Selegiline

Selegiline (l-deprenyl, Eldepryl, Zelapar, or Anipryl veterinary) is a drug used for the treatment of early-stage Parkinson's disease, depression and senile dementia. In normal clinical doses it is a selective irreversible MAO-B inhibitor, however in larger doses it loses its specificity and also inhibits MAO-A. Dietary restrictions are common for MAOI treatments, but special dietary restrictions for lower doses have been found to be unnecessary.¹ The drug was researched by Jozsef Knoll et al. (Hungary). Selegiline belongs to a class of drugs called phenethylamines. Selegiline consists of an methamphetamine skeleton with a propargyl group attached to the nitrogen atom.

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.³⁴

Pharmacology

Pharmacokinetics

Selegiline's oral bioavailability is drastically increased in females taking oral contraceptives (10- to 20-fold).⁵ This could lead to loss of MAO-B selectivity, which in turn would make patients suspectible to the usual risks of unselective MAOIs such as tyramine-induced hypertensive crisis and serotonin toxicity when combined with serotonergics such as SSRIs.⁵

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.⁶ Desmethylselegiline is metabolized by CYP2C19.⁷

L-amphetamine and L-methamphetamine

Selegiline is partly metabolized to l-methamphetamine, one of the two enantiomers of methamphetamine in vivo.⁸ A characteristic metabolic pattern was noted, exemplified by a ratio of l-methamphetamine to l-amphetamine of about 2.8.⁹ This stereoisomer is not considered psychoactive and has little abuse potential.¹⁰ 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.

Mechanism of Action

Selegiline is a selective inhibitor of MAO-B; MAO-B metabolizes dopamine.¹¹ Selegiline exhibits little therapeutic benefit when used independently, but enhances and prolongs the anti-Parkinson effects of levodopa.¹²

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 transdermal patch for use in treating major depression. The once a day patch works by delivering selegiline 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.

Zelapar

Zelapar is a transmucosal preparation for human administration of selegiline. The quickly-dissolving lozenge is placed between cheek and gum and the medication enters the bloodstream directly. Because hepatic first-pass metabolism is bypassed, the effective dose is lower than oral (swallowed) selegiline. GI side effects are reportedly reduced compared to oral (swallowed) selegiline. Zelapar is manufactured by Valeant Pharmaceuticals [1].

References

^ Amsterdam, J. D. (2003-02). "A double-blind, placebo-controlled trial of the safety and efficacy of selegiline transdermal system without dietary restrictions in patients with major depressive disorder". Journal of Clinical Psychiatry 64 (2): 208–214.
^ FDA Approves Emsam (Selegiline) as First Drug Patch for Depression
^ "Effectiveness of Selegiline in Treating Marijuana Dependent Individuals". ClinicalTrials.gov. National Institute on Drug Abuse (March 2005). Retrieved on 2007-02-16.
^ "Usefulness of Selegiline as an Aid to Quit Smoking". ClinicalTrials.gov. National Institute on Drug Abuse (July 2004). Retrieved on 2007-02-16.
^ ^a ^b Laine K, Anttila M, Helminen A, Karnani H, Huupponen R (March 1999). "Dose linearity study of selegiline pharmacokinetics after oral administration: evidence for strong drug interaction with female sex steroids". Br J Clin Pharmacol 47 (3): 249–54. PMID 10215747. PMC: 2014223, http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0306-5251&date=1999&volume=47&issue=3&spage=249.
^ Katzung, Bertram G. Basic & Clinical Pharmacology. 9th Edition. 2004. page 453. Lange Medical Books - McGraw Hill Publishers.
^ http://www.blackwell-synergy.com/doi/abs/10.1034/j.1600-0773.2000.d01-38.x Selegiline Metabolism and Cytochrome P450 Enzymes
^ Engberg G, Elebring T, Nissbrandt H (1991). "Deprenyl (selegiline), a selective MAO-B inhibitor with active metabolites; effects on locomotor activity, dopaminergic neurotransmission and firing rate of nigral dopamine neurons". J. Pharmacol. Exp. Ther. 259 (2): 841–7. PMID 1658311.
^ www.astm.org/JOURNALS/FORENSIC/PAGES/2587.htm
^ Are metabolites of l-deprenyl (selegiline) useful ...[J Neural Transm Suppl. 1996] - PubMed Result
^ Katzung, Bertram G. Basic & Clinical Pharmacology. 9th Edition. 2004. page 453. Lange Medical Books - McGraw Hill Publishers.
^ Katzung. Page 453

Contents