Ondansetron and chest pain

Torsades de Pointes after Ondansetron Infusion in 2 Patients

Drugs that prolong the electrocardiographic QT interval increase the risk of ventricular arrhythmias, particularly torsades de pointes. Ondansetron, a 5-hydroxytryptamine type 3 receptor antagonist antiemetic, is one such drug. We present the cases of 2 patients who were given intravenous ondansetron and subsequently developed torsades de pointes. Both had normal QT intervals at baseline but were discovered to have risk factors that predisposed them to drug-induced QT prolongation and ventricular arrhythmias. We briefly review the mechanisms for torsades de pointes caused by QT-prolonging medications, describe characteristics that increase patients' susceptibility to drug-induced QT prolongation, and call attention to the risk of ventricular arrhythmias in patients who are given ondansetron.

Fatal Cardiac Arrest in 2 Children: Possible Role of Ondansetron

INTRODUCTION

Ondansetron is commonly used to treat vomiting in gastroenteritis, but has a United States Food and Drug Administration black box warning for risk of Q wave to T wave time interval (QT) prolongation. We report 2 pediatric cases of fatal refractory cardiac arrest after administration of ondansetron.

CASES

A 10-year-old previously healthy boy presented to the emergency room with gastroenteritis symptoms. After intravenous fluids, morphine, antibiotics, and 2 doses of ondansetron, the patient became unresponsive with agonal respirations and a wide complex tachycardia consistent with ventricular tachycardia. In a second case, an 86-day-old infant with previously unidentified congenital cardiomyopathy presented to our emergency department with gastroenteritis symptoms. The patient received ondansetron and subsequently experienced repeated bouts of supraventricular tachycardia which progressed to ventricular fibrillation. Resuscitation efforts failed in each case, and both patients expired.

DISCUSSION

Ondansetron can cause dose-dependent QT prolongation effects, which are more clinically relevant when other proarrhythmic elements are present. There is very limited published experience on use of ondansetron in children younger than 2 years. Our 2 cases join 2 previous case reports of death after ondansetron administration for gastroenteritis. The pharmacology of ondansetron's cardiac effects and drug-induced QT prolongation is discussed.

CONCLUSIONS

Patients may have hidden risk factors that, together with ondansetron, could result in a proarrhythmic state that could lead to adverse effects, such as arrhythmias. Administration of ondansetron should be individualized and used cautiously in patients with risk factors for arrhythmia.

Effects of Palonosetron on Perioperative Cardiovascular Complications in Patients Undergoing Noncardiac Surgery With General Anesthesia: A Retrospective Cohort Study

We retrospectively investigated whether palonosetron administered during the induction of general anesthesia is associated with an increased risk of perioperative cardiovascular complications in a single tertiary center cohort consisting of 4,517 palonosetron-exposed patients and 4,517 propensity score-matched patients without palonosetron exposure. The primary endpoint was a composite of perioperative cardiovascular complications, including intraoperative cardiac arrhythmia, intraoperative cardiac death, and myocardial injury within the first postoperative week, and there was no significant difference between the groups (odds ratio [OR] = 1.04; 95% confidence interval [CI] = 0.92-1.19). As secondary endpoints, intraoperative cardioversion, cardiac compression, use of cardiovascular drugs, postoperative hospital stay, and in-hospital mortality showed no differences between the groups. However, the palonosetron group showed decreased intraoperative hypotension (OR = 0.88; 95% CI = 0.79-0.97) and length of postoperative intensive care unit (ICU) stay (4.26 ± 9.86 vs. 6.14 ± 16.75; P = 0.026). Palonosetron did not increase the rate of perioperative cardiovascular complications, and can therefore be used safely during anesthetic induction.

Ondansetron and the risk of cardiac arrhythmias: a systematic review and postmarketing analysis

STUDY OBJECTIVE

To explore the risk of cardiac arrhythmias associated with ondansetron administration in the context of recent recommendations for identification of high-risk individuals.

METHODS

We conducted a postmarketing analysis and systematically reviewed the published literature, grey literature, manufacturer's database, Food and Drug Administration Adverse Events Reporting System, and the World Health Organization Individual Safety Case Reports Database (VigiBase). Eligible cases described a documented (or perceived) arrhythmia within 24 hours of ondansetron administration. The primary outcome was arrhythmia occurrence temporally associated with the administration of a single, oral ondansetron dose. Secondary objectives included identifying all cases associating ondansetron administration (any dose, frequency, or route) to an arrhythmia.

RESULTS

Primary: No reports describing an arrhythmia associated with single oral ondansetron dose administration were identified. Secondary: Sixty unique reports were identified. Route of administration was predominantly intravenous (80%). A significant medical history (67%) or concomitant use of a QT-prolonging medication (67%) was identified in 83% of reports. Approximately one third occurred in patients receiving chemotherapeutic agents, many of which are known to prolong the QT interval. An additional third involved administration to prevent postoperative vomiting.

CONCLUSION

Current evidence does not support routine ECG and electrolyte screening before single oral ondansetron dose administration to individuals without known risk factors. Screening should be targeted to high-risk patients and those receiving ondansetron intravenously.

Intravenous palonosetron increases the incidence of QTc prolongation during sevoflurane general anesthesia for laparotomy

Background

Palonosetron is a recently introduced 5-hydroxytryptamine-3 (5-HT₃) receptor antagonist useful for postoperative nausea and vomiting prophylaxis. However, 5-HT₃ receptor antagonists increase the corrected QT (QTc) interval in patients who undergo general anesthesia. This retrospective study was performed to evaluate whether palonosetron would induce a QTc prolongation in patients undergoing general anesthesia with sevoflurane.

Methods

We reviewed a database of 81 patients who underwent general anesthesia with sevoflurane. We divided the records into palonosetron (n = 41) and control (n = 40) groups according to the use of intraoperative palonosetron, and analyzed the electrocardiographic data before anesthesia and 30, 60, 90, and 120 min after skin incision. Changes in the QTc interval from baseline, mean blood pressure, heart rate, body temperature, and sevoflurane concentrations at each time point were compared between the two groups.

Results

The QTc intervals at skin incision, and 30, 60, 90, and 120 min after the skin incision during general anesthesia were significantly longer than those at baseline in the two groups (P < 0.001). The changes in the QTc intervals were not different between the two groups (P = 0.41). However, six patients in the palonosetron group showed a QTc interval > 500 ms 30 min after skin incision, whereas no patient did in the control group (P = 0.01). No significant differences were observed between the two groups in mean blood pressure, body temperature, heart rate, or sevoflurane concentrations.

Conclusions

Palonosetron may induce QTc prolongation during the early general anesthesia period with sevoflurane.

Comparative electrocardiographic effects of intravenous ondansetron and granisetron in patients undergoing surgery for carcinoma breast: A prospective single-blind randomised trial

Background:

Postoperative nausea and vomiting (PONV) are common and distressing symptoms after surgery performed under general anaesthesia. 5-hydroxytryptamine₃ antagonists are routinely used for prevention and treatment of PONV. The aim of our study was to compare the incidence of QTc prolongation and quantify the amount of QTc prolongation with ondansetron and granisetron.

Methods:

This prospective, randomised, single-blind study was carried out in the OT and Recovery Room (RR) of a tertiary referral cancer centre. After obtaining Institutional Review Board approval and written informed consent from the patients, 70 patients undergoing elective surgery for carcinoma breast were included. In the RR, patients randomly received 8 mg of ondansetron or 1 mg of granisetron intravenously. Serial ECGs were recorded at various intervals, Non-invasive blood pressure and SpO₂ were also recorded. Chi-square test and Mann-Whiteny test were used for statistical analysis.

Results:

The demographics were similar in both groups. The incidence of significant QTc prolongation was significantly higher in the ondansetron group (22 of 37 (59.4%) vs. 11 of 33 patients (33.33%) (P<0.05)). There was an increase in the QTc interval in both the groups as compared to the baseline. The median prolongation in QTc interval from baseline was much more in the ondansetron group; this was statistically significant only at 5 and 15 min.

Conclusion:

Granisetron may be a safer option than ondanasetron for prevention and treatment of PONV due to lesser prolongation QTc interval. (ClinicalTrials.gov ID: NCT01352130)

Effect of competition bias in safety signal generation: analysis of a research database of spontaneous reports in France

BACKGROUND

Automated disproportionality analysis of spontaneous reporting is increasingly used routinely. It can theoretically be influenced by a competition bias for signal detection owing to the presence of reports related to well-established drug-event associations.

OBJECTIVE

The aim of the study was to explore the effects of competition bias on safety signals generated from a large spontaneous reporting research database.

METHODS

Using the case/non-case approach in the French spontaneous reporting research database, which includes data of reporting in France from January 1986 to December 2001, the effects of the competition bias were explored by generating safety signals associated with six events of interest (gastric and oesophageal haemorrhages, central nervous system haemorrhage and cerebrovascular accidents, ischaemic coronary disorders, migraine headaches, muscle pains, and hepatic enzymes and function abnormalities) before and after removing from the database reports relating to drugs known to be strongly associated with these events, whether they constituted cases or non-cases. As this study was performed on a closed database (last data entered 31 December 2001), potential signals unmasked by removal were considered as real signals if no or only incomplete knowledge about the association was available from the literature before 1 January 2002.

RESULTS

For gastric and oesophageal haemorrhages, after removing reports involving antithrombotic agents or NSAIDs, three potential signals were unmasked (prednisone, rivastigmine and isotretinoin). For central nervous system haemorrhage and cerebrovascular accidents, after removing reports involving antithrombotic agents, three potential signals were unmasked (ethinylestradiol, interferon-α-2B and methylprednisolone). For ischaemic coronary disorders, after removing reports involving anthracyclines, bleomycine, anti-HIV drugs or triptans, one potential signal was unmasked (ondansetron). For migraine headaches, after removing reports involving nitrates, calcium channel blockers, opioid analgesics or intravenous immunoglobulins, six potential signals were unmasked (ammonium chloride, leflunomide, milnacipran, montelukast, proguanil and pyridostigmine). For muscle pains, after removing reports involving statins or fibrates, seven potential signals were unmasked (hydroxychloroquine, lactulose, levodopa in combination with dopadecarboxylase inhibitor, nevirapine, nomegestrol, ritonavir and stavudine). Finally, for hepatic enzymes and function abnormalities, after removing reports involving NSAIDs, anilides, antituberculosis drugs, antiepileptics, ketoconazole, tacrine, or amineptine, two potential signals were unmasked (caffeine, metformin). Of all these unmasked potential signals, ten appeared non/incompletely documented as at 1 January 2002 and were considered as real signals, with three of these later being confirmed by the literature and finally considered as true positives (isotretinoin, methylprednisolone and milnacipran).

CONCLUSION

This study confirms that a competition bias can occur when performing safety signal generation in spontaneous reporting databases. The minimization of this bias could lead to previously masked signals being revealed.

Acute effect of palonosetron on electrocardiographic parameters in cancer patients: a prospective study

OBJECTIVES

Palonosetron is a novel 5-hydroxytryptamine(3) (5 HT(3)) receptor antagonist, which has been shown to be superior to first generation 5 HT(3) receptor antagonists regarding the prevention of acute, delayed and overall chemotherapy-induced nausea and vomiting. First generation 5 HT(3) receptor antagonists may induce electrocardiographic changes of heart rate and repolarization. The acute cardiac effect of palonosteron is unknown. The purpose of this study is to determine acute effects of palonosetron on electrocardiographic (ECG) parameters in cancer patients.

MATERIALS AND METHODS

The study had a prospective design. Seventy-six cancer patients with normal cardiac function who received palonosetron for prevention of chemotherapy-induced nausea and vomiting were enrolled. Standard 12-lead ECG recordings were performed at baseline and 30 min after palonosetron administration. P wave durations and corrected QT intervals were measured; P wave dispersion (Pd) and QTc dispersion were calculated.

RESULTS

Median heart rate did not differ among 76 patients enrolled before and after palonosetron administration (p: 0.6). Systolic and diastolic blood pressures were not significantly different before and after palonosteron (p values 0.9 and 0.3, respectively). Although median QT min value was higher after palonosetron administration than before palonosetron administration, the difference was not statistically significant (p: 0.6).

CONCLUSION

Palonosetron seems to have no acute arrhythmogenic potential.

Fluorouracil Induces Myocardial Ischemia With Increases of Plasma Brain Natriuretic Peptide and Lactic Acid but Without Dysfunction of Left Ventricle

Purpose

Fluorouracil (FU) is a cornerstone of colorectal cancer treatment; however, it has clinical and subclinical influence on the heart. This study aimed to clarify the pathophysiology, risk factors, and long-term effects of FU cardiotoxicity.

Patients and Methods

The study prospectively accrued colorectal cancer patients (n = 106) completely resected and adjuvantly treated with FU and oxaliplatin according to the FOLFOX4 regimen (infusional FU, folinic acid, and oxaliplatin). Serial measurements were made of systolic and diastolic features of the left ventricle by radionuclide ventriculography, plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP), lactic acid, and ECG before chemotherapy, immediately after a treatment infusion, and at follow-up 2 weeks after cessation of the intended 12 treatment courses and were further evaluated by multivariate regression analysis that included cardiovascular history and its risk factors.

Results

In the entire cohort, NT-proBNP significantly increased from baseline 14.5 ± 3.2 pmol/L (mean ± standard error) to 28.3 ± 5.3 pmol/L during FU therapy (P < .001). Nine patients (8.5%) with cardiotoxicity had significantly higher NT-proBNP of 55.3 ± 40.8 pmol/L compared with 25.4 ± 4.1 pmol/L in those without (P < .001). In multivariate analysis, the FU-induced rise of NT-proBNP was significantly higher in females (P < .001). Plasma lactic acid significantly increased from baseline (1.3 ± 0.1 mmol/L to 1.8 ± 0.1 mmol/L) during FU therapy (P < .001). Left ventricular ejection fraction at baseline of 0.66 ± 0.01 remained unchanged at 0.65 ± 0.01 during FU therapy and 0.66 ± 0.01 at follow-up (P = .4).

Conclusion

FU therapy generally induces myocardial neuroendocrine changes with increasing plasma NT-proBNP and lactic acid but without long-term dysfunction of the left ventricle. The usability of NT-proBNP as a predictive marker for FU cardiotoxicity remains to be clarified.

Coronary Vasospasm and Atrial Fibrillation Associated with Ondansetron Therapy

Objective:

To provide further evidence of cardiovascular adverse effects of ondansetron, including new-onset atrial fibrillation, ST segment elevation, and chest pain subsequent to ondansetron administration, and to review cardiovascular adverse events related to several 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists.

Case Summary:

A 51-year-old male with an uncomplicated past medical history was admitted for an elective inguinal hernia repair and septoplasty. His maintenance medications were discontinued prior to surgery. After a second 4-mg dose of intravenous ondansetron was administered, he developed nausea and diaphoresis. His electrocardiograph revealed new-onset atrial fibrillation and inferolateral ST segment elevation with ST segment alternans. During emergent cardiac catheterization, no obstructive coronary artery disease was evident. The patient's heart rhythm was electrically converted to normal sinus rhythm. During 3 years of follow-up, he has had no return of chest pain or hypotension.

Discussion:

Although considered a safe class of medications by many clinicians, several of the 5-HT3 receptor antagonists have been associated with serious cardiovascular effects. Three case reports described cardiac dysrhythmias and 9 documented coronary vasospasm and chest pain, possibly resulting from ondansetron. This is the first reported case of a combination of hypotension, atrial fibrillation, ST segment elevation, and chest pain following ondansetron administration after elective surgery in a healthy adult male with a nonconfounding medication profile. The Naranjo probability scale indicated that ondansetron was the probable cause of these cardiovascular events.

Conclusions:

This case report supports the concern regarding cardiovascular adverse effects of ondansetron. Clinicians should be aware of cardiovascular adverse reactions that may be associated with intravenous ondansetron and monitor for electrocardiographic changes as indicated. Further investigation is needed to delineate the actual incidence of cardiovascular effects associated with ondansetron and whether the intravenous rate of administration is a contributing factor.

Polyphenol contents in grape-seed extracts correlate with antipica effects in cisplatin-treated rats

BACKGROUND

Grape-seed (Vitis spp.) extract (GSE) is a widely used antioxidant dietary supplement. Chemotherapeutic agents such as cisplatin induce oxidative damage in the gastrointestinal tract and cause nausea and vomiting.

MATERIALS AND METHODS

A rat model of simulated emesis was used to observe that cisplatin significantly increased kaolin consumption (or pica). Three GSEs from different sources were used in this study.

RESULTS

High-performance liquid chromatographic analysis of five major constituents (gallic acid, catechin, epicatechi, procyanidin B2, and epicatechin gallate) revealed that each constituent had different levels in the three GSEs. Extract #1, prepared in the laboratory of the investigators, had the lowest total polyphenol content (27.27 mg/g); Extract #2, obtained from a dietary supplement company in the United States, had a somewhat higher level (35.84 mg/g); and Extract #3, obtained from China, had the highest level (194.21 mg/g). Subsequently these GSEs were intraperitoneally administered in rats to evaluate their ability to decreasing cisplatin induced pica. At 10 mg/kg all three GSEs, with varying degrees of effect, decreased cisplatin-induced pica. The areas under the curves of kaolin intake from time 0 to 72 hours, compared to those in the cisplantin-only group, were reduced 45% for Extract #1 (p < 0.01), 54% for Extract #2 (p < 0.01), and 66% Extract #3 (p < 0.001).

CONCLUSIONS

The study data showed variable polyphenol contents and proportions in the three GSEs correlated to variable pharmacologic effects, indicating the importance of standardization of herbal product preparations. However further increasing of the GSE doses reversed the antipica effects of GSEs, probably because of their pro-oxidant effects. Results from this study suggest that an appropriate dose of GSE has therapeutic value in treating cisplatin-induced emesis.

Coronary vasospasm leading to an acute myocardial infarction after the administration of dolasetron

The 5-hydroxytryptamine antagonists are commonly used agents for the treatment of postoperative nausea and vomiting. However, these drugs can have significant cardiovascular adverse effects. We report a case of acute myocardial infarction after administration of dolasetron in a 17-year-old adolescent girl during strabismus corrective surgery.

Benefits and risks of newer treatments for chemotherapy-induced and postoperative nausea and vomiting

Nausea and vomiting are common adverse effects of chemotherapy, radiation therapy, anaesthesia and surgery. The incidence of chemotherapy-induced nausea and vomiting (CINV) is estimated to vary from 30 to 90%, depending on the type of chemotherapeutic agent used. Radiation-induced emesis varies with anatomical site radiated but is estimated to have an overall incidence of approximately 40%. The incidence of postoperative nausea and vomiting (PONV) depends on the type of anaesthesia and surgery, but overall is estimated to be 20-30%. Evidence-based medicine and meta-analysis have been used to direct medical therapy to help determine equivalence, optimal dose, timing, safety and efficacy of antiemetic medications. Concepts such as the number needed to treat and number needed to harm are helpful to guide the clinician regarding the benefits and risks of a particular treatment. The serotonin 5-HT(3) receptor antagonists ondansetron, granisetron, tropisetron and dolasetron have been important additions to the antiemetic armamentarium. The 5-HT(3) receptor antagonists are similar in chemical structure, efficacy and adverse effect profile. They appear to have no important differences among themselves in clinical outcomes for CINV and PONV. Headache, dizziness, constipation and diarrhoea are their most common adverse effects, and when they occur they are usually mild and easily managed. Haemodynamic changes and extrapyramidal adverse effects are uncommon. ECG changes such as prolonged corrected QT (QTc) interval are infrequent, dose-related and overall judged to be clinically insignificant. As most studies with the 5-HT(3) antagonists have been conducted on relatively healthy patients, caution should be exercised when these drugs are used in susceptible patients with co-morbidities. The clinician must weigh the benefit of administering an antiemetic for CINV or PONV against the risk of occurrence of an adverse event.

Atrial fibrillation after ondansetron for the prevention and treatment of postoperative nausea and vomiting: a case report

PURPOSE

Even though clinical safety has been established in large studies, ondansetron has been reported to cause adverse cardiovascular events. We present a case of atrial fibrillation in association with ondansetron in the postoperative period.

CLINICAL FEATURES

A 47-yr-old, 81 kg female presented with a benign lump in her left breast for lumpectomy. Her past medical history was unremarkable. Physically she was very active, non-smoker and had no allergies. She underwent the procedure under general anesthesia. She received 4 mg of ondansetron intravenously for postoperative nausea and vomiting prophylaxis at the end of the procedure and an additional 4 mg in the recovery room for nausea. Within 15 min after the second dose she was noted to be in atrial fibrillation that required admission to the hospital and procainamide infusion for conversion to normal sinus rhythm. She did not have any evidence of myocardial ischemia, valvular abnormality or pulmonary embolism.

CONCLUSION

The 5-hydroxytryptamine 3 receptor (5-HT(3)) antagonist ondansetron has been reported to cause myocardial ischemia, supraventricular and ventricular tachycardia. Postulated mechanism includes inhibition of Bezold-Zarisch cardiac reflex and coronary vasoconstriction. Inhibition of 5-HT(3) receptors in the heart could lead to unopposed action of other serotonin receptors leading to atrial fibrillation or other tachyarrhythmias described in the literature.

The cardiotoxic potential of the 5-HT(3) receptor antagonist antiemetics: is there cause for concern?

PURPOSE

To review and evaluate the potential cardiac effects of 5-HT(3) antiemetic treatment in patients who may be predisposed to cardiac complications resulting from malignancy, cytotoxic oncologic regimens, or preexisting comorbid conditions.

DESIGN

A literature review was conducted on the negative cardiovascular effects of chemotherapeutic agents, and, more specifically, on the cardiac interactions of the 5-HT(3) receptor antagonists commonly used to treat chemotherapy-induced nausea and vomiting.

RESULTS

Clinical studies in healthy subjects have reported electrocardiograph changes following administration of 5-HT(3) receptor antagonists. However, there are limited data on the use of 5-HT(3) antiemetics when administered with cardiotoxic chemotherapy. Nonetheless, the development of significant electrocardiograph changes with some agents may indicate a potential for significant cardiac effects in patients, particularly those who may be predisposed to cardiac complication.

CONCLUSIONS

As the predicted human life span increases, clinicians will be treating a larger, older oncology population. Because two of the most common major comorbidities are cardiovascular related, we need to be acutely aware of the toxic effects of chemotherapy, as well as the possible cardiac interaction of supportive agents, specifically the 5-HT(3) antiemetics. Until more data are made available, the best antiemetic option for patients receiving emetogenic and cardiotoxic chemotherapy may be the agent with the fewest apparent cardiac effects.

The efficacy of RS-25259, a long-acting selective 5-HT3 receptor antagonist, for preventing postoperative nausea and vomiting after hysterectomy procedures

We evaluated the safety and efficacy of RS-25259, a potent and long-acting selective 5-HT3 receptor antagonist, for the prevention of postoperative nausea and vomiting (PONV) in women undergoing hysterectomy procedures. In this randomized, double-blind, placebo controlled, dose-ranging study, 218 healthy, consenting women were assigned to one of the six treatment groups: placebo or RS-25259 0.1, 0.3, 1.0, 3.0, or 30 microg/kg. All patients underwent a standardized general anesthetic technique. The study medication was administered i.v. 20-30 min before the end of surgery. During the initial 24-h period after surgery, the incidence of vomiting, the need for rescue antiemetics, the time to the first episode of emesis, and administration of rescue antiemetic medication, as well as a nausea visual analog scale and verbal categorical scale scores were recorded. In addition, recovery times from the end of anesthesia and the incidences of perioperative side effects were noted. Only 30 microg/kg RS-25259 significantly decreased the incidence of vomiting and the requirement for rescue antiemetics. The largest dose of RS-25259 also delayed the time to the first emetic episode and reduced the number of treatment failures. However, no differences were found in the severity of postoperative nausea (versus saline), and postoperative headaches were more common after the administration of RS-25259 0.3-30 microg/kg i.v. In conclusion, RS-25259 30 microg/kg i.v. was effective in reducing the incidence of PONV after major gynecologic surgery, but the occurrence of headaches with the larger doses of RS-25259 is a concern.

IMPLICATIONS

RS-25259, a long-acting 5-HT3 antagonist, was effective in reducing postoperative vomiting only at the largest dose studied (30 microg/kg). However, RS-25259 had no antinausea activity, and the larger doses were associated with an increased incidence of headaches in the postoperative period.

A risk-benefit assessment of serotonin 5-HT3 receptor antagonists in antineoplastic therapy-induced emesis

Insight into the pathophysiology of antineoplastic therapy-induced nausea and vomiting led to the development of the serotonin 5-HT3 receptor antagonists as the most potent class of antiemetic agents. Among those which have been investigated are ondansetron, granisetron, tropisetron and dolasetron. A risk-benefit analysis of these drugs must not only account for the modest clinical differences in efficacy and tolerability, but also should include such issues as ease of use, route of administration, dosage considerations and patient preference. Pharmacokinetic and preclinical studies reveal distinctions among these antiemetics, but, overall, these distinctions do not translate in to clinically significant differences. In clinical trials, the most widely studied members of the 5-HT3 receptor antagonists are granisetron and ondansetron, which have been found to possess equivalent antiemetic efficacy. Dolasetron and tropisetron are also available, and some randomised trials have also documented their similar antiemetic activity, depending on the doses and schedules used. The equivalent efficacy of oral granisetron 2 mg versus intravenous ondansetron 32 mg has recently been demonstrated in prospective randomised clinical trials in patients receiving either highly emetogenic or moderately emetogenic antineoplastic therapy. The utilisation and efficacy of oral ondansetron and dolasetron in patients receiving moderately emetogenic antineoplastic therapy has also been documented. This review offers a brief overview of the pharmacokinetic and preclinical research on the 5-HT3 antagonists, a review of the comparative clinical trials of the major members of this class and a summary risk-benefit assessment that considers clinical applicability and cost, as well as efficacy and safety.

Pharmacological characterization of RS 25259-197, a novel and selective 5-HT3 receptor antagonist, in vivo

1. The pharmacological effects in vivo, of RS 25259-197, a selective 5-HT3 receptor antagonist, have been investigated. 2. In anaesthetized rats, RS 25259-197, administered by the intravenous, intraduodenal or transdermal route, dose-dependently inhibited the von Bezold-Jarisch reflex induced by 2-methyl 5-HT (ID50 = 0.04 micrograms kg-1, i.v., 3.2 micrograms kg-1, i.d. and 32.8 micrograms per chamber, respectively). In this regard, when administered intraduodenally, RS 25259-197 was more potent and exhibited a longer duration of action than either ondansetron or granisetron. 3. In conscious ferrets, RS 25259-197, administered intravenously or orally, dose-dependently inhibited emesis induced by cisplatin. The ID50 estimates of RS 25259-197 were 1.1 micrograms kg-1, i.v. and 3.2 micrograms kg-1, p.o. In this respect, RS 25259-197 was more potent than ondansetron and equipotent with granisetron. 4. In conscious dogs, RS 25259-197, administered intravenously or orally, dose-dependently inhibited emesis induced by cisplatin (ID50 = 1.9 micrograms kg-1, i.v. and 8.5 micrograms kg-1, p.o.), dacarbazine (ID50 = 4.1 micrograms kg-1, i.v. and 9.7 micrograms kg-1, p.o.), actinomycin D (ID50 = 4.9 micrograms kg-1, i.v. and 2.5 micrograms kg-1, p.o.) and mechlorethamine (ID50 = 4.4 micrograms kg-1, i.v. and 3.0 micrograms kg-1, p.o.). Against each of the emetogenic agents, RS 25259-197 was very much more potent than ondansetron. When tested at equi-effective intravenous doses against cisplatin-induced emesis in dogs, RS 25259-197 had a longer duration of anti-emetic activity (7 h) than ondansetron (4 h). At doses up to and including 1000 microg kg-1, p.o., neither RS25259-197 nor ondansetron was capable of inhibiting apomorphine-induced emesis.5. At doses up to 1000 microg kg-1, i.v., RS 25259-197 produced no meaningful haemodynamic changes in anaesthetized dogs.6. In summary, RS 25259-197 is a novel, highly potent and orally active 5-HT3 receptor antagonist in vivo. With respect to its anti-emetic activity, RS 25259-197 appears to be a significant improvement over ondansetron in terms of potency and duration of action.

Block of the delayed rectifier current (IK) by the 5-HT3 antagonists ondansetron and granisetron in feline ventricular myocytes

1. We investigated the effects of two 5-HT3 antagonists, ondansetron and granisetron, on the action potential duration (APD) and the delayed rectifier current (IK) of feline isolated ventricular myocytes. Whole-cell current and action potential recordings were performed at 37 degrees C with the patch clamp technique. 2. Ondansetron and granisetron blocked IK with a KD of 1.7 +/- 1.0 and 4.3 +/- 1.7 microM, respectively. At a higher concentration (30 microM), both drugs blocked the inward rectifier (IKl). 3. The block of IK was dependent on channel activation. Both drugs slowed the decay of IK tail currents and produced a crossover with the pre-drug current trace. These results are consistent with block and unblock from the open state of the channel. 4. Granisetron showed an intrinsic voltage-dependence as the block increased with depolarization. The equivalent voltage-dependency of block (delta) was 0.10 +/- 0.04, suggesting that granisetron blocks from the intracellular side at a binding site located 10% across the transmembrane electrical field. 5. Ondansetron (1 microM) and granisetron (3 microM) prolonged APD by about 30% at 0.5 Hz. The prolongation of APD by ondansetron was abolished at faster frequencies (3 Hz) showing reverse rate dependence. 6. In conclusion, the 5-HT3 antagonists, ondansetron and granisetron, are open state blockers of the ventricular delayed rectifier and show a clear class III action.

Antiemetics in cancer chemotherapy: historical perspective and current state of the art

Chemotherapy-related nausea and vomiting can today be controlled with available antiemetics in a high percentage of patients but emesis remains a problem for some patients, with certain drugs and with repeated cycles of chemotherapy. The fundamental steps of clinical research in antiemetics towards the improvement of the control of nausea and vomiting with new drugs or combinations are presented. Special emphasis is given to cisplatin-induced nausea and vomiting because of the frequency and relevance of this phenomenon. The use of high-dose metoclopramide, its combination with steroids, and later the addition of lorazepam or diphenhydramine represented the evolving standard of the 1980s, with the level of complete protection from vomiting improving from 30%-40% to 60%-70% with the three-drug combination. The introduction of new agents such as the 5-hydroxytryptamine 3 (5-HT3) receptor antagonists has recently offered new possibilities because of their activity and lack of toxicity. In particular, the combination of ondansetron plus dexamethasone is today the most efficacious and least toxic antiemetic treatment for prevention of emesis in patients treated with a single high dose or low repeated doses of cisplatin. A comparison of different 5-HT3 antagonists, always in combination with steroids, is now considered necessary. For patients treated with moderately emetogenic chemotherapy the use of steroids can still be considered the standard treatment. In this setting, the role of 5-HT3 receptor antagonists, alone or in combination with steroids, has to be better defined through large, well-planned clinical trials, which should have a cost-effectiveness analysis as one of their goals.