- First-in-class H3R antagonist/inverse agonist with wake-promoting and anticataplectic effects.
- Approved in the EU and the US for narcolepsy treatment.
- Dose range: 4.5–36 mg/day (EU), 17.8–35.6 mg/day (US).
- Mechanism of Action: Acts on histaminergic neurons in the brain, enhancing histamine release.
- PK/DDI: Rapid absorption, median tmax 3.5 h, metabolized by CYP3A4 and CYP2D6, affected by renal and hepatic impairment.
- Efficacy: Improved ESS scores, MWT sleep latency, cataplexy frequency reduction.
- Safety: Common AEs include insomnia, headache, nausea; potential for CYP interactions and QTc prolongation.

Recently approved Treatments for Narcolepsy: Pitolisant

Thorpy M. J. (2020). Recently Approved and Upcoming Treatments for Narcolepsy. CNS drugs, 34(1), 9–27. https://doi.org/10.1007/s40263-019-00689-1

Reference for Recently approved Treatments for Narcolepsy

Solriamfetol is a dopamine and norepinephrine reuptake inhibitor used to improve wakefulness. It is approved in the United States for narcolepsy and obstructive sleep apnea, with a listed dose range of 75–150 mg/day. Inhibition of DAT and NET increases extracellular dopamine and norepinephrine concentrations. Solriamfetol has linear pharmacokinetics, minimal metabolism, and renal clearance; renal impairment requires dose adjustment. Reported efficacy includes increased MWT sleep latency and improved ESS, PGI-C, and CGI-C scores. Common adverse effects include headache, decreased appetite, nausea, anxiety, and insomnia. Potential safety concerns include increased blood pressure and heart rate and QTc prolongation.

Solriamfetol Treatment Profile for Narcolepsy

State University of New York at Buffalo

People with narcolepsy can differ substantially in how their symptoms appear and in how well available treatments work. McCarty's case study illustrates this variability: a 50-year-old woman had excessive sleepiness during waking hours, unusual right-sided cataplexy, no dream-like hallucinations, little improvement with a stimulant alone, and major improvement when the stimulant was paired with an antidepressant.

Variability in Narcolepsy Symptoms and Treatment Response

Mayo Foundation for Medical Education and Research. (2020, November 6). Narcolepsy. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/narcolepsy/diagnosis-treatment/drc-20375503. 

Mayo Clinic Narcolepsy

Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs used to treat conditions like depression, which is often associated with low serotonin levels. Unlike agonists or antagonists that bind to receptors, SSRIs work by blocking the reuptake process. This action prevents unused serotonin from being reabsorbed by the presynaptic neuron, allowing it to remain in the synaptic cleft for a longer period. The extended presence of serotonin enhances its interaction with postsynaptic receptors, thereby strengthening its overall effect. Common examples of SSRIs include Prozac, Paxil, and Zoloft.

SSRIs and SNRIs

These older antidepressants can be helpful for alleviating cataplexy. Side effects include dry mouth and lightheadedness. 

Tricyclic antidepressants

This medication is very effective in treating cataplexy and improving nighttime sleep. In higher doses, it may also help with daytime sleepiness. It needs to be taken at bedtime and four hours later though, so it can be inconvenient in this sense. Side effects include nausea, bedwetting, and sleepwalking. Taking this with other sleep medications, narcotic pain relievers, or alcohol can be incredibly dangerous. 

Sodium oxybate (Xyrem)

Traditional stimulant medications used to treat narcolepsy do not directly affect the hypocretin system, a key signaling pathway that is deficient in individuals with the disorder. Consequently, it is anticipated that new medications will be developed to specifically target and act upon the hypocretin system to provide more effective treatment.

Future of Narcolepsy Medication: Targeting the Hypocretin System

Psychomotor stimulant drugs, such as amphetamines, are a primary treatment for narcolepsy. These medications function by increasing overall levels of neural activity to combat daytime sleepiness. Examples include modafinil, armodafinil, and various amphetamines.

Stimulants for Narcolepsy

McCarty's (2010) case study describes a 50-year-old woman who was diagnosed with narcolepsy after sleep testing. She had experienced excessive sleepiness during normal waking hours for several years and had fallen asleep in inappropriate or dangerous situations, including while eating, socializing, and driving. During emotional arousal, she experienced unusual right-sided cataplexy but did not have dream-like hallucinations. A stimulant alone was not successful, but combining the stimulant with an antidepressant led to dramatic improvement.

Case Study of Narcolepsy: Symptom Variability and Combination Therapy

A patient diagnosed with narcolepsy begins treatment with a standard psychomotor stimulant. After a month, they report that their excessive daytime sleepiness has only slightly improved, and they still experience frequent episodes of sudden muscle weakness triggered by laughter. Based on the typical challenges in treating this condition, what is the most appropriate next step for the healthcare provider to consider, and what is the underlying reason for this strategy?

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