Mechanism of action of narcolepsy medications.
The medications used to treat narcolepsy are targeted toward alleviating symptoms such as excessive sleepiness and cataplexy. The cause of this neurological sleep disorder is still not completely clear, though a destruction of hypocretin/orexin neurons has been implicated. The destruction of these neurons is linked to inactivity of neurotransmitters including histamine, norepinephrine, acetylcholine, and serotonin, causing a disturbance in the sleep/wake cycles of narcoleptic patients. Stimulants and MAOIs have traditionally been used to counteract excessive daytime sleepiness and sleep attacks by inhibiting the breakdown of catecholamines. Newer drugs, called wake-promoting agents, have recently become first-line agents due to their better side-effect profile, efficacy, and lesser potential for abuse. These agents similarly inhibit reuptake of dopamine, but have a novel mechanism of action, as they have been found to increase neuronal activity in the tuberomamillary nucleus and in orexin neurons. Sodium oxybate, a sodium salt of gamma-hydroxybutyrate (GHB), is another class that is used to treat many symptoms of narcolepsy, and is the only U.S. Food and Drug Administration (FDA)-approved medication for cataplexy. It has a different mechanism of action than either stimulants or wake-promoting agents, as it binds to its own unique receptor. Antidepressants, like selective serotonin re-uptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), have also been used, as similar to stimulants, they inhibit reuptake of specific catecholamines. In this article, we seek to review the mechanisms behind these classes of drugs in relation to the proposed pathophysiology of narcolepsy. Appropriate clinical strategies will be discussed, including specific combinations of medications that have been shown to be effective.
1Arizona College of Osteopathic Medicine,Midwestern University,Glendale,Arizona,USA.
Chandan R
CR
Gowda
2Santa Barbara County Alcohol,Drug and Mental Health Services,Psychiatric Health Facility,Santa Barbara,CA,USA.
Leslie P
LP
Lundt
D000928:Antidepressive Agents / Q000627:therapeutic use; D000929:Antidepressive Agents, Tricyclic / Q000627:therapeutic use*; D002385:Cataplexy / Q000188:drug therapy / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D018765:Dopamine Uptake Inhibitors / Q000627:therapeutic use*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008996:Monoamine Oxidase Inhibitors / Q000627:therapeutic use*; D009290:Narcolepsy / Q000188:drug therapy* / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism; D000068797:Orexins; D012978:Sodium Oxybate / Q000627:therapeutic use; D064690:Wakefulness-Promoting Agents / Q000627:therapeutic use*
D000928:Antidepressive Agents; D000929:Antidepressive Agents, Tricyclic; D000697:Central Nervous System Stimulants; D018765:Dopamine Uptake Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D008996:Monoamine Oxidase Inhibitors; D009479:Neuropeptides; D000068797:Orexins; D064690:Wakefulness-Promoting Agents; D012978:Sodium Oxybate
Cataplexy; hypersomnia; hypocretin; narcolepsy; orexin; sleep