Core Body and Skin Temperature in Type 1 Narcolepsy in Daily Life; Effects of Sodium Oxybate and Prediction of Sleep Attacks

STUDY OBJECTIVES

Previous laboratory studies in narcolepsy patients showed altered core body and skin temperatures, which are hypothesised to be related to a disturbed sleep wake regulation. In this ambulatory study we assessed temperature profiles in normal daily life, and whether sleep attacks are heralded by changes in skin temperature. Furthermore, the effects of three months of treatment with sodium oxybate (SXB) were investigated.

METHODS

Twenty-five narcolepsy patients and 15 healthy controls were included. Core body, proximal and distal skin temperatures, and sleep-wake state were measured simultaneously for 24 hours in ambulatory patients. This procedure was repeated in 16 narcolepsy patients after at least 3 months of stable treatment with SXB.

RESULTS

Increases in distal skin temperature and distal-to-proximal temperature gradient (DPG) strongly predicted daytime sleep attacks (P < 0.001). As compared to controls, patients had a higher proximal and distal skin temperature in the morning, and a lower distal skin temperature during the night (all P < 0.05). Furthermore, they had a higher core body temperature during the first part of the night (P < 0.05), which SXB decreased (F = 4.99, df = 1, P = 0.03) to a level similar to controls. SXB did not affect skin temperature.

CONCLUSIONS

This ambulatory study demonstrates that daytime sleep attacks were preceded by clear changes in distal skin temperature and DPG. Furthermore, changes in core body and skin temperature in narcolepsy, previously only studied in laboratory settings, were partially confirmed. Treatment with SXB resulted in a normalisation of the core body temperature profile. Future studies should explore whether predictive temperature changes can be used to signal or even prevent sleep attacks.

[Pitolisant for the treatment of narcolepsy with or without cataplexy]

Since March 2016, a new treatment option for adult patients with narcolepsy – with or without cataplexy – has been granted marketing authorization in Europe. Pitolisant (Wakix®) is an inverse agonst at the histamine-3 (H3) receptor. In clinical studies, tests for measurement of wakefulness and attention, pitolisant showed significantly better results in comparison with placebo and similar results in comparison with modafinil. Pitolisant is well tolerated. Postmarketing analyses have to collect data about the long-term safety of pitolisant when used in a real-life setting.

Clinical applications of sodium oxybate (GHB): from narcolepsy to alcohol withdrawal syndrome

Gamma-hydroxybutyrate (GHB) is a short chain fatty acid endogenously produced within the central nervous system (CNS) and acts as a precursor and metabolite of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Although, it is an illegal recreational drug of abuse, its sodium salt (sodium oxybate) has been utilized as a medication for a number of medical conditions. The first aim of this review was to focus on current applications of sodium oxybate for the treatment of narcolepsy, with a particular emphasis on the key symptoms of this disorder: cataplexy and excessive daytime sleepiness (EDS). Secondly, the effectiveness of sodium oxybate therapy for the treatment of alcohol withdrawal syndrome (AWS) and the maintenance of alcohol abstinence has been assessed. Nowadays, sodium oxybate is the first-line treatment for narcolepsy and it is highly effective in meliorating sleep architecture, decreasing EDS and the frequency of cataplexy attacks in narcoleptic patients. Sodium oxybate currently finds also application in the treatment of AWS and the maintenance of alcohol abstinence in alcoholics. Most of the studies evaluating the efficacy of GHB in the treatment of AWS use a dosage of 50 mg/kg divided in three or four administrations per day. Human studies showed that GHB (dose of 50 mg/kg, divided in three administrations per day) is capable to increase the number of abstinent days, reduce alcohol craving and decrease the number of drinks per day. However, there is limited randomized evidence and, thus, GHB cannot be reliably compared to clomethiazole or benzodiazepines. Some randomized data suggest that GHB is better than naltrexone and disulfiram regarding abstinence maintenance and prevention of craving in the medium term i.e. 3-12 months. It is recommended that GHB should be used only under strict medical supervision, since concerns about the abuse/misuse of the drug and the addiction potential have been arisen.

Narcolepsy Type 1 and Idiopathic Generalized Epilepsy: Diagnostic and Therapeutic Challenges in Dual Cases

STUDY OBJECTIVES

The aim of this study is to describe the possible co-occurrence of narcolepsy type 1 and generalized epilepsy, focusing on diagnostic challenge and safety of dual treatments.

METHODS AND RESULTS

Four patients with comorbidity for narcolepsy type 1 and idiopathic generalized epilepsy are reported: in three cases the onset of epilepsy preceded narcolepsy type 1 appearance, whereas in one case epileptic spells onset was subsequent. Patients presented with absences, myoclonic and tonic-clonic seizure type: in the patient with tonic-clonic seizures the dual pathology was easily recognized, in the other cases the first diagnosis caused the comorbid disease to be overlooked, independent of the time-course sequence. All four patients underwent neurological examination, video-electroencephalogram during which ictal and interictal epileptic discharges were recorded, and sleep polysomnographic studies. Repeated sleep onset rapid eye movement periods (SOREMPs) were documented with the multiple sleep latency test (MLST) in all the four cases. All patients had unremarkable brain magnetic resonance imaging studies and cerebrospinal hypocretin-1 was assessed in two patients, revealing undetectable levels. The association of antiepileptic drugs and substances currently used to treat narcolepsy type 1, including sodium oxybate, was effective in improving seizures, sleep disturbance, and cataplexy.

CONCLUSIONS

Narcolepsy type 1 may occur in association with idiopathic generalized epilepsy, leading to remarkable diagnostic and therapeutic challenges. Electrophysiological studies as well as a comprehensive somnologic interview can help confirm the diagnosis in patients with ambiguous neurological history. Sodium oxybate in combination with antiepileptic drugs is safe and effective in treating cataplexy and excessive daytime sleepiness.

[Clinical effect of atomoxetine hydrochloride in 66 children with narcolepsy]

OBJECTIVE

To observe the efficacy and safety of atomoxetine hydrochloride in children with narcolepsy.

METHOD

Totally 66 patients with narcolepsy who were conformed international classification of sleep disturbances (ICSD-2) diagnostic criteria treated with atomoxetine hydrochloride seen from November 2010 to December 2014 were enrolled into this study, 42 of them were male and 24 female, mean age of onset was 7.5 years (3.75-13.00 years), mean duration before diagnosis was 1.75 years (0.25-5.00 years). Complete blood count, liver and kidney function, multiple sleep latency test (MSLT), polysomnography (PGS), neuroimaging and electroencephalography (EEG) were performed for each patient. For some of the children HLA-DR2 gene and serum markers of infection were tested. The 66 cases were followed up from 2 to 49 months (average 18 months) to observe the clinical efficacy and adverse reactions.

RESULTS

In 62 cases excessive daytime sleepiness was improved, in 11 cases (16.7%) it was controlled (16.7%), in 29 cases (43.9%) the treatment was obviously effective and in 22 (33.3%) it was effective; cataplexy occurred in 54 cases, in 18 (33.3%) it was controlled, in 19 (35.2%) the treatment was obviously effective and in 10 (18.5%) effective; night sleep disorders existed in 55 cases, in 47 cases it was improved, in 14 (25.5%) it was controlled, in 20 (36.4%) the treatment was obviously effective and in 13 (23.6%) effective; hypnagogic or hypnopompic hallucination was present in 13 cases, in only 4 these symptoms were controlled. Sleep paralysis existed in 4 cases, it was controlled in only 1 case. In 18 cases attention and learning efficiency improved.Anorexia occurred in 18 cases, mood disorder in 5 cases, depression in 2 cases, nocturia, muscle tremors, involuntary tongue movement each occurred in 1 case. P-R interval prolongation and atrial premature contraction were found in 1 case.

CONCLUSION

Atomoxetine hydrochloride showed good effects in patients with narcolepsy on excessive daytime sleepiness, cataplexy and night sleep disorders, the effects on hallucinations and sleep paralysis were not significant. Adverse reactions were slight, anorexia and mood disorder were common. As a non-central nervous system stimulant, atomoxetine hydrochloride does not induce drug dependence and has no prescription limits; it has good tolerability, safety and effectiveness, it can be a good alternative in treatment of children with narcolepsy.

Is it safe to breastfeed while taking methylphenidate?

QUESTION

My patient has narcolepsy and is currently breastfeeding her 3-month-old infant. Lately she has had difficulties adjusting to caring for her baby, especially staying alert with the demands of breastfeeding. If she starts taking methylphenidate again, should I advise her to switch to formula?

ANSWER

Methylphenidate is excreted in breast milk only in small amounts, and to date there have been no reports of breastfed infants demonstrating any adverse effects. Based on the available data, methylphenidate appears to be compatible with breastfeeding; however, the long-term neurodevelopmental effects have not been adequately studied.

[Methylphenidate]

Methylphenidate enhances dopaminergic neurotransmission in the central nervous system. Methylphenidate improves social functions as well as clinical symptoms of patients suffered of narcolepsy and attention deficit hyperactivity disorder (ADHD), though it has the potential of abuse. It is reported that approximately 4% of older teens and emerging adults in the US annually misusing methylphenidate. Non-medical/illegal use of methylphenidate causes many consequences including addiction, negative reactions and medical complications. Growing number of illegal trades of methylphenidate and medical complications caused by misuse of methylphenidate urged Japanese government to introduce regulations limiting access to prescribed methylphenidate in 2008. Clinicians should be cautious about prescribing methylphenidate, especially patients with complaint of excessive daytime sleepiness.

Pharmacological treatment of sleep disorders and its relationship with neuroplasticity

Sleep and wakefulness are regulated by complex brain circuits located in the brain stem, thalamus, subthalamus, hypothalamus, basal forebrain, and cerebral cortex. Wakefulness and NREM and REM sleep are modulated by the interactions between neurotransmitters that promote arousal and neurotransmitters that promote sleep. Various lines of evidence suggest that sleep disorders may negatively affect neuronal plasticity and cognitive function. Pharmacological treatments may alleviate these effects but may also have adverse side effects by themselves. This chapter discusses the relationship between sleep disorders, pharmacological treatments, and brain plasticity, including the treatment of insomnia, hypersomnias such as narcolepsy, restless legs syndrome (RLS), obstructive sleep apnea (OSA), and parasomnias.

Pharmacological management of narcolepsy and cataplexy in pediatric patients

Narcolepsy is a neurological disorder frequently occurring from childhood and persisting through adolescence and adulthood. Individuals suffering from narcolepsy exhibit excessive daytime somnolence, sleep attacks, cataplexy, dysomnia, metabolic perturbations including weight gain, and problems in social interaction and academic performance. The prevalence of narcolepsy in childhood is not known but can be estimated from adult studies to be greater than 20-60 per 100,000 in Western countries. The 2009 (A) H1N1 vaccination campaign led to an increase of narcoleptic cases both in children and in adults, supporting the autoimmune hypothesis of the disease. This article focuses on the epidemiology, etiology, and particularities of treatment in pediatric narcolepsy and details the effects of the drugs used to treat this condition, including recent trends in the field. Future therapeutic directions are also discussed. At present, medications used to treat children or adolescents have shown efficacy mostly based on clinical experience, given the lack of level 1 evidence-based studies in the pediatric population. Therefore, most compounds used in adult narcolepsy to target clinical symptoms such as wake-promoting or anticataplectic agents are prescribed off-label in pediatric patients. Published research shows the benefit of drug therapy for narcoleptic children, but these must be dispensed with caution in the absence of well conducted clinical trials.

Current and emerging options for the drug treatment of narcolepsy

Narcolepsy/hypocretin deficiency (now called type 1 narcolepsy) is a lifelong neurologic disorder with well-established diagnostic criteria and etiology. Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness (EDS) and symptoms of dissociated rapid eye movement sleep such as cataplexy (sudden loss of muscle tone), hypnagogic hallucinations (sensory events that occur at the transition from wakefulness to sleep), sleep paralysis (inability to perform movements upon wakening or sleep onset), and nocturnal sleep disruption. As these symptoms are often disabling, most patients need life-long treatment. The treatment of narcolepsy is well defined, and, traditionally, amphetamine-like stimulants (i.e., dopaminergic release enhancers) have been used for clinical management to improve EDS and sleep attacks, whereas tricyclic antidepressants have been used as anticataplectics. However, treatments have evolved to better-tolerated compounds such as modafinil or armodafinil (for EDS) and adrenergic/serotonergic selective reuptake inhibitors (as anticataplectics). In addition, night-time administration of a short-acting sedative, c-hydroxybutyrate (sodium oxybate), has been used for the treatment for EDS and cataplexy. These therapies are almost always needed in combination with non-pharmacologic treatments (i.e., behavioral modification). A series of new drugs is currently being tested in animal models and in humans. These include a wide variety of hypocretin agonists, melanin- concentrating hormone receptor antagonists, antigenspecific immunopharmacology, and histamine H3 receptor antagonists/inverse agonists (e.g., pitolisant), which have been proposed for specific therapeutic applications, including the treatment of Alzheimer's disease, attention-deficit hyperactivity disorder, epilepsy, and more recently, narcolepsy. Even though current treatment is strictly symptomatic, based on the present state of knowledge of the pathophysiology of narcolepsy, we expect that more pathophysiology-based treatments will be available in the near future.

[Orexin: clinical and therapeutic implications]

INTRODUCTION. Recent research has reported the existence of a new class of neuropeptides, called orexins or hypocretins, which are produced by a small group of neurons in the hypothalamus and whose actions are mediated by two types of receptors: OX1R and OX2R. More specifically, the orexinergic neurons have been located exclusively in cells in the lateral, dorsomedial and perifornical areas of the hypothalamus. Despite this highly specific anatomical origin, the orexinergic neurons are projected widely into a number of brainstem, cortical and limbic regions. DEVELOPMENT. This fuzzy pattern of distribution of the orexinergic fibres would be indicating the involvement of this peptidic system in a wide range of functions; indeed, it has been related with the mechanisms that enable regulation of the sleep-wake cycle, the ingestion of food and drink, and some particular types of learning, such as learning certain preferences regarding tastes. It has also been suggested that upsets in the functioning of the orexinergic system would explain the appearance of certain clinical disorders like narcolepsy, obesity or addiction to drug of abuse. CONCLUSIONS. Further research will help to determine the functioning of orexinergic neurons and the interaction between the systems that regulate emotion, energetic homeostasis and the reward mechanisms, on the one hand, and the systems that regulate the sleep-wake cycle on the other. That knowledge would almost certainly make it possible to develop new drugs that, by acting upon the orexinergic system, would be effective in the treatment of sleep disorders such as insomnia or narcolepsy, eating disorders or drug addiction.

Sodium oxybate for narcolepsy

Sodium oxybate (Xyrem), also known as gamma-hydroxybutyric acid, is the only therapeutic specifically approved in the USA for the treatment of cataplexy in narcolepsy. The US FDA has recently expanded its indication to include excessive daytime sleepiness associated with narcolepsy. In contrast to the antidepressants and stimulants commonly used to treat the disorder, sodium oxybate is the only compound that addresses both sets of symptoms and, when used properly, is less likely to lead to the development of tolerance and other undesirable side effects. In this review, the results of clinical trials and the place of sodium oxybate in narcolepsy treatment are discussed.

Orexin neurons suppress narcolepsy via 2 distinct efferent pathways

The loss of orexin neurons in humans is associated with the sleep disorder narcolepsy, which is characterized by excessive daytime sleepiness and cataplexy. Mice lacking orexin peptides, orexin neurons, or orexin receptors recapitulate human narcolepsy phenotypes, further highlighting a critical role for orexin signaling in the maintenance of wakefulness. Despite the known role of orexin neurons in narcolepsy, the precise neural mechanisms downstream of these neurons remain unknown. We found that targeted restoration of orexin receptor expression in the dorsal raphe (DR) and in the locus coeruleus (LC) of mice lacking orexin receptors inhibited cataplexy-like episodes and pathological fragmentation of wakefulness (i.e., sleepiness), respectively. The suppression of cataplexy-like episodes correlated with the number of serotonergic neurons restored with orexin receptor expression in the DR, while the consolidation of fragmented wakefulness correlated with the number of noradrenergic neurons restored in the LC. Furthermore, pharmacogenetic activation of these neurons using designer receptor exclusively activated by designer drug (DREADD) technology ameliorated narcolepsy in mice lacking orexin neurons. These results suggest that DR serotonergic and LC noradrenergic neurons play differential roles in orexin neuron-dependent regulation of sleep/wakefulness and highlight a pharmacogenetic approach for the amelioration of narcolepsy.

[Hypersomnia: a diagnostic problem]

Hypersomnia is a frequently occurring problem. When taking a medical history it is important to distinguish between fatigue and sleepiness. We present a 14-year-old girl with narcolepsy and a 59-year-old man with idiopathic hypersomnia. Features that are typical of narcolepsy are cataplexy and weight gain. Features that are typical of both narcolepsy and idiopathic hypersomnia are daytime naps, insomnia, sleep paralysis and hypnagogic hallucinations. Additional testing in patients with hypersomnia should include a polysomnography in order to exclude other sleeping disorders, and a mean sleep latency test. Practice shows that both patients with narcolepsy and those with idiopathic hypersomnia benefit from treatment with stimulating drugs such as modafinil.

γ-Hydroxybutyric acid (GHB) is not an agonist of extrasynaptic GABAA receptors

γ-Hydroxybutyric acid (GHB) is an endogenous compound and a drug used clinically to treat the symptoms of narcolepsy. GHB is known to be an agonist of GABAB receptors with millimolar affinity, but also binds with much higher affinity to another site, known as the GHB receptor. While a body of evidence has shown that GHB does not bind to GABAA receptors widely, recent evidence has suggested that the GHB receptor is in fact on extrasynaptic α4β1δ GABAA receptors, where GHB acts as an agonist with an EC50 of 140 nM. We investigated three neuronal cell types that express a tonic GABAA receptor current mediated by extrasynaptic receptors: ventrobasal (VB) thalamic neurons, dentate gyrus granule cells and striatal medium spiny neurons. Using whole-cell voltage clamp in brain slices, we found no evidence that GHB (10 µM) induced any GABAA receptor mediated current in these cell types, nor that it modulated inhibitory synaptic currents. Furthermore, a high concentration of GHB (3 mM) was able to produce a GABAB receptor mediated current, but did not induce any other currents. These results suggest either that GHB is not a high affinity agonist at native α4β1δ receptors, or that these receptors do not exist in classical areas associated with extrasynaptic currents.

[Diagnosis and treatment of epilepsy and narcolepsy comorbid]

OBJECTIVE

To analyze the clinical diagnosis and treatment process of narcolepsy and epilepsy co-existence, and thereby to improve awareness of such cases.

METHOD

The clinical manifestations of 2 cases were observed, and video-electroencephalogram (VEEG), multiple sleep latency tests (MSLT) were performed. Hypocretin 1 level in cerebrospinal fluid was examined in one case.

RESULT

The onset of disease of case one was started with epilepsy with myoclonic seizure. After half a year, catalepsy induced by emotion especially laughing and excessive daytime sleepiness appeared. MSLT was positive and hypocretin 1 level decreased. Narcolepsy-cataplexy was definitely diagnosed in this case. Valproate was given and seizure was controlled completely, but the excessive daytime sleepiness was aggravated. Combination of valproate, methylphenidate and clomipramine treatment improved the symptoms of narcolepsy and the patient was still free of epileptic seizures. The onset symptoms of case 2 were catalepsy and excessive daytime sleepiness. MSLT was positive. The treatment was ineffective because of bad compliance. After 2 years, episodes of impairment of consciousness with automatism occurred. VEEG showed slow waves and spikes in right temporal area. Complex partial seizure was determined. Oxcarbazepine was used and then the patients became seizures free, but the symptoms of narcolepsy were still obvious.

CONCLUSION

Comorbidity of narcolepsy and epilepsy is a rare phenomenon. Clinical symptoms, predisposing factor, VEEG and MSLT can help diagnosis and differential diagnosis. The antiepileptic drugs might aggravate drowsiness. Based on therapy of epilepsy by using antiepileptic drugs, low dosage of central nervous system stimulants might improve the drowsiness and catalepsy symptoms of narcolepsy.

The Pharmacokinetics of Sodium Oxybate Oral Solution following Acute and Chronic Administration to Narcoleptic Patients

This trial was conducted to evaluate the pharmacokinetics and safety of a sodium oxybate (gamma-hydroxybutyrate [GHB]) oral solution in narcoleptic patients after acute and chronic treatment. An open-label, two-period, two-treatment study design was used. Trial subjects included 13 patients with polysomnographically confirmed narcolepsy. The patients were administered a bedtime dose of 4.5 g of sodium oxybate while in a sleep research center. They were subsequently treated with sodium oxybate at the nightly dose of 4.5 g for 8 weeks. The patients then returned to the sleep center and were again treated with the 4.5-g sodium oxybate dose at bedtime. Blood samples (5 mL) were collected at 18 time points before and up to 7 hours after both the first dose of sodium oxybate and following 8 weeks of dosing. Plasma samples were analyzed for oxybate content by a validated liquid chromatography/tandem mass spectrometry (LC/MS/MS) method. Noncompartmental methods were applied in the determination of pharmacokinetic parameters from each patient's plasma oxybate concentration versus time curve. No serious adverse events were recorded, and all patients completed the study. Headache, enuresis, and leg cramps were reported as adverse experiences. With both acute and chronic dosing, sodium oxybate was rapidly absorbed and eliminated with an apparent half-life of about 40 minutes. The only changes observed in the kinetics of oxybate after 8 weeks of treatment were a 13% and 16% increase in peak concentration (C(max)) and systemic exposure (AUC), respectively. The pharmacokinetics of sodium oxybate in narcoleptic patients were not changed in any clinically significant manner when the drug was chronically administered. The drug was well tolerated.