan and thus can only be obtained with a prescription or special government license. Selegiline is not a controlled substance in the US but a prescription is required to obtain it.

EMSAM

February 28, 2006 - The Food and Drug Administration approved Emsam (selegiline), the first skin (transdermal) patch for use in treating major depression. The once a day patch works by delivering selegiline, a monoamine oxidase inhibitor or MAOI, through the skin and into the bloodstream. At its lowest strength, Emsam can be used without the dietary restrictions that are needed for all oral MAO inhibitors that are approved for treating major depression. It comes in three sizes that deliver 6, 9, or 12 mg of selegiline per 24 hours. The patch is a matrix containing three layers consisting of a backing, and adhesive drug layer, and a release liner that is placed against the skin. EMSAM was developed by Somerset Pharmaceuticals, Inc. In December 2004, Bristol-Myers Squibb and Somerset entered into an agreement that provides Bristol-Myers Squibb with distribution rights to market EMSAM after approval in the United States.

References