Treatment of nausea and vomiting: gaps in our knowledge

The chemical coding of 5-hydroxytryptamine containing enteroendocrine cells in the mouse gastrointestinal tract

The majority of 5-HT (serotonin) in the body is contained in enteroendocrine cells of the gastrointestinal mucosa. From the time of their discovery over 80 years ago, the 5-HT-containing cells have been regarded as a class of cell that is distinct from enteroendocrine cells that contain peptide hormones. However, recent studies have cast doubt on the concept of there being distinct classes of enteroendocrine cells, each containing a single hormone or occasionally more than one hormone. Instead, data are rapidly accumulating that there are complex patterns of colocalisation of hormones that identify multiple subclasses of enteroendocrine cells. In the present work, multiple labelling immunohistochemistry is used to investigate patterns of colocalisation of 5-HT with enteric peptide hormones. Over 95 % of 5-HT cells in the duodenum also contained cholecystokinin and about 40 % of them also contained secretin. In the jejunum, about 75 % of 5-HT cells contained cholecystokinin but not secretin and 25 % contained 5-HT plus both cholecystokinin and secretin. Small proportions of 5-HT cells contained gastrin or somatostatin in the stomach, PYY or GLP-1 in the small intestine and GLP-1 or somatostatin in the large intestine. Rare or very rare 5-HT cells contained ghrelin (stomach), neurotensin (small and large intestines), somatostatin (small intestine) and PYY (in the large intestine). It is concluded that 5-HT-containing enteroendocrine cells are heterogeneous in their chemical coding and by implication in their functions.

Nausea: a review of pathophysiology and therapeutics

The sensation of nausea is a common occurrence with diverse causes and a significant disease burden. Nausea is considered to function as a protective mechanism, warning the organism to avoid potential toxic ingestion. Less adaptive circumstances are also associated with nausea, including post-operative nausea, chemotherapy-induced nausea, and motion sickness. A common definition of nausea identifies the symptom as a precursor to the act of vomiting. The interaction, though present, does not appear to be a simple relationship. Nausea is unfortunately the 'neglected symptom', with current accepted therapy generally directed at improving gastrointestinal motility or acting to relieve emesis. Improved understanding of the pathophysiological basis of nausea has important implications for exploiting novel mechanisms or developing novel therapies for nausea relief.

Motion Sickness: Current Knowledge and Recent Advance

Motion sickness (MS) is a common physiological response to real or virtual motion. Numerous studies have investigated the neurobiological mechanism and the control measures of MS. This review summarizes the current knowledge about pathogenesis and pathophysiology, prediction, evaluation, and countermeasures of MS. The sensory conflict hypothesis is the most widely accepted theory for MS. Both the hippocampus and vestibular cortex might play a role in forming internal model. The pathophysiology focuses on the visceral afference, thermoregulation and MS-related neuroendocrine. Single-nucleotide polymorphisms (SNPs) in some genes and epigenetic modulation might contribute to MS susceptibility and habituation. Questionnaires, heart rate variability (HRV) and electrogastrogram (EGG) are useful for diagnosing and evaluating MS. We also list MS medications to guide clinical practice. Repeated real motion exposure and combined visual-vestibular interaction training accelerate the progress of habituation. Behavioral and dietary countermeasures, as well as physiotherapy, are also effective in alleviating MS symptoms.

NextGen nuclear DNA sequencing in cyclic vomiting syndrome reveals a significant association with the stress-induced calcium channel (RYR2)

BACKGROUND

Cyclic vomiting syndrome (CVS) is a common, frequently disabling, 'functional' condition characterized by recurring, stereotypical attacks of intense nausea, vomiting, and lethargy, with the essential absence of these symptoms between episodes. Although the pathogenesis of CVS is yet unexplained, evidence has accumulated which suggest pathogenic roles for stress-related, autonomic, neuroendocrine, and mitochondrial factors. The objective of this pilot study was to elucidate mechanism(s) by identifying genes involved in the presumed multifactorial pathogenesis of CVS.

METHODS

In this pilot study, DNA from 75 unrelated CVS cases and 60 healthy controls were assayed by Courtagen Life Science's next-generation sequencing platform (nucSEEK(™) ), including over 1100 nuclear-encoded genes involved with mitochondria, metabolism, or ion channels. Significant sequence variants were defined as evolutionary conservation at least to Xenopus (frog) per the UCSC Genome Browser.

KEY RESULTS

The RYR2 gene, encoding a stress-induced calcium channel present in many neurons, was the only gene demonstrating a statistically significant difference in the proportion of conserved sequence variants among the groups (18/75 CVS, 24%, vs 3/60 controls, 5%; p = 0.0018, OR = 6.0, 95% CI = 1.7-22).

CONCLUSIONS & INFERENCES

We propose a mechanism in which RYR2 sequence variants result in aberrant stress-induced calcium release into the mitochondria of autonomic neurons, resulting in an increased risk to develop autonomic/functional disease such as CVS, and related conditions such as migraine and gut dysmotility. This model incorporates the existing hypotheses regarding CVS pathogenesis into a cohesive mechanism, and might have treatment implications.

Triple Therapy with Scopolamine, Ondansetron, and Dexamethasone for Prevention of Postoperative Nausea and Vomiting in Moderate to High-Risk Patients Undergoing Craniotomy Under General Anesthesia: A Pilot Study

Introduction

Postoperative nausea and vomiting (PONV) is one of the most common complaints from patients and clinicians after a surgical procedure. According to the current Society of Ambulatory Anesthesia Consensus Guidelines, the general incidence of vomiting and nausea is around 30 and 50%, respectively; and up to 80% in high-risk patients. In previous studies, the reported incidence of PONV at 24 h after craniotomy was 43–70%. The transdermal scopolamine (TDS) delivery system contains a 1.5-mg drug reservoir, which is designed to deliver a continuous slow release of scopolamine through intact skin during the first 72 h of patch application. Therefore, we designed this single arm, non-randomized, pilot study to assess the efficacy and safety of triple therapy with scopolamine, ondansetron, and dexamethasone to prevent PONV.

Materials and methods

In the preoperative area, subjects received an active TDS 1.5 mg that was applied to a hairless patch of skin in the mastoid area approximately 2 h prior to the operation. Immediately after anesthesia induction, all patients received a single 4 mg dose of ondansetron IV and a single 10 mg dose of dexamethasone IV. Patients who experienced nausea and/or vomiting received ondansetron 4 mg IV as the initial rescue medication. Postoperative nausea and vomiting assessments were performed for up to 120 h after surgery.

Results

A total of 36 subjects were analyzed. The overall incidence of PONV during the first 24 h after neurological surgery was 33% (n = 12). The incidence of nausea and emesis during the first 24 h after surgery was recorded as 33% (n = 12) and 16% (n = 6), respectively.

Conclusion

Our data showed that this triple therapy regimen may be an efficient alternative regimen for PONV prophylaxis in patients undergoing neurological surgery with general anesthesia. Further studies using regimens affecting different receptor pathways should be performed to better prove the efficacy and safety in the prevention or delay of PONV.

Galvanic Vestibular Stimulation: a new model of placebo-induced nausea

OBJECTIVE

Traditional rotation-based models of placebo nausea are limited because they do not have vehicle settings and are tied to their context. The present study introduces a new model for examining placebo-induced nausea in the laboratory that overcomes these limitations, namely, Galvanic Vestibular Stimulation (GVS). GVS stimulates the vestibular system to cause nausea through sensory mismatch with visual cues and importantly has a non-nauseating placebo setting. Using this, we tested whether conditioning could elicit placebo nausea when participants were later exposed to placebo stimulation as well as whether this placebo nausea was generalised across contexts--something that is extremely difficult to test with rotation-based models of placebo nausea.

METHODS

Thirty healthy undergraduate students were randomised to receive either placebo GVS (controls) or active GVS during training (Context-Consistent and Context-Change). On test, all groups received placebo GVS. The controls and Context-Consistent groups were tested in the same context as training, whereas the Context-Change group was tested in a new context.

RESULTS

Participants conditioned with nausea during training had significantly higher nausea symptom ratings after placebo stimulation on test than those given no conditioning. This placebo-induced nausea also generalised to a novel test context with no differences observed between the Context-Change and Context-Consistent groups.

CONCLUSION

GVS provides a new model of placebo-induced nausea that overcomes limitations to traditional rotation-based paradigms. Future studies should use this device to explore the effect of instructions and conditioning on the development of placebo nausea and to assess the efficacy of conditioning-based interventions for clinical use.

Thermoregulatory correlates of nausea in rats and musk shrews

Nausea is a prominent symptom and major cause of complaint for patients receiving anticancer chemo- or radiation therapy. The arsenal of anti-nausea drugs is limited, and their efficacy is questionable. Currently, the development of new compounds with anti-nausea activity is hampered by the lack of physiological correlates of nausea. Physiological correlates are needed because common laboratory rodents lack the vomiting reflex. Furthermore, nausea does not always lead to vomiting. Here, we report the results of studies conducted in four research centers to investigate whether nausea is associated with any specific thermoregulatory symptoms. Two species were studied: the laboratory rat, which has no vomiting reflex, and the house musk shrew (Suncus murinus), which does have a vomiting reflex. In rats, motion sickness was induced by rotating them in their individual cages in the horizontal plane (0.75 Hz, 40 min) and confirmed by reduced food consumption at the onset of dark (active) phase. In 100% of rats tested at three centers, post-rotational sickness was associated with marked (~1.5°C) hypothermia, which was associated with a short-lasting tail-skin vasodilation (skin temperature increased by ~4°C). Pretreatment with ondansetron, a serotonin 5-HT3 receptor antagonist, which is used to treat nausea in patients in chemo- or radiation therapy, attenuated hypothermia by ~30%. In shrews, motion sickness was induced by a cyclical back-and-forth motion (4 cm, 1 Hz, 15 min) and confirmed by the presence of retching and vomiting. In this model, sickness was also accompanied by marked hypothermia (~2°C). Like in rats, the hypothermic response was preceded by transient tail-skin vasodilation. In conclusion, motion sickness is accompanied by hypothermia that involves both autonomic and thermoeffector mechanisms: tail-skin vasodilation and possibly reduction of the interscapular brown adipose tissue activity. These thermoregulatory symptoms may serve as physiological correlates of nausea.

Pharmacogenetics of chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) is associated with distressing adverse effects observed in patients during cytotoxic chemotherapy. One of the potential factors explaining suboptimal response to currently used antiemetics is variability in genes encoding enzymes and proteins that play a role in the action of antiemetic drugs. Pharmacogenomics studies of CINV are sparse and focus mainly on polymorphisms associated with serotonin receptor, drug metabolism and drug transport. Currently, the role of pharmacogenetics in mechanisms of CINV has not been fully unraveled, and it is premature to implement results of pharmacogenetic association studies of antiemetic drugs in clinical practice. More uniform studies, with genetic profiles and biomarkers relevant for the proposed target and transporter mechanisms, are needed.

Pediatric migraine and episodic syndromes that may be associated with migraine

Importance

Migraine is a common disorder and a frequent cause of medical consultation in children. Many childhood episodic syndromes have been described as common precursors of migraine.

Objective

To review current knowledge on migraine and childhood episodic syndromes, and to discuss future directions for research and clinical practice.

Findings

For most children it is difficult to describe a headache and fully verbalize symptoms such as photophobia and phonophobia that must be inferred from behaviour. Classical migraine features are rare before the age of 6 years, but some migraine-related syndromes have been described. Benign paroxysmal torticollis of infancy, benign paroxysmal vertigo of childhood, cyclic vomiting syndrome and abdominal migraine are currently classified as childhood episodic syndromes, and therefore common precursors of migraine. A strong association between infantile colic and migraine has recently been reported. There are similarities between children with episodic syndromes and children with migraine, regarding social and demographic factors, precipitating and relieving factors, and accompanying gastrointestinal, neurologic, and vasomotor features. The real pathophysiological mechanisms of migraine are not fully understood. Current data obtained through molecular and functional studies provide a complex model in which vascular and neurologic events cooperate in the pathogenesis of migraine attacks. Genetic factors causing disturbances in neuronal ion channels, make a migraineur more sensitive to multiple trigger factors that activate the nociception cascade. The expanding knowledge on migraine genetics and pathophysiology may be applicable to childhood episodic syndromes. Migraine preventive strategies are particularly important in children, and could be beneficial in childhood episodic syndromes. Nonspecific analgesics like ibuprofen and acetaminophen are widely used in pediatrics to control pain and have been found to be effective also in the treatment of acute migraine attacks. Triptans are the specific fist-line drugs for acute migraine treatment.

Conclusions and relevance

Migraine phenotype differs somewhat in the developing brain, and childhood episodic syndromes may arise before typical migraine headache. Diagnosing pediatric migraine may be difficult because of children’s language and cognitive abilities. The risk of underestimating migraine in pediatric age is high. An adequate diagnosis is important to maintain a good quality of life and to avoid inappropriate therapy.

Nausea: current knowledge of mechanisms, measurement and clinical impact

Nausea is a subjective sensation, which often acts as a signal that emesis is imminent. It is a widespread problem that occurs as a clinical sign of disease or as an adverse effect of a drug therapy or surgical procedure. The mechanisms of nausea are complex and the neural pathways are currently poorly understood. This review summarises the current knowledge of nausea mechanisms, the available animal models for nausea research and the anti-nausea properties of commercially available anti-emetic drugs. The review also presents subjective assessment and scoring of nausea. A better understanding of the underlying mechanisms of nausea might reveal potential clinically useful biomarkers for objective measurement of nausea in species of veterinary interest.

Both exogenous 5-HT and endogenous 5-HT, released by fluoxetine, enhance distension evoked propulsion in guinea-pig ileum in vitro

The roles of 5-HT3 and 5-HT4 receptors in the modulation of intestinal propulsion by luminal application of 5-HT and augmentation of endogenous 5-HT effects were studied in segments of guinea-pig ileum in vitro. Persistent propulsive contractions evoked by saline distension were examined using a modified Trendelenburg method. When 5-HT (30 nM), fluoxetine (selective serotonin reuptake inhibitor; 1 nM), 2-methyl-5-HT (5-HT3 receptor agonist; 1 mM), or RS 67506 (5-HT4 receptor agonist, 1 μM) was infused into the lumen, the pressure needed to initiate persistent propulsive activity fell significantly. A specific 5-HT4 receptor antagonist, SB 207266 (10 nM in lumen), abolished the effects of 5-HT, fluoxetine, and RS 67506, but not those of 2-methyl-5-HT. Granisetron (5-HT3 receptor antagonist; 1 μM in lumen) abolished the effect of 5-HT, fluoxetine, RS 67506, and 2-methyl-5-HT. The NK3 receptor antagonist SR 142801 (100 nM in lumen) blocked the effects of 5-HT, fluoxetine, and 2-methyl-5-HT. SB 207266, granisetron, and SR 142801 had no effect by themselves. Higher concentrations of fluoxetine (100 and 300 nM) and RS 67506 (3 and 10 μM) had no effect on the distension threshold for propulsive contractions. These results indicate that luminal application of exogenous 5-HT, or increased release of endogenous mucosal 5-HT above basal levels, acts to lower the threshold for propulsive contractions in the guinea-pig ileum via activation of 5-HT3 and 5-HT4 receptors and the release of tachykinins. The results further indicate that basal release of 5-HT is insufficient to alter the threshold for propulsive motor activity.

Efficacy of the neurokinin-1 receptor antagonist aprepitant in children with cyclical vomiting syndrome

BACKGROUND

Aprepitant (Emend, Merck Sharp & Dohme Ltd, Haarlem, the Netherlands), a neurokinin-1 receptor antagonist, prevents vomiting in a range of conditions. No data are available on its use in children with cyclical vomiting syndrome (CVS).

AIM

We investigated the efficacy of aprepitant as prophylactic treatment or acute intervention in CVS children refractory to conventional therapies.

METHODS

Forty-one children (median age: 8 years) fulfilling NASPGHAN criteria treated acutely (RegA) or prophylactically (RegP) with aprepitant were retrospectively reviewed. Primary outcome was the clinical response (decrease in frequency and intensity of CVS episodes). Secondary outcomes were: number of CVS episodes/year, number of hospital admissions/year, CVS episode duration, number of vomits/h, symptom-free interval length (days), and school attendance percentage. The follow-up period was 18-60 months.

RESULTS

Sixteen children received RegP and 25 RegA. One child on RegP stopped treatment due to severe migraine. At 12-months on intention-to-treat analysis, 13 children on RegP (81%) achieved either complete (3/16, 19%) or partial (10/16, 62%) clinical response. On RegA, 19 children (76%) had either complete (3/25, 12%) or partial (16/25, 64%) response (P = 0.8 vs. RegP). In both RegP and RegA, there was a significant decrease in CVS episodes/year, hospital admission number/year, CVS episode length, number of vomits/h, as well as an increase in symptom-free interval duration and school attendance percentage. Side effects were reported only in RegP (5/16, 31%) including hiccough (3/16, 19%), asthenia/fatigue (2/16, 12.5%), increased appetite (2/16, 12.5%), mild headache (1/16, 6%) and severe migraine (1/16, 6%).

CONCLUSION

Aprepitant appears effective for both acute and prophylactic management of paediatric cyclical vomiting syndrome refractory to conventional therapies.

Drugs acting at 5-HT4 , D2 , motilin, and ghrelin receptors differ markedly in how they affect neuromuscular functions in human isolated stomach

BACKGROUND

Progress in identifying safer, effective drugs to increase gastric emptying is impeded by failed clinical trials. One potential reason for failure is lack of translation from animal models to the human condition. To make progress, the actions of existing drugs and new therapeutic candidates need to be understood in human isolated stomach.

METHODS

Neuromuscular activities were evoked in human gastric antrum circular muscle by electrical field stimulation (EFS), defined phenotypically using pharmacological tools.

KEY RESULTS

EFS evoked cholinergically mediated contractions, attenuated by simultaneous nitrergic activation. The 5-HT4 receptor agonist/D2 antagonist metoclopramide and the selective 5-HT4 agonist prucalopride, facilitated contractions in the absence (respectively, Emax 95 ± 29% and 42 ± 9%, n = 3-6 each concentration) and presence (139 ± 38%, 55 ± 13%, n = 3-5) of the NO synthase inhibitor L-NAME, without affecting submaximal contractions to carbachol; the 5-HT4 antagonist SB204070 prevented facilitation by metoclopramide 100 μM (respectively, -5 (range -26 to 34) and 167 (12-1327)% in presence and absence; n = 5-6). The selective motilin receptor agonist camicinal provided considerably greater facilitation (478 (12-2080)% at 30 μM, n = 8). Domperidone (0.001-100 μM; n = 3-6) and acylated or des-acylated ghrelin (1-300 nM; n = 2-4) had no consistent activity, even with protease inhibitors.

CONCLUSIONS & INFERENCES

5-HT4 receptor agonists show different efficacies. Motilin receptor activation has greater potential to increase gastric emptying, whereas ghrelin and D2 receptor antagonism have no direct activity. Drugs stimulating human gastric motility directly can act regardless of disease mechanisms, whereas drugs without direct activity but an ability to block nausea/vomiting may be effective only if these symptoms exist.

Measuring the nausea-to-emesis continuum in non-human animals: refocusing on gastrointestinal vagal signaling

Nausea and vomiting are ubiquitous as drug side effects and symptoms of disease; however, the systems that determine these responses are arguably designed for protection against food poisoning occurring at the level of the gastrointestinal (GI) tract. This basic biological pathway using GI vagal afferent communication to the brain is not well understood. Part of this lack of insight appears to be related to current experimental approaches, such as the use of experimental drugs, including systemic chemotherapy and brain penetrant agents, which activate parts of the nausea and vomiting system in potentially unnatural ways. Directly related to this issue is our ability to understand the link between nausea and vomiting, which are sometimes argued to be completely separate processes, with nausea as an unmeasurable response in animal models. An argument is made that nausea and emesis are the efferent limbs of a unified sensory input from the GI tract that is likely to be impossible to understand without more specific animal electrophysiological experimentation of vagal afferent signaling. The current paper provides a review on the use of animal models and approaches to defining the biological systems for nausea and emesis and presents a potentially testable theory on how these systems work in combination.

Genetic factors associated with pharmacotherapy and background sensitivity to postoperative and chemotherapy-induced nausea and vomiting

Postoperative nausea and vomiting (PONV) continues to be a most common complication of surgery and anesthesia. It has been suggested that the inherited factors may play a significant role in the background sensitivity to both PONV and also chemotherapy-induced nausea and vomiting (CINV), including resistance to antiemetic prophylaxis and/or therapy. This notion could be best exemplified by occurrence of PONV in several generations of families and concordance of PONV in monozygotic twins. The most frequently addressed issue in the research on genomic background of PONV/CINV relates to the inherited resistance to the antiemetic treatment (pharmacogenomics), and in lesser degree to their genomic background. The most common group of antiemetics consists of 5HT3 receptor antagonists, and this group was an initial target of pharmacogenomic research. Most research approaches have been based on the investigation of polymorphic variations in the target for the antiemetic 5HT3 receptor antagonists, i.e., serotonin receptor subunits A and B (HTR3A and HTR3B). The other area of pharmacogenomic investigations includes metabolic pathways of 5HT3 antagonists, in particular polymorphic variants of the CYP450 2D6 isoform (CYP2D6) because most of them are metabolized in various degrees by the CYP2D6 system. The results of targeted genomic association studies indicate that other genes are also associated with PONV and CINV, including OPRM1, and ABCB1. In addition, genes such as DRD2 and CHRM3 genes have recently been associated with PONV. The new genome-wide association studies seem also to indicate that the background genomic sensitivity to PONV and CINV might be multifactorial and include several genomic pathways.

Why does vomiting stop a migraine attack?

Migraine is commonly associated with nausea and vomiting, though, interestingly, vomiting has also been reported by some patients to be therapeutic, and may actually stop a migraine attack. In this review, we will first discuss the epidemiology of nausea and vomiting in migraine. Further, we will briefly review the connections between the enteric nervous system, the autonomic nervous system, and the central nervous system as they pertain to understanding the question of "Why does vomiting stop a migraine attack?"

Regulation of nausea and vomiting by cannabinoids and the endocannabinoid system

Nausea and vomiting (emesis) are important elements in defensive or protective responses that animals use to avoid ingestion or digestion of potentially harmful substances. However, these neurally-mediated responses are at times manifested as symptoms of disease and they are frequently observed as side-effects of a variety of medications, notably those used to treat cancer. Cannabis has long been known to limit or prevent nausea and vomiting from a variety of causes. This has led to extensive investigations that have revealed an important role for cannabinoids and their receptors in the regulation of nausea and emesis. With the discovery of the endocannabinoid system, novel ways to regulate both nausea and vomiting have been discovered that involve the production of endogenous cannabinoids acting centrally. Here we review recent progress in understanding the regulation of nausea and vomiting by cannabinoids and the endocannabinoid system, and we discuss the potential to utilize the endocannabinoid system in the treatment of these frequently debilitating conditions.

The gut as a sensory organ

The gastrointestinal tract presents the largest and most vulnerable surface to the outside world. Simultaneously, it must be accessible and permeable to nutrients and must defend against pathogens and potentially injurious chemicals. Integrated responses to these challenges require the gut to sense its environment, which it does through a range of detection systems for specific chemical entities, pathogenic organisms and their products (including toxins), as well as physicochemical properties of its contents. Sensory information is then communicated to four major effector systems: the enteroendocrine hormonal signalling system; the innervation of the gut, both intrinsic and extrinsic; the gut immune system; and the local tissue defence system. Extensive endocrine-neuro-immune-organ-defence interactions are demonstrable, but under-investigated. A major challenge is to develop a comprehensive understanding of the integrated responses of the gut to the sensory information it receives. A major therapeutic opportunity exists to develop agents that target the receptors facing the gut lumen.

Musk shrews selectively bred for motion sickness display increased anesthesia-induced vomiting

Susceptibility to motion sickness is a predictor of postoperative nausea and vomiting, and studies in humans suggest that genetic factors determine sensitivity to motion sickness. The aim of the current study was to determine if a preclinical model could be selectively bred for motion-induced emesis and to assess a potential relationship to anesthesia-induced emesis. Musk shrews were tested for motion-induced emesis using a shaker plate (10min, 1Hz, and 4cm of lateral displacement). Animals were rank ordered for motion-induced emesis and selectively bred to produce high and low response strains. Shrews were also tested with nicotine (5mg/kg, sc), copper sulfate (CuSO4; 120mg/kg, ig), and isoflurane anesthesia (10min; 3%) to measure responses to a panel of emetic stimuli. High response strain shrews demonstrated significantly more emetic episodes to motion exposure compared to low response strain animals in the F1 and F2 generations. In F2 animals, there were no significant differences in total emetic responses or emetic latency between strains after nicotine injection or CuSO4 gavage. However, isoflurane exposure stimulated more emesis in F1 and F2 high versus low strain animals, which suggests a relationship between vestibular- and inhalational anesthesia-induced emesis. Overall, these results indicate genetic determinants of motion sickness in a preclinical model and a potential common mechanism for motion sickness and inhalational anesthesia-induced emesis. Future work may include genetic mapping of potential "emetic sensitivity genes" to develop novel therapies or diagnostics for patients with high risk of nausea and vomiting.

Pathophysiological and neurochemical mechanisms of postoperative nausea and vomiting

Clinical research shows that postoperative nausea and vomiting (PONV) is caused primarily by the use of inhalational anesthesia and opioid analgesics. PONV is also increased by several risk predictors, including a young age, female sex, lack of smoking, and a history of motion sickness. Genetic studies are beginning to shed light on the variability in patient experiences of PONV by assessing polymorphisms of gene targets known to play roles in emesis (serotonin type 3, 5-HT3; opioid; muscarinic; and dopamine type 2, D2, receptors) and the metabolism of antiemetic drugs (e.g., ondansetron). Significant numbers of clinical trials have produced valuable information on pharmacological targets important for controlling PONV (e.g., 5-HT3 and D2), leading to the current multi-modal approach to inhibit multiple sites in this complex neural system. Despite these significant advances, there is still a lack of fundamental knowledge of the mechanisms that drive the hindbrain central pattern generator (emesis) and forebrain pathways (nausea) that produce PONV, particularly the responses to inhalational anesthesia. This gap in knowledge has limited the development of novel effective therapies of PONV. The current review presents the state of knowledge on the biological mechanisms responsible for PONV, summarizing both preclinical and clinical evidence. Finally, potential ways to advance the research of PONV and more recent developments on the study of postdischarge nausea and vomiting (PDNV) are discussed.

Neurochemical mechanisms and pharmacologic strategies in managing nausea and vomiting related to cyclic vomiting syndrome and other gastrointestinal disorders

Nausea and vomiting are common gastrointestinal complaints which could be triggered by stimuli in both the peripheral and central nervous systems. They may be considered as defense mechanisms when threatening toxins/agents enter the gastrointestinal tract or there is excessive retention of gastrointestinal contents due to obstruction. The pathophysiology of nausea and vomiting is complex and much still remains unknown. Therefore, treatments are restricted or ineffective in many cases. Nausea and vomiting with functional etiologies including cyclic vomiting syndrome are challenging in gastroenterology. In this article, we review potential pathways, neurochemical transmitters, and their receptors which are possibly involved in the pathophysiology of nausea and vomiting including the entity cyclic vomiting syndrome.

Current pharmacotherapy for chemotherapy-induced nausea and vomiting in cancer patients

INTRODUCTION

Nausea and vomiting are two of the most frequent and troubling side effects patients experience during chemotherapy, interfering with compliance with cancer therapies and quality of life. While newly available treatments have improved our ability to manage nausea and vomiting, anticipatory and delayed nausea and vomiting are still major problems for patients receiving chemotherapy. Many cancer patients consider delaying future chemotherapy cycles and some contemplate stopping chemotherapy altogether because of their fear of experiencing further nausea and vomiting.

AREAS COVERED

The purpose of this article is to provide an overview of the pathopsychophysiology of chemotherapy-induced nausea and vomiting (CINV), the recommended guidelines for treatment, and current agents in late-stage clinical trials, and future research needs to address the continued challenges of treatment-related nausea and vomiting.

EXPERT OPINION

Despite advances in pharmaceutical and behavioral therapies, and the provision of standard clinical guidelines for effectively managing CINV, patients continue to experience it. Moreover, control of nausea, acute and delayed, and anticipatory nausea and vomiting remains an important, unmet need among cancer patients. It is critical to focus attention on better understanding the mechanisms underlying nausea, anticipatory symptoms and delayed symptoms.

Nausea in specific phobia of vomiting

Specific phobia of vomiting (SPOV) is a clinical condition with early onset, chronic course and substantial psychosocial impairment due to a rigorous avoidance behavior. A primary symptom which drives patients to consult a medical practitioner is nausea. In this study our aim was to further analyze this symptom of SPOV and examined its role in the development and manifestation of the phobia. We conducted an internet survey in the german SPOV-internet-forum. We calculated a nausea score and grouped participants in a high-and low-nausea group to examine the relationship between nausea and characteristics of the fear of vomiting. In this sample (N = 131), nausea was fairly common in most participants with fear of vomiting. Participants in the high-nausea group had significantly higher ratings of subjective fear and significantly longer duration of fear of vomiting. Additionally, the high-nausea group contained more participants with a body mass index below 19 than the low-nausea group. The present findings suggest that nausea is a core symptom in SPOV which is closely related to intensity of the fear, duration of the fear, and body weight. Future research should investigate if nausea-specific design of treatment could improve therapy outcome.

Chemotherapy-induced nausea and vomiting: pathophysiology and therapeutic principles

Chemotherapy-induced nausea and vomiting (CINV) is a major determinant of quality of life in cancer patients. In addition, the perceptions that oncology professionals have about CINV quite often do not coincide with reality. Antineoplastic agents and their combinations can be categorised according to their emetogenic level, and this categorisation is helpful for classifying the severity of CINV and treating it. All CINV treatment guidelines emphasise the need to administer prophylaxis to patients who receive highly or moderately emetogenic chemotherapy. With the introduction of NK1 receptor antagonists, the control of acute and delayed CINV after highly or moderately emetogenic chemotherapy schedules has improved in the great majority of patients. NK1 receptor antagonists have been demonstrated to improve the control of CINV in all risk subgroups of patients.

Extrinsic primary afferent signalling in the gut

Visceral sensory neurons activate reflex pathways that control gut function and also give rise to important sensations, such as fullness, bloating, nausea, discomfort, urgency and pain. Sensory neurons are organised into three distinct anatomical pathways to the central nervous system (vagal, thoracolumbar and lumbosacral). Although remarkable progress has been made in characterizing the roles of many ion channels, receptors and second messengers in visceral sensory neurons, the basic aim of understanding how many classes there are, and how they differ, has proven difficult to achieve. We suggest that just five structurally distinct types of sensory endings are present in the gut wall that account for essentially all of the primary afferent neurons in the three pathways. Each of these five major structural types of endings seems to show distinctive combinations of physiological responses. These types are: 'intraganglionic laminar' endings in myenteric ganglia; 'mucosal' endings located in the subepithelial layer; 'muscular-mucosal' afferents, with mechanosensitive endings close to the muscularis mucosae; 'intramuscular' endings, with endings within the smooth muscle layers; and 'vascular' afferents, with sensitive endings primarily on blood vessels. 'Silent' afferents might be a subset of inexcitable 'vascular' afferents, which can be switched on by inflammatory mediators. Extrinsic sensory neurons comprise an attractive focus for targeted therapeutic intervention in a range of gastrointestinal disorders.

Efficacy of the oral neurokinin-1 receptor antagonist aprepitant administered with ondansetron for the prevention of postoperative nausea and vomiting

Background

5-HT₃ receptor antagonist, dexamethasone and droperidol were used for the prevention of postoperative nausea and vomiting (PONV). Recently, neurokinin-1 (NK1) antagonist has been used for PONV. We evaluated the effect of oral aprepitant premedication in addition to ondansetron.

Methods

A total 90 patients scheduled for elective rhinolaryngological surgery were allocated to three groups (Control, Ap80, Ap125), each of 30 at random. Ondansetron 4 mg was injected intravenously to all patients just before the end of surgery. On the morning of surgery, 80 mg and 125 mg aprepitant were additionally administered into the Ap80 group and Ap125 group, respectively. The rhodes index of nausea, vomiting and retching (RINVR) was checked at 6 hr and 24 hr after surgery.

Results

Twelve patients who used steroids unexpectedly were excluded. Finally 78 patients (control : Ap80 : Ap125 = 24 : 28 : 26) were enrolled. Overall PONV occurrence rate of Ap125 group (1/26, 3.9%) was lower (P = 0.015) than the control group (7/24, 29.2%) at 6 hr after surgery. The nausea distress score of Ap125 group (0.04 ± 0.20) was lower (P = 0.032) than the control group (0.67 ± 1.24) at 6 hr after surgery. No evident side effect of aprepitant was observed.

Conclusions

Oral aprepitant 125 mg can be used as combination therapy for the prevention of PONV.

Intravenous buspirone for the prevention of postoperative nausea and vomiting

RATIONALE

Buspirone, a partial 5HT(1A) agonist and D₂ and D₃ antagonist, has shown promising antiemetic efficacy when given parenterally in animal models, but its efficacy for the prevention of postoperative nausea and vomiting (PONV) is unknown.

OBJECTIVE

To study the efficacy and dose-responsiveness of intravenous buspirone for the prevention of PONV.

METHODS

A randomised, double-blind, placebo-controlled study was performed in adults at moderate to high PONV risk undergoing surgery with a general anaesthetic. Patients were randomised to receive an intravenous dose of buspirone (0.3, 1.0, 2.0, 3.0 mg) or placebo at the end of surgery. The primary endpoint was the cumulative 24-h PONV incidence (i.e. any nausea and/or vomiting). Vomiting included retching. Nausea was defined as a score of ≥ 4 on an 11-point verbal rating scale running from zero (no nausea) to ten (the worst nausea imaginable).

RESULTS

A total of 257 patients received the study drug and fulfilled the criteria for inclusion in the primary efficacy and safety analyses. With placebo, the mean 24-h PONV incidence was 49.0 % (90 % confidence interval [CI] 37.5-60.5 %). With buspirone, that incidence ranged from a mean of 40.8 % (29.3-52.4 %) in the 1 mg arm to 58.0 % (46.5-69.5 %) in the 0.3 mg arm (P > 0.05 for all comparisons). There was no difference between placebo and buspirone at any dose for any other efficacy endpoint, nor in the number or severity of adverse events or any other safety measures.

CONCLUSION

We were unable to show that intravenous single-dose buspirone, at the tested dose-range, was effective at preventing PONV in surgical adult patients. The present study emphasises the difficulty in extrapolating from animal models of emesis to clinical efficacy in PONV.

Post-anesthesia vomiting: impact of isoflurane and morphine on ferrets and musk shrews

Although partially controlled with antiemetic drugs, postoperative nausea and vomiting (PONV) continues to be a problem for many patients. Clinical research suggests that opioid analgesics and volatile anesthetics are the main triggers of PONV. The aim of this study was to develop an animal model for post-anesthesia vomiting for future studies to further determine mechanisms and preclinical drug efficacy. Ferrets (N=34) were initially used because they have served as a gold standard for emesis research. Ferrets were tested with several doses of morphine, inhaled isoflurane, and a positive control injection of cisplatin (a chemotherapy agent) to induce emesis. Musk shrews (a small animal model; N=36) were also tested for emesis with isoflurane exposure. A control injection of cisplatin produced emesis in ferrets (ip, 129.8±22.0 retches; 13.7±2.3 vomits; mean±SEM). Morphine also produced a dose-response on emesis in ferrets, with maximal responses at 0.9 mg/kg (sc, 29.6±12.6 retches; 1.8±0.9, vomits). Isoflurane exposure (2-4% for 10 min to 6h exposure) failed to induce vomiting, was not associated with an increased frequency in emesis when combined with a low dose of morphine (0.1 mg/kg, sc), and failed to produce consistent effects on food and water intake. In contrast to ferrets, musk shrews were very sensitive to isoflurane-induced emesis (0.5 to 3%, 10 min exposure; up to 11.8±2.4 emetic episodes). Overall, these results indicate that ferrets will not be useful for delineating mechanisms responsible for isoflurane-induced emesis; however, musk shrews may prove to be a model for vomiting after inhalation of volatile agents.

5-HT(3) and 5-HT(4) receptors contribute to the anti-motility effects of Garcinia buchananii bark extract in the guinea-pig distal colon

BACKGROUND

Garcinia buchananii bark extract is an anti-motility diarrhea remedy. We investigated whether G. buchananii bark extract has components that reduce gastrointestinal peristaltic activity via 5-HT(3) and 5-HT(4) receptors.

METHODS

Aqueous G. buchananii extract was separated into fractions using preparative thin layer chromatography (PTLC), and major chemical components were identified using standard tests. The anti-motility effects of the extract and its fractions (PTLC1-5) were studied through pellet propulsion assays using isolated guinea-pig distal colons.

KEY RESULTS

Anti-motility (PTLC1 & PTLC5) and pro-motility (PTLC2) fractions were isolated from the extract. Flavonoids, steroids, alkaloids, tannins, and phenols were identified in the extract and PTLC1&5. The potency of the extract applied via the mucosal surface was reduced by 5-HT, 5-HT(3) receptor agonist RS-56812, 5-HT(4) receptor agonists cisapride and CJ-033466, 5-HT(3) receptor antagonist granisetron, and 5-HT(4) receptor antagonist GR-113808. The anti-motility effects of the aqueous extract and PTLC1&5 when applied serosally were reversed by RS-56812, cisapride, and CJ-033466. The 5-HT(3) receptor antagonists, granisetron and ondansetron, reduced the effects of the extract to an extent and completely reversed the anti-motility effects of PTLC1&5. GR-113808 inhibited the actions of the extract during the initial 10 min, but enhanced the extracts' anti-motility effects after 15 min. GR-113808 augmented the anti-motility activities of PTLC1 and PTLC5 by 30%.

CONCLUSIONS & INFERENCES

These results indicate that the anti-motility effects of G. buchananii aqueous extract are potentially mediated by compounds that affect 5-HT(3) and 5-HT(4) receptors. Identification and characterization of the bioactive compounds within G. buchananii could lead to the discovery of new non-opiate anti-diarrhea formulations.

Resolution of cyclic vomiting after appendectomy in a girl

Cyclic vomiting syndrome is a disorder characterized by recurrent, discrete, stereotypical episodes of nausea and vomiting. Although chronic or recurrent appendicitis may be a cause of recurrent abdominal pain, it rarely meets the diagnostic criteria for cyclic vomiting syndrome. Furthermore, mast cell counts are histologically high in chronic appendicitis. We report a 10-year-old Japanese girl with a cyclic pattern of vomiting that met the stringent diagnostic criteria for cyclic vomiting syndrome, and which was resolved after appendectomy. Histopathologic examination of the resected appendix showed not only acute mucosal inflammation but also chronic inflammatory changes. Because we speculated that recurrent or chronic appendicitis may have been related to the patient's vomiting bouts, we also immunohistochemically investigated the density of mast cells in the specimen. We found that the mast cell density was markedly high in the lamina propria of the appendix. In our patient, a type I hypersensitivity reaction with release of mediators by mast cells could have been the initial factor triggering the recurrent appendicitis, and this stressor could have initiated the vomiting cascade. In conclusion, chronic or recurrent appendicitis could be one of the causes of cyclic vomiting, and must be considered in the differential diagnosis of cyclic vomiting syndrome.

Behavioral patterns associated with chemotherapy-induced emesis: a potential signature for nausea in musk shrews

Nausea and vomiting are common symptoms in patients with many diseases, including cancer and its treatments. Although the neurological basis of vomiting is reasonably well known, an understanding of the physiology of nausea is lacking. The primary barrier to mechanistic research on the nausea system is the lack of an animal model. Indeed investigating the effects of anti-nausea drugs in pre-clinical models is difficult because the primary readout is often emesis. It is known that animals show a behavioral profile of sickness, associated with reduced feeding and movement, and possibly these general measures are signs of nausea. Studies attempting to relate the occurrence of additional behaviors to emesis have produced mixed results. Here we applied a statistical method, temporal pattern (t-pattern) analysis, to determine patterns of behavior associated with emesis. Musk shrews were injected with the chemotherapy agent cisplatin (a gold standard in emesis research) to induce acute (<24 h) and delayed (>24 h) emesis. Emesis and other behaviors were coded and tracked from video files. T-pattern analysis revealed hundreds of non-random patterns of behavior associated with emesis, including sniffing, changes in body contraction, and locomotion. There was little evidence that locomotion was inhibited by the occurrence of emesis. Eating, drinking, and other larger body movements including rearing, grooming, and body rotation, were significantly less common in emesis-related behavioral patterns in real versus randomized data. These results lend preliminary evidence for the expression of emesis-related behavioral patterns, including reduced ingestive behavior, grooming, and exploratory behaviors. In summary, this statistical approach to behavioral analysis in a pre-clinical emesis research model could be used to assess the more global effects and limitations of drugs used to control nausea and its potential correlates, including reduced feeding and activity levels.

Chemotherapy-and cancer-related nausea and vomiting

Approximately one half of cancer patients will experience nausea or vomiting during the course of their disease either because of the cancer itself or because of their treatment. Emesis attributable to cancer warrants a careful investigation to determine whether a treatable underlying cause is responsible. Interventions using dexamethasone and octreotide may reduce vomiting attributable to bowel obstruction. In the absence of a bowel obstruction or a correctable cause, the usual approach is a sequential trial of antiemetics guided by considerations of cost and side effects.

Major progress in managing chemotherapy-induced emesis followed from the use of a combination of a corticosteroid and 5-hydroxytryptamine₃ (5-HT₃) receptor antagonist for moderately to highly emetogenic chemotherapy. Nevertheless, vomiting still occurred in approximately 40% of women receiving chemotherapy containing an anthracycline plus cyclophosphamide and in approximately 50% of patients receiving high-dose cisplatin. The addition of aprepitant, a neurokinin 1 receptor antagonist, improved control of emesis by a further 15%–20%, and that agent is now recommended as part of standard antiemetic therapy for patients at high risk of emesis. Based largely on anecdotal experience, cannabinoids and olanzapine are sometimes also recommended in patients with refractory emesis. Phase iii trials are required to confirm their efficacy as add-ons to a corticosteroid, a 5-HT₃ receptor antagonist, and possibly aprepitant.

Management of opioid-induced nausea and vomiting in cancer patients: systematic review and evidence-based recommendations

The objectives were to review the existing literature on management of opioid-induced nausea and vomiting in cancer patients and summarize the findings into evidence-based recommendations. Systematic searches of MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were performed, using free text and MeSH/EMTREE search terms. The searches were limited to articles published in English from each database set-up date to 31 July 2009. Reference lists and relevant international conference proceedings were hand-searched. Fifty-five studies were identified, providing data on 5741 patients. The studies were classified into: (A) studies in which treatment of nausea/vomiting was the primary outcome (a total of 18 studies, of which eight studies specifically addressed opioid-induced emesis); and (B) studies in which nausea/vomiting were secondary or tertiary outcomes (37 studies). The existing evidence had several limitations, there was a lack of consistency and the overall quality was grade D. By applying the principles of the Grading of Recommendations Assessment, Development and Evaluations (GRADE) system, three weak recommendations were formulated. The current evidence is too limited to give evidence-based recommendations for the use of antiemetics for opioid-induced nausea or vomiting in cancer patients. The evidence suggests that nausea and vomiting in cancer patients receiving an opioid might be reduced by changing the opioid or opioid administration route. The evidence was also too limited to prioritize between symptomatic treatment and adjustment of the opioid treatment.

Therapeutics of 5-HT3 receptor antagonists: current uses and future directions

The 5-Hydroxytryptamine3 (5-HT3) receptor is a member of the cys-loop family of ligand gated ion channels, of which the nicotinic acetylcholine receptor is the prototype. All other 5-HT receptors identified to date are metabotropic receptors. The 5-HT3 receptor is present in the central and peripheral nervous systems, as well as a number of non-nervous tissues. As an ion channel that is permeable to the cations, Na(+), K(+), and Ca(2+), the 5-HT3 receptor mediates fast depolarizing responses in pre- and post-synaptic neurons. As such, 5-HT3 receptor antagonists that are used clinically block afferent and efferent synaptic transmission. The most well established physiological roles of the 5-HT3 receptor are to coordinate emesis and regulate gastrointestinal motility. Currently marketed 5-HT3 receptor antagonists are indicated for the treatment of chemotherapy, radiation, and anesthesia-induced nausea and vomiting, as well as irritable bowel syndrome. Other therapeutic uses that have been explored include pain and drug addiction. The 5-HT3 receptor is one of a number of receptors that play a role in mediating nausea and vomiting, and as such, 5-HT3 receptor antagonists demonstrate the greatest anti-emetic efficacy when administered in combination with other drug classes.