Tropisetron: an update of its use in the prevention of chemotherapy-induced nausea and vomiting

Indole Derivatives: A Versatile Scaffold in Modern Drug Discovery-An Updated Review on Their Multifaceted Therapeutic Applications (2020-2024)

Indole derivatives have become an important class of compounds in medicinal chemistry, recognized for their wide-ranging biological activities and therapeutic potential. This review provides a comprehensive overview of recent advances in the evaluation of indole-based compounds in the last five years, highlighting their roles in cancer treatment, infectious disease management, anti-inflammatory therapies, metabolic disorder interventions, and neurodegenerative disease management. Indole derivatives have shown significant efficacy in targeting diverse biological pathways, making them valuable scaffolds in designing new drugs. Notably, these compounds have demonstrated the ability to combat drug-resistant cancer cells and pathogens, a significant breakthrough in the field, and offer promising therapeutic options for chronic diseases such as diabetes and hypertension. By summarizing recent key findings and exploring the underlying biological mechanisms, this review underscores the potential of indole derivatives in addressing major healthcare challenges, thereby instilling hope and optimism in the field of modern medicine.

Tropisetron attenuates neuroinflammation and chronic neuropathic pain via α7nAChR activation in the spinal cord in rats

OBJECTIVES

Tropisetron is an alpha 7 nicotinic acetylcholine receptor (α7nAChR) agonist and is a commonly used antiemetic clinically. α7nAChRs activation modulating nociception transmissions and cholinergic anti-inflammation may decrease neuropathic pain. This study was set to investigate the effects of tropisetron on neuropathic pain and neuroinflammation as well as the underlying mechanisms in rats.

METHODS

Neuropathic pain behavior was assessed in rats using the paw mechanical withdrawal threshold and paw thermal withdrawal latency before and after the establishment of a spared nerve injury (SNI) pain model in rats treated with tropisetron treatment in the presence or absence of the α7nAChR antagonist methyllycaconitine (MLA) through intrathecal injection. Their spinal cords were then harvested for inflammatory cytokines, the α7nAChR, p38 mitogen-activated protein kinase (p-p38MAPK) and cAMP-response element binding protein (CREB) measurement.

RESULTS

Tropisetron effectively alleviated mechanical allodynia and thermal hyperalgesia; decreased IL-6, IL-1ß and TNF-a; and down-regulated the phosphorylation of p38MAPK and CREB. Pre-treatment with MLA abolished these effects of tropisetron.

CONCLUSION

Our data indicate that tropisetron alleviates neuropathic pain may through inhibition of the p38MAPK-CREB pathway via α7nAChR activation. Thus, tropisetron may be a potential new therapeutic strategy for chronic neuropathic pain.

Positive Allosteric Modulators of Glycine Receptors and Their Potential Use in Pain Therapies

Glycine receptors are ligand-gated ion channels that mediate synaptic inhibition throughout the mammalian spinal cord, brainstem, and higher brain regions. They have recently emerged as promising targets for novel pain therapies due to their ability to produce antinociception by inhibiting nociceptive signals within the dorsal horn of the spinal cord. This has greatly enhanced the interest in developing positive allosteric modulators of glycine receptors. Several pharmaceutical companies and research facilities have attempted to identify new therapeutic leads by conducting large-scale screens of compound libraries, screening new derivatives from natural sources, or synthesizing novel compounds that mimic endogenous compounds with antinociceptive activity. Advances in structural techniques have also led to the publication of multiple high-resolution structures of the receptor, highlighting novel allosteric binding sites and providing additional information for previously identified binding sites. This has greatly enhanced our understanding of the functional properties of glycine receptors and expanded the structure activity relationships of novel pharmacophores. Despite this, glycine receptors are yet to be used as drug targets due to the difficulties in obtaining potent, selective modulators with favorable pharmacokinetic profiles that are devoid of side effects. This review presents a summary of the structural basis for how current compounds cause positive allosteric modulation of glycine receptors and discusses their therapeutic potential as analgesics. SIGNIFICANCE STATEMENT: Chronic pain is a major cause of disability, and in Western societies, this will only increase as the population ages. Despite the high level of prevalence and enormous socioeconomic burden incurred, treatment of chronic pain remains limited as it is often refractory to current analgesics, such as opioids. The National Institute for Drug Abuse has set finding effective, safe, nonaddictive strategies to manage chronic pain as their top priority. Positive allosteric modulators of glycine receptors may provide a therapeutic option.

Comparison of the Effects of Metoclopramide and Ondansetron on Emergency Service Observation Times in Acute Gastroenteritis-Related Nausea and Vomiting Cases

Objectives:

The aim of the present study was to compare the effect of metoclopramide and ondansetron treatments on the emergency department observation time in acute gastroenteritis-related nausea and vomiting (NV).

Methods:

The study was conducted retrospectively on 297 patients diagnosed with acute gastroenteritis in a training and research hospital’s emergency service observation unit within 6 months. Patients with gastroenteritis who were diagnosed with NV were divided into two groups according to the treatment they received in the observation unit. Patients who received 4 mg ondansetron slow infusion therapy were classified as Group 1, and patients who received 10 mg metoclopramide slow infusion therapy were classified as Group 2.

Results:

The average age of the patients was 39.57±18.75 years. Of the 297 participants, 56.6% (168) were female. Among them, 51.5% (153) received ondansetron (Group 1), and 48.5% (144) received metoclopramide (Group 2). 6.9% weakness–numbness and 4.9% akathisia were detected due to metoclopramide use. There were no adverse effects related to ondansetron use. The duration of observation ranged from 19 to 75 min in Group 1 and from 42 to 122 min in Group 2. Nineteen (13.2%) patients in Group 2 and 5 (3.3%) patients in Group 1 revisited the emergency department within 24 h due to ongoing complaints.

Conclusion:

In conclusion, side effects of weakness and akathisia due to metoclopramide use were observed. However, no side effects were observed due to ondansetron use. Additionally, the use of ondansetron showed a shorter observation time and less recurrent admission to the emergency department. Therefore, ondansetron is a more effective drug in the treatment of NV associated with acute gastroenteritis.

Tropisetron enhances recognition memory in rats chronically treated with risperidone or quetiapine

While impairments of cognition in schizophrenia have the greatest impact on long-term functional outcome, the currently prescribed treatments, antipsychotic drugs (APDs), do not effectively improve cognition. Moreover, while more than 20 years have been devoted to the development of new drugs to treat cognitive deficits in schizophrenia, none have been approved to date. One area that has not been given proper attention at the preclinical or clinical stage of drug development is the chronic medication history of the test subject. Hence, very little is known about how chronic treatment with drugs that affect multiple receptors like APDs influence the response to a potential pro-cognitive agent. Therefore, the purpose of this study was to evaluate the α7 nicotinic acetylcholine receptor (α7 nAChR) partial agonist, tropisetron in rats chronically treated with APDs with distinct pharmacological profiles. Rats were treated orally with either risperidone (2.5 mg/kg/day) or quetiapine (25.0 mg/kg/day) for 30 or 90 days and then an acute injection of vehicle or tropisetron (3.0 mg/kg) was administered before training in a novel object recognition (NOR) task. After a 48 h delay (when recollection of the familiar object was impaired in vehicle-treated animals) neither 30 nor 90 days of risperidone or quetiapine treatment improved NOR performance. In contrast, tropisetron markedly improved NOR performance in rats treated with either APD for 30 or 90 days. These animal data reinforce the argument that two commonly prescribed APDs are not pro-cognitive agents and that α7 nAChR ligands like tropisetron have potential as adjunctive treatments in schizophrenia.

Molecular Pharmacology of Phytocannabinoids

Cannabis sativa has been used for recreational, therapeutic and other uses for thousands of years. The plant contains more than 120 C₂₁ terpenophenolic constituents named phytocannabinoids. The Δ⁹-tetrahydrocannabinol type class of phytocannabinoids comprises the largest proportion of the phytocannabinoid content. Δ⁹-tetrahydrocannabinol was first discovered in 1971. This led to the discovery of the endocannabinoid system in mammals, including the cannabinoid receptors CB₁ and CB₂. Δ⁹-Tetrahydrocannabinol exerts its well-known psychotropic effects through the CB₁ receptor but this effect of Δ⁹-tetrahydrocannabinol has limited the use of cannabis medicinally, despite the therapeutic benefits of this phytocannabinoid. This has driven research into other targets outside the endocannabinoid system and has also driven research into the other non-psychotropic phytocannabinoids present in cannabis. This chapter presents an overview of the molecular pharmacology of the seven most thoroughly investigated phytocannabinoids, namely Δ⁹-tetrahydrocannabinol, Δ⁹-tetrahydrocannabivarin, cannabinol, cannabidiol, cannabidivarin, cannabigerol, and cannabichromene. The targets of these phytocannabinoids are defined both within the endocannabinoid system and beyond. The pharmacological effect of each individual phytocannabinoid is important in the overall therapeutic and recreational effect of cannabis and slight structural differences can elicit diverse and competing physiological effects. The proportion of each phytocannabinoid can be influenced by various factors such as growing conditions and extraction methods. It is therefore important to investigate the pharmacology of these seven phytocannabinoids further, and characterise the large number of other phytocannabinoids in order to better understand their contributions to the therapeutic and recreational effects claimed for the whole cannabis plant and its extracts.

Management of Chemotherapy-Induced Nausea and Vomiting in Pediatric Patients

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life and is perceived by patients as a major adverse effect of the treatment. This review summarizes the safety and efficacy of current antiemetic agents for the prevention of CINV in children. Information on antiemetic prophylaxis for CINV in children was obtained from a literature review of current peer-reviewed articles and recent international guidelines. The literature review and the international antiemetic guidelines provide recommendations for use of specific antiemetics in children based on the emetogenicity of the chemotherapy. 5-Hydroxytryptamine-3 (5-HT₃) receptor antagonists have been safe and effective in the prevention of acute emesis with a few patients experiencing mild headache. No adequate studies have been conducted to date for specific recommendations for the prevention of delayed nausea and vomiting in children. The neurokinin (NK)-₁ receptor antagonist aprepitant has been approved by the US FDA for use in children of a specific age and weight. No studies for the NK₁ receptor antagonists netupitant and rolapitant in children have been conducted. Olanzapine, an antipsychotic, has been shown to be safe and effective in preventing nausea and emesis in adult patients receiving chemotherapy. Its use in children has been limited to children with poor control of CINV; more studies are necessary in this population. In conclusion, practitioners should follow international antiemetic guidelines to provide patients with the specific antiemetics in the recommended dose for the highest possible quality of care.

Comparative Pharmacology and Guide to the Use of the Serotonin 5-HT3 Receptor Antagonists for Postoperative Nausea and Vomiting

Since the introduction of the serotonin 5-hydroxy tryptamine 3 (5-HT₃) receptor antagonists in the early 1990s, the incidence of postoperative nausea and vomiting (PONV) and post-discharge nausea and vomiting (PDNV) has decreased, yet continues to be a problem for the surgical patient. The clinical application of the 5-HT₃ receptor antagonists has helped define the approach and role of these antiemetics in the prevention and treatment of PONV and PDNV. Pharmacological and clinical differences exist among these medications resulting in corresponding differences in effectiveness, safety, optimal dosage, time of administration, and use as combination and rescue antiemetic therapy. The clinical application of the 5-HT₃ receptor antagonist antiemetics has improved the prevention and treatment of PONV and PDNV. The most recent consensus guidelines for PONV published in 2014 outline the use of these antiemetics. The 5-HT₃ receptor antagonists play an important role to help prevent PONV and PDNV in perioperative care pathways such as Enhanced Recovery After Surgery (ERAS). Comparisons and guidelines for use of the 5-HT₃ receptor antagonists in relation to the risk for PONV and PDNV are reviewed.

Tropisetron sensitizes α7 containing nicotinic receptors to low levels of acetylcholine in vitro and improves memory-related task performance in young and aged animals

Tropisetron, a 5-HT₃ receptor antagonist commonly prescribed for chemotherapy-induced nausea and vomiting also exhibits high affinity, partial agonist activity at α7 nicotinic acetylcholine receptors (α7 nAChRs). α7 nAChRs are considered viable therapeutic targets for neuropsychiatric disorders such as Alzheimer's disease (AD). Here we further explored the nAChR pharmacology of tropisetron to include the homomeric α7 nAChR and recently characterized heteromeric α7β2 nAChR (1:10 ratio) and we evaluated its cognitive effects in young and aged animals. Electrophysiological studies on human nAChRs expressed in Xenopus oocytes confirmed the partial agonist activity of tropisetron at α7 nAChRs (EC₅₀ ∼2.4 μM) with a similar effect at α7β2 nAChRs (EC₅₀ ∼1.5 μM). Moreover, currents evoked by irregular pulses of acetylcholine (40 μM) at α7 and α7β2 nAChRs were enhanced during sustained exposure to low concentrations of tropisetron (10 and 30 nM) indicative of a "priming" or co-agonist effect. Tropisetron (0.1-10 mg/kg) improved novel object recognition performance in young Sprague-Dawley rats and in aged Fischer rats. In aged male and female rhesus monkeys, tropisetron (0.03-1 mg/kg) produced a 17% increase from baseline levels in delayed match to sample long delay accuracy while combination of non-effective doses of donepezil (0.1 mg/kg) and tropisetron (0.03 and 0.1 mg/kg) produced a 24% change in accuracy. Collectively, these animal experiments indicate that tropisetron enhances cognition and has the ability to improve the effective dose range of currently prescribed AD therapy (donepezil). Moreover, these effects may be explained by tropisetron's ability to sensitize α7 containing nAChRs to low levels of acetylcholine.

Controlled transdermal iontophoresis for poly-pharmacotherapy: Simultaneous delivery of granisetron, metoclopramide and dexamethasone sodium phosphate in vitro and in vivo

Iontophoresis has been used to deliver small molecules, peptides and proteins into and across the skin. In principle, it provides a controlled, non-invasive method for poly-pharmacotherapy since it is possible to formulate and to deliver multiple therapeutic agents simultaneously from the anodal and cathodal compartments. The objective of this proof-of-principle study was to investigate the simultaneous anodal iontophoretic delivery of granisetron (GST) and metoclopramide (MCL) and cathodal iontophoresis of dexamethasone sodium phosphate (DEX-P). In addition to validating the hypothesis, these are medications that are routinely used in combination to treat chemotherapy-induced emesis. Two preliminary in vitro studies using porcine skin were performed: Study 1 - effect of formulation composition on anodal co-iontophoresis of GST and MCL and Study 2 - combined anodal iontophoresis of GST (10mM) and MCL (110 mM) and cathodal iontophoresis of DEX-P (40 mM). The results from Study 1 demonstrated the dependence of GST/MCL transport on the respective drug concentrations when co-iontophoresed at 0.3 mA·cm(-2). Although they possess similar physicochemical properties, MCL seemed to be a more efficient charge carrier (JMCL=0.0591∗CMCLvs JGST=0.0414∗CGST). In Study 2, MCL permeation was markedly superior to that of GST (2324.83 ± 307.85 and 209.83 ± 24.84 μg·cm(-2), respectively); this was consistent with the difference in their relative concentrations; DEX-P permeation was 336.94 ± 71.91 μg·cm(-2). The in vivo studies in Wistar rats (10mM GST, 110 mM MCL and 40 mM DEX-P (0.5 mA·cm(-2) for 5h with Ag/AgCl electrodes and salt bridges) demonstrated that significant drug levels were achieved rapidly for each drug. This was most noticeable for dexamethasone (DEX) where relatively constant plasma levels were obtained from the 1 to 5h time-points; DEX-P was not detected in the plasma since it was completely hydrolyzed to the active metabolite. The calculated input rates in vivo (k01) for GST, MCL and DEX were 0.45 ± 0.05, 3.29 ± 0.48 and 1.97 ± 0.38 μg·cm(-2) · min(-1), respectively. The study confirmed that iontophoresis provided a controlled method for the simultaneous administration of multiple therapeutic agents and that it could be of use for poly-pharmacotherapy in general and more specifically that it was able to deliver different drugs used in the treatment of chemotherapy-induced emesis.

Palonosetron for the treatment of chemotherapy-induced nausea and vomiting

INTRODUCTION

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. The introduction of 5-hydroxytryptamine-3 (5-HT3) receptor antagonists has been a major factor in the improvement of the prevention of chemotherapy-induced acute and delayed emesis. Palonosetron , a second-generation 5-HT3 receptor antagonist with a different half-life, a different binding capacity, and a different mechanism of action than the first-generation 5-HT3 receptor antagonists appears to be the most effective agent in this drug class.

AREAS COVERED

Palonosetron's chemistry, pharmacodynamics, pharmacokinetics, metabolism, clinical efficacy, including comparison with other antiemetics, role in controlling nausea, potential role in multi-day chemotherapy and bone marrow transplantation, and overall safety are discussed.

EXPERT OPINION

The clinical data in the literature have established palonosetron as the 5-HT3 receptor antagonist of choice in terms of efficacy and safety for the prevention of CINV for patients receiving moderately or highly emetogenic chemotherapy. Three international guidelines have listed palonosetron as the preferred 5-HT3 receptor antagonist. Due to its higher efficacy, the use of palonosetron may be more cost effective compared to the generic first-generation 5-HT3 receptor antagonists. Clinical organizations' pharmacy and formulary committees should consider efficacy when making recommendations for agents for the prevention of CINV.

Aprepitant: a neurokinin-1 receptor antagonist for the treatment of chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life, and although the use of 5-hydroxytryptamine-3 (5-HT3) receptor antagonists plus dexamethasone has significantly improved the control of acute CINV, delayed nausea and vomiting remain a significant clinical problem. Aprepitant (Emend), Merck) is the first agent available in the new drug class of neurokinin-1 receptor antagonists. When added to a standard regimen of a 5-HT3 receptor antagonist and dexamethasone in patients receiving highly emetogenic chemotherapy, it improves the complete response rate of acute CINV. Aprepitant also improves the complete response of delayed CINV when used in combination with dexamethasone compared with dexamethasone alone. Based on these studies, new guidelines for the prevention of CINV have been developed for patients receiving highly emetogenic chemotherapy. The use of aprepitant in patients receiving moderately emetogenic chemotherapy will await the review and analysis of recently completed Phase III trials. Aprepitant is a substrate, a moderate inhibitor and an inducer of cytochrome P450 (CYP)3A4 and CYP2C9. Drug interactions should be monitored when aprepitant is coadministered with agents affected by CYP3A4 and CYP2C9 isoenzymes. The safety and efficacy of aprepitant has not been established in pediatric or adolescent patients, and aprepitant has not been evaluated in the treatment of patients with established nausea and vomiting. Future studies may consider the use of aprepitant with current and other new agents in moderately and highly emetogenic chemotherapy, as well in the clinical settings of multiple-day chemotherapy and bone marrow transplantation.

The multi-functional drug tropisetron binds APP and normalizes cognition in a murine Alzheimer's model

Tropisetron was identified in a screen for candidates that increase the ratio of the trophic, neurite-extending peptide sAPPα to the anti-trophic, neurite-retractive peptide Aβ, thus reversing this imbalance in Alzheimer's disease (AD). We describe here a hierarchical screening approach to identify such drug candidates, moving from cell lines to primary mouse hippocampal neuronal cultures to in vivo studies. By screening a clinical compound library in the primary assay using CHO-7W cells stably transfected with human APPwt, we identified tropisetron as a candidate that consistently increased sAPPα. Secondary assay testing in neuronal cultures from J20 (PDAPP, huAPP(Swe/Ind)) mice showed that tropisetron consistently increased the sAPPα/Aβ 1-42 ratio. In in vivo studies in J20 mice, tropisetron improved the sAPPα/Aβ ratio along with spatial and working memory in mice, and was effective both during the symptomatic, pre-plaque phase (5-6 months) and in the late plaque phase (14 months). This ameliorative effect occurred at a dose of 0.5mg/kg/d (mkd), translating to a human-equivalent dose of 5mg/day, the current dose for treatment of postoperative nausea and vomiting (PONV). Although tropisetron is a 5-HT3 receptor antagonist and an α7nAChR partial agonist, we found that it also binds to the ectodomain of APP. Direct comparison of tropisetron to the current AD therapeutics memantine (Namenda) and donepezil (Aricept), using similar doses for each, revealed that tropisetron induced greater improvements in memory and the sAPPα/Aβ1-42 ratio. The improvements observed with tropisetron in the J20 AD mouse model, and its known safety profile, suggest that it may be suitable for transition to human trials as a candidate therapeutic for mild cognitive impairment (MCI) and AD, and therefore it has been approved for testing in clinical trials beginning in 2014.

Management of chemotherapy-induced nausea and vomiting : focus on newer agents and new uses for older agents

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. The use of a combination of a serotonin 5-HT3 receptor antagonist, dexamethasone and a neurokinin 1 (NK1) receptor antagonist has significantly improved the control of acute and delayed emesis in single-day chemotherapy. Palonosetron, a second-generation 5-HT3 receptor antagonist with a different half-life, a different binding capacity and a different mechanism of action than the first-generation 5-HT3 receptor antagonists appears to be the most effective agent in its class. Aprepitant, the first and only agent clinically available in the NK1 receptor antagonist drug class has been used effectively as an additive agent to the 5-HT3 receptor antagonists and dexamethasone to control CINV. Rolapitant and netupitant are other NK1 receptor antagonists that are currently in phase III clinical trials. Despite the control of emesis, nausea has not been well controlled by current agents. Olanzapine, a US-FDA approved antipsychotic, has emerged in recent trials as an effective preventative agent for CINV, as well as a very effective agent for the treatment of breakthrough emesis and nausea. Clinical trials using gabapentin, cannabinoids and ginger have not been definitive regarding their efficacy in the prevention of CINV. Additional studies are necessary for the control of nausea and for the control of CINV in the clinical settings of multiple-day chemotherapy and bone marrow transplantation.

Evaluating the role of the alpha-7 nicotinic acetylcholine receptor in the pathophysiology and treatment of schizophrenia

The group of schizophrenia disorders affects approximately 1% of the population and has both genetic and environmental etiologies. Sufferers report various behavioral abnormalities including hallucinations and delusions (positive symptoms), reduced joy and amotivation (negative symptoms), plus inattention and poor learning (cognitive deficits). Despite the heterogeneous symptoms experienced, most patients smoke. The self-medication hypothesis posits that patients smoke to alleviate symptoms, consistent with evidence for nicotine-induced enhancement of cognition. While nicotine acts on multiple nicotinic acetylcholine receptors (nAChRs), the primary target of research is often the homomeric α7 nAChR. Given genetic linkages between schizophrenia and this receptor, its association with P50 sensory gating deficits, and its reduced expression in post-mortem brains, many have attempted to develop α7 nAChR ligands for treating schizophrenia. Recent evidence that ligands can be orthosteric agonists or positive allosteric modulators (PAMs) has revitalized the hope for treatment discovery. Herein, we present evidence regarding: (1) pathophysiological alterations of α7 nAChRs that might occur in patients; (2) mechanistic evidence for the normal action of α7 nAChRs; (3) preclinical studies using α7 nAChR orthosteric agonists and type I/II PAMs; and (4) where successful translational testing has occurred for particular compounds, detailing what is still required. We report that the accumulating evidence is positive, but that greater work is required using positron emission tomography to understand current alterations in α7 nAChR expression and their relationship to symptoms. Finally, cross-species behavioral tasks should be used more regularly to determine the predictive efficacy of treatments.

Protective effect of tropisetron on rodent hepatic injury after trauma-hemorrhagic shock through P38 MAPK-dependent hemeoxygenase-1 expression

Tropisetron can decrease inflammatory cell responses and alleviate organ damage caused by trauma-hemorrhage, but the mechanism of these effects remains unknown. The p38 mitogen-activated protein kinase/hemeoxygenase-1 (p38 MAPK/HO-1) pathway exerts anti-inflammatory effects on different tissues. The aim of this study was to investigate whether p38 MAPK/HO-1 plays any role in the tropisetron-mediated attenuation of hepatic injury after trauma-hemorrhage. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure maintained at approximately 35–40 mmHg for 90 min), followed by fluid resuscitation. During resuscitation, several treatment regimens were administered: four doses of tropisetron alone (0.1, 0.3, 1, 3 mg/kg body weight), or a single dose of tropisetron (1 mg/kg body weight) with and without a p38 MAPK inhibitor (SB-203580, 2 mg/kg body weight) or HO antagonist (chromium-mesoporphyrin, 2.5 mg/kg body weight). Various parameters were measured, and the animals were sacrificed at 24 h post-resuscitation. The results showed that trauma-hemorrhage increased the following parameters: plasma concentrations of aspartate (AST) and alanine aminotransferases (ALT), hepatic myeloperoxidase (MPO) activity, and levels of cytokine-induced neutrophil chemoattractant-1 and -3 (CINC-1 and CINC-3), intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein-1α (MIP-1α). These parameters were significantly improved in the tropisetron-treated rats subjected to trauma-hemorrhage. Tropisetron treatment also increased hepatic p38 MAPK and HO-1 expression compared with vehicle-treated trauma-hemorrhaged rats. Co-administration of SB-203580 or chromium-mesoporphyrin with tropisetron abolished the tropisetron-induced beneficial effects on the above parameters and hepatic injury. These results suggest that the protective effect of tropisetron administration on alleviation of hepatic injury after trauma-hemorrhage is likely mediated through p38 MAPK-dependent HO-1 expression.

Tropisetron attenuates cardiac injury in a rat trauma-hemorrhage model

Tropisetron is widely used for antiemesis. Recent evidence shows that tropisetron possesses anti-inflammatory properties. Protein kinase B (Akt) is known to play an important role in negating proinflammatory response in injury. The aim of this study was to determine whether tropisetron provides cardioprotection mediated via an Akt-dependent pathway in trauma-hemorrhaged animals. Male Sprague-Dawley rats underwent trauma-hemorrhage and resuscitation. Tropisetron (1 mg/kg) with or without a PI3K inhibitor (wortmannin, 1 mg/kg) or vehicle was administered intravenously during the resuscitation. At 24 h after either the trauma-hemorrhage or sham operation, the cardiac function parameters (cardiac output, left ventricle pressure variability) were measured. Cardiac myeloperoxidase activity, interleukin 6 and intercellular adhesion molecule 1 levels, Akt activity, and apoptosis were measured. One-way analysis of variance and Tukey test were used for statistical analysis. Cardiac function was depressed and cardiac myeloperoxidase activity, interleukin 6 and intercellular adhesion molecule 1 levels, and cardiac apoptosis were markedly increased after trauma-hemorrhage. Administration of tropisetron significantly improved cardiac function and proinflammatory parameters in the tropisetron-treated rats subjected to trauma-hemorrhage. The increase in cardiac apoptosis was attenuated in rats that received tropisetron. Although trauma-hemorrhage decreased cardiac Akt phosphorylation (p-Akt), tropisetron treatment prevented the same decrease in cardiac p-Akt following trauma-hemorrhage. Coadministration of wortmannin prevented the beneficial effects of tropisetron on the attenuation of proinflammatory responses and cardiac injury after trauma-hemorrhage. Tropisetron attenuates cardiac injury following trauma-hemorrhage, which is, at least in part, through Akt-dependent anti-inflammatory pathway.

The role of the α7 nicotinic receptor in cognitive processing of persons with schizophrenia

PURPOSE OF REVIEW

Cognitive abilities are established as major deficits in those with schizophrenia and represent significant impediments toward successful psychosocial functioning within the community. Pharmacological treatments have historically focused on reducing the positive and negative symptoms of schizophrenia, with recent increased attention to developing agents to improve cognition as a treatment outcome. This review will highlight the recent advances in developing agents that act at neuronal α7 nicotinic acetylcholine receptors (nAChRs).

RECENT FINDINGS

A number of agents have demonstrated improvements in cognitive deficits in studies using both preclinical and clinical models. Evidence suggests that α7 nAChR activation impacts rule acquisition and initial learning in preclinical models. Preclinical studies indicate improved spatial working memory and reversal of phencyclidine-induced learning and memory deficits. Clinical studies indicate normalization of neuronal default network activity using functional magnetic resonance imaging methods. In addition, research on new agents developed to improve cognition suggests improved cognitive functioning in multiple domains (e.g., attention, memory, executive functioning, sensory gating and overall cognition) and promising safety profiles of additional agents.

SUMMARY

Improvements in cognitive functioning within preclinical and clinical studies of schizophrenia are evident through the use of α7 nAChR agonists, while positive allosteric modulators may gain increased attention in the future.

Occupancy of α7 Nicotinic Acetylcholine Receptors in the Brain by Tropisetron: A Positron Emission Tomography Study Using [(11)C]CHIBA-1001 in Healthy Human Subjects

OBJECTIVE

Agonists of α7-nicotinic acetylcholine receptors (nAChRs) have been developed as potential therapeutic drugs for neuropsychiatric diseases such as schizophrenia and Alzheimer's disease. Positron emission tomography (PET) is a noninvasive brain imaging technique to measure receptor occupancy in the living human brain. Although much effort has been expended to create specific PET radioligands for α7-nAChRs in the brain, only 4-[(11)C]methylphenyl-1,4-diazabicyclo[3.2.2.]nonane-4-carboxylate ([(11)C]CHIBA-1001) is currently available for clinical studies. In contrast, two 5-hydroxytryptamine-3 (5-HT(3)) receptor antagonists, tropisetron and ondansetron, have been used to treat patients with chemotherapy-induced or postoperative nausea and vomiting. Furthermore, tropisetron, but not ondansetron, possesses high affinity for α7-nAChRs. In the present study, we evaluated the receptor occupancy in the human brain after a single oral administration of tropisetron and ondansetron using [(11)C]CHIBA-1001 and PET.

METHODS

Two serial dynamic PET scans using [(11)C]CHIBA-1001 in healthy non-smoking male subjects were performed before and after receiving an oral administration of these medications.

RESULTS

A single oral administration of tropisetron, but not ondansetron, decreased the total distribution volume of [(11)C]CHIBA-1001 in the human brain.

CONCLUSION

This study shows that tropisetron, but not ondansetron, could bind to α7-nAChRs in the human brain after a single oral administration. Therefore, [(11)C]CHIBA-1001 may be a useful PET radioligand to measure the occupancy of α7-nAChRs in the human brain.

α7 Nicotinic acetylcholine receptors in the central amygdaloid nucleus alter naloxone-induced withdrawal following a single exposure to morphine

RATIONALE

Negative motivational withdrawal from acute opiate dependence was induced by an opioid antagonist, and the withdrawal signs prevented by pretreatment with nicotine.

OBJECTIVES

The present study was undertaken to examine the mechanism of nicotine-induced attenuation of withdrawal precipitated by naloxone in rats administered a single dose of morphine.

METHODS

Conditioned place aversion (CPA) was precipitated by naloxone in rats exposed once to morphine. Nicotinic acetylcholine receptor (nAChR) agonists were microinjected into the central amygdaloid nucleus (CeA) before naloxone was administered. Additionally, c-Fos expression in the amygdala was measured in rats exposed to α7 nAChR ligands.

RESULTS

The microinjection of nicotine (0.3 and 1.0 μg/μl) into the CeA dose-dependently inhibited naloxone-induced CPA. This inhibition of CPA was reversed by methyllycaconitine (MLA), an α7 nAChR antagonist. CPA was also significantly attenuated by the microinjection of tropisetron (3.0 μg/μl), an α7 nAChR agonist and 5-hydroxytriptamine 3 (5-HT(3)) receptor antagonist, but not by ondansetron (1.0 and 3.0 μg/μl), a 5-HT(3) receptor antagonist. The microinjection of PNU-282987 (3.0 μg/μl), a selective α7 nAChR agonist, into the CeA also inhibited CPA. Furthermore, nicotine increased c-Fos expression in the CeA, but not the medial or basolateral amygdaloid nucleus. The increase of c-Fos in the CeA was significantly inhibited by MLA.

CONCLUSION

Nicotine-induced attenuation of CPA precipitated by naloxone is mediated by the α7 nAChR subtype, and the CeA is one of the regions of the brain involved in the effect of nicotine on acutely opiate-dependent subjects.

Fibromyalgia: diagnosis and treatment options

BACKGROUND

Fibromyalgia is a widespread, chronic pain disorder that includes a complex constellation of somatic and emotional symptoms. Controlled clinical trials for both medication and nonmedication therapies have led to sound, evidence-based recommendations for the care of patients with fibromyalgia.

OBJECTIVE

This review article was designed to provide updated information from database literature searches on fibromyalgia epidemiology, including gender differences, psychological comorbidity, and treatment with medication and nonmedication therapies.

METHODS

A literature review was performed by identifying fibromyalgia articles published in English from January 2000 to October 2008 using the PubMed and EMBASE databases. Search terms included fibromyalgia, exercise, gender, nonpharmacologic, placebo-controlled, randomized, and treatment.

RESULTS

New epidemiologic data support important differences in fibromyalgia symptom severity between the sexes and the important role of comorbid psychological distress. Physicians diagnose fibromyalgia in women at an approximately 3- to 6-fold rate compared with men. Well-conducted clinical trials and recently published treatment guidelines reinforce effective treatment with medication and nonpharmacologic therapy. The strongest evidence suggests effective treatment of fibromyalgia with duloxetine and milnacipran. Studies also report efficacy with gabapentin, pramipexole, pregabalin, tramadol, and IV tropisetron. Nonpharmacologic treatments should include fitness and strengthening exercise, as well as warm-water therapy and psychological pain management techniques.

CONCLUSIONS

Fibromyalgia is a common, disabling, chronic pain condition that predominantly affects women. Symptoms can be effectively treated using both drug and nondrug therapies. In general, treatment benefits in fibromyalgia appear largely independent of patient sex.

Palonosetron for the prevention of chemotherapy-induced nausea and vomiting in patients with cancer

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles and patient characteristics (e.g., female gender, younger age, low alcohol consumption and history of motion sickness) are the major risk factors for CINV. This article provides a detailed description of palonosetron, a second-generation 5-hydroxytryptamine-3 (5-HT3) receptor antagonist, which has been approved for the prevention of acute CINV in patients receiving either moderately or highly emetogenic chemotherapy and for the prevention of delayed CINV in patients receiving moderately emetogenic chemotherapy. In recent studies, compared with the first-generation 5-HT3 receptor antagonists, palonosetron in combination with dexamethasone demonstrated better control of delayed CINV in patients receiving highly emetogenic chemotherapy and had a similar safety profile. Owing to its efficacy in controlling both acute and delayed CINV, palonosetron may be very effective in the clinical setting of multiple-day chemotherapy and bone marrow transplantation.

A randomised, double-blind, placebo-controlled trial of tropisetron in patients with schizophrenia

BACKGROUND

Cognitive deficits in schizophrenia are associated with psychosocial deficits that are primarily responsible for the poor long-term outcome of this disease. Auditory sensory gating P50 deficits are correlated with neuropsychological deficits in attention, one of the principal cognitive disturbances in schizophrenia. Our studies suggest that the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) agonist tropisetron might be a potential therapeutic drug for cognitive deficits in schizophrenia. Therefore, it is of particular interest to investigate the effects of tropisetron on the cognitive deficits in patients with schizophrenia.

METHODS

A randomised, placebo-controlled trial of tropisetron in patients with schizophrenia was performed. A total of 40 patients with chronic schizophrenia who had taken risperidone (2 to 6 mg/day) were enrolled. Subjects were randomly assigned to a fixed titration of tropisetron (n = 20, 10 mg/day) or placebo (n = 20) in an 8-week double-blind trial. Auditory sensory gating P50 deficits and Quality of Life Scale (QLS), Cambridge Neuropsychological Test Automated Battery (CANTAB), and Positive and Negative Syndrome Scale (PANSS) scores were measured.

RESULTS

In all, 33 patients completed the trial. Tropisetron was well tolerated. Administration of tropisetron, but not placebo, significantly improved auditory sensory gating P50 deficits in non-smoking patients with schizophrenia. The score on the rapid visual information processing (sustained visual attention) task of CANTAB was significantly improved by tropisetron treatment. Total and subscale scores of PANSS were not changed by this trial. QLS scores in the all patients, but not non-smoking patients, were significantly improved by tropisetron trial.

CONCLUSIONS

This first randomised, double-blind, placebo-controlled trial supports the safety and efficacy of adjunctive tropisetron for treatment of cognitive deficits in schizophrenia.

Palonosetron for the prevention of chemotherapy-induced nausea and vomiting: approval and efficacy

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient characteristics (female gender, younger age, low alcohol consumption, history of motion sickness) are the major risk factors for CINV. This review provides a detailed description of palonosetron, a second-generation 5-hydroxytryptamine 3 (5-HT(3)) receptor antagonist. The chemistry and pharmacology of palonosetron are described, as well as the initial and recent clinical trials. Palonosetron has a longer half-life and a higher binding affinity than the first-generation 5-HT(3) receptor antagonists. Palonosetron has been approved for the prevention of acute CINV in patients receiving either moderately or highly emetogenic chemotherapy and for the prevention of delayed CINV in patients receiving moderately emetogenic chemotherapy. In recent studies, compared to the first-generation 5-HT(3) receptor antagonists, palonosetron in combination with dexamethasone demonstrated better control of delayed CINV in patients receiving highly emetogenic chemotherapy. There were no clinically relevant adverse reactions reported in the palonosetron clinical trials which were different from the common reactions reported for the 5-HT(3) receptor antagonist class. Due to its efficacy in controlling both acute and delayed CINV, palonosetron may be very effective in the clinical setting of multiple-day chemotherapy and bone marrow transplantation.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Ondansetron results in improved auditory gating in DBA/2 mice through a cholinergic mechanism

The 5-HT(3) receptor antagonist, ondansetron, has been shown to correct the auditory gating deficit in medicated schizophrenia patients. Inhibition of 5-HT(3) receptors releases acetylcholine, the endogenous ligand for nicotinic acetylcholine receptors. The schizophrenia-related auditory gating deficit is modulated, in part, by nicotinic acetylcholine receptors, as is the mouse (DBA/2) model of the deficit. The present study assessed the effects of both acute and chronically administered ondansetron on auditory gating in DBA/2 mice. Auditory gating is defined as a decrease in amplitude of response to the second of a paired identical auditory stimulus presented 0.5 s following an initial auditory stimulus. Acute ondansetron administration at the lowest dose (0.1 mg/kg, IP) tested had no effect, while other doses (0.33 and 1 mg/kg, IP) produced improvements in auditory gating. The improvements were produced through both an increase in response to the first auditory stimulus and a decrease in the response to the second auditory stimulus. Co-administration of an alpha7 nicotinic acetylcholine receptor antagonist, alpha-bungarotoxin, or the alpha4beta2 nicotinic acetylcholine receptor antagonist dihydro-beta-erythroidine, with the 0.33 mg/kg dose of ondansetron blocked the improvement in auditory gating produced by ondansetron alone. There was no difference in response between the chronically injected mice and naive mice. Both showed improved auditory gating, thus, demonstrating no "carry over" effect of daily injections. These data demonstrate that indirect stimulation of nicotinic acetylcholine receptors by ondansetron can improve auditory gating parameters in DBA/2 mice.

Antiemetic control: toward a new standard of care for emetogenic chemotherapy

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. 5-hydroxytryptamine-3 (5-HT(3)) receptor antagonists plus dexamethasone have significantly improved the control of acute CINV, but delayed CINV remains a significant clinical problem. Two new agents, palonosetron and aprepitant, have been approved for the prevention of both acute and delayed CINV. Palonosetron is a second-generation 5-HT(3) receptor antagonist with a longer half-life and a higher binding affinity than first-generation 5-HT(3) receptor antagonists. Aprepitant is the first agent available in the new drug class of neurokinin-1 (NK-1) receptor antagonists. Casopitant is another NK-1 receptor antagonist that is under review by the FDA after recent completion of Phase III clinical trials. The introduction of these new agents has generated revised antiemetic guidelines for the prevention of CINV. Future studies may consider the use of palonosetron, aprepitant and casopitant with other antiemetic agents (olanzapine, gabapentin, cannabinoids) in moderately and highly emetogenic chemotherapy, as well as in the clinical settings of multiple-day chemotherapy and bone marrow transplantation.

Tropisetron attenuates naloxone-induced place aversion in single-dose morphine-treated rats: role of alpha7 nicotinic receptors

We have previously reported that acute dependence can occur when naloxone is administered 24 h after even a single dose of morphine, and that nicotine attenuates this naloxone-precipitated withdrawal syndrome. In the present study, we studied the effect of tropisetron, an alpha7 nicotinic receptor agonist and 5-hydroxytryptamine 3 (5-HT(3)) receptor antagonist, on place aversion induced by naloxone in morphine-treated rats. Place aversion was significantly attenuated by pre-administered tropisetron (1.0 and 2.0 mg/kg, i. p.) in a dose-dependent manner, however tropisetron alone had no effect in a place-conditioning paradigm. This attenuation was completely antagonized by mecamylamine (1.0 mg/kg, s.c.), which is a central nicotinic receptor antagonist, but not by ondansetron (0.3 and 1.0 mg/kg, s.c.), a 5-HT(3) receptor antagonist. Furthermore, methyllycaconitine (1.0 and 2.0 mg/kg, s.c.), an alpha7 nicotinic acetylcholine receptor antagonist, but not dihydroxy-beta-erithroidine (1.0 and 2.0 mg/kg, s.c.), an alpha4beta2 nicotinic acetylcholine receptor antagonist, also antagonized the inhibitory effect of tropisetron. These findings suggest that tropisetron attenuates place aversion induced by naloxone in single-dose morphine-treated rats via alpha7 nicotinic receptors.

Acetaminophen reinforces descending inhibitory pain pathways

The mechanism of the analgesic action of acetaminophen involves the serotonergic system. This study explores how acetaminophen interferes with serotonergic descending pain pathways. Eighteen rapid metabolizers of tropisetron were included in this double-blind cross-over study. After ethical approval, the healthy volunteers took 1 g oral acetaminophen (A) or placebo (p) combined with either the 5-HT3 antagonist tropisetron (T) (5 mg) or saline, intravenously, at weekly intervals. Mechanical pain thresholds, determined before and after a cold pressor test (CPT), were repeated seven times during the three post-dosing hours, and area under the concentration-time curves (AUCs) of the three treatments were compared. After CPT, AUC (%*min) of Ap (1,561+/-429) was larger than before CPT (393+/-382, P<0.05); these effects were totally inhibited by tropisetron. Acetaminophen reinforces descending inhibitory pain pathways; it suggests a supraspinal target for acetaminophen's antinociceptive action. This study also confirmed that there is a central serotonergic mechanism of action for acetaminophen that is not stimulus-dependent.

Systemic anticancer therapy in gynecological cancer patients with renal dysfunction

Chronic kidney disease is a common occurrence in patients with gynecological cancer. Systemic anticancer treatment in such patients is a challenge for clinicians because of altered drug pharmacokinetics. For those drugs that are excreted mainly by the kidneys, decreased renal function may lead to increased systemic exposure and increased toxicity. Dose adjustment based on pharmacokinetic changes is required in this situation to avoid life-threatening toxicity. In this review, we summarize the nephrotoxicity and pharmacokinetic data of agents commonly used in systemic anticancer treatment of gynecological cancers and dose adjustment guidelines in the presence of impaired renal function. We review 17 medications that need dose adjustment (cisplatin, carboplatin, doxorubicin, epirubicin, cyclophosphamide, ifosfamide, topotecan, irinotecan, etoposide, capecitabine, bleomycin, methotrexate, actinomycin D, granulocyte-macrophage colony-stimulating factor, metoclopramide, cimetidine, and diphenhydramine) as well as 27 drugs that do not (paclitaxel, docetaxel, pegylated liposomal doxorubicin, gemcitabine, oxaliplatin, fluorouracil, vincristine, letrozole, anastrozole, tamoxifen, leuprorelin, megestrol, gefitinib, erlotinib, trastuzumab, leucovorin, granulocyte colony-stimulating factor, erythropoietin, ondansetron, granisetron, palonosetron, tropisetron, dolasetron, aprepitant, dexamethasone, lorazepam, and diazepam). We also review the formulae commonly used to estimate creatinine clearance, including Cockcroft-Gault, Chatelut, Jelliffe, Wright, and the Modification of Diet in Renal Disease study formulae.

Determination of tropisetron in human plasma by high performance liquid chromatographic method with UV detection and its application to a bioequivalence study

A simple and sensitive high performance liquid chromatography method with UV detection was described for the determination of tropisetron in human plasma. The prepared sample solution was injected onto BDS-C(8) reversed column using a mixture of ammonium acetate (100 mM, PH adjusted to 4.3 with glacial acetic acid) and acetonitrile (80:20, v/v) as mobile phase. The wavelength of UV detector was set at 285 nm. No interference from any endogenous substances was observed during the elution of tropisetron and internal standard (ondansetron hydrochloride). The lower limit of quantification was evaluated to be 1 ng/mL. The method was used in a randomized crossover bioequivalence study of two different tropisetron preparations in 20 healthy volunteers.

Palonosetron: a second-generation 5-hydroxytryptamine receptor antagonist

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles and patient risk factors (female gender, younger age, alcohol consumption, history of motion sickness) are the major risk factors for CINV. The use of 5-hydroxytryptamine (5-HT)3 receptor antagonists plus dexamethasone has significantly improved the control of acute CINV, but delayed nausea and vomiting remains a clinical problem. A new agent, palonosetron, has recently been approved for the prevention of acute CINV in patients receiving either moderately or highly emetogenic chemotherapy and for the prevention of delayed CINV in patients receiving moderately emetogenic chemotherapy. Palonosetron is a 5-HT3 receptor antagonist with a longer half-life and a higher binding affinity than first-generation 5-HT3 receptor antagonists. In a single dosing study, palonosetron was highly effective in controlling CINV compared with a single dose of dolasetron or ondansetron in patients receiving moderately emetogenic chemotherapy. Palonosetron in combination with dexamethasone demonstrated control of CINV in patients receiving highly emetogenic chemotherapy. Palonosetron appeared to be as effective in subsequent courses of chemotherapy compared with the initial course of chemotherapy. There were no clinically relevant differences seen among palonosetron, ondansetron or dolasetron in laboratory, electrocardiographic or vital-sign changes, and adverse reactions reported in the clinical trials were the most common reactions reported for the 5-HT3 receptor antagonist class. Recent studies using palonosetron-based anti-emetic combinations in moderately and highly emetogenic chemotherapy, as well as in the clinical setting of multiple-day chemotherapy, have been reported. Future studies may consider the use of palonosetron with current and other new agents and in other clinical settings, such as bone marrow transplantation and radiation therapy.

Dual role of 5-HT3 receptors in a rat model of delayed stress-induced visceral hyperalgesia

Despite its beneficial effect in IBS patients, the mechanism of action of the 5-HT3 receptor (5-HT3R) antagonist alosetron is still incompletely understood. We aimed to characterize the effect and site(s) of action in a model of stress-induced sensitization of visceral nociception in rats. Adult male Wistar rats were equipped for recording of visceromotor response (VMR) to phasic colorectal distension (CRD; 10-60 mmHg). VMR to CRD was recorded 24 h after an acute session of water avoidance (WA) stress (post-WA). Baseline and post-WA responses were measured in rats exposed to WA or sham-WA, treated with alosetron at 0.3 mg/kg subcutaneously (s.c.) 25 nmol intrathecally (i.t.) or vehicle before post-WA CRD. Some rats were treated with capsaicin/vehicle on the cervical vagus nerve and received alosetron (0.3 mg/kg, s.c.) 15 min before post-WA CRD. WA stress led to visceral hyperalgesia 24 h later. Alosetron (0.3 mg/kg, s.c.), failed to inhibit WA-induced exacerbation of VMR to CRD. Stress-induced visceral hyperalgesia was abolished when alosetron was injected intrathecally (P<0.05) in intact rats or subcutaneously (0.3 mg/kg) in capsaicin-pretreated animals (P<0.05). Capsaicin-pretreatment did not affect the exacerbating effect of stress on visceral sensitivity. Alosetron had no inhibitory effect on normal visceral pain responses when administered subcutaneously or intrathecally. We demonstrated that 5-HT3Rs on central terminals of spinal afferents are engaged in the facilitatory effect of stress on visceral sensory information processing. In addition, we showed that stress-induced sensitization of visceral nociception is independent of 5-HT3R activation on vagal afferents.

Phencyclidine-induced cognitive deficits in mice are improved by subsequent subchronic administration of tropisetron: Role of α7 nicotinic receptors

We examined the effects of tropisetron, a 5-hydroxytryptamine (5-HT(3)) receptor antagonist and alpha7 nicotinic receptor agonist, on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were significantly improved by subsequent subchronic (2 weeks) administration of tropisetron, but not ondansetron. Effects of tropisetron were significantly antagonized by co-administration of the alpha7 nicotinic receptor antagonist methyllycaconitine, suggesting the role of alpha7 nicotinic receptors in the active mechanisms of tropisetron. These findings suggest that tropisetron could be a potential therapeutic drug for cognitive deficits in schizophrenic patients.

Anti-emetic prophylaxis with oral tropisetron and/or dexamethasone

BACKGROUND

The corticosteroid dexamethasone and the serotonine3 -antagonist tropisetron are both effective drugs for the prophylaxis of post-operative nausea and vomiting (PONV) when given intravenously. The aim of this trial was to evaluate the oral use of both drugs as part of a routine oral premedication and to compare their single and combined effectiveness.

MATERIALS AND METHODS

In this randomized, placebo-controlled, double-blind study, 320 inpatients with a moderate-high risk of PONV (> or = 40% according to two validated risk scores) received an oral premedication 1-2 h pre-operatively with placebo, a fixed dose of tropisetron 5 mg, dexamethasone 8 mg, or a combination of both drugs. A standardized general anaesthesia was performed, including benzodiazepine premedication, propofol, rocuronium, desflurane in air/O2, fentanyl or sufentanil followed by a continuous infusion of remifentanil. Post-operative analgesia and anti-emetic rescue medication were standardized. The main outcome measures were the severity of PONV within the first 24 h (rated by a standardized scoring algorithm). The incidence of PONV was used as the secondary outcome.

RESULTS

Data from 310 patients were analyzed. The mean severity score in the placebo-, tropisetron-, dexamethasone- and the combined-groups was 1.37, 0.8, 0.8 and 0.38, respectively. The incidence of PONV of any severity was 59.2%, 37.5%, 40% and 22.8%, respectively. The reduction of the incidence and the severity of PONV were statistically significant with all three interventions. Results from additional analyses suggested that both drugs were equally effective and that there was a simple additive effect of tropisetron and dexamethasone compared with placebo.

CONCLUSION

Oral tropisetron and dexamethasone were both equally effective in reducing the severity and incidence of post-operative nausea and vomiting. The latter could be reduced by approximately 35% in a population of moderate-high risk for PONV. Both drugs had an additive effect. However, even in the combination group there still remained an unacceptably high incidence of PONV of more than 20%. This highlighted the need for a multimodal anti-emetic approach in high-risk patients and the importance of treatment of PONV.

Early vs late intraoperative administration of tropisetron for the prevention of nausea and vomiting in children undergoing tonsillectomy and/or adenoidectomy

BACKGROUND

Tropisetron is a long-acting 5HT3 receptor antagonist and was shown to be effective in the prevention of postoperative nausea and vomiting (PONV) after tonsillectomy. The aim of the study was to compare the effects of early vs late intraoperative administration of tropisetron with regard to prevention of PONV during the first 48 h after extubation.

METHODS

In a randomized double-blind study, we investigated 120 children aged 1-12 years undergoing general anesthesia for tonsillectomy or adenotonsillectomy. Patients received 0.1 mg x kg(-1) tropisetron (maximum 2 mg) immediately after inhalational induction (early) and establishment of intravenous access or after the end of surgery before extubation (late). PONV and the need for antiemetic rescue medications were recorded within the following 48 h. Patient data were analyzed using t-test, chi-squared test (significance level of alpha = 0.05) and Spearman rank correlation test.

RESULTS

The overall incidence of vomiting was 55.3%, with 60% (36/60) in the early treatment and 51.6% (31/60) in the late treatment group (P = 0.46). The observed time course 48 h postoperatively showed no difference regarding the number of vomiting episodes between the two groups and the need for antiemetic rescue medication. The incidence of nausea was higher in the late application group in the first 6 h after extubation (P = 0.001) and higher in the early application group between 24 and 48 h after extubation (P = 0.02). Morphine and the age over 3 years had a strong influence on the incidence of vomiting.

CONCLUSION

The intraoperative time point (early vs late) of intravenous administration of a single prophylactic dose of tropisetron has no impact on the incidence of PONV during the first 48 h after tonsillectomy and/or adenoidectomy in children.

Emerging drugs for chemotherapy-induced emesis

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles and patient risk factors (female gender, younger age, no alcohol consumption, history of motion sickness) are the major risk factors for CINV. The use of 5-hydroxytryptamine-3 (5-HT3) receptor antagonists plus dexamethasone has significantly improved the control of acute CINV, but delayed nausea and vomiting remains a significant clinical problem. Two new agents, palonosetron and aprepitant, have recently been approved for the prevention of both acute and delayed CINV. Palonosetron is a 5-HT3 receptor antagonist with a longer half-life and a higher binding affinity than first-generation 5-HT3 receptor antagonists. Aprepitant is the first agent available in the new drug class of neurokinin-1 receptor (NK-1) antagonists. There are a number of 5-HT3 receptor antagonists and NK-1 receptor antagonists currently in Phase II and III clinical trials. Revised antiemetic guidelines for the prevention of CINV are reviewed. Future studies may consider the use of palonosetron and aprepitant with current and other new agents (olanzapine, gabapentin) in moderately and highly emetogenic chemotherapy, as well as in the clinical settings of multiple-day chemotherapy and bone marrow transplantation.

Tropisetron improves deficient inhibitory auditory processing in DBA/2 mice: role of alpha 7 nicotinic acetylcholine receptors

RATIONALE

Deficient inhibitory processing of the P50 auditory evoked potential is a pathophysiological feature of schizophrenia. Several lines of evidence suggest that alpha 7 nicotinic receptors play a critical role in this phenomenon. Similar to schizophrenic patients, DBA/2 mice spontaneously exhibit a deficit in inhibitory processing of the P20-N40 auditory evoked potential, which is thought to be a rodent analog of the human P50 auditory evoked potential.

OBJECTIVE

The present study was undertaken to examine whether tropisetron, a partial agonist at alpha 7 nicotinic receptors and an antagonist at 5-hydroxytryptamine-3 receptors, improves this deficit in DBA/2 mice.

RESULTS

Administration of tropisetron (1 mg/kg i.p.) significantly improved the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice. Coadministration of methyllycaconitine (MLA; 3 mg/kg i.p.), a partially selective antagonist at alpha 7 nicotinic receptors, significantly blocked the normalizing effect of tropisetron. Furthermore, MLA alone did not alter the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice.

CONCLUSIONS

The data suggest that tropisetron improves the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice by effects on alpha 7 and perhaps alpha 4 beta 2 nicotinic receptors. Tropisetron may be useful for the treatment of deficient inhibitory processing in schizophrenia.

WIN 55,212-2-induced reduction of cocaine hyperlocomotion: Possible inhibition of 5-HT3 receptor function

We examined the effect of WIN 55,212-2 (an agonist of cannabinoid receptors) and its enantiomer WIN 55,212-3, as well as of ondansetron (an antagonist of serotonin (5-HT)(3) receptors) on the cocaine-induced locomotor hyperactivity in rats. WIN 55,212-2, but not WIN 55,212-3, in doses of 3 and 6 mg/kg which did not affect the basal locomotor activity, dose-dependently reduced the hyperactivation evoked by cocaine. The inhibitory effect of WIN 55,212-2 was not affected by rimonabant (an antagonist of cannabinoid receptors). Like in the case of WIN 55,212-2, the cocaine-induced hyperlocomotion was reduced in a dose-dependent manner by ondansetron (0.03-0.3 mg/kg). The obtained results indicate that the inhibitory effect of WIN 55,212-2 on cocaine hyperactivation is stereoselective and is not mediated by cannabinoid receptors. Moreover, together with the literature data they may suggest that this effect of WIN 55,212-2 involves inhibition of the 5-HT(3) receptor function.