Histamine Plays an Important Role in Promoting and Stabilizing Wakefulness^1-3

In the brain, histamine acts as a key wake-promoting neurotransmitter^1,4

Histamine is synthesized in the presynaptic neuron¹
When released into the synapse, histamine binds to postsynaptic H₁ receptors¹

Histamine neuronal activity in the brain is modulated by H₁ and H₃ receptors¹

H₁ receptors increase neuronal activity, which allows for communication with brain regions that are important for sleep and wakefulness^1-3
H₃ receptors are found primarily in the brain and help regulate histamine synthesis and release^1,5-7
- Normally, when histamine levels in the brain are high, histamine binds to presynaptic H₃ autoreceptors to inhibit further synthesis and release of histamine in the brain^1,5

Hypocretin (orexin) and histamine neurons play complementary roles in the brain⁸

Hypocretin and histamine promote wakefulness by activating the cortex and activating other wake-promoting neurons^2,3
Hypocretin and histamine also help to stabilize wakefulness by inhibiting non-REM sleep–promoting neurons and REM sleep–promoting neurons^1-3

Loss of hypocretin neurons leads to reduced activation of histamine and other wake-promoting neurons, ultimately resulting in the sleep-wake state instability seen in narcolepsy^9,10

The Role of Histamine in Promoting and Stabilizing Wakefulness

Watch this video to learn about the role of histamine in the brain and the importance of histamine in promoting wakefulness.

The Role of Histamine in Promoting Wakefulness video

WAKIX is indicated for the treatment of excessive daytime sleepiness (EDS) or cataplexy in adult patients with narcolepsy.

Contraindications

WAKIX is contraindicated in patients with known hypersensitivity to pitolisant or any component of the formulation. Anaphylaxis has been reported. WAKIX is also contraindicated in patients with severe hepatic impairment.

Warnings and Precautions

WAKIX prolongs the QT interval; avoid use of WAKIX in patients with known QT prolongation or in combination with other drugs known to prolong the QT interval. Avoid use in patients with a history of cardiac arrhythmias, as well as other circumstances that may increase the risk of the occurrence of torsade de pointes or sudden death, including symptomatic bradycardia, hypokalemia or hypomagnesemia, and the presence of congenital prolongation of the QT interval.
The risk of QT prolongation may be greater in patients with hepatic or renal impairment due to higher concentrations of pitolisant; monitor these patients for increased QTc. Dosage modification is recommended in patients with moderate hepatic impairment and moderate or severe renal impairment (see full prescribing information). WAKIX is not recommended in patients with end-stage renal disease (ESRD).

Adverse Reactions

In the placebo-controlled clinical trials conducted in patients with narcolepsy with or without cataplexy, the most common adverse reactions (≥5% and twice placebo) for WAKIX were insomnia (6%), nausea (6%), and anxiety (5%). Other adverse reactions that occurred at ≥2% and more frequently than in patients treated with placebo included headache, upper respiratory infection, musculoskeletal pain, heart rate increased, hallucinations, irritability, abdominal pain, sleep disturbance, decreased appetite, cataplexy, dry mouth, and rash.

Drug Interactions

Concomitant administration of WAKIX with strong CYP2D6 inhibitors increases pitolisant exposure by 2.2-fold. Reduce the dose of WAKIX by half.
Concomitant use of WAKIX with strong CYP3A4 inducers decreases exposure of pitolisant by 50%. Dosage adjustments may be required (see full prescribing information).
H₁ receptor antagonists that cross the blood-brain barrier may reduce the effectiveness of WAKIX. Patients should avoid centrally acting H₁ receptor antagonists.
WAKIX is a borderline/weak inducer of CYP3A4. Therefore, reduced effectiveness of sensitive CYP3A4 substrates may occur when used concomitantly with WAKIX. The effectiveness of hormonal contraceptives may be reduced when used with WAKIX and effectiveness may be reduced for 21 days after discontinuation of therapy.

Use in Specific Populations

WAKIX may reduce the effectiveness of hormonal contraceptives. Patients using hormonal contraception should be advised to use an alternative non-hormonal contraceptive method during treatment with WAKIX and for at least 21 days after discontinuing treatment.
There is a pregnancy exposure registry that monitors pregnancy outcomes in women who are exposed to WAKIX during pregnancy. Patients should be encouraged to enroll in the WAKIX pregnancy registry if they become pregnant. To enroll or obtain information from the registry, patients can call 1-800-833-7460.
The safety and effectiveness of WAKIX have not been established in patients less than 18 years of age.
WAKIX is extensively metabolized by the liver. WAKIX is contraindicated in patients with severe hepatic impairment. Dosage adjustment is required in patients with moderate hepatic impairment.
WAKIX is not recommended in patients with end-stage renal disease. Dosage adjustment of WAKIX is recommended in patients with moderate or severe renal impairment.
Dosage reduction is recommended in patients known to be poor CYP2D6 metabolizers; these patients have higher concentrations of WAKIX than normal CYP2D6 metabolizers.

To report suspected adverse reactions, contact Harmony Biosciences at 1-800-833-7460 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Please see accompanying
Full Prescribing Information.

References

Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y. Histamine: neural circuits and new medications. Sleep. 2019;42(1). doi:10.1093/sleep/zsy183.
Scammell TE, Arrigoni E, Lipton JO. Neural circuitry of wakefulness and sleep. Neuron. 2017;93(4):747-765.
Haas HL, Sergeeva OA, Selbach O. Histamine in the nervous system. Physiol Rev. 2008;88(3):1183-1241.
España RA, Scammell TE. Sleep neurobiology from a clinical perspective. Sleep. 2011;34(7):845-858.
Nieto-Alamilla G, Marquez-Gomez R, Garcia-Galvez AM, Morales-Figueroa GE, Arias-Montano JA. The histamine H₃ receptor: structure, pharmacology, and function. Mol Pharmacol. 2016;90(5):649-673.
Schlicker E, Kathmann M. Role of the histamine H₃ receptor in the central nervous system. Handb Exp Pharmacol. 2017;241:277-299.
Panula P, Chazot PL, Cowart M, et al. International union of basic and clinical pharmacology. XCVIII. Histamine receptors. Pharmacol Rev. 2015;67(3):601-655.
Anaclet C, Parmentier R, Ouk K, et al. Orexin/hypocretin and histamine: distinct roles in the control of wakefulness demonstrated using knock-out mouse models. J Neurosci. 2009;29(46):14423-14438.
Saper CB, Fuller PM, Pedersen NP, Lu J, Scammell TE. Sleep state switching. Neuron. 2010;68(6):1023-1042.
Scammell TE. Narcolepsy. N Engl J Med. 2015;373(27):2654-2662.

AASM, American Academy of Sleep Medicine.
*	Clinical practice guideline on the treatment of central disorders of hypersomnolence, published in the Journal of Clinical Sleep Medicine, includes recommendations for treatment of narcolepsy in adults.

Histamine Plays an Important Role in Promoting and Stabilizing Wakefulness1-3

In the brain, histamine acts as a key wake-promoting neurotransmitter1,4

Histamine neuronal activity in the brain is modulated by H1 and H3 receptors1

Hypocretin (orexin) and histamine neurons play complementary roles in the brain8

The Role of Histamine in Promoting and Stabilizing Wakefulness

Histamine Plays an Important Role in Promoting and Stabilizing Wakefulness^1-3

In the brain, histamine acts as a key wake-promoting neurotransmitter^1,4

Histamine neuronal activity in the brain is modulated by H₁ and H₃ receptors¹

Hypocretin (orexin) and histamine neurons play complementary roles in the brain⁸