Population and Noncompartmental Pharmacokinetics of Sodium Oxybate Support Weight-Based Dosing in Children and Adolescents With Narcolepsy With Cataplexy.

The pharmacokinetics (PKs) of sodium oxybate (SXB) was evaluated in a subset of participants from a study of SXB treatment in children (aged 7-11 years; n = 11) and adolescents (aged 12-17 years; n = 18) with narcolepsy with cataplexy. PK evaluation was conducted over 2 nights during the period when participants received a stable nightly SXB dose. The SXB dose on night 1 was half of night 2 and was administered in two equally divided doses: dose 1 was administered > 2 hours after the evening meal, and dose 2 was administered ≥ 4 hours after dose 1. Noncompartmental PK analysis demonstrated higher plasma concentrations post-dose 2 vs. post-dose 1, higher than dose-proportional increases in area under the concentration-time curve from 0 to 4 hours (AUC0-4h ) after dose 1, indicating nonlinear clearance, and better correlation between exposure and mg/kg than exposure and gram dose. To confirm the noncompartmental findings, identify factors affecting SXB PK, and compare with prior results in adults, a population PK (PopPK) model was established combining PK data from the current study with prior data from adults (132 healthy volunteers and 13 with narcolepsy). A two-compartment PopPK model with first-order absorption and nonlinear clearance from the central compartment described the data well. PopPK identified weight as the main intrinsic factor and food as the main extrinsic factor affecting SXB PK, and predicts similar PK profiles on a mg/kg basis across ages. These results, along with previously reported efficacy and safety outcomes, support weight-based SXB dose initiation in pediatric patients.

High bicarbonate levels in narcoleptic children.

The objective of this study was to evaluate the levels of plasma bicarbonate levels in narcoleptic children. Clinical, electrophysiological data and bicarbonate levels were evaluated retrospectively in children seen in our paediatric national reference centre for hypersomnia. The cohort included 23 control subjects (11.5 ± 4 years, 43% boys) and 51 patients presenting de-novo narcolepsy (N) (12.7 ± 3.7 years, 47% boys). In narcoleptic children, cataplexy was present in 78% and DQB1*0602 was positive in 96%. The control children were less obese (2 versus 47%, P = 0.001). Compared with control subjects, narcoleptic children had higher bicarbonate levels (P = 0.02) as well as higher PCO2 (P < 0.01) and lower venous pH gas (P < 0.01). Bicarbonate levels higher than 27 mmol L(-1) were found in 41.2% of the narcoleptic children and 4.2% of the controls (P = 0.001). Bicarbonate levels were correlated with the Adapted Epworth Sleepiness Scale (P = 0.01). Narcoleptic patients without obesity often had bicarbonate levels higher than 27 mmol L (-1) (55 versus 25%, P = 0.025). No differences were found between children with and without cataplexy. In conclusion, narcoleptic patients had higher bicarbonate plasma levels compared to control children. This result could be a marker of hypoventilation in this pathology, provoking an increase in PCO2 and therefore a respiratory acidosis, compensated by an increase in plasma bicarbonates. This simple screening tool could be useful for prioritizing children for sleep laboratory evaluation in practice.

miRNA profiles in plasma from patients with sleep disorders reveal dysregulation of miRNAs in narcolepsy and other central hypersomnias.

STUDY OBJECTIVES: MicroRNAs (miRNAs) have been implicated in the pathogenesis of human diseases including neurological disorders. The aim is to address the involvement of miRNAs in the pathophysiology of central hypersomnias including autoimmune narcolepsy with cataplexy and hypocretin deficiency (type 1 narcolepsy), narcolepsy without cataplexy (type 2 narcolepsy), and idiopathic hypersomnia. DESIGN: We conducted high-throughput analysis of miRNA in plasma from three groups of patients-with type 1 narcolepsy, type 2 narcolepsy, and idiopathic hypersomnia, respectively-in comparison with healthy controls using quantitative real-time polymerase chain reaction (qPCR) panels. SETTING: University hospital based sleep clinic and research laboratories. PATIENTS: Twelve patients with type 1 narcolepsy, 12 patients with type 2 narcolepsy, 12 patients with idiopathic hypersomnia, and 12 healthy controls. MEASUREMENTS AND RESULTS: By analyzing miRNA in plasma with qPCR we identified 50, 24, and 6 miRNAs that were different in patients with type 1 narcolepsy, type 2 narcolepsy, and idiopathic hypersomnia, respectively, compared with healthy controls. Twenty miRNA candidates who fulfilled the criteria of at least two-fold difference and p-value < 0.05 were selected to validate the miRNA changes in an independent cohort of patients. Four miRNAs differed significantly between type 1 narcolepsy patients and healthy controls. Levels of miR-30c, let-7f, and miR-26a were higher, whereas the level of miR-130a was lower in type 1 narcolepsy than healthy controls. The miRNA differences were not specific for type 1 narcolepsy, since the levels of the four miRNAs were also altered in patients with type 2 narcolepsy and idiopathic hypersomnia compared with healthy controls. CONCLUSION: The levels of four miRNAs differed in plasma from patients with type 1 narcolepsy, type 2 narcolepsy and idiopathic hypersomnia suggesting that alterations of miRNAs may be involved in the pathophysiology of central hypersomnias.

Increased plasma IL-6, IL-8, TNF-alpha, and G-CSF in Japanese narcolepsy.

Narcolepsy is a chronic hypersomnia involving excessive daytime sleepiness and cataplexy. Some susceptibility genes and environmental factors suggest that post-infectious immunological alterations underlie its pathophysiology. To investigate the immunological alterations in narcolepsy patients, we examined cytokines. Nine healthy controls and twenty-one narcolepsy patients with cataplexy were studied. All subjects were positive for the HLA-DRB1(∗)1501-DQB1(∗)0602 allele. Age-, sex-, and body mass index -matched healthy controls were selected. Plasma samples were separated using EDTA-2K-coated blood collection tubes. Bioplex Pro Human Cytokine 17-Plex Assays were used to measure plasma cytokines. Elevations of interleukin (IL)-6, IL-8, granulocyte- colony stimulating factor (G-CSF), and tumor necrosis factor-alpha were found in the narcolepsy group compared with healthy controls (p<0.05). G-CSF values were significantly correlated with the disease duration in narcolepsy patients (r=0.426, p<0.05). IL-8 and G-CSF play major roles in neutrophil activation in respiratory diseases. Since environmental factors including infection are reportedly associated with narcolepsy onset, elevated IL-8 and G-CSF may be involved in the pathophysiology of narcolepsy.

Hypothalamo-pituitary-adrenal axis, glucose metabolism and TNF-α in narcolepsy.

Narcolepsy with cataplexy is caused by a deficiency in the production of hypocretin/orexin, which regulates sleep and wakefulness, and also influences appetite, neuroendocrine functions and metabolism. In this case-control study, 11 patients with narcolepsy with cataplexy and 11 healthy adults underwent an oral glucose tolerance test, and dexamethasone suppression/corticotropin-releasing hormone stimulation test. The average age of patients and controls was 35.1 ± 13.2 and 41.0 ± 2.9 years, respectively, body mass index was 28.1 ± 6.6 and 25.5 ± 4.7 kg m(-2) . We did not find evidence of a significantly increased prevalence of disturbed glucose tolerance in patients with narcolepsy. After hypothalamo-pituitary-adrenal axis suppression, the number of non-suppressors did not differ between the groups, indicating normal negative feedback sensitivity. The level of cortisol after dexamethasone suppression was significantly lower in patients with narcolepsy, suggesting a slight basal downregulation and/or a slightly increased negative feedback sensitivity of the major endocrine stress system in narcolepsy. Following corticotropin-releasing hormone stimulation, there were no significant differences in levels of adrenocorticotropic hormone or cortisol, and in adrenocortical responsivity to adrenocorticotropic hormone. Finally, patients with narcolepsy displayed significantly higher plasma levels of tumour necrosis factor alpha, soluble tumour necrosis factor receptor p55, soluble tumour necrosis factor receptor p75 and interleukin 6 after adjustment for body mass index. The present study confirms that narcolepsy by itself is not associated with disturbances of glucose metabolism, but goes along with a subtle dysregulation of inflammatory cytokine production. We also found that dynamic hypothalamo-pituitary-adrenal system response is not altered, whereas negative feedback to dexamethasone might be slightly enhanced.

Cerebrospinal fluid and serum cytokine profiles in narcolepsy with cataplexy: a case-control study.

Recent advances in the identification of susceptibility genes and environmental exposures provide strong support that narcolepsy-cataplexy is an immune-mediated disease. Only few serum cytokine studies with controversial results were performed in narcolepsy and none in the cerebrospinal fluid. We measured a panel of 12 cytokines by a proteomic approach in the serum of 35 patients with narcolepsy-cataplexy compared to 156 healthy controls, and in the cerebrospinal fluid of 34 patients with narcolepsy-cataplexy compared to 17 non-narcoleptic patients; and analyzed the effect of age, duration and severity of disease on the cytokine levels. After multiple adjustments we reported lower serum IL-2, IL-8, TNF-α, MCP-1 and EGF levels, and a tendency for higher IL-4 level in narcolepsy compared to controls. Significant differences were only found for IL-4 in cerebrospinal fluid, being higher in narcolepsy. Positive correlations were found in serum between IL-4, daytime sleepiness, and cataplexy frequency. The expression of some pro-inflammatory cytokines (MCP-1, VEGF, EGF, IL2, IL-1ß, IFN-γ) in either serum or CSF was negatively correlated with disease severity and duration. No correlation was found for any specific cytokine in 18 of the patients with narcolepsy with peripheral and central samples collected the same day. Significant decreased pro/anti-inflammatory cytokine profiles were found at peripheral and central levels in narcolepsy, together with a T helper 2/Th1 serum cytokine secretion imbalance. To conclude, we showed some evidence for alterations in the cytokine profile in patients with narcolepsy-cataplexy compared to controls at peripheral and central levels, with the potential role of IL-4 and significant Th1/2 imbalance in the pathophysiology of narcolepsy.

Low vitamin D in narcolepsy with cataplexy.

BACKGROUND: Narcolepsy with cataplexy (NC) is currently thought to be an autoimmune-mediated disorder in which environmental risk factors make a significant contribution to its development. It was proposed that vitamin D deficiency plays a role in autoimmune diseases. Here we investigated whether NC can be associated with 25-hydroxyvitamin D (25(OH)D) level deficiency in patients with NC compared with gender- and age-matched normal controls. METHODOLOGY: Serum level of 25 (OH)D was determined in 51 European patients with typical NC compared to 55 age-, gender-, and ethnicity-matched healthy controls. Demographic and clinical data (age at onset, duration and severity of disease at baseline, and treatment intake at time of study) and season of blood sampling were collected to control for confounding variables. PRINCIPAL FINDINGS: Serum 25(OH)D concentration was lower in NC compared to controls (median, 59.45 nmol/l [extreme values 24.05-124.03] vs. 74.73 nmol/l [26.88-167.48] p = 0.0039). Patients with NC had significantly greater vitamin D deficiency (<75 nmol/l) than controls (72.5% vs 50.9%, p = 0.0238). Division into quartiles of the whole sample revealed that the risk of being affected with NC increased with lower 25(OH)D level, with a 5.34 OR [1.65-17.27] for the lowest quartile (p = 0.0051). Further adjustment for BMI did not modify the strength of the association (OR: 3.63, 95% CI = 1.06-12.46, p = 0.0191). No between BMI and 25(OH)D interaction, and no correlation between 25(OH)D level and disease duration or severity or treatment intake were found in NC. CONCLUSION: We found a higher frequency of vitamin D deficiency in NC. Further studies are needed to assess the contribution of hypovitaminosis D to the risk of developing narcolepsy, and to focus on the utility of assessing vitamin D status to correct potential deficiency.

Pharmacotherapy for excessive daytime sleepiness.

Excessive daytime sleepiness (EDS) has recognized detrimental consequences such as road traffic accidents, impaired psychological functioning and reduced work performance. EDS can result from multiple causes such as sleep deprivation, sleep fragmentation, neurological, psychiatric and circadian rhythm disorders. Treating the underlying cause of EDS remains the mainstay of therapy but in those who continue to be excessively sleepy, further treatment may be warranted. Traditionally, the amphetamine derivatives, methylphenidate and pemoline (collectively sympathomimetic) psychostimulants were the commonest form of therapy for EDS, particularly in conditions such as narcolepsy. More recently, the advent of modafinil has broadened the range of therapeutic options. Modafinil has a safer side-effect profile and as a result, interest in this drug for the management of EDS in other disorders, as well as narcolepsy, has increased considerably. There is a growing school of thought that modafinil may have a role to play in other indications such as obstructive sleep apnea/hypopnea syndrome already treated by nasal continuous positive airway pressure but persisting EDS, shift work sleep disorders, neurological causes of sleepiness, and healthy adults performing sustained operations, particularly those in the military. However, until adequately powered randomised-controlled trials confirm long-term efficacy and safety, the recommendation of wakefulness promoters in healthy adults cannot be justified.

Cataplexy and monoamine oxidase deficiency in Norrie disease.

Norrie disease (ND) is an X-linked recessive disorder causing ocular atrophy, mental retardation, deafness, and dysmorphic features. Virtually absent monoamine oxidase (MAO) type-A and -B activity has been found in some boys with chromosome deletions. We report the coexistence of cataplexy and abnormal REM sleep organization with ND. Three related boys, referred for treatment of medically refractory atonic spells and apneas, underwent extended EEG-video-polysomnographic monitoring. They demonstrated attacks of cataplexy and inappropriate periods of REM sleep during which they were unarousable. One boy also had generalized tonic-clonic seizures. Previous testing revealed that all three have complete ND gene deletions. In all subjects, platelet MAO-B activity was absent, serum serotonin levels were markedly increased, and plasma catecholamine levels were normal. Data from the canine narcolepsy syndrome model implicate abnormal catecholaminergic and cholinergic activities in the pathogenesis of cataplexy. Our findings suggest that abnormal MAO activity or an imbalance between serotonin and other neurotransmitter levels may be involved in the pathogenesis of human cataplexy.

The effect of zimelidine, a serotonin-reuptake blocker, on cataplexy and daytime sleepiness of narcoleptic patients.

Narcolepsy is a neurological syndrome characterized by two major symptoms: excessive daytime sleepiness and cataplexy. Pharmacological and biochemical evidence support the hypothesis that dopaminergic mechanisms are involved in excessive daytime sleepiness. The pathophysiology of cataplexy and the action mechanisms of anticataplectic agents remain controversial issues. Cataplexy is usually controlled by tricyclic antidepressants, but these drugs interact with several central monoamine systems and also exert an anticholinergic effect. In the present study, zimelidine, a selective serotonin reuptake inhibitor without anticholinergic activity, was administered to 11 narcoleptic patients for 1-16 months. Cataplexy improved markedly in all patients, while no changes could be documented on excessive daytime sleepiness, either by self-report or polysomnographic nap recording. These results confirm the hypothesis that hypersomnolence and cataplexy are subject to different control mechanisms; support a serotoninergic, but not a cholinergic, theory of cataplexy; and suggest that selective serotonin reuptake inhibitors may be the treatment of choice for cataplexy.