Selective serotonin 5-HT3 receptor antagonists for postoperative nausea and vomiting: are they all the same?

An overview of the clinical use of ondansetron in preschool age children

The introduction of 5-HT₃ receptor antagonist has revolutionized the prevention and treatment of nausea and vomiting in preschool aged children. These distressing symptoms, arising from multiple etiologies such as anesthesia, chemotherapy, and viral infection, are a major concern of patients and their families. Clinical research has demonstrated the antiemetic effectiveness of ondansetron in children. Although most of these studies focus primarily on preventing vomiting across the pediatric age group, they provide strong evidence for the use of ondansetron in preschool age children. For children at high risk, pediatric practice guidelines recommend ondansetron in conjunction with other antiemetics to achieve complete control of symptoms.

5-HT(3) receptors: role in disease and target of drugs

Serotonin type 3 (5-HT(3)) receptors are pentameric ion channels belonging to the superfamily of Cys-loop receptors. Receptor activation either leads to fast excitatory responses or modulation of neurotransmitter release depending on their neuronal localisation. 5-HT(3) receptors are known to be expressed in the central nervous system in regions involved in the vomiting reflex, processing of pain, the reward system, cognition and anxiety control. In the periphery they are present on a variety of neurons and immune cells. 5-HT(3) receptors are known to be involved in emesis, pain disorders, drug addiction, psychiatric and GI disorders. Progress in molecular genetics gives direction to personalised medical strategies for treating complex diseases such as psychiatric and functional GI disorders and unravelling individual drug responses in pharmacogenetic approaches. Here we discuss the molecular basis of 5-HT(3) receptor diversity at the DNA and protein level, of which our knowledge has greatly extended in the last decade. We also evaluate their role in health and disease and describe specific case-control studies addressing the involvement of polymorphisms of 5-HT3 subunit genes in complex disorders and responses to drugs. Furthermore, we focus on the actual state of the pharmacological knowledge concerning not only classical 5-HT(3) antagonists--the setrons--but also compounds of various substance classes targeting 5-HT(3) receptors such as anaesthetics, opioids, cannabinoids, steroids, antidepressants and antipsychotics as well as natural compounds derived from plants. This shall point to alternative treatment options modulating the 5-HT(3) receptor system and open new possibilities for drug development in the future.

Update on the management of postoperative nausea and vomiting and postdischarge nausea and vomiting in ambulatory surgery

Postoperative nausea and vomiting (PONV) continues to be one of the most common complaints following surgery, occurring in more than 30% of surgeries, or as high as 70% to 80% in certain high-risk populations without prophylaxis. The 5-hydroxytryptamine type 3 (5-HT(3)) receptor antagonists continue to be the mainstay of antiemetic therapy, but newer approaches, such as neurokinin-1 antagonists, a longer-acting serotonin receptor antagonist, multimodal management, and novel techniques for managing high-risk patients are gaining prominence. The related problem of postdischarge nausea and vomiting (PDNV) has received increasing attention from health care providers. The issues of PONV and PDNV are especially significant in the context of ambulatory surgeries, which comprise more than 60% of the combined 56.4 million ambulatory and inpatient surgery visits in the United States. Because of the relatively brief period that ambulatory patients spend in health care facilities, it is particularly important to prevent and treat PONV and PDNV swiftly and effectively.

Postoperative management after loop ileostomy closure: are we keeping patients in hospital too long?

INTRODUCTION

Recent studies have shown that closure of loop ileostomy can be performed in the day-case setting, reducing the length and cost of hospitalisation. By analysing our patients who have undergone reversal, we aimed to determine the length of hospital stay and potential factors behind stays beyond 24 h.

PATIENTS AND METHODS

A database of patients undergoing closure of loop ileostomy at one colorectal unit was examined. The times taken to discharge, morbidity and re-admission rates were recorded.

RESULTS

Eighty patients underwent reversal of ileostomy between January 2001 and January 2006. Median age was 63 years (range, 22-81 years). The median length of stay was 4 days (range, 2-32 days). The median length of stay in patients without complications was 4 days. Many appeared able to be discharged earlier. Seventy-two patients (90%) were able to tolerate a solid diet within 48 h and 54 (67.5%) had bowel function within 3 days. Six patients went home before bowel function; none of these were re-admitted. Twenty patients (25%) developed complications, which included wound infection (8%), small bowel obstruction/ileus (6%), enterocutaneous fistula (1%), anastomotic leak (1%), and late abdominal wall abscess (1%). Of the patients, 16% stayed longer than 5 days despite having no postoperative complications.

CONCLUSIONS

The majority of patients undergoing loop ileostomy reversal at our institution can be discharged earlier than they are at present. Support in the community and the implementation of modified UK day-case surgery protocols are suggested to help shorten patients' length of stay.

Aprepitant: a review of its use in the prevention of nausea and vomiting

Aprepitant (Emend) is a neurokinin-1 (NK(1)) receptor antagonist that is able to alleviate the emetic effects of substance P. When combined with a standard regimen of a corticosteroid (dexamethasone) and a serotonin 5-HT(3) receptor antagonist (ondansetron), oral aprepitant (125 mg on day 1 then 80 mg once daily on days 2 and 3) was effective in the prevention of acute and delayed chemotherapy-induced nausea and vomiting (CINV) associated with single or multiple cycles of highly emetogenic chemotherapy (HEC). This aprepitant regimen was also effective in the prevention of CINV in patients treated with single or multiple cycles of moderately emetogenic chemotherapy (MEC). A single oral dose of aprepitant 40 mg administered prior to patients undergoing abdominal surgery was also effective in the prevention of postoperative nausea and vomiting (PONV). Aprepitant was generally well tolerated. Aprepitant is a recommended option for the treatment of PONV, and when combined with a corticosteroid and 5-HT(3) receptor antagonist is a recommended regimen for the treatment of CINV.

Comparison of azasetron and ondansetron for preventing postoperative nausea and vomiting in patients undergoing gynecological laparoscopic surgery

PURPOSE

We compared the prophylactic effects of intravenously administered azasetron (10 mg) and ondansetron (8 mg) on postoperative nausea and vomiting (PONV) in patients undergoing gynecological laparoscopic surgery under general anesthesia.

MATERIALS AND METHODS

We studied 98 ASA physical status I or II 20-65 years old, female patients, in this prospective, randomized, double blind study. Patients were randomly divided into two groups and received ondansetron 8 mg (group O) or azasetron 10 mg (group A) 5 min before the end of surgery. The incidence of PONV, Visual Analogue Scale (VAS) for pain, need for rescue antiemetic and analgesics, and adverse effects were checked at 1, 6, 12, 24, and 48 h postoperatively.

RESULTS

The overall incidence of PONV was 65% in group O and 49% in group A. The incidence of PONV was significantly higher in group O than in group A at 12-24 h postoperatively (nausea; 24% vs. 45%, p = 0.035, vomiting; 2% vs. 18%, p = 0.008), but there were no significant differences at 0-1, 1-6, 6-12 or 24-48 h.

CONCLUSION

In conclusion, azasetron (10 mg) produced same incidence of PONV as ondansetron (8 mg) in patients undergoing general anesthesia for gynecological laparoscopic surgery. Azasetron was more effective, in the intermediate post-operative period, between 12 and 24 h.

A randomized, double-blind study to evaluate the efficacy and safety of three different doses of palonosetron versus placebo for preventing postoperative nausea and vomiting

BACKGROUND

In this randomized, double-blind study we assessed the efficacy and safety of three different doses of the 5-HT(3) receptor antagonist palonosetron, compared with placebo, on the incidence and severity of postoperative nausea and vomiting (PONV) for 72 h postsurgery.

METHODS

Five hundred seventy-four patients undergoing either outpatient abdominal or gynecological laparoscopic surgery were stratified according to gender, history of PONV or motion sickness, and nonsmoking status. Patients with > or =2 PONV risk factors were eligible and randomized to receive one of three doses of IV palonosetron (0.025 mg, 0.050 mg, or 0.075 mg) or placebo immediately prior to induction of anesthesia. Co-primary efficacy end-points included complete response (CR: no emetic episodes and no rescue medication) during the 0 to 24 h and 24 to 72 h postoperative time intervals.

RESULTS

A dose-response trend in the proportion of patients with a CR was observed with increasing doses of palonosetron in the first 24 hrs. CR rates for placebo and palonosetron 0.075 mg were 26% and 43%, respectively, for the 0 to 24 h postoperative interval (P = 0.004), and 41% and 49%, respectively, for the 24 to 72 h interval (P = 0.188). Compared with placebo, palonosetron 0.075 mg was associated with a significant downward shift toward less intense nausea (P = 0.042) and with significant reduction in the impact of PONV on patient functioning (P = 0.004) during the 0 to 24 h interval.

CONCLUSIONS

A single 0.075-mg IV dose of palonosetron significantly increased the CR rate (no emetic episodes and no rescue medication) from 0 to 24 h, decreased nausea severity and patients experienced significantly less interference in their postoperative function due to PONV.

Detrimental effects of tropisetron on permanent ischemic stroke in the rat

Background

Recent in vitro evidence indicates that blockade of 5-hydroxytryptamine (5-HT) receptor 3 (5-HT₃) is able to confer protection in different models of neuronal injury. The purpose of the present study was to investigate the effect of tropisetron, a 5-HT₃ receptor antagonist, on infarct size and neurological score in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in the rat.

Methods

Two different doses of tropisetron (5 and 10 mg/kg) or vehicle were administered intraperitoneally 30 min before pMCAO. Neurological deficit scores, mortality rate and infarct volume were determined 24 h after permanent focal cerebral ischemia.

Results

Tropisetron failed to reduce cerebral infarction. Animals receiving tropisetron showed a significant increase (p < 0.05) in neurological deficits and mortality rate.

Conclusion

Data from this study indicate that blockade of 5-HT₃ receptors with tropisetron worsens ischemic brain injury induced by pMCAO. These findings could have important clinical implications. Patients taking tropisetron, and possibly other 5-HT₃ antagonists, could potentially have a worse outcome following a brain infarct.

Superior anti-emetic efficacy of granisetron-dexamethasone combination in children undergoing middle ear surgery

AIM

To compare the effectiveness of granisetron and a granisetron-dexamethasone combination for the prevention of post-operative vomiting in children undergoing middle ear surgery.

METHODS

Ninety ASA physical status I or II children, aged 3-12 years, were randomly assigned to three groups of 30 each to receive a single dose of placebo (normal saline), granisetron 40 microg/kg or a combination of granisetron 40 microg/kg and dexamethasone 150 microg/kg intravenously after the induction of anaesthesia. Peri-operative anaesthetic care was standardized in all children. Post-operatively, during the first 24 h after anaesthesia, the frequencies of retching and vomiting and the incidence of adverse events were recorded. Rescue anti-emetic was administered if two or more episodes of emesis occurred. Post-operative pain was treated with morphine intravenously, followed by acetaminophen orally.

RESULTS

There were no differences between the treatment groups with regard to demographic data. A complete response (no retching/vomiting and no need for rescue anti-emetic) was achieved in 50%, 80% and 96.67% of children who received saline, granisetron and granisetron-dexamethasone, respectively (P < 0.05). Six children who received placebo and one who received granisetron alone required another rescue anti-emetic. The incidence of adverse events was comparable in the three groups.

CONCLUSION

The prophylactic granisetron-dexamethasone combination was more effective than granisetron alone in the prevention of post-operative emesis during the first 24 h after anaesthesia in children undergoing middle ear surgery.

Pharmacology, pharmacogenetics, and clinical efficacy of 5-hydroxytryptamine type 3 receptor antagonists for postoperative nausea and vomiting

PURPOSE OF REVIEW

The use of selective 5-hydroxytryptamine type 3 receptor antagonists has improved the management of postoperative nausea and vomiting, but has not completely eliminated it. In this article, we discuss the pharmacology of 5-hydroxytryptamine type 3 receptor antagonists and the impact of pharmacogenetics on postoperative nausea and vomiting.

RECENT FINDINGS

Dolasetron, granisetron, ondansetron, palonosetron, and tropisetron have similar mechanisms of action but different pharmacokinetic and pharmacodynamic properties. Genetic polymorphism in the cytochrome P450 mono-oxygenase system, drug efflux transporter adenosine triphosphate-binding cassette subfamily B member 1 and 5-hydroxytryptamine type 3 receptor subunits also contribute to the interindividual variation in response to different 5-hydroxytryptamine type 3 receptor antagonists. These differences account for differences in the duration of action and clinical efficacy of these agents.

SUMMARY

Pharmacogenetics testing in patients may help differentiate responders to 5-hydroxytryptamine type 3 receptor antagonists from non-responders and allow the anesthesiologist to individualize antiemetic therapy. The cost-effectiveness of such screening in postoperative nausea and vomiting management has, however, not been evaluated. Given the multifactorial nature of postoperative nausea and vomiting, a multimodal approach to reduce or eliminate risk factors will be most successful in its management.

Lack of Reciprocity between Opioid and 5-HT3 Receptors for Antinociception in Rat Spinal Cord

We examined the properties of the drug interaction between morphine and 5-HT(3) receptor antagonist at the spinal level. The nociceptive state was induced by subcutaneously injecting formalin solution (5%, 50 microl) into the hindpaw of the rats. Intrathecal morphine and m-CPBG (5-HT(3) receptor agonist) dose-dependently decreased the flinching response during phase 1 and phase 2 in the formalin test. Intrathecal 5-HT(3) receptor antagonists (LY-278,584 and ondansetron) did not reverse the antinociceptive effect of intrathecal morphine. Intrathecal naloxone had little effect on attenuation of the antinociception of intrathecal m-CPBG. Taken together, no reciprocal interaction was noted between 5-HT(3) receptor and opioid receptors at the spinal level. Thus, the 5-HT(3) receptor antagonist may be useful to manage opioid-induced emesis at the spinal level.

Prevention of Postoperative Nausea and Vomiting with Granisetron and Dolasetron in Relation to CYP2D6 Genotype

We investigated the efficacy of granisetron and dolasetron in preventing postoperative nausea and vomiting. Because the metabolism of the various antiemetic 5-hydroxytryptamine type 3 (5-HT3) antagonists involves different isoforms of the hepatic cytochrome P450 system, we examined the relationship between the clinical efficacy of these drugs and polymorphic cytochrome P450 2D6 (CYP2D6) genotype. This prospective, randomized, double-blind study involved 150 adult patients with a moderate to high risk for postoperative nausea and vomiting. All subjects received dexamethasone at induction of anesthesia followed by either 12.5 mg of dolasetron or 1 mg of granisetron. We analyzed the number of complete responders (no vomiting or rescue medication) during the first 24 hours after surgery. CYP2D6 genotyping was performed using a TaqMan real-time polymerase chain reaction. A complete response was more frequent in the granisetron group (54.7%) compared with the dolasetron group (38.7%, P < 0.05). In subjects receiving dolasetron, carriers of the duplication of the CYP2D6 allele predicting ultrarapid metabolizer status had more frequent vomiting episodes (P < 0.05) than patients in the granisetron group. It is postulated that the difference in the antiemetic efficacy between two investigated 5-HT3 receptor antagonists may be associated with differences in the carrier status for the duplication of the CYP2D6 allele.

PURIFICATION AND CHARACTERIZATION OF AKR1B10 FROM HUMAN LIVER: ROLE IN CARBONYL REDUCTION OF XENOBIOTICS

Members of the aldo-keto reductase (AKR) superfamily have a broad substrate specificity in catalyzing the reduction of carbonyl group-containing xenobiotics. In the present investigation, a member of the aldose reductase subfamily, AKR1B10, was purified from human liver cytosol. This is the first time AKR1B10 has been purified in its native form. AKR1B10 showed a molecular mass of 35 kDa upon gel filtration and SDS-polyacrylamide gel electrophoresis. Kinetic parameters for the NADPH-dependent reduction of the antiemetic 5-HT3 receptor antagonist dolasetron, the antitumor drugs daunorubicin and oracin, and the carcinogen 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) to the corresponding alcohols have been determined by HPLC. Km values ranged between 0.06 mM for dolasetron and 1.1 mM for daunorubicin. Enzymatic efficiencies calculated as kcat/Km were more than 100 mM-1 min-1 for dolasetron and 1.3, 0.43, and 0.47 mM-1 min-1 for daunorubicin, oracin, and NNK, respectively. Thus, AKR1B10 is one of the most significant reductases in the activation of dolasetron. In addition to its reducing activity, AKR1B10 catalyzed the NADP+-dependent oxidation of the secondary alcohol (S)-1-indanol to 1-indanone with high enzymatic efficiency (kcat/Km=112 mM-1 min-1). The gene encoding AKR1B10 was cloned from a human liver cDNA library and the recombinant enzyme was purified. Kinetic studies revealed lower activity of the recombinant compared with the native form. Immunoblot studies indicated large interindividual variations in the expression of AKR1B10 in human liver. Since carbonyl reduction of xenobiotics often leads to their inactivation, AKR1B10 may play a role in the occurrence of chemoresistance of tumors toward carbonyl group-bearing cytostatic drugs.