Anti-nausea Effects Research Articles

Does an Antipsychotic Hold the Key to Nausea Treatment in Cancer Patients? A Review on the Anti-Nausea Effects of Olanzapine in Oncology

Does an Antipsychotic Hold the Key to Nausea Treatment in Cancer Patients? A Review on the Anti-Nausea Effects of Olanzapine in Oncology

Pharmacokinetics and anti-nausea effects of intravenous ondansetron in hospitalized dogs exhibiting clinical signs of nausea.

The purpose of this study was to evaluate the pharmacokinetics of intravenous (IV) ondansetron in a population of hospitalized dogs exhibiting clinical signs of nausea. The causes of nausea included pancreatitis, gastroenteritis, endocarditis, chemotherapy-induced nausea, diabetes mellitus and ketoacidosis, acute kidney injury with aspiration pneumonia, pyometra, uroabdomen, neoplasia, and hepatopathy. Twenty-four dogs were randomly assigned to one of the following IV ondansetron protocols: 1mg/kg q12h, 0.5mg/kg q12h, 1mg/kg q8h, 0.5mg/kg q8h. Serum was collected at 0, 0.25, 0.5, 1, 2, 4, 8, 16, and 24 h after the first dose, and nausea scores were recorded at multiple time points. Ondansetron and arginine vasopressin (AVP) concentrations were measured via high-performance liquid chromatography coupled to tandem mass spectrometry and ELISA, respectively. Noncompartmental pharmacokinetic modeling and dose interval modeling were performed. Ondansetron displayed linear pharmacokinetics. In the 0.5mg/kg group, mean Cmax =214 ng/ml, AUC0-8h =463 ng/ml*h, and calculated half-life was 1.9h. In the 1mg/kg group, mean Cmax =541 ng/ml, AUC0-8h =1057 ng/ml*h and calculated half-life was 1.6h. Serum ondansetron concentrations were not significantly different between dogs that required rescue anti-nausea medication (non-responders) and dogs that did not require rescue therapy (responders). In total, 83.3% of patients in the 0.5 mg/kg q8h, 0.5 mg/kg q12h, and 1 mg/kg q8h groups had improvement in nausea scores. In total, 66.7% of patients in the 1 mg/kg q12h group had improvement in nausea scores. In total, 33% of patients had resolution of nausea in the 0.5 mg/kg q8h, 1 mg/kg q8h, and 1 mg/kg q12h groups, and 16% of patients had resolution of nausea in the 0.5 mg/kg q12h group. AVP concentrations were highly variable and did not correlate with nausea scores. Nausea scores significantly decreased regardless of dosage protocol. AVP was not a reliable biomarker of nausea in this group of dogs.

A brainstem circuit for nausea suppression.

SUMMARYNausea is a discomforting sensation of gut malaise that remains a major clinical challenge. Several visceral poisons induce nausea through the area postrema, a sensory circumventricular organ that detects blood-borne factors. Here, we use genetic approaches based on an area postrema cell atlas to reveal inhibitory neurons that counteract nausea-associated poison responses. The gut hormone glucose insulinotropic peptide (GIP) activates area postrema inhibitory neurons that project locally and elicit inhibitory currents in nausea-promoting excitatory neurons through γ-aminobutyric acid (GABA) receptors. Moreover, GIP blocks behavioral responses to poisons in wild-type mice, with protection eliminated by targeted area postrema neuron ablation. These findings provide insights into the basic organization of nausea-associated brainstem circuits and reveal that area postrema inhibitory neurons are an effective pharmacological target for nausea intervention.

UPLC-HRMS Polyphenolic Characterization, Contents and Antioxidant Activity of Zingiber officinale Roscoe rhizomes from Costa Rica

Zingiber officinale Roscoe rhizomes have been associated with multiple health benefits, such as blocking blood clotting, digestive and antinausea effects and aid in respiratory conditions. These effects have been linked with their polyphenolic main metabolites, gingerols and shogaols. Herewith, we report a detailed study on the polyphenolic profile and in the contents of main gingerols and shogaol as well as the antioxidant activity of extracts from Z. officinale rhizomes (n = 17) produced in Costa Rica. Using UPLC-QTOF-ESI MS, a total of 34 polyphenols were identified, grouped in 12 types of structures. In addition, our findings on the main metabolites using UPLC-DAD show all rhizomes complying with total gingerols (TG) content established by the United States Pharmacopeia (USP). At an individual level, samples SR-1 and NR-4 show the higher contents and also exhibit the highest Folin–Ciocalteu (FC) reducing capacity results as well as the best DPPH antioxidant values. In addition, Pearson correlation analysis results showed positive correlation (p < 0.05) between TG and 6-gingerol with FC results and negative correlation (p < 0.05) between 6-gingerol, TG and FC with DPPH results. In turn, Principal Component Analysis (PCA) indicated variability in the composition associated with their region of origin and confirmed that NR-3, NR-4, and especially SR-1 stand out significatively, showing the highest PC1 because of its particularly high TG, 6-gingerol and antioxidant activities. Finally, results from controlled experimental plots of Z. officinale rhizomes (n = 6) indicated influence on metabolites content with higher values for a shorter harvest time and high tunnel cultivation. Therefore, our findings indicate the value of Z. officinale in the elaboration of products with potential benefits for health, delivering extracts with higher levels of gingerols than previous reports and exhibiting high antioxidant activity.

Zingerone Attenuates Pi-induced Vascular Calcification via AMPK-mediated TIMP4 Expression.

ObjectiveVascular calcification requires the differentiation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells. This phenomenon can be enhanced by inflammation and oxidative stress. Zingerone is one of the active ingredients present in the ginger plant that has anti-inflammatory and antioxidant effects. Other functions include anti-obesity, anti-nausea effects. However, the functions of zingerone on vascular calcification has not yet been elucidated. This study investigated the effect of zingerone on vascular calcification and its molecular mechanism.MethodsReverse transcription-polymerase chain reaction (PCR), real-time PCR and Western blot analysis was used to measure expression levels of osteogenic marker genes and to investigate whether calcification was regulated by the expression of AMP-activated protein kinase (AMPK) and tissue inhibitor of metalloproteinase 4 (TIMP4). Alizarin red S staining was used to measure calcium deposition. Studies were carried out in VSMCs.ResultsZingerone induced the expression of 2 markers of VSMCs differentiation (α-smooth muscle actin (α-SMA) and smooth muscle 22α (SM22α)) and decreased the expression of core-binding factor α-1 (CBFA1). Additionally, zingerone decreased inorganic phosphate (Pi)-induced expression of distal-less homeobox 5 and CBFA1. AMPK phosphorylation and TIMP4 expression were increased by zingerone. Importantly, zingerone protected VSMCs from calcification, and this protective effect was confirmed by increased TIMP4 via overexpression of AMPK, and inhibition of TIMP4 by Compound C. Zingerone upregulated AMPK/TIMP4 expression and recovered Pi-induced inhibition of TIMP4.ConclusionsTaken together, our results show that zingerone inhibits Pi-induced vascular calcification by regulating the AMPK/TIMP4 signaling cascade in VSMCs. These results suggest that the natural product zingerone could be useful for treating vascular and metabolic diseases.

Evaluation of repeated or acute treatment with cannabidiol (CBD), cannabidiolic acid (CBDA) or CBDA methyl ester (HU-580) on nausea and/or vomiting in rats and shrews

When acutely administered intraperitoneally, the non-psychoactive cannabinoid cannabidiol (CBD), its acidic precursor cannabidiolic acid (CBDA) and a stable methyl ester of CBDA (HU-580) reduce lithium chloride (LiCl)-induced conditioned gaping in male rats (a selective preclinical model of acute nausea) via activation of the serotonin 1A (5-HT1A) receptor. To utilise these compounds to manage nausea in the clinic, we must determine if their effectiveness is maintained when injected subcutaneously (s.c) and when repeatedly administered. First, we compared the effectiveness of each of these compounds to reduce conditioned gaping following repeated (7-day) and acute (1-day) pretreatments and whether these anti-nausea effects were mediated by the 5-HT1A receptor. Next, we assessed whether the effectiveness of these compounds can be maintained when administered prior to each of 4 conditioning trials (once per week). We also evaluated the ability of repeated CBD (7 days) to reduce LiCl-induced vomiting in Suncus murinus. Finally, we examined whether acute CBD was equally effective in male and female rats. Both acute and repeated (7 day) s.c. administrations of CBD (5 mg/kg), CBDA (1 μg/kg) and HU-580 (1 μg/kg) similarly reduced LiCl-induced conditioned gaping, and these effects were blocked by 5HT1A receptor antagonism. When administered over 4 weekly conditioning trials, the anti-nausea effectiveness of each of these compounds was also maintained. Repeated CBD (5 mg/kg, s.c.) maintained its anti-emetic efficacy in S. murinus. Acute CBD(5 and 20 mg/kg, s.c.) administration reduced LiCl-induced conditioned gaping similarly in male and female rats. When administered repeatedly (7 days), CBD, CBDA and HU-580 did not lose efficacy in reducing nausea and continued to act via agonism of the 5-HT1A receptor. When administered across 4 weekly conditioning trials, they maintained their effectiveness in reducing LiCl-induced nausea. Repeated CBD also reduced vomiting in shrews. Finally, CBD's anti-nausea effects were similar in male and female rats. This suggests that these cannabinoids may be useful anti-nausea and anti-emetic treatments for chronic conditions, without the development of tolerance.

Les nausées : données actuelles

Nausea is a common feeling felt by the subject as a state likely to evolve into vomiting. However a lot of nausea is maintained without being followed by vomiting. Nausea can be isolated or accompanied by a clinical picture. Some situations are often accompanied by nausea like dizziness, migraines, transport sickness, pregnancy, acute or chronic digestive disorders or anxious state. Outside of a know pathological context, there must be an etiologic investigation. When they are accompanied by vomiting and general signs -especially a fever- nausea must first eliminate a potentially serious disease (intracranial hypertension, meningitis, occlusion…). Nausea resounds on the patient's quality of life, they can decrease concentration and professional activities. Many patients do not treat nausea and use rest and waiting for the resolution of symptoms. In the absence of signs of gravity taking a treatment without a medical prescription can be considered (recommendation ANSM 2008) especially for recurrent crisis whose cause can be precisely identified. They are many pharmacological substances with antinausea effects. If the etiological approach is essential and sometimes sufficient, symptomatic relief can be helped by some agents with less intense nausea and shorter duration especially by using of antihistaminics, anticholinergic agents and derivatives of phenothiazines.

Management of Sea Sickness in Susceptible Flight Crews.

Sea sickness may greatly impact the readiness of Service personnel deployed aboard naval vessels. Medications used in the treatment of sea sickness may have adverse effects, limiting their use as flight crew. Although the prevalence of sea sickness in flight crews remains unclear, individual susceptibility and high sea states are established risk factors. Literature review can guide optimized management strategies for this population. The first author conducted a PubMed search using the terms "sea sickness" "flight crew" "scopolamine," "hyoscine," and "cinnarizine," identifying 15 articles of 350 matches, which addressed potential impact to flight performance. Analysis also included two historic reports about motion sickness maintained within the U.K. Army Aviation Centre's aeromedical archives in Middle Wallop, Hampshire. Both authors reviewed aeromedical policy for the International Civil Aviation Organization, U.K. Civil Aviation Authority, U.S. Federal Aviation Authority, the National Aeronautics Space Administration, U.S. Army, U.S. Navy, and U.S. Air Force. Scopolamine, also known as hyoscine, has fewer operationally relevant side effects than cinnarizine or first-generation antihistamines. Although no aeromedical authorities endorse the unsupervised use of scopolamine, many will consider authorizing its temporary use following an initial assessment on the ground. Evidence supports the concomitant use of stimulant medication for augmenting antinausea effects and countering the potential sedative effects of scopolamine. Scopolamine should be considered as a first-line medication for flight crews at risk of sea sickness but such use must be guided by the appropriate aeromedical authority, ideally in conjunction with a ground trial to evaluate individual response. The limited evidence to support concurrent use of stimulants must be weighed against the challenges of maintaining accountability of controlled substances in the operational environment.

Anti-nausea effects and pharmacokinetics of ondansetron, maropitant and metoclopramide in a low-dose cisplatin model of nausea and vomiting in the dog: a blinded crossover study

BackgroundNausea is a subjective sensation which is difficult to measure in non-verbal species. The aims of this study were to determine the efficacy of three classes of antiemetic drugs in a novel low dose cisplatin model of nausea and vomiting and measure change in potential nausea biomarkers arginine vasopressin (AVP) and cortisol. A four period cross-over blinded study was conducted in eight healthy beagle dogs of both genders. Dogs were administered 18 mg/m2 cisplatin intravenously, followed 45 min later by a 15 min infusion of either placebo (saline) or antiemetic treatment with ondansetron (0.5 mg/kg; 5-HT3 antagonist), maropitant (1 mg/kg; NK1 antagonist) or metoclopramide (0.5 mg/kg; D2 antagonist). The number of vomits and nausea associated behaviours, scored on a visual analogue scale, were recorded every 15 min for 8 h following cisplatin administration. Plasma samples were collected to measure AVP, cortisol and antiemetic drug concentrations.ResultsThe placebo treated group vomited an average number of 7 times (range 2–13). None of the dogs in either the ondansetron or maropitant treated groups vomited during the observation period. The onset of nausea-like behaviour in the placebo-treated group occurred at t3.5h and peaked at t4.75h with nausea behaviour score of 58.5 ± 4.6 mm. Ondansetron and maropitant reduced overall the area under the curve of nausea behaviour score by 90% and 25%, respectively. Metoclopramide had no effect on either vomiting or nausea.Cisplatin-induced nausea and vomiting caused concomitant increases in AVP and cortisol. In the placebo-treated group, AVP and cortisol increased from t2.5h, peaked at t5h (11.3 ± 2.9 pmol L−1 and 334.0 ± 46.7 nmol/L, respectively) and returned to baseline by t8h. AVP and cortisol increases were completely prevented by ondansetron and only partially by maropitant, while metoclopramide had no effect. The terminal half-lives (harmonic mean ± pseudo SD) for ondansetron, maropitant and metoclopramide were 1.21 ± 0.51, 5.62 ± 0.77 and 0.87 ± 0.17 h respectively.Conclusions5-HT3 receptor antagonist ondansetron demonstrates the greatest anti-emetic and anti-nausea efficacy of the three drugs. AVP and cortisol appear to be selective biomarkers of nausea rather than emesis, providing a means of objectively measuring of nausea in the dog.

Electrothermal acupuncture in the prevention and treatment of chemotherapy-induced nausea and vomiting:a randomized controlled trial

To observe the effectiveness and safety of electrothermal acupuncture in the prevention and treatment of chemotherapy-induced nausea and vomiting (CINV) in the cancerous patients of phlegm-stasis interaction in cisplatin-containing chemotherapy. Sixty cases of phlegm-stasis interaction in cisplatin-containing chemotherapy were randomized into a trial group and a control group, 30 cases in each one. In the control group, the intravenous drip of granisetron hydrochloride injection was adopted, 3 mg before and after cisplatin-containing chemotherapy 30 min, continuously for 3 days. 43 to 45℃ electrothermal acupuncture at zusanli(ST 36) for 30 min was used on the basis of the treatment as the control group in the trial group,once a day for 3 days. CINV, anti-nausea effects, Karnofsky score, the syndrome score of phlegm-stasis interaction, and relevant indices of safety were observed on the 1st and 7th days of cisplatin-containing chemotherapy separately. 1.Regarding CINV and anti-nausea effect, CINV did not occur before chemotherapy in the patients of the two groups. On the 1st and 7th days of chemotherapy, CINV in the trial group were milder than those in the control group (both P<0.05).The anti-nausea effects in the trail group were better than those of the control group.2.Regarding Karnofsky score and the syndrome score of phlegm-stasis interaction, the improvements on the 7th days of chemotherapy in the trial group were better than those in the control group, indicating the significant differences (both P<0.05). 3.Regarding the safety indies, there was no adverse reaction during the treatment in the two groups. The electrothermal acupuncture effectively relieves CINV, and improves self-care dbility and the symptoms of phlegm-stasis interaction.

Issue Highlights

Issue Highlights

Cannabinoids suppress acute and anticipatory nausea in preclinical rat models of conditioned gaping.

The sensation of nausea is one of the most debilitating human experiences. Current antiemetic therapies are effective in reducing vomiting, but are less effective in reducing acute and delayed nausea and are completely ineffective in reducing anticipatory nausea. Recent preclinical evidence using a selective rat model of nausea (conditioned gaping reactions) has revealed that cannabinoids have great promise as treatments for nausea and that their antinausea effects may be mediated by the interoceptive insular cortex.

Intra-visceral insular cortex 2-arachidonoylglycerol, but not N-arachidonoylethanolamide, suppresses acute nausea-induced conditioned gaping in rats

The visceral insular cortex (VIC) has previously been shown to play a critical role during acute nausea-induced conditioned gaping in rats. Specifically, localized administration of the conventional anti-emetic, ondansetron or the synthetic cannabinoid, HU210, interferes with the establishment of conditioned gaping, likely by reducing the effects of an illness-inducing treatment. However the precise role of the VIC in endocannabinoid-suppression of nausea remains unknown; thus we investigated the potential of localized intra-VIC endocannabinoid administration to interfere with acute nausea-induced conditioned gaping behavior in male Sprague–Dawley rats. Animals received an intraoral infusion of saccharin (0.1%) followed by intra-VIC exogenous N-arachidonoylethanolamide (AEA; 0.4, 4μg) or 2-arachidonoylglycerol (2-AG; 0.5, 1μg), and were subsequently injected with nausea-inducing LiCl (0.15M) 15min later. Bilateral intra-VIC infusions of 2-AG (1μg, but not 0.5μg) dose-dependently suppressed conditioned gaping, whereas exogenous AEA was without effect. Interestingly, 2-AG reduced conditioned gaping despite additional pretreatment with the selective cannabinoid receptor type 1 (CB1) antagonist, AM-251; however, concomitant pretreatment with the cyclooxygenase inhibitor, indomethacin (0.5μg), blocked the suppressive effects of intra-VIC 2-AG. These findings suggest that the modulatory role of the endocannabinoid system during nausea is driven largely by the endocannabinoid, 2-AG, and that its anti-nausea effects may be partly independent of CB1-receptor signaling through metabolic products of the endocannabinoid system.

Suppression of lithium chloride-induced conditioned gaping (a model of nausea-induced behaviour) in rats (using the taste reactivity test) with metoclopramide is enhanced by cannabidiolic acid

We aimed to determine the potential of various doses of metoclopramide (MCP, a dopamine antagonist) to reduce lithium chloride (LiCl)-induced conditioned gaping (a nausea-induced behaviour) in rats, using the taste reactivity test. We then evaluated whether an ineffective low dose of cannabidiolic acid (CBDA, 0.1μg/kg, Rock and Parker, 2013), the potent acidic precursor of cannabidiol (CBD, a non-psychoactive component of cannabis) could enhance the anti-nausea effects of an ineffective low dose of MCP. MCP (3.0mg/kg) reduced conditioned gaping responses. Coadministration of ineffective doses of MCP (0.3mg/kg) and CBDA (0.1μg/kg) enhanced the suppression of conditioned gaping, over that of either drug alone, without interfering with conditioned taste avoidance. MCP dose-dependently reduced nausea-induced conditioned gaping in rats. As well, the suppression of conditioned gaping was enhanced when ineffective doses of MCP and CBDA were coadministered. These data suggest that CBDA could be a powerful adjunct treatment to anti-emetic regimens for chemotherapy-induced nausea.

Effect of low doses of cannabidiolic acid and ondansetron on LiCl‐induced conditioned gaping (a model of nausea‐induced behaviour) in rats

To determine the minimally effective dose of cannabidiolic acid (CBDA) that effectively reduces lithium chloride (LiCl)-induced conditioned gaping reactions (nausea-induced behaviour) in rats and to determine if these low systemic doses of CBDA (5-0.1 μg·kg⁻¹) relative to those of CBD could potentiate the anti-nausea effects of the classic 5-hydroxytryptamine 3 (5-HT₃) receptor antagonist, ondansetron (OND). We investigated the efficacy of low doses of CBDA to suppress acute nausea, assessed by the establishment of conditioned gaping to a LiCl-paired flavour in rats. The potential of threshold and subthreshold doses of CBDA to enhance the reduction of nausea-induced conditioned gaping by OND were then determined. CBDA (at doses as low as 0.5 μg·kg⁻¹) suppressed nausea-induced conditioned gaping to a flavour. A low dose of OND (1.0 μg·kg⁻¹) alone reduced nausea-induced conditioned gaping, but when it was combined with a subthreshold dose of CBDA (0.1 μg·kg⁻¹) there was an enhancement in the suppression of LiCl-induced conditioned gaping. CBDA potently reduced conditioned gaping in rats, even at low doses and enhanced the anti-nausea effect of a low dose of OND. These findings suggest that combining low doses of CBDA and OND will more effectively treat acute nausea in chemotherapy patients.

Themed issue on cannabinoids in biology and medicine

Themed issue on cannabinoids in biology and medicine

Interaction between non-psychotropic cannabinoids in marihuana: effect of cannabigerol (CBG) on the anti-nausea or anti-emetic effects of cannabidiol (CBD) in rats and shrews

The interaction between two non-psychotropic cannabinoids, cannabidiol (CBD) and cannabigerol (CBG), which have been reported to act as a 5-hydroxytryptamine 1A (5-HT(1A)) agonist and antagonist, respectively, was evaluated. To evaluate the potential of CBG to reverse the anti-nausea, anti-emetic effects of CBD. In experiment 1, rats were pre-treated with CBG (0.0, 1, 5, and 10 mg/kg, ip), 15 min prior to being treated with CBD (experiment 1a: VEH or 5 mg/kg, ip) or 8-OH-DPAT (experiment 1b: VEH or 0.01 mg/kg, ip). Thirty minutes later, all rats received a pairing of 0.1% saccharin solution and LiCl (20 ml/kg of 0.15 M, ip). Seventy-two hours later, the rats received a drug-free taste reactivity test with saccharin to evaluate the effects of the treatments on the establishment of conditioned gaping reactions (a model of nausea). As well, conditioned saccharin avoidance was measured. In experiment 2, Suncus murinus were injected with CBG (5 mg/kg, ip) or VEH 15 min prior to CBD (5 mg/kg) or VEH and 30 min later were injected with LiCl (60 ml/kg of 0.15 M, i.p.), and the number of vomiting episodes were measured. CBD (5 mg/kg) suppressed conditioned gaping in rats and vomiting in shrews, which were reversed by pre-treatment with all doses of CBG. CBG also prevented the anti-nausea effects of 8-OH-DPAT. Interactions between moderate doses of CBG and CBD may oppose one another at the 5-HT(1A) receptor in the regulation of nausea and vomiting.

New Drugs on the Horizon May Improve the Quality and Safety of Anesthesia

New Drugs on the Horizon May Improve the Quality and Safety of Anesthesia

Cancer chemotherapy and cachexia: mirtazapine and olanzapine are 5-HT3 antagonists with good antinausea effects

Mirtazapine and olanzapine are easy-to-use psychiatric drugs with potent antinausea effects. Ondansetron and later members of the 'setron class are currently standard treatments for cancer chemotherapy-related nausea and emesis. They are potent 5-HT3 blockers, but it is often not appreciated that mirtazapine and olanzapine bind with similar affinity to 5-HT3 receptors, have a longer half-life, are considerably cheaper than the 'setron class, and often offer better and smoother 24-h nausea control than 'setron class drugs. Mirtazapine and olanzapine often have salutary antianxiety effects and improve sleep quality. They occasionally relieve chemotherapy-related and advanced cancer-related nausea and appetite decrease better than the 'setron group that are specifically marketed for nausea control. Mirtazapine and olanzapine frequently give potent nausea reduction and appetite increase in advanced cancer-related cachexia. Several cytokine changes potentially induced by mirtazapine and olanzapine use are discussed that may have salutary effects in several cancers. We suggest mirtazapine and olanzapine be included as first-line options in treating both chemotherapy- and advanced cancer-related nausea. Multiple clinical and economic advantages of mirtazapine and olanzapine over currently used 'setron class medicines are reviewed. Double-blind studies against the 'setron class drugs are warranted.

The effect of CP-99994 on the responses to provocative motion in the cat.

1. The NK1 receptor antagonist CP-99994 has been shown to prevent vomiting elicited by both peripherally and centrally acting emetogens in ferrets and dogs. These results have now been extended to another stimulus, provocative motion, and another species, the cat. 2. CP-99994 displaced [3H]-substance P from cat cortex with IC50 of 0.52 +/- 0.08 nM. Following s.c. administration, peak plasma drug levels were achieved at 30 min. The plasma drug half life was 1.4 h. 3. Subcutaneous administration of CP-99994 inhibited motion-induced vomiting in the cat with an ED50 of 144 micrograms kg-1 but did not change the epiphenomena associated with provocative motion in the cat over the dose range of 30 to 300 micrograms kg-1. The antiemetic effect of CP-99994 can be attributed to antagonism of the NK1 receptor because its enantiomer, CP-100,263, which is 900 fold weaker as an NK1 antagonist, had no effects on any response to provocative motion. 4. The inhibitory effect of CP-99994 on motion-induced retching and vomiting is consistent with a central site of antiemetic action, potentially at the level of the motor nuclei responsible for these behaviours. 5. An investigation into whether the failure of CP-99994 to alter the epiphenomena will also predict a lack of anti-nausea effects in man will provide critical information on the neural organization of the emetic reflex.