5-HT3 receptor antagonists: differences and similarities

Single-dose palonosetron and dexamethasone in preventing nausea and vomiting induced by moderately emetogenic chemotherapy in breast and colorectal cancer patients

Aims and background

Palonosetron, a unique second-generation 5-HT3 receptor antagonist, has been demonstrated to control emesis related to chemotherapy-induced nausea and vomiting (CINV). The aim of this study was to evaluate the efficacy and tolerability of palonosetron followed by a single dose of dexamethasone in patients with breast cancer (BC) or colorectal cancer (CRC) receiving moderate emetogenic chemotherapy (MEC).

Methods and study design

Chemotherapy-naive BC and CRC patients were given MEC as adjuvant or first-line treatment. Palonosetron (0.25 mg IV) and dexamethasone (8 mg IV) were administered before chemotherapy on day 1. The primary endpoint was complete response (CR; no vomiting and no use of rescue medication) during the overall study period (days 1–5). The antiemetic response was evaluated during the acute (day 1) and delayed (days 2–5) phases.

Results

Sixty-eight patients were enrolled (median age 61 years, 56 females; BC = 40, CRC = 28). CR was observed in 46 of 68 patients (67.6%), while CR during the acute and delayed phases was 75.0% in each cancer group. The antiemetic regimen was well tolerated.

Conclusions

A single administration of palonosetron and dexamethasone on day 1 in BC and CRC patients adequately controls CINV during the entire period of emetic risk.

In silico investigation into the interactions between murine 5-HT3 receptor and the principle active compounds of ginger (Zingiber officinale)

Gingerols and shogaols are the primary non-volatile actives within ginger (Zingiber officinale). These compounds have demonstrated in vitro to exert 5-HT3 receptor antagonism which could benefit chemotherapy-induced nausea and vomiting (CINV). The site and mechanism of action by which these compounds interact with the 5-HT3 receptor is not fully understood although research indicates they may bind to a currently unidentified allosteric binding site. Using in silico techniques, such as molecular docking and GRID analysis, we have characterized the recently available murine 5-HT3 receptor by identifying sites of strong interaction with particular functional groups at both the orthogonal (serotonin) site and a proposed allosteric binding site situated at the interface between the transmembrane region and the extracellular domain. These were assessed concurrently with the top-scoring poses of the docked ligands and included key active gingerols, shogaols and dehydroshogaols as well as competitive antagonists (e.g. setron class of pharmacologically active drugs), serotonin and its structural analogues, curcumin and capsaicin, non-competitive antagonists and decoys. Unexpectedly, we found that the ginger compounds and their structural analogs generally outscored other ligands at both sites. Our results correlated well with previous site-directed mutagenesis studies in identifying key binding site residues. We have identified new residues important for binding the ginger compounds. Overall, the results suggest that the ginger compounds and their structural analogues possess a high binding affinity to both sites. Notwithstanding the limitations of such theoretical analyses, these results suggest that the ginger compounds could act both competitively or non-competitively as has been shown for palonosetron and other modulators of CYS loop receptors.

Translational utility of rodent hippocampal auditory gating in schizophrenia research: a review and evaluation

Impaired gating of the auditory evoked P50 potential is one of the most pharmacologically well-characterized features of schizophrenia. This deficit is most commonly modeled in rodents by implanted electrode recordings from the hippocampus of the rodent analog of the P50, the P20-N40. The validity and effectiveness of this tool, however, has not been systematically reviewed. Here, we summarize findings from studies that have examined the effects of pharmacologic modulation on gating of the rodent hippocampal P20-N40 and the human P50. We show that drug effects on the P20-N40 are highly predictive of human effects across similar dose ranges. Furthermore, mental status (for example, anesthetized vs alert) does not appear to diminish the predictive capacity of these recordings. We then discuss hypothesized neuropharmacologic mechanisms that may underlie gating effects for each drug studied. Overall, this review supports continued use of hippocampal P20-N40 gating as a translational tool for schizophrenia research.

Cisplatin : an old drug with a newfound efficacy -- from mechanisms of action to cytotoxicity

INTRODUCTION

Cisplatin is a highly effective antineoplastic drug with an extremely current mechanism of action. Cisplatin-induced side effects are dose-dependent and limit the administration of increased dosages, thus compromising its therapeutic efficacy.

AREAS COVERED

This review aims to describe the emerging knowledge about the biochemical mechanisms that mediate cisplatin cytotoxicity and side effects. A specific section is devoted to discuss the pathogenesis of cisplatin-related toxicities and the potential measures to counteract them.

EXPERT OPINION

Although cisplatin has been used for a long time, only recently its exact mechanism of action has been better defined. The cytotoxic activity of cisplatin is largely dependent on the glycolytic metabolism of tumor cells: cisplatin redirects cancer cells to oxidative phosphorylation from the 'Warburg effect', which is considered one of the most important mechanisms of tumor cell survival. The interference of cisplatin with glucose metabolism is also a cause of its relevant toxicities. The emerging knowledge on the complex mechanisms, which mediate cisplatin cytotoxicity and side effect, may lead to a more appropriate and safe use of this drug. Further studies are warranted to define and implement its effectiveness in combination with targeted drugs able to interfere with cellular energy metabolism, such as mTOR inhibitors.

Reappraisal of the role of dolasetron in prevention and treatment of nausea and vomiting associated with surgery or chemotherapy

Chemotherapy-induced nausea and vomiting and postoperative nausea and vomiting are one of the most frequent but also very concerning consequences for patients undergoing chemotherapy or surgical procedures under general anesthesia. There are a variety of mechanisms involved in the activation of nausea and vomiting. Serotonin, a ubiquitous central and peripheral neurotransmitter, is thought to be the predominant mediator of the perception of nausea and triggering of the vomiting response in both the brain and the periphery via the 5-hydroxytryptamine type 3 (5-HT₃) receptor pathways. 5-HT₃ receptor antagonists disrupt this pathway, largely at the level of the vagal afferent pathways, to decrease nausea and vomiting. This review will focus on dolasetron, an older but sill commonly used 5-HT₃ receptor antagonist and its multimodal mechanism of action, safety and tolerability, patient considerations, and a review of the current literature on its use to combat both chemotherapy-induced and postoperative nausea and vomiting in these two important patient populations.

SEROTONIN-INDUCED MUSCULAR ACTIVITY IN SCHISTOSOMA MANSONI LARVAL STAGES: IMPORTANCE OF 5-HT TRANSPORT AND ROLE IN DAUGHTER SPOROCYST PRODUCTION

Mother sporocysts of Schistosoma mansoni transport exogenously supplied serotonin (5-hydroxytrypamine; 5-HT), and respond to it with increases in motility. In the present study, we investigated the importance of 5-HT transporter activity in the manifestation of these 5-HT-induced motility changes, and further examined the role of 5-HT in the development of daughter sporocysts in vitro. Serotonin-induced motility of in vitro-derived sporocysts is not inhibited by antidepressant compounds, e.g., fluoxetine, that block 5-HT transport, suggesting that the receptors responsible for motility responses to 5-HT are surface exposed. Using a sporocyst in vitro culture system, we show that depletion of larval stores of 5-HT reduces production of daughter sporocysts, the second intramolluscan larval stage. Moreover, we demonstrate a strong correlation between endogenous 5-HT levels and basal mother sporocyst muscle activity. Overall, these data suggest that larval stages of S. mansoni can detect exogenous 5-HT via surface-exposed receptors, and they are consistent with the hypothesis that endogenous stores of 5-HT are important for the proper regulation of muscular contractions in mother sporocysts, and for the successful emergence of daughter sporocysts.

Using decision modeling to determine pricing of new pharmaceuticals: The case of neurokinin-1 receptor antagonist antiemetics for cancer chemotherapy

Objectives:Decision analysis is commonly used to perform economic evaluations of new pharmaceuticals. The outcomes of such studies are often reported as an incremental cost per quality-adjusted life year (QALY) gained with the new agent. Decision analysis can also be used in the context of estimating drug cost before market entry. The current study used neurokinin-1 (NK-1) receptor antagonists, a new class of antiemetics for cancer patients, as an example to illustrate the process using an incremental cost of $Can20,000 per QALY gained as the target threshold.

Methods:A decision model was developed to simulate the control of acute and delayed emesis after cisplatin-based chemotherapy. The model compared standard therapy with granisetron and dexamethasone to the same protocol with the addition of an NK-1 before chemotherapy and continued twice daily for five days. The rates of complete emesis control were abstracted from a double-blind randomized trial. Costs of standard antiemetics and therapy for breakthrough vomiting were obtained from hospital sources. Utility estimates characterized as quality-adjusted emesis-free days were determined by interviewing twenty-five oncology nurses and pharmacists by using the Time Trade-Off technique. These data were then used to estimate the unit cost of the new antiemetic using a target threshold of $Can20,000 per QALY gained.

Results:A cost of $Can6.60 per NK-1 dose would generate an incremental cost of $Can20,000 per QALY. The sensitivity analysis on the unit cost identified a range from $Can4.80 to $Can10.00 per dose. For the recommended five days of therapy, the total cost should be $Can66.00 ($Can48.00–$Can100.00) for optimal economic efficiency relative to Canada's publicly funded health-care system.

Conclusions:The use of decision modeling for estimating drug cost before product launch is a powerful technique to ensure value for money. Such information can be of value to both drug manufacturers and formulary committees, because it would facilitate negotiations for optimal pricing in a given jurisdiction.

Does increasing the steroid dose enhance the efficacy of the antiemetic combination of granisetron and methylprednisolone in gynecologic cancer patients--a randomized study

OBJECTIVE

The authors administered two doses of oral methylprednisolone in combination with 3mg granisetron intravenously for the prophylaxis of cisplatin-induced emesis in gynecologic cancer patients.

MATERIALS AND METHODS

Thirty-nine patients received 100mg (group A) and 25 received 200mg (group B) methylprednisolone in the antiemetic combination in a randomized prospective trial.

RESULTS

No vomiting in 90.2 and 96.7%, one emetic episode in 3 and 1.1% and two episodes in 3 and 2.2% were detected in groups A and B, respectively. More than two emetic episodes were considered to be a failure and were observed only in group A (3.8%). There was no significant difference between the two treatment groups (P=0.3160).

CONCLUSIONS

There was no evidence for enhanced antiemetic effect of elevated steroidal dose in combination with granisetron.

5-HT3 antagonist ICS 205–930 enhances naltrexone's effects on ethanol intake

Opioid receptor antagonist naltrexone has shown some efficacy in decreasing ethanol consumption in humans. However, naltrexone treatment is not always efficacious and produces several aversive effects such as nausea, anxiety and weight loss. Serotonin-3 (5-HT3) receptor antagonists also modulate some of the behavioral effects of alcohol and may decrease alcohol consumption. We examined the effects of the combination of 5-HT3 receptor antagonist ICS 205-930 ((3-tropanyl-indole-1-carboxylate, tropisetron) and naltrexone on ethanol and food intake in Sprague-Dawley rats. Both naltrexone (0.56-10 mg/kg) and ICS 205-930 (5.6 mg/kg), when administered intraperitoneally 30 min before the scheduled 3-h access to ethanol, significantly suppressed ethanol intake. Naltrexone (1 mg/kg) when given in combination with ICS 205-930 (5.6 mg/kg) was significantly more efficacious in suppressing ethanol intake in comparison with naltrexone (1 mg/kg) administered alone. The drug combination did not affect the food intake. These data suggest that 5-HT3 receptor antagonist ICS 205-930 may be used as an effective adjunct for pharmacotherapy of alcoholism.

Electrocardiographic and cardiovascular effects of the 5-hydroxytryptamine3 receptor antagonists

OBJECTIVE

To review the electrocardiographic (ECG) and cardiovascular effects of 5-hydroxytryptamine(3) (5-HT(3)) receptor antagonists preclinically, in healthy volunteers, and in patients undergoing chemotherapy or surgery.

DATA SOURCES

A MEDLINE search was performed of clinical trials and preclinical data published between 1963 and December 2002 assessing the ECG and cardiovascular effects of 5-HT(3) receptor antagonists, supplemented with reviews and secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All of the articles identified were evaluated and all information deemed relevant was included in this review.

DATA SYNTHESIS

There are no clinically relevant differences in efficacy and safety among the available 5-HT(3) receptor antagonists for prevention and treatment of chemotherapy-induced and postoperative nausea and vomiting. As a class, they have well-defined electrophysiologic activity. Changes in ECG parameters (PR, QRS, QT, QTc, JT intervals) are small, reversible, clinically insignificant, and independent of the patient population studied, and patients are asymptomatic during these changes. ECG changes are most prominent 1-2 hours after a dose of dolasetron, ondansetron, and granisetron and return to baseline within 24 hours. Clinically important adverse cardiovascular events associated with these changes are rare. No serious cardiac events (including torsade de pointes) arising from ECG interval changes have been attributed to 5-HT(3) receptor antagonist use.

CONCLUSIONS

Clinical data demonstrate that ECG interval changes are a class effect of the 5-HT(3) receptor antagonists. Theoretical concern regarding cardiovascular adverse events with these agents is not supported by clinical experience. The significant benefits of these agents outweigh the theoretical small risk of meaningful cardiovascular events.

Possible involvement of peripheral serotonin 5-HT3 receptors in fluvoxamine-induced emesis in Suncus murinus

Selective serotonin reuptake inhibitors fluvoxamine and fluoxetine, as well as serotonin (5-HT), induced vomiting in Suncus murinus (a house musk shrew). Fluvoxamine- and fluoxetine-induced vomiting gradually decreased with their repeated administration. Vomiting induced by serotonin also decreased with repeated treatment with serotonin. In these shrews, fluvoxamine-induced vomiting was partially inhibited. Fluvoxamine might induce vomiting, at least partially, by indirectly activating peripheral 5-HT(3) receptors, since serotonin has been reported to induce vomiting by activating peripheral 5-HT(3) receptors and granisetron, a 5-HT(3) antagonist, partially suppressed fluvoxamine-induced vomiting in our previous finding. In addition, fluvoxamine-induced vomiting was impaired more effectively using a step-wise dose-up schedule of fluvoxamine than a fixed high-dose schedule. Therefore, a careful dosing strategy starting with a low dose might be effective for avoiding emesis associated with the clinical use of fluvoxamine.

Superficial NK1-expressing neurons control spinal excitability through activation of descending pathways

The increase in pain sensitivity that follows injury is regulated by superficially located projection neurons in the dorsal horn of the spinal cord that express the neurokinin-1 (NK1) receptor. After selective ablation of these neurons in rats, we identified changes in receptive field size, mechanical and thermal coding and central sensitization of deeper dorsal horn neurons that are important for both pain sensations and reflexes. We were able to reproduce these changes by pharmacological block of descending serotonergic facilitatory pathways. Using Fos histochemistry, we found changes in the activation of serotonergic neurons in the brainstem as well as evidence for a loss of descending control of spinal excitability. We conclude that NK1-positive spinal projection neurons, activated by primary afferent input, project to higher brain areas that control spinal excitability--and therefore pain sensitivity--primarily through descending pathways from the brainstem.

Antiemetic effects of granisetron, droperidol and dexamethasone in otologic surgery

The objective was to assess the antiemetic activity of granisetron, dexamethasone and droperidol in the otologic surgeries. Sixty patients in ASA (American Society of Anesthesiologists) I and II risk groups who underwent surgery for chronic otitis media were assessed in a double blind and randomized trial. The patients were divided into three equal groups. Single intravenous dose of granisetron (3 mg), granisetron (3 mg) plus dexamethasone (8 mg) and droperidol (1.25 mg) were prophylactically administered to the patients in group 1, group 2 and group 3, respectively, and their antiemetic actions were compared. The antiemetic effects of the drugs were not significantly different between the groups (P>0.05). The antiemetic effects also did not differ significantly in the early and late postoperative periods (P>0.05). In conclusion, the results of prophylactic use or side effects of granisetron, granisetron plus dexamethasone or droperidol are similar in middle ear surgery. Therefore, cost effectivity of the antiemetic prophylaxis should be reconsidered in otologic surgery in the light of the results of this study.

The prophylactic effect of tropisetron on epidural morphine-related nausea and vomiting: a comparison of dexamethasone with saline

Tropisetron is a 5-hydroxytryptamine subtype 3 receptor antagonist that is primarily used in the prevention of chemotherapy-induced nausea and vomiting. We evaluated the prophylactic effect of tropisetron on postoperative nausea and vomiting associated with epidural morphine. Dexamethasone and saline served as controls. One-hundred twenty women (n = 40 in each of three groups) undergoing abdominal total hysterectomy under epidural anesthesia were enrolled in this randomized, double-blinded, and placebo-controlled study. At the end of surgery, Group 1 received IV tropisetron 5 mg, whereas Groups 2 and 3 received dexamethasone 5 mg and saline, respectively. We found that tropisetron did not significantly reduce the occurrence of nausea and vomiting associated with epidural morphine. Dexamethasone, however, reduced the total incidence of nausea and vomiting from 59% to 21% (P < 0.01) and the percentage of patients requiring rescue antiemetic from 38% to 13% (P < 0.05). We conclude that IV tropisetron 5 mg did not prevent the occurrence of postoperative nausea and vomiting associated with epidural morphine. IV dexamethasone 5 mg was effective for this purpose.

IMPLICATIONS

We compared the prophylactic IV administration of tropisetron 5 mg to prevent postoperative nausea and vomiting (PONV) associated with epidural morphine with dexamethasone 5 mg and saline in women undergoing hysterectomy. We found that tropisetron 5 mg did not significantly reduce the occurrence of PONV associated with epidural morphine. Dexamethasone 5 mg was effective for this purpose.

Ondansetron: a review of its use as an antiemetic in children

Ondansetron, a selective serotonin (5-hydroxytryptamine; 5-HT) 5-HT3 receptor antagonist, is an antiemetic agent available for use in adults and children. In children receiving ondansetron (multiple 5 mg/m2 or 0.15 mg/kg intravenous and/or oral doses) in addition to chemotherapy in 2 large (n > 100) non-comparative analyses, < or =2 emetic episodes were observed in 33 and 40% of cisplatin recipients, 48 and 68% of ifosfamide recipients, and 70 and 72% of patients receiving other chemotherapeutic regimens. In comparative trials, ondansetron was significantly more effective at reducing nausea and vomiting than metoclopramide or chlorpromazine (both combined with dexamethasone), although the incidence of delayed symptoms were similar between children receiving ondansetron and metoclopramide. In addition, dexamethasone significantly improved the antiemetic efficacy of ondansetron in 1 randomised trial. When used in children undergoing conditioning therapy (including total body irradiation) prior to bone marrow transplantation, ondansetron was significantly better at controlling nausea and vomiting than combined perphenazine and diphenhydramine therapy. In dose-ranging and large placebo-controlled trials, intravenous (0.075 to 0.15 mg/kg) or oral (0.1 mg/kg) ondansetron was significantly more effective than placebo in preventing emesis in children undergoing surgery associated with a high risk of postoperative nausea and vomiting (PONV) including tonsillectomy or strabismus repair. In comparative studies, intravenous administration of ondansetron 0.1 to 0.15 mg/kg was significantly superior to droperidol 0.02 to 0.075 mg/kg or metoclopramide 0.2 to 0.25 mg/kg in preventing emesis in children undergoing various surgical procedures. In comparison with other antiemetics, including prochlorperazine and dimenhydrinate, ondansetron generally showed greater prophylactic antiemetic efficacy. Ondansetron combined with dexamethasone was significantly more effective than ondansetron or dexamethasone alone, as was the combination of ondansetron with a propofol-based anaesthetic compared with either agent alone. Ondansetron is generally well tolerated in children, rarely necessitating treatment withdrawal. The most frequently reported adverse events were mild to moderate headache, constipation and diarrhoea in patients receiving chemotherapy. Wound problems, anxiety, headache, drowsiness and pyrexia were reported most frequently in patients postsurgery.

CONCLUSIONS

Ondansetron has shown good efficacy in the prevention of acute nausea and vomiting in children receiving moderately or highly emetogenic chemotherapy and/or irradiation, particularly when combined with dexamethasone. In the chemotherapy setting, ondansetron is significantly better than metoclopramide and chlorpromazine and has a more favourable tolerability profile. In children undergoing surgery, ondansetron demonstrated superior prophylactic antiemetic efficacy compared with placebo, droperidol and metoclopramide, and was relatively free of adverse events. Ondansetron is thus an effective first-line antiemetic in children undergoing chemotherapy, radiotherapy and surgery.

Does intravenous ondansetron affect gastric emptying of a solid meal, gastric electrical activity or blood hormone levels in healthy volunteers?

BACKGROUND

In previous studies, tropisetron has been shown to accelerate gastric emptying of a solid meal. However, it is uncertain whether other specific 5-hydroxytryptamine-3 receptor antagonists, such as ondansetron, also have a gastroprokinetic effect in humans.

AIM

To evaluate the effect of ondansetron on gastric half-emptying time (T1/2) of a solid meal, gastric myoelectrical activity and hormone levels in 14 healthy volunteers.

METHODS

In a placebo-controlled, randomized, crossover study, we investigated the effects of ondansetron (8 mg intravenously) on the gastric emptying of solids (by scintigraphy), gastric myoelectrical activity (by electrogastrography) and the post-prandial release of cholecystokinin, gastrin, human pancreatic polypeptide, gastric inhibitory polypeptide, vasoactive intestinal polypeptide, motilin, substance P and galanin.

RESULTS

The average T1/2 values were 86 min and 85.5 min without lag time (P=0.082) and 92 min and 93 min with lag time (P=0.158) for the placebo and ondansetron treatments, respectively. The average T1/2 of female volunteers was significantly longer than that of male volunteers. The dominant gastric electrical frequency and hormone plasma concentrations were not altered by ondansetron.

CONCLUSIONS

Ondansetron did not affect the gastric emptying of solids, the dominant gastric electrical frequency or the plasma concentrations of the analysed gastrointestinal peptides.

Ondansetron: a selective 5-HT(3) receptor antagonist and its applications in CNS-related disorders

Ondansetron is a selective 5-hydroxytryptamine(3) (5-HT(3)) receptor antagonist that has been introduced to clinical practice as an antiemetic for cancer treatment-induced and anesthesia-related nausea and vomiting. Its use under these circumstances is both prophylactic and therapeutic. It has a superior efficacy, safety and pharmacoeconomic profile compared with other groups of antiemetics, namely antidopaminergics, antihistamines and anticholinergics. However, its place in the management of anticipatory and delayed vomiting in cancer treatment and as a rescue antiemetic in surgical patients needs to be further explored. Furthermore, recent animal and human research also reflects its possible novel application in the treatment of other disease states, such as alcoholism, cocaine addiction, opioid withdrawal syndrome, anxiety disorders, gastrointestinal motility disorders, Tourette's syndrome and pruritus. This review revisits the widespread physiological and pathological effects of 5-HT and discusses both the basic science literature and the clinical developments responsible for the conventional and novel uses of ondansetron. In addition, new discoveries relating to the effects of ondansetron on other receptors/channels and their possible therapeutic applications are presented.

In vitro and in vivo ligand binding to the 5HT(3) serotonin receptor characterised by time-resolved fluorescence spectroscopy

The binding of the fluorescein-labelled antagonist GR-flu ([1,2,3,9-tetrahydro-3-[(5-methyl-1H-imidazol-4-yl)methyl]-9-(3-amino-(N-fluoresceinthiocarbamoyl)propyl)-4H-carbazol-4-one]) to a purified, detergent-solubilised ligand-gated ion channel, the type-3 serotonin (5-hydroxytryptamine, 5HT) receptor (5HT(3)R), was characterised by frequency-domain time-resolved fluorescence spectroscopy (TRFS). Detailed understanding of how ligands interact with the homopentameric receptor was obtained. While a 1:1 stoichiometry was observed for the GR-flu-receptor complex, the agonist quipazine bound cooperatively to the receptor, suggesting multiple binding sites for this ligand. The GR-flu-binding site of the receptor was proven to provide an acidic environment as shown by determining the fraction of bound GR-flu in the protonated state. Fluorescence anisotropy relaxation experiments indicated a hindered but still high mobility for the receptor-bound GR-flu. Hence, the binding site is expected to present a wide opening to the ligand. Finally, we succeeded in measuring the binding of GR-flu to 5HT(3) receptors in live cells. These results show that the purified and the native receptor behave identically and demonstrate that time-resolved fluorescence measurements are suited to selectively investigate biomolecular interactions in live cells.

Economics and health-related quality of life in antiemetic therapy: recommendations for trial design

Emesis (nausea and vomiting) is one of the most important toxicities associated with chemotherapy. Although it is not life threatening, it has a major impact on a patient's health-related quality of life (HRQL) and overall response to chemotherapy. New antiemetics are expensive and well-conducted comparative health economic studies are rare. The aim of the study was to review the literature in the area of chemotherapy-induced emesis in cancer patients and to offer recommendations for the inclusion of these outcomes in the design of clinical trials for new antiemetic therapies. The economic literature was reviewed based on methodological standards for economic evaluation. Many studies did not comply with standards, specifically with regard to the choice of alternatives, chosen perspective, setting, type of emesis, measurement of costs and defining outcomes (including health-related quality of life). These issues are described for each study and recommendations for trial design are presented. The role of economic data is to support decision making in choosing between competing antiemetic therapies. It is the combination of clinical outcomes, costs and health-related quality of life, which will allow treating physicians to comprehensively assess the relative value of antiemetic therapies and to provide the most cost-effective therapy for their patients.

Prevention and treatment of postoperative nausea and vomiting

Pain, nausea and vomiting are frequently listed by patients as their most important perioperative concerns. With the change in emphasis from an inpatient to outpatient hospital and office-based medical/surgical environment, there has been increased interest in the 'big little problem' of postoperative nausea and vomiting (PONV). Currently, the overall incidence of PONV is estimated to be 25 to 30%, with severe, intractable PONV estimated to occur in approximately 0.18% of all patients undergoing surgery. PONV can lead to delayed postanaesthesia care unit (PACU) recovery room discharge and unanticipated hospital admission, thereby increasing medical costs. The aetiology and consequences of PONV are complex and multifactorial, with patient-, medical- and surgery-related factors. A thorough understanding of these factors, as well as the neuropharmacology of multiple emetic receptors [dopaminergic, muscarinic, cholinergic, opioid, histamine, serotonin (5-hydroxy-tryptamine; 5-HT)] and physiology [cranial nerves VIII (acoustic-vestibular), IX (glossopharyngeal) and X (vagus), gastrointestinal reflex] relating to PONV are necessary to most effectively manage PONV. Commonly used older, traditional antiemetics for PONV include the anticholinergics (scopolamine), phenothiazines (promethazine), antihistamines (diphenhydramine), butyrophenones (droperidol) and benzamides (metoclopramide). These antiemetics have adverse effects such as dry mouth, sedation, hypotension, extrapyramidal symptoms, dystonic effects and restlessness. The newest class of antiemetics used for the prevention and treatment of PONV are the serotonin receptor antagonists (ondansetron, granisetron, tropisetron, dolasetron). These antiemetics do not have the adverse effects of the older, traditional antiemetics. Headache and dizziness are the main adverse effects of the serotonin receptor antagonists in the dosages used for PONV. The serotonin receptor antagonists have improved antiemetic effectiveness but are not as completely efficacious for PONV as they are for chemotherapy-induced nausea and vomiting. Older, traditional antiemetics (such as droperidol) compare favourably with the serotonin receptor antagonists regarding efficacy for PONV prevention. Combination antiemetic therapy improves efficacy for PONV prevention and treatment. In the difficult-to-treat PONV patient (as in the chemotherapy patient), suppression of numerous emetogenic peripheral stimuli and central neuroemetic receptors may be necessary. This multimodal PONV management approach includes use of: (i) multiple different antiemetic medications (double or triple combination antiemetic therapy acting at different neuroreceptor sites); (ii) less emetogenic anaesthesia techniques; (iii) adequate intravenous hydration; and (iv) adequate pain control.

Comparison of ondansetron and tropisetron combined with droperidol for the prevention of emesis in women with a history of post-operative nausea and vomiting

The anti-emetic efficacy of prophylactic ondansetron and tropisetron in combination with a low dose of droperidol in patients with high probability for post-operative nausea and vomiting undergoing gynaecological laparoscopy was compared. Patients were randomly allocated in a double-blind manner to receive either ondansetron 8 mg (n = 45) or tropisetron 5 mg (n = 43) at the end of surgery. A standardized general anaesthetic technique was used, including droperidol 0.75 mg. The incidence of nausea was 36% and 49% (P = 0.28), and vomiting occurred in 13% and 14% of the patients in the ondansetron and tropisetron groups, respectively. The onset time for rescue medication was significantly sooner after tropisetron than ondansetron (3 h 18 min vs. 6 h 25 min; P = 0.007). There were no statistically significant differences in efficacy between prophylactic ondansetron and tropisetron combined with droperidol in a high-risk population. However, ondansetron appeared to be more effective in preventing post-operative nausea and vomiting in the early hours after surgery compared with tropisetron.

Essential drugs for cancer therapy: a World Health Organization consultation

The WHO has previously produced recommendations on the essential drugs required for cancer therapy. Over the last five years several new anti cancer drugs have been aggressively marketed. Most of these are costly and produce only limited benefits. We have divided currently available anti-cancer drugs into three priority groups. Curable cancers and those cancers where the cost-benefit ratio clearly favours drug treatment can be managed appropriately with regimens based on only 17 drugs. All of these are available, at relatively low cost, as generic preparations. The wide availability of these drugs should be the first priority. The second group of drugs may have some advantages in certain clinical situations. Based on current evidence, drugs in the third group are judged as currently not essential for the effective delivery of cancer care. Adequate supportive care programmes with the widespread availability of effective drugs for pain control are of considerably greater importance. The adoption of these priorities will help to optimise the effectiveness and efficiency of chemotherapy and ensure equitable access to essential drugs especially in low resource environments. Clearly this paper represents the views of its contributors. The WHO welcomes feedback from all oncologists so that the advice it gives to governments in prioritising the procurement of anti cancer drugs can be as comprehensive as possible.

Ligand binding to the serotonin 5HT3 receptor studied with a novel fluorescent ligand

The thermodynamics and kinetics of ligand binding to the purified serotonin 5HT3 receptor and the local environment of the bound ligand were studied by fluorescence spectroscopy using a novel fluorescein-labeled ligand GR-flu [1,2,3, 9-tetrahydro-3-[(5-methyl-1H-imidazol-4-yl)methyl]-9-(3-amino-(N-fluo rescien-thiocarbamoyl)-propyl)-4H-carbazol-4-one]. Electrophysiological investigations demonstrated GR-flu to be an antagonist, and radioligand competition assays delivered a dissociation constant of 0.32 nM. Changes in the fluorescence intensity and anisotropy upon specific binding to the receptor yielded dissociation constants of approximately 0.2 nM. Fluorescence measurements showed that selective 5HT3 receptor ligands competed for GR-flu binding with a rank order of potency identical to that established with the radioligand [3H]-GR65630. The kinetics of GR-flu binding to the 5HT3 receptor revealed a bimolecular association process with an on-rate constant of 1.17 x 10(6) s-1 M-1 and a biphasic dissociation reaction with off-rate constants of 275 x 10(-)6 and 43 x 10(-)6 s-1. The temperature dependence of the dissociation constant yielded an enthalpic term of -26 kJ mol-1 and an entropic term of 94 J K-1 mol-1 for the binding of GR-flu to the receptor, indicating that both quantities contribute equally to the reaction. An activation enthalpy DeltaH#on and entropy DeltaS#on of binding of 50 kJ mol-1 and 43 J mol-1 K-1 were obtained, indicating that the entropy facilitates the initial steps of GR-flu binding to the 5HT3 receptor. The fluorescence anisotropy of receptor-bound GR-flu and the environmental sensitivity of the fluorescent probe suggest that the binding site has a wide entrance and that it is 0.8 pH unit more acidic than the bulk solution.

La Ricerca Sugli Antiemetici: Un Modello Italiano Di Successo

At the beginning of the 80's the Italian Group for Clinical Research (G.O.I.R.C.) identified chemotherapy-induced nausea and vomiting as one of the most distressing adverse events, and decided to plan and execute clinical trials on antiemetics in order to reduce this negative impact on patients.

Therefore, some consecutive double-blind randomized trials were conducted on cisplatin-treated patients. The first was a dose-finding study on four different high-doses of domperidone, followed by a study comparing two different high-doses of metoclopramide, and a study comparing the addition of a corticosteroid to high-dose metoclopramide with respect to metoclopramide alone. Finally, a study demonstrating that a combination of a higher dose of metoclopramide (3 mg/kg x2) plus dexamethasone and diphenhydramine was significantly superior with respect to a lower dose of metoclopramide (1 mg/kg x 4) combined with methylprednisolone was carried out.

With the introduction of the 5-HT3 receptor antagonists the interest for antiemetic therapy increased and other Italian gynecological and medical oncology centres became involved in the antiemetic research. The Italian Group for Antiemetic Research was formed in 90's and its first study demonstrated the superiority of a combination of a 5-HT3 receptor antagonist plus dexamethasone with respect to the standard three drug combination of high doses of metoclopramide in the prevention of cisplatin-induced acute emesis.

In the following years, the Group contributed to the identification of the best antiemetic prophylaxis for acute emesis induced by moderately emetogenic chemotherapy, and for delayed emesis induced by cisplatin. Also a drug utilization review on antiemetics in clinical practice has recently been carried out.

Today, the interest of the Group is concentrated in studying the optimal antiemetic prophylaxis for delayed emesis induced by moderately emetogenic chemotherapy.

The rules always followed by the Italian Group for Antiemetic Research are: - complete independence of judgement on the efficacy and the tolerability of antiemetic drugs from the pharmaceutical companies; - priority of ethical problems in designing clinical trials; - strict adherence to the methodological problems of antiemetic research and - complete autonomy concerning the study planned, the data computerization and the data elaboration.

In the last twelve years approximately 70 Italian centres have enrolled their patients into the studies of the Italian Group for Antiemetic Research.