Reduction of sleep-disordered breathing after physostigmine

Tackling obstructive sleep apnea with pharmacotherapeutics: expert guidance

INTRODUCTION

The efficacy of non-pharmacotherapeutic treatment of obstructive sleep apnea, a highly prevalent condition with serious cardiometabolic and neurocognitive health consequences, is well established. Supplementing traditional treatment strategies with medications can improve symptoms and reduce side effects. Efforts to identify medications that target the causes of sleep apnea have met with mixed success. However, this remains a worthwhile objective for researchers to pursue, given the potential benefit pharmacotherapy could bring to those patients who reject or struggle to adhere to existing treatments.

AREAS COVERED

This article presents the case for obstructive sleep apnea pharmacotherapy including drugs that reduce the occurrence of apnea events, such as weight loss agents, ventilation activators and muscle and nervous system stimulants, drugs that alleviate symptoms, such as wake-promoting agents for excessive daytime sleepiness, and drugs that improve adherence to existing treatments, such as hypnotics. Literature was accessed from PubMed between 1 March 2024 and 18 April 2024.

EXPERT OPINION

Exciting recent advances in both our understanding of obstructive sleep apnea pathology and in the techniques used to identify therapeutic agents and their targets combine to embolden a positive outlook for the expanded use of drugs in tackling this consequential disease.

Summary of drug therapy to treat cognitive impairment-induced obstructive sleep apnea

Obstructive sleep apnea (OSA) is a severe sleep disorder associated with intermittent hypoxia and sleep fragmentation. Cognitive impairment is a signifi- cant and common OSA complication often described in such patients. The most commonly utilized methods in clinical OSA treatment are oral appliances and continuous positive airway pressure (CPAP). However, the current therapeutic methods for improving cognitive function could not achieve the expected efficacy in same patients. Therefore, further understanding the molecular mechanism behind cognitive dysfunction in OSA disease will provide new treatment methods and targets. This review briefly summarized the clinical manifestations of cognitive impairment in OSA disease. Moreover, the pathophysiological molecular mechanism of OSA was outlined. Our study concluded that both SF and IH could induce cognitive impairment by multiple signaling pathways, such as oxidative stress activation, inflammation, and apoptosis. However, there is a lack of effective drug therapy for cognitive impairment in OSA. Finally, the therapeutic potential of some novel compounds and herbal medicine was evaluated on attenuating cognitive impairment based on certain preclinical studies.

Advances in Molecular Pathology of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a common syndrome that features a complex etiology and set of mechanisms. Here we summarized the molecular pathogenesis of OSA, especially the prospective mechanism of upper? airway dilator fatigue and the current breakthroughs. Additionally, we also introduced the molecular mechanism of OSA in terms of related studies on the main signaling pathways and epigenetics alterations, such as microRNA, long non-coding RNA, and DNA methylation. We also reviewed small molecular compounds, which are potential targets for gene regulations in the future, that are involved in the regulation of OSA. This review will be beneficial to point the way for OSA research within the next decade.

Differential pharmacological and sex-specific effects of antimuscarinic agents at the hypoglossal motor nucleus in vivo in rats

Successful cholinergic-noradrenergic pharmacotherapy for obstructive sleep apnea (OSA) is thought to be due to effects at the hypoglossal motor nucleus (HMN). Clinical efficacy varies with muscarinic-receptor (MR) subtype affinities. We hypothesized that oxybutynin (cholinergic agent in successful OSA pharmacotherapy) is an effective MR antagonist at the HMN and characterized its efficacy with other antagonists. We recorded tongue muscle activity of isoflurane anesthetized rats (121 males and 60 females, 7-13 per group across 13 protocols) in response to HMN microperfusion with MR antagonists with and without: (i) eserine-induced increased endogenous acetylcholine at the HMN and (ii) muscarine. Eserine-induced increased acetylcholine decreased tongue motor activity (p < 0.001) with lesser cholinergic suppression in females versus males (p = 0.017). Motor suppression was significantly attenuated by the MR antagonists atropine, oxybutynin, and omadacycline (MR2 antagonist), each p < 0.001, with similar residual activity between agents (p ≥ 0.089) suggesting similar efficacy at the HMN. Sex differences remained with atropine and oxybutynin (p < 0.001 to 0.05) but not omadacycline (p = 0.722). Muscarine at the HMN also decreased motor activity (p < 0.001) but this was not sex-specific (p = 0.849). These findings have translational relevance to antimuscarinic agents in OSA pharmacotherapy and understanding potential sex differences in HMN suppression with increased endogenous acetylcholine related to sparing nicotinic excitation.

Turning Over a New Leaf-Pharmacologic Therapy in Obstructive Sleep Apnea

Despite extensive research, there is currently no approved drug for obstructive sleep apnea (OSA) treatment. OSA is a heterogeneous condition that involves multiple dominating pathophysiological traits. Drug development in this field needs to address both pathophysiological mechanisms and associated comorbid conditions in order to meet requirements for long-term therapy in OSA. Several drug candidates have been proposed and ongoing phase II trials that target various forms of sleep-disordered breathing have been initiated. The field is moving toward tailored therapeutic approaches in patients with OSA.

Effects of Donepezil and Medroxyprogesterone Versus Placebo on Weaning in Adult Patients With Non-Pulmonary Etiologies Receiving Invasive Mechanical Ventilation: A triple-blind Randomized Clinical Trial

Background: Medroxyprogesterone and donepezil could be used as respiratory stimulants in ventilated patients. However, no randomized placebo-controlled trial is available to confirm this approach and compare these drugs. The aim of the current study was to evaluate the effects of donepezil or medroxyprogesterone compared to the placebo in improvement in respiratory status and weaning facilitation in critically ill adult patients receiving mechanical ventilation.

Material and Methods: This randomized, triple-blind trial was conducted on 78 ventilated patients in intensive care units (ICU). Patients who were intubated due to pulmonary disorders were ruled out. Patients were randomized in a 1:1:1 ratio to receive 5 mg donepezil (n = 23) or 5 mg medroxyprogesterone (n = 26), or placebo (n = 24) twice a day until weaning (maximum 10 days). The primary endpoints were weaning duration, and duration of invasive mechanical ventilation. Secondary endpoints included rate of successful weaning, changes in arterial blood gas (ABG) parameters, GCS and sequential organ failure assessment (SOFA) score, hemoglobin (Hgb), ICU-mortality, and duration of ICU stay, were measured before and after the intervention and if successful weaning was recorded.

Results: Of 78 studied patients who were randomized, 59 weaned successfully. 87% patients in donepezil and 88.5% patients in medroxyprogesterone groups were successfully weaned compared to 66.7% patients in the placebo group. However, this difference was not statistically significant (p-Value = 0.111). Changes in pH, mean duration of intubation, and weaning duration were statistically different in donepezil compared with the control group (p-Value < 0.05). No significant difference in ABG, Hgb, GCS and SOFA score, and duration of intubation were seen in the medroxyprogesterone group, but weaning duration was significantly reduced to 1.429 days compared with the control group (p-Value = 0.038).

Conclusion: The results of this clinical trial have demonstrated that the administered dose of medroxyprogesterone and donepezil can expedite the weaning process by reducing the weaning duration compared to placebo. Furthermore, the total duration of invasive ventilation was significantly lower in the donepezil group compared to the control group. Future clinical trials with a larger sample size will determine the exact role of medroxyprogesterone and donepezil in mechanically ventilated patients.

Clinical Trial Registration:https://irct.ir/IRCT20190810044500N2 (April 1, 2020).

Effects of acetylcholine on hypoglossal and C4 nerve activity in brainstem-spinal cord preparations from newborn rat

Effects of acetylcholine (ACh) on respiratory activity have been an intriguing theme especially in relation to central chemoreception and the control of hypoglossal nerve activity. We studied the effects of ACh on hypoglossal and phrenic (C4) nerve activities and inspiratory and pre-inspiratory neurons in the rostral ventrolateral medulla in brainstem-spinal cord preparations from newborn rats. ACh application increased respiratory rhythm, decreased inspiratory hypoglossal and C4 nerve burst amplitude, and enhanced pre-inspiratory hypoglossal activity. ACh induced membrane depolarization of pre-inspiratory neurons that might be involved in facilitation of respiratory rhythm by ACh. Effects of ACh on hypoglossal and C4 nerve activity were partially reversed by a nicotinic receptor blocker, mecamylamine. Further application of a muscarinic receptor antagonist, oxybutynin, resulted in slight increase of hypoglossal (but not C4) burst amplitude. Thus, ACh induced different effects on hypoglossal and C4 nerve activity in the brainstem-spinal cord preparation.

[Drugs affecting obstructive sleep apnea syndrome]

Sleep-disordered breathing is one of the most common sleep-associated disorders. At the same time, their prevalence tends to increase with age. One of the most common forms of respiratory failure during sleep is obstructive sleep apnea syndrome (OSA), which is characterized by repeated episodes of cessation of breathing or a significant decrease in respiratory flow while maintaining respiratory effort as a result of obstruction of the upper respiratory tract. Drugs have different effects on OSA. There are drugs that worsen OSA, drugs that do not affect OSA, and drugs that improve OSA. Benzodiazepines, opioids, muscle relaxants, and male hormones adversely affect OSA. Also of clinical interest are drugs that do not affect OSA and can even potentially improve respiratory function during sleep. These include anti-inflammatory drugs, diuretics, bronchodilators, acetylcholinesterase inhibitors, antiparkinsonian, decongestant drugs, drugs for intranasal use, topical soft tissue lubricant, female sex hormones. Finally, the effect of a number of drugs on OSA is not definitively established and requires further study (benzodiazepine receptor agonist hypnotics, angiotensin-converting enzyme inhibitors, opiate receptor antagonists, antidepressants, proton-pump inhibitors, TNF-α antagonists, glutamate receptor antagonists, drugs for the treatment of acromegaly, drugs for the treatment of narcolepsy). Raising awareness of doctors of different specialties about the impact of various drugs on OSA can not only prevent the deterioration of respiratory distress during sleep, but also, with a rational individual approach, makes it possible to even improve the quality of sleep and blood saturation, thereby contributing to a more favorable course of OSA and the underlying disease.

Obstructive Sleep Apnea Syndrome: A Preliminary Navigated Transcranial Magnetic Stimulation Study

PURPOSE

An increase in resting motor threshold (RMT), prolonged cortical silent period duration (CSP), and reduced short-latency afferent inhibition (SAI), confirmed with previous transcranial magnetic stimulation (TMS), suggest decreased cortical excitability in obstructive sleep apnea syndrome (OSAS). The present study included MRI of OSAS patients for navigated TMS assessment of the RMT, as an index of the threshold for corticospinal activation at rest, and SAI as an index of cholinergic neurotransmission. We hypothesize to confirm findings on SAI and RMT with adding precision in the targeting of motor cortex in OSAS.

SUBJECTS AND METHODS

After acquiring head MRIs for 17 severe right-handed OSAS and 12 healthy subjects, the motor cortex was mapped with nTMS to assess the RMT and SAI, with motor evoked potentials (MEPs) recorded from the abductor-pollicis brevis (APB) muscle. The 120%RMT intensity was used for the SAI by a paired-pulse paradigm in which the electrical stimulation to the median nerve is followed by magnetic stimulation of the motor cortex at inter-stimulus intervals (ISIs) of 18-28 ms (ISIs_18-28). The SAI control condition included a recording of MEPs without peripheral stimulation. Latency and amplitude of MEP at RMT at 120%RMT for eleven different at ISIs_18-28 were analyzed.

RESULTS

The study showed a significantly lower percentage deviation of MEP amplitude at ISIs_(18-28ms) from the control condition between OSAS and healthy subjects (U=44.0, p=0.01). The intensity of stimulation at RMT was significantly higher in OSAS subjects (U=55.0, p=0.04*). Correlation analysis showed that BMI significantly negatively correlated (ρ=-0.47) with MEP amplitude percentage deviation in OSAS patients.

CONCLUSION

The nTMS study results in increased RMT, and reduced cortical afferent inhibition in OSAS patients for SAI at ISIs_18-28, confirming previous findings of impaired cortical afferent inhibition in OSAS. Future nTMS studies are desirable to elucidate the role of RMT and SAI in diagnostics and treatment of OSAS, and to elucidate the usefulness of nTMS in OSAS research.

Targeting Endotypic Traits with Medications for the Pharmacological Treatment of Obstructive Sleep Apnea. A Review of the Current Literature

Obstructive sleep apnea (OSA) is a highly prevalent condition with few therapeutic options. To date there is no approved pharmacotherapy for this disorder, but several attempts have been made in the past and are currently ongoing to find one. The recent identification of multiple endotypes underlying this disorder has oriented the pharmacological research towards tailored therapies targeting specific pathophysiological traits that contribute differently to cause OSA in each patient. In this review we retrospectively analyze the literature on OSA pharmacotherapy dividing the medications tested on the basis of the four main endotypes: anatomy, upper airway muscle activity, arousal threshold and ventilatory instability (loop gain). We show how recently introduced drugs for weight loss that modify upper airway anatomy may play an important role in the management of OSA in the near future, and promising results have been obtained with drugs that increase upper airway muscle activity during sleep and reduce loop gain. The lack of a medication that can effectively increase the arousal threshold makes this strategy less encouraging, although recent studies have shown that the use of certain sedatives do not worsen OSA severity and could actually improve patients' sleep quality.

Impact of concomitant medications on obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is characterized by repeated episodes of apnoea and hypopnoea during sleep. Little is known about the potential impact of therapy drugs on the underlying respiratory disorder. Any influence should be taken into account and appropriate action taken, including drug withdrawal if necessary. Here, we review drugs in terms of their possible impact on OSA; drugs which (1) may worsen OSA; (2) are unlikely to have an impact on OSA; (3) those for which data are scarce or contradictory; and (4) drugs with a potentially improving effect. The level of evidence is ranked according to three grades: A - randomized controlled trials (RCTs) with high statistical power; B - RCTs with lower power, non-randomized comparative studies and observational studies; C - retrospective studies and case reports. Our review enabled us to propose clinical recommendations. Briefly, agents worsening OSA or inducing weight gain, that must be avoided, are clearly identified. Drugs such as 'Z drugs' and sodium oxybate should be used with caution as the literature contains conflicting results. Finally, larger trials are needed to clarify the potential positive impact of certain drugs on OSA. In the meantime, some, such as diuretics or other antihypertensive medications, are helpful in reducing OSA-associated cardiovascular morbidity.

Emerging drugs for common conditions of sleepiness: obstructive sleep apnea and narcolepsy

INTRODUCTION

Obstructive sleep apnea (OSA) and narcolepsy are sleep disorders associated with high prevalence and high symptomatic burden including prominent sleepiness, daytime dysfunction and poor nocturnal sleep. Both have elevated risk of poor health outcomes. Current therapies are often underutilized, cumbersome, costly or associated with residual symptoms.

AREAS COVERED

This review covers current available therapies for OSA and narcolepsy as well as discusses areas for potential drug development, and agents in the therapeutic pipeline, including the cannabinoid dronabinol (OSA), the histamine inverse agonist/ antagonist pitolisant (narcolepsy), and stimulants with uncertain and/or multiple activities such as JZP-110 and JZP-386 (narcolepsy, possibly OSA). Finally it addresses new approaches and uses for therapies currently on the market such as the carbonic anhydrase inhibitor acetazolamide (OSA).

EXPERT OPINION

Both OSA and narcolepsy are conditions of sleepiness for which lifelong treatments are likely to be required. In OSA, while continuous positive airway pressure will likely remain the gold standard therapy for the foreseeable future, there is plenty of room for integrating phenotypes and variants of OSA into therapeutic strategies to lead to better, more personalized disease modification. In narcolepsy, unlike OSA, drug therapy is the current mainstay of treatment. Advances using novel mechanisms to treat targeted symptoms such as sleepiness and/or novel agents that can treat more than one symptom of narcolepsy, hold promise. However, cost, convenience and side effects remain challenges.

Obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome (OSAS) is a common clinical condition in which the throat narrows or collapses repeatedly during sleep, causing obstructive sleep apnoea events. The syndrome is particularly prevalent in middle-aged and older adults. The mechanism by which the upper airway collapses is not fully understood but is multifactorial and includes obesity, craniofacial changes, alteration in upper airway muscle function, pharyngeal neuropathy and fluid shift towards the neck. The direct consequences of the collapse are intermittent hypoxia and hypercapnia, recurrent arousals and increase in respiratory efforts, leading to secondary sympathetic activation, oxidative stress and systemic inflammation. Excessive daytime sleepiness is a burden for the majority of patients. OSAS is also associated with cardiovascular co-morbidities, including hypertension, arrhythmias, stroke, coronary heart disease, atherosclerosis and overall increased cardiovascular mortality, as well as metabolic dysfunction. Whether treating sleep apnoea can fully reverse its chronic consequences remains to be established in adequately designed studies. Continuous positive airway pressure (CPAP) is the primary treatment modality in patients with severe OSAS, whereas oral appliances are also widely used in mild to moderate forms. Finally, combining different treatment modalities such as CPAP and weight control is beneficial, but need to be evaluated in randomized controlled trials. For an illustrated summary of this Primer, visit: http://go.nature.com/Lwc6te.

Can donepezil facilitate weaning from mechanical ventilation in difficult to wean patients? An interventional pilot study

Background

Management of difficult to wean patients is a dilemma for health care system. Recently published studies demonstrated efficacy of donepezil to counteract respiratory depression in sleep apnea. However, to the best of our knowledge, pharmaceutical interventions with donepezil to facilitate weaning have not been tested so far. Therefore in the present study, we evaluated the efficacy of using donepezil on weaning course in difficult to wean patients.

Methods

In this non-randomized interventional clinical study, difficult to wean patients with prior inappropriately depressed respiratory responses were included from two referral intensive care units (ICU) in Iran. Patients with another potentially reasons of weaning failure were excluded from the study. Donepezil was started for eligible patients at dose of 10 mg daily for 2–4 weeks. For the primary outcomes, arterial blood gas (ABG) parameters were also measured before and after intervention to evaluate the possible effects of donepezil on them. In addition, weaning outcomes of patients were reported as final outcome in response to this intervention.

Results

Twelve out of 16 studied patients experienced successful results to facilitate weaning with donepezil intervention. The mean duration of donepezil treatment until outcome measurement was 12 days. There were not any significant differences in ABG parameters among patients with successful and failed weaning trial on day of donepezil initiation. However after donepezil intervention, mean of PCO2 and HCO3 decreased in patients with successful weaning trial and mean of PCO2 increased in those with weaning failure.

Conclusions

Reduced central respiratory drive was infrequently reason of failed weaning attempts but it must be considered especially in patients with hypercapnia secondary to inefficient gas exchange and slow breathing. Our results in the clinical setting suggest that, the use of donepezil can expedite weaning presumably by stimulation of respiratory center and obviate the need to re-intubation in cases of respiratory drive problem in difficult to wean patients. We suggest decrease PCO2 and HCO3 during donepezil steady could be valuable predictors for positive response to donepezil intervention.

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.

K+ channel modulation causes genioglossus inhibition in REM sleep and is a strategy for reactivation

Rapid eye movement (REM) sleep is accompanied by periods of upper airway motor suppression that cause hypoventilation and obstructive apneas in susceptible individuals. A common idea has been that upper airway motor suppression in REM sleep is caused by the neurotransmitters glycine and γ-amino butyric acid (GABA) acting at pharyngeal motor pools to inhibit motoneuron activity. Data refute this as a workable explanation because blockade of this putative glycine/GABAergic mechanism releases pharyngeal motor activity in all states, and least of all in REM sleep. Here we summarize a novel motor-inhibitory mechanism that suppresses hypoglossal motor activity largely in REM sleep, this being a muscarinic receptor mechanism linked to G-protein-coupled inwardly rectifying potassium (GIRK) channels. We then outline how this discovery informs efforts to pursue therapeutic targets to reactivate hypoglossal motor activity throughout sleep via potassium channel modulation. One such target is the inwardly rectifying potassium channel Kir2.4 whose expression in the brain is almost exclusive to cranial motor nuclei.

Drug therapy for obstructive sleep apnoea in adults

BACKGROUND

The treatment of choice for moderate to severe obstructive sleep apnoea (OSA) is continuous positive airways pressure (CPAP) applied via a mask during sleep. However, this is not tolerated by all individuals and its role in mild OSA is not proven. Drug therapy has been proposed as an alternative to CPAP in some patients with mild to moderate sleep apnoea and could be of value in patients intolerant of CPAP. A number of mechanisms have been proposed by which drugs could reduce the severity of OSA. These include an increase in tone in the upper airway dilator muscles, an increase in ventilatory drive, a reduction in the proportion of rapid eye movement (REM) sleep, an increase in cholinergic tone during sleep, an increase in arousal threshold, a reduction in airway resistance and a reduction in surface tension in the upper airway.

OBJECTIVES

To determine the efficacy of drug therapies in the specific treatment of sleep apnoea.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of trials. Searches were current as of July 2012.

SELECTION CRITERIA

Randomised, placebo controlled trials involving adult patients with confirmed OSA. We excluded trials if continuous positive airways pressure, mandibular devices or oxygen therapy were used. We excluded studies investigating treatment of associated conditions such as excessive sleepiness, hypertension, gastro-oesophageal reflux disease and obesity.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by The Cochrane Collaboration.

MAIN RESULTS

Thirty trials of 25 drugs, involving 516 participants, contributed data to the review. Drugs had several different proposed modes of action and the results were grouped accordingly in the review. Each of the studies stated that the participants had OSA but diagnostic criteria were not always explicit and it was possible that some patients with central apnoeas may have been recruited.Acetazolamide, eszopiclone, naltrexone, nasal lubricant (phosphocholinamine) and physiostigmine were administered for one to two nights only. Donepezil in patients with and without Alzheimer's disease, fluticasone in patients with allergic rhinitis, combinations of ondansetrone and fluoxetine and paroxetine were trials of one to three months duration, however most of the studies were small and had methodological limitations. The overall quality of the available evidence was low.The primary outcomes for the systematic review were the apnoea hypopnoea index (AHI) and the level of sleepiness associated with OSA, estimated by the Epworth Sleepiness Scale (ESS). AHI was reported in 25 studies and of these 10 showed statistically significant reductions in AHI.Fluticasone in patients with allergic rhinitis was well tolerated and reduced the severity of sleep apnoea compared with placebo (AHI 23.3 versus 30.3; P < 0.05) and improved subjective daytime alertness. Excessive sleepiness was reported to be altered in four studies, however the only clinically and statistically significant change in ESS of -2.9 (SD 2.9; P = 0.04) along with a small but statistically significant reduction in AHI of -9.4 (SD 17.2; P = 0.03) was seen in patients without Alzheimer's disease receiving donepezil for one month. In 23 patients with mild to moderate Alzheimer's disease donepezil led to a significant reduction in AHI (donepezil 20 (SD 15) to 9.9 (SD 11.5) versus placebo 23.2 (SD 26.4) to 22.9 (SD 28.8); P = 0.035) after three months of treatment but no reduction in sleepiness was reported. High dose combined treatment with ondansetron 24 mg and fluoxetine 10 mg showed a 40.5% decrease in AHI from the baseline at treatment day 28. Paroxetine was shown to reduce AHI compared to placebo (-6.10 events/hour; 95% CI -11.00 to -1.20) but failed to improve daytime symptoms.Promising results from the preliminary mirtazapine study failed to be reproduced in the two more recent multicentre trials and, moreover, the use of mirtazapine was associated with significant weight gain and sleepiness. Few data were presented on the long-term tolerability of any of the compounds used.

AUTHORS' CONCLUSIONS

There is insufficient evidence to recommend the use of drug therapy in the treatment of OSA. Small studies have reported positive effects of certain agents on short-term outcomes. Certain agents have been shown to reduce the AHI in largely unselected populations with OSA by between 24% and 45%. For donepezil and fluticasone, studies of longer duration with a larger population and better matching of groups are required to establish whether the change in AHI and impact on daytime symptoms are reproducible. Individual patients had more complete responses to particular drugs. It is possible that better matching of drugs to patients according to the dominant mechanism of their OSA will lead to better results and this also needs further study.

Drug effects on ventilatory control and upper airway physiology related to sleep apnea

Understanding the inter-relationship between pharmacological agents, ventilatory control, upper airway physiology and their consequent effects on sleep-disordered breathing may provide new directions for targeted drug therapy. Where available, this review focuses on human studies that contain both drug effects on sleep-disordered breathing and measures of ventilatory control or upper airway physiology. Many of the existing studies are limited in sample size or comprehensive methodology. At times, the presence of paradoxical findings highlights the complexity of drug therapy for OSA. The existing studies also highlight the importance of considering inter-individual pharmacokinetics and underlying causes of sleep apnea in interpreting drug effects on sleep-disordered breathing. Practical ways to assess an individual's ventilatory control and how it interacts with upper airway physiology is required for future targeted pharmacotherapy in sleep apnea.

Lower frequency of obstructive sleep apnea in spondyloarthritis patients taking TNF-inhibitors

STUDY OBJECTIVES

Sleep disturbances, including obstructive sleep apnea (OSA), commonly limit function and quality of life in people with spondyloarthritis (SpA). Systemic inflammation has been implicated in the pathophysiology of both OSA and SpA, and suppression of inflammation with tumor necrosis factor α (TNF) inhibitors may decrease OSA severity. In this study, we compared the frequency of OSA in patients receiving and not receiving TNF-inhibitor therapy.

METHODS

Data were collected from 63 consecutively screened veterans with SpA. Participant interviews, examinations, chart reviews, and referrals to the Salt Lake City Veteran Affairs (SLCVA) Sleep Center were used to obtain demographic data, comorbidities, SpA features, therapy data, and sleep study outcomes.

RESULTS

OSA occurred in 76% of SpA patients. OSA was less common in patients receiving TNF-inhibitor therapy (57%), compared to patients not receiving TNF-inhibitor therapy (91%) (p = 0.01).

CONCLUSIONS

OSA is underrecognized in veterans with SpA, and TNF-inhibition was associated with a lower frequency of OSA.

Muscarinic acetylcholine receptors enhance neonatal mouse hypoglossal motoneuron excitability in vitro

In brain stem slices from neonatal ( postnatal days 0–4) CD-1 mice, muscarinic ACh receptors (MAChRs) increased rhythmic inspiratory-related and tonic hypoglossal nerve discharge and depolarized single hypoglossal motoneurons (HMs) via an inward current without changing input resistance. These responses were blocked by the MAChR antagonist 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4-DAMP; 100 nM). MAChRs shifted voltage-dependent activation of the hyperpolarization-activated cation current to more positive levels. MAChRs increased the HM repetitive firing rate and decreased rheobase, with both effects being blocked by 4-DAMP. Muscarinic agonists reduced the afterhyperpolarization of single action potentials (APs), suggesting that small-conductance Ca2+-dependent K+ current inhibition increased the HM firing rate. Muscarinic agonists also reduced the AP amplitude and slowed its time course, suggesting that MAChRs inhibited voltage-gated Na+ channels. To compare muscarinic excitation of single HMs to muscarinic excitatory effects on motor output in thicker brain stem slices requiring higher extracellular K+ for rhythmic activity, we tested the effects of muscarinic agonists on single HM excitability in high-K+ artificial cerebrospinal fluid (aCSF). In high-K+ aCSF, muscarinic agonists still depolarized HMs and altered AP size and shape, as in standard aCSF, but did not increase the steady-state firing rate, decrease afterhyperpolarization, or alter threshold potential. These results indicate that the basic cellular response of HMs to muscarinic receptors is excitatory, via a number of distinct mechanisms, and that this excitatory response will be largely preserved in rhythmically active brain stem slices.

Obstructive sleep apnea syndrome: from phenotype to genetic basis

Obstructive sleep apnea syndrome (OSAS) is a complex chronic clinical syndrome, characterized by snoring, periodic apnea, hypoxemia during sleep, and daytime hypersomnolence. It affects 4-5% of the general population. Racial studies and chromosomal mapping, familial studies and twin studies have provided evidence for the possible link between the OSAS and genetic factors and also most of the risk factors involved in the pathogenesis of OSAS are largely genetically determined. A percentage of 35-40% of its variance can be attributed to genetic factors. It is likely that genetic factors associated with craniofacial structure, body fat distribution and neural control of the upper airway muscles interact to produce the OSAS phenotype. Although the role of specific genes that influence the development of OSAS has not yet been identified, current researches, especially in animal model, suggest that several genetic systems may be important. In this chapter, we will first define the OSAS phenotype, the pathogenesis and the risk factors involved in the OSAS that may be inherited, then, we will review the current progress in the genetics of OSAS and suggest a few future perspectives in the development of therapeutic agents for this complex disease entity.

Alternatives to positive airway pressure for obstructive sleep apnea syndrome

Owing to the prevalence, the considerable risk of accidents and cardiovascular consequences, optimal treatment of obstructive sleep apnea syndrome is of crucial importance. However, many patients look for alternative conservative or surgical therapies to continuous positive airway pressure to avoid discomfort and local side-effects owing to the mask. Scientific data are lacking for most of the alternative methods. However, it has been proven that intra-oral appliances can reduce mild-to-moderate respiratory disturbances; the maxillo-mandibular osteotomy is efficient in the short- and long-term but is preferred in special situations such as craniofacial dysmorphias. Weight reduction and body positioning cannot be recommended as a single treatment for obstructive sleep apnea syndrome. Resections of muscular tissue within the soft palate have to be strictly avoided. Efficacy of gentle soft palate procedures is difficult to predict and often decreases in the years following this treatment. Multilevel surgery concepts are of increasing interest, although more data from prospective, controlled studies are needed.

Pathophysiology of sleep apnea

Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anatomically compromised, collapsible airway, the sleep-induced loss of compensatory tonic input to the upper airway dilator muscle motor neurons leads to collapse of the pharyngeal airway. In turn, the ability of the sleeping subject to compensate for this airway obstruction will determine the degree of cycling of these events. Several of the classic neurotransmitters and a growing list of neuromodulators have now been identified that contribute to neurochemical regulation of pharyngeal motor neuron activity and airway patency. Limited progress has been made in developing pharmacotherapies with acceptable specificity for the treatment of sleep-induced airway obstruction. We review three types of major long-term sequelae to severe OSA that have been assessed in humans through use of continuous positive airway pressure (CPAP) treatment and in animal models via long-term intermittent hypoxemia (IH): 1) cardiovascular. The evidence is strongest to support daytime systemic hypertension as a consequence of severe OSA, with less conclusive effects on pulmonary hypertension, stroke, coronary artery disease, and cardiac arrhythmias. The underlying mechanisms mediating hypertension include enhanced chemoreceptor sensitivity causing excessive daytime sympathetic vasoconstrictor activity, combined with overproduction of superoxide ion and inflammatory effects on resistance vessels. 2) Insulin sensitivity and homeostasis of glucose regulation are negatively impacted by both intermittent hypoxemia and sleep disruption, but whether these influences of OSA are sufficient, independent of obesity, to contribute significantly to the "metabolic syndrome" remains unsettled. 3) Neurocognitive effects include daytime sleepiness and impaired memory and concentration. These effects reflect hypoxic-induced "neural injury." We discuss future research into understanding the pathophysiology of sleep apnea as a basis for uncovering newer forms of treatment of both the ventilatory disorder and its multiple sequelae.

Central cholinergic regulation of respiration: nicotinic receptors

Nicotinic acetylcholine receptors (nAChRs) are expressed in brainstem and spinal cord regions involved in the control of breathing. These receptors mediate central cholinergic regulation of respiration and effects of the exogenous ligand nicotine on respiratory pattern. Activation of alpha4* nAChRs in the preBötzinger Complex (preBötC), an essential site for normal respiratory rhythm generation in mammals, modulates excitatory glutamatergic neurotransmission and depolarizes preBötC inspiratory neurons, leading to increases in respiratory frequency. nAChRs are also present in motor nuclei innervating respiratory muscles. Activation of post- and/or extra-synaptic alpha4* nAChRs on hypoglossal (XII) motoneurons depolarizes these neurons, potentiating tonic and respiratory-related rhythmic activity. As perinatal nicotine exposure may contribute to the pathogenesis of sudden infant death syndrome (SIDS), we discuss the effects of perinatal nicotine exposure on development of the cholinergic and other neurotransmitter systems involved in control of breathing. Advances in understanding of the mechanisms underlying central cholinergic/nicotinic modulation of respiration provide a pharmacological basis for exploiting nAChRs as therapeutic targets for neurological disorders related to neural control of breathing such as sleep apnea and SIDS.

Pharmacotherapy of obstructive sleep apnea

Obstructive sleep apnea (OSA) is associated with serious comorbid illnesses and diminished quality of life. At this time, continuous positive airway pressure (CPAP) therapy is the treatment of choice. However, only half of those individuals who accept CPAP are still using it at the end of one year. Furthermore, efficacy for improving self-reported sleepiness appears to be greater for patients with severe sleep apnea and severe sleepiness than other patient groups. Some patients, notwithstanding optimized therapy and therapeutic adherence continue experiencing excessive daytime somnolence. Consequently, other treatment modalities have developed, including oral appliances, surgery and pharmacotherapy. It is widely believed, albeit not empirically demonstrated, that an effective medication to treat OSA would elicit better acceptance and adherence than having to use a machine for many hours on a nightly basis. Nonetheless, paucity of data (i.e. lack of large-scale randomized controlled trials), variability of perceived and actual benefits, and adverse side-effects of the drugs thus far tested have prevented the use of pharmacotherapy until now. In this paper we review the outcome data from published trials designed to evaluate efficacy and safety of various medications proposed for treating obstructive sleep apnea.

Two randomized placebo-controlled trials to evaluate the efficacy and tolerability of mirtazapine for the treatment of obstructive sleep apnea

OBJECTIVE

Mirtazapine is an a2A antagonist and mixed 5-HT2/5-HT3 antagonist that has been proposed as a potential treatment for obstructive sleep apnea (OSA). A small, randomized, controlled trial has previously found an approximate halving in the severity of OSA with daily doses of 4.5 and 15 mg. We aimed to confirm and extend these findings in 2 randomized placebo-controlled, proof-of-concept trials.

METHODS

Two randomized, double-blind, placebo-controlled trials of mirtazapine for OSA (apnea-hypopnea index 10-40/h). Study 1: 3-way crossover, dose-finding study testing the self-administration of mirtazapine (7.5, 15, 30, and/or 45 mg) or placebo 30 minutes prior to bedtime for 2 weeks at each dose. Twenty patients were randomly assigned to 1 of 6 different dose-sequence groups, with each patient exposed to a maximum of 3 doses. Study 2: 3-arm, randomized, parallel-group trial of mirtazapine at 15 mg or mirtazapine 15 mg + Compound CD0012 or placebo for 4 weeks in 65 patients with OSA.

RESULTS

Two patients withdrew from Study 1 after complaints of unacceptable lethargy. Fifteen patients were withdrawn from study 2, 7 after complaints of unacceptable lethargy or other side-effects. No measurement of sleep apnea improved due to mirtazapine in either study. Weight gain was significantly greater on mirtazapine than on placebo in both trials.

CONCLUSIONS

Mirtazapine did not improve sleep apnea in either trial. Mirtazapine caused weight gain, which may further worsen OSA. Therefore, mirtazapine is not recommended for the treatment of OSA.

Donepezil improves obstructive sleep apnea in Alzheimer disease: a double-blind, placebo-controlled study

BACKGROUND

There is an association between Alzheimer disease and sleep-disordered breathing. Donepezil is the drug most frequently used to treat cognitive symptoms in Alzheimer disease. This study evaluates the effects of donepezil on obstructive sleep apnea in patients with Alzheimer disease.

METHODS

Randomized, double-blind, placebo-controlled design. Twenty-three patients with mild-to-moderate Alzheimer disease and apnea-hypopnea index (AHI) > 5/h were allocated to two groups: donepezil treated (n = 11) and placebo treated (n = 12). Polysomnography and cognitive evaluation using Alzheimer disease assessment scale-cognitive (ADAS-cog) subscale were performed at baseline and after 3 months. Cognitive and sleep data were analyzed using analysis of variance.

RESULTS

AHI and oxygen saturation improved significantly after donepezil treatment compared to baseline and placebo (p < 0.05). Rapid eye movement (REM) sleep duration increased after donepezil treatment (p < 0.05). ADAS-cog scores improved after donepezil treatment, although they did not correlate with REM sleep increase and sleep apnea improvement (p < 0.01).

CONCLUSIONS

Donepezil treatment improved AHI and oxygen saturation in patients with Alzheimer disease. Treatment also increased REM sleep duration and reduced ADAS-cog scores.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00480870.

Respiratory motor activity: influence of neuromodulators and implications for sleep disordered breathing

Sleep, especially rapid-eye-movement sleep, causes fundamental modifications of respiratory muscle activity and control mechanisms, modifications that can predispose individuals to sleep-related breathing disorders. One of the most common of these disorders is obstructive sleep apnea (OSA) that affects approximately 4% of adults. OSA is caused by repeated episodes of pharyngeal airway obstruction that can occur hundreds of times per night, leading to recurrent asphyxia, arousals from sleep, daytime sleepiness, and adverse cardiovascular and cerebrovascular consequences. OSA is caused by the effects of sleep on pharyngeal muscle tone in individuals with already narrow upper airways. Moreover, since OSA occurs only in sleep, this disorder by definition is a state-dependent process ultimately caused by the influence of sleep neural mechanisms on the activity of pharyngeal motoneurons. This review synthesizes recent findings relating to control of pharyngeal muscle activity across sleep-wake states, with special emphasis on the influence of neuromodulators acting at the hypoglossal motor nucleus that inervates the genioglossus muscle of the tongue. The results of such basic physiological studies may be relevant to identifying and developing new pharmacological strategies to augment pharyngeal muscle activity in sleep, especially rapid-eye-movement sleep, as potential treatments for OSA.

Drug therapy for obstructive sleep apnoea in adults

BACKGROUND

The treatment of choice for moderate to severe obstructive sleep apnoea (OSA) is continuous positive airways pressure (CPAP) via a mask during sleep. However this is not tolerated by all patients and its role in mild OSA is not proven. Drug therapy has been proposed as an alternative to CPAP in some patients with mild to moderate sleep apnoea and could be of value in patients intolerant of CPAP. A number of mechanisms have been proposed by which drugs could reduce the severity of OSA. These include an increase in tone in the upper airway dilator muscles, an increase in ventilatory drive, a reduction in the proportion of REM sleep, an increase in cholinergic tone during sleep, a reduction in airway resistance and a reduction in surface tension in the upper airway.

OBJECTIVES

To determine the efficacy of drug therapies in the treatment of sleep apnoea.

SEARCH STRATEGY

We carried out searches on the Cochrane Airways Group Specialised Register of trials. Searches were current as of July 2005.

SELECTION CRITERIA

Randomised, placebo controlled trials involving adult patients with confirmed OSA . We excluded trials if continuous positive airways pressure, mandibular devices or oxygen therapy were used. No restriction was placed upon publication language or trial duration.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed studies for inclusion, undertook data extraction according to pre-specified entry criteria, and quality assessment of studies. No response for further information was forthcoming from study authors. Results were expressed as mean differences and 95% Confidence Intervals (CI).

MAIN RESULTS

Twenty-six trials of 21 drugs, involving 394 participants contributed data to the review. Most of the studies were small and many trials had methodological limitations. Each of the studies states that the subjects had OSA but diagnostic criteria were not always explicit and it is possible that some patients with central apnoeas may have been recruited. Six drugs had some impact on OSA severity and two altered daytime symptoms. One study reported that apnoea hypopnea index (AHI) was lower following treatment with intranasal fluticasone compared with placebo (23.3 versus 30.3) in 24 participants with sleep apnoea and rhinitis. Subjective alertness in the daytime also improved. Physostigmine gave an AHI of 41 compared to 54 on placebo (10 participants) and in a similar study Mirtazipine 15 mg produced an AHI of 13 compared to 23.7 for placebo (10 participants). Topical nasal lubricant given twice overnight resulted in an AHI of 14 compared to 24 with placebo (10 participants). These three latter studies were of single night crossover design and so there are no data on the acceptability of these treatments or their effect on symptoms. Paroxetine was shown to reduce AHI to 23.3 compared to 30.3 for placebo, most of the 20 participants tolerated the treatment but there was no improvement in daytime symptoms. Acetazolamide also reduced the AHI (one crossover trial of nine patients, mean difference 24 (95% CI 4 to 44). However there was no symptomatic benefit from the drug and it was poorly tolerated in the long term. Protriptyline led to a symptomatic improvement (improved versus not improved) in two out of three crossover trials (13 participants, Peto Odds Ratio 29.2 (95% CI 2.8 to 301.1) but there was no change in the apnoea frequency. In one trial naltrexone did reduce AHI, but total sleep time favoured placebo. No significant beneficial effects were found for medroxy progesterone, clonidine, mibefradil, cilazapril, buspirone, aminophylline, theophylline doxapram, ondansetron or sabeluzole.

AUTHORS' CONCLUSIONS

There is insufficient evidence to recommend the use of drug therapy in the treatment of OSA. Small studies have reported positive effects of certain agents on short-term outcome. Certain agents have been shown to reduce the AHI in largely unselected populations with OSA by between 24 and 45%. For fluticasone, mirtazipine, physostigmine and nasal lubricant, studies of longer duration are required to establish whether this has an impact on daytime symptoms. Individual patients had more complete responses to particular drugs. It is likely that better matching of drugs to patients according to the dominant mechanism of their OSA will lead to better results and this also needs further study.

Pharmacological management of sleep apnoea

Obstructive sleep apnoea poses a significant health hazard that is associated with leading causes of mortality and morbidity. Nasal continuous positive airway pressure is the primary treatment modality, with surgical treatments as alternatives. Oral appliances and pharmacological therapy remain adjunctive modalities. Non-specific treatments include weight loss, postural therapy and behavioural measures. Pharmacotherapy goals include the reduction of risk factors for sleep apnoea; correction of underlying predisposing metabolic diseases, such as hypothyroidism or acromegaly; treatment of associated symptoms, including excessive daytime sleepiness; and prevention of apnoeas/hypopnoeas. This paper reviews data supporting the treatment of sleep apnoea with various pharmacological agents, including intranasal corticosteroids, decongestant sprays, nicotine therapy, opiate antagonists, methylxanthine derivatives, oestrogen and progesterone, testosterone, thyroid hormone, growth hormone therapy for acromegaly, beta-blockers, alpha-adrenergic agonists, angiotensin-converting enzyme inhibitors, glutamate antagonists, acetazolamide, selective serotonin re-uptake inhibitors, tricyclic antidepressants, physostigmine, modafinil and TNF-alpha antagonists, in addition to supplemental oxygen, and carbon dioxide inhalation. Some of these drugs have received very little testing and are the subject of few research articles.