Characterization of the novel 5-HT3 antagonists MDL 73147EF (dolasetron mesilate) and MDL 74156 in NG108-15 neuroblastoma x glioma cells

5-HT3 Receptor Antagonists in Neurologic and Neuropsychiatric Disorders: The Iceberg Still Lies beneath the Surface

5-HT₃ receptor antagonists, first introduced to the market in the mid-1980s, are proven efficient agents to counteract chemotherapy-induced emesis. Nonetheless, recent investigations have shed light on unappreciated dimensions of this class of compounds in conditions with an immunoinflammatory component as well as in neurologic and psychiatric disorders. The promising findings from multiple studies have unveiled several beneficial effects of these compounds in multiple sclerosis, stroke, Alzheimer disease, and Parkinson disease. Reports continue to uncover important roles for 5-HT₃ receptors in the physiopathology of neuropsychiatric disorders, including depression, anxiety, drug abuse, and schizophrenia. This review addresses the potential of 5-HT₃ receptor antagonists in neurology- and neuropsychiatry-related disorders. The broad therapeutic window and high compliance observed with these agents position them as suitable prototypes for the development of novel pharmacotherapeutics with higher efficacy and fewer adverse effects.

Effects of 5-hydroxytryptamine on spermatozoal hyperactivation and in vitro fertilization in mice

In this study, we examined the effects of 5-hydroxytryptamine (5-HT) on the motility and hyperactivation of mouse spermatozoa. In addition, we examined whether 5-HT increases the success of in vitro fertilization (IVF) in mice. Interestingly, 5-HT and agonists of the 5-HT₂, 5-HT₃, 5-HT₄, and 5-HT₇ receptors significantly increased the percentage of hyperactivated spermatozoa but did not affect the percentage of motile spermatozoa. Moreover, agonists of the 5-HT₂, 5-HT₃, and 5-HT₄ receptors significantly affected the velocities, linearity, straightness, wobbler coefficient, amplitude and/or frequency of spermatozoa. In particular, the improvement of hyperactivation by 5-HT was strongly inhibited by antagonists of the receptors 5-HT₄ and 5-HT₇ and was completely inhibited by a mixture of the four 5-HT-receptor antagonists. The increase in hyperactivation by the agonists was significantly inhibited by the corresponding 5-HT-receptor antagonist. Moreover, 5-HT significantly increased the percentage of two-cell embryos. The increase in the IVF success rate by 5-HT was significantly inhibited by a 5-HT₄-receptor antagonist. These results suggest that 5-HT increased hyperactivation through the 5-HT receptors and increased the success of IVF in mice.

Ondansetron: a review of pharmacokinetics and clinical experience in postoperative nausea and vomiting

INTRODUCTION

Postoperative nausea and vomiting (PONV) is associated with poor patient satisfaction and delayed recovery after general anesthesia. Multiple neurotransmitters are involved in the mediation of PONV but despite the introduction of new antiemetics, no completely effective drug exists for its prevention or treatment.

AREAS COVERED

This review provides a detailed description of ondansetron's chemistry, pharmacokinetics, pharmacodynamics, toxicity and a brief review of clinical trials involving ondansetron and the management of PONV. We searched reviews, meta-analysis and randomized controlled trials (Medline, Embase and article reference lists).

EXPERT OPINION

According to current literature, administering ondansetron 4 mg i.v. near the end of surgery provides sufficient protection against PONV in low- and moderate-risk patients, comparable to traditional antiemetics such as antihistamines and droperidol. High-risk patients require a multimodal approach since one quarter of them will not respond to monotherapy. In the future, transdermal formulation or formulations for nasal or buccal delivery will be available. The development of non-racemic mixture consisting of R-ondansetron would enhance the safety profile and probably the efficacy too.

Lack of Effect of Aprepitant on Hydrodolasetron Pharmacokinetics in CYP2D6 Extensive and Poor Metabolizers

To prevent chemotherapy-induced nausea and vomiting, aprepitant is given with a corticosteroid and a 5-hydroxytryptamine type 3 antagonist, such as dolasetron. Dolasetron is converted to the active metabolite hydrodolasetron, which is cleared largely via CYP2D6. The authors determined whether aprepitant, a moderate CYP3A4 inhibitor, alters hydrodolasetron pharmacokinetics in CYP2D6 poor and extensive metabolizers. Six CYP2D6 poor and 6 extensive metabolizers were randomized in an open-label, crossover fashion to treatment A (dolasetron 100 mg on day 1) and treatment B (dolasetron 100 mg plus aprepitant 125 mg on day 1, aprepitant 80 mg on days 2-3). For hydrodolasetron area under the concentration-versus-time curve (AUC0-infinity) and peak plasma concentration (Cmax), geometric mean ratios (B/A) and 90% confidence intervals (CIs) fell below the predefined limit (2.0) for clinical significance (AUC0-infinity, 1.09 [90% CI, 1.01-1.18], Cmax, 1.08 [90% CI, 0.94-1.24]). Aprepitant did not affect the pharmacokinetics of hydrodolasetron, regardless of CYP2D6 metabolizer type, and was generally well tolerated when coadministered with dolasetron in volunteers.

Optimization of sample pretreatment methods for simultaneous determination of dolasetron and hydrodolasetron in human plasma by HPLC-ESI-MS

A high-performance liquid chromatographic method coupled with electrospray mass spectrometry was developed for the simultaneous determination of dolasetron and its major metabolite, hydrodolasetron, in human plasma. A new sample pretreatment method, i.e., salt induced phase separation extraction (SIPSE), was proposed and compared with four other methods, i.e., albumin precipitation, liquid-liquid extraction, hydrophobic solvent-induced phase separation extraction and subzero-temperature induced phase separation extraction. Among these methods, SIPSE showed the highest extraction efficiency and the lowest matrix interferences. The extraction recoveries obtained from the SIPSE method were all more than 96% for dolasetron, hydrodolasetron and ondansetron (internal standard). The SIPSE method is also very fast and easy because protein precipitation, analyte extraction and sample cleanup are combined into one simple process by mixing acetonitrile with plasma and partitioning with 2 mol/L sodium carbonate aqueous solution. The correlation coefficients of the calibration curves were all more than 0.997, in the range of 7.9-4750.0 ng/mL and 4.8-2855.1 ng/mL for dolasetron and hydrodolasetron, respectively. The limits of quantification were 7.9 and 4.8 ng/mL for dolasetron and hydrodolasetron, respectively. The intra-day and inter-day repeatability were all less than 10%. The method was successfully applied to the pharmacokinetic study of dolasetron.

Lack of analgesic efficacy of spinal ondansetron on thermal and mechanical hypersensitivity following spinal nerve ligation in the rat

The balance between descending inhibition and facilitation is thought to be disturbed in chronic pain states. Increased facilitation by spinally released serotonin has been suggested by demonstration that mechanically evoked neuronal responses of wide dynamic range neurons are inhibited by 5-HT3 receptor antagonists in rats following spinal nerve ligation (SNL) but not sham operation. Despite these physiologic data, the effects of spinal 5-HT3 receptor blockade on behavioral hypersensitivity and neurochemical alterations in spinal serotonergic system have not been thoroughly investigated following spinal nerve ligation in the rat. To test this, we acutely injected intrathecal ondansetron in rats between 14 and 30 days after SNL and assessed effects on thermal and mechanical hypersensitivity. We also determined the density of serotonergic nerve fibers, serotonin content and the levels of 5-HT3 receptors within the spinal cord at this time point. Intrathecal ondansetron (1, 3, 10, 30, and 100microg) produced no effect on behavioral measures of thermal or mechanical hypersensitivity whereas intrathecal morphine (1microg) and gabapentin (200microg) partially reversed thermal and mechanical hypersensitivity following SNL. In addition, SNL did not alter the density of serotonergic fibers or 5-HT3 receptor immunoreactivity or spinal tissue content of 5-HT within the dorsal horn. These results do not support anatomic plasticity of descending serotonergic pathways or tonic 5-HT3 receptor activity in maintaining hypersensitivity after nerve injury and in contrast to previous studies fail to demonstrate an anti-hypersensitivity effect of intrathecal injection of the 5-HT3 receptor antagonist ondansetron. Importantly, behavioral measures of mechanical hypersensitivity assess threshold responses whereas physiological studies of mechanically evoked neuronal responses involve application of suprathreshold stimuli. Thus, suprathreshold or more intense stimuli may be necessary to recruit descending serotonergic facilitatory drive required to observe the inhibitory effects of ondansetron on spinal neuronal excitability and behavioral hypersensitivity.

Carbonyl Reductases and Pluripotent Hydroxysteroid Dehydrogenases of the Short-chain Dehydrogenase/reductase Superfamily

Carbonyl reduction of aldehydes, ketones, and quinones to their corresponding hydroxy derivatives plays an important role in the phase I metabolism of many endogenous (biogenic aldehydes, steroids, prostaglandins, reactive lipid peroxidation products) and xenobiotic (pharmacologic drugs, carcinogens, toxicants) compounds. Carbonyl-reducing enzymes are grouped into two large protein superfamilies: the aldo-keto reductases (AKR) and the short-chain dehydrogenases/reductases (SDR). Whereas aldehyde reductase and aldose reductase are AKRs, several forms of carbonyl reductase belong to the SDRs. In addition, there exist a variety of pluripotent hydroxysteroid dehydrogenases (HSDs) of both superfamilies that specifically catalyze the oxidoreduction at different positions of the steroid nucleus and also catalyze, rather nonspecifically, the reductive metabolism of a great number of nonsteroidal carbonyl compounds. The present review summarizes recent findings on carbonyl reductases and pluripotent HSDs of the SDR protein superfamily.

The 5-HT3 receptor as a therapeutic target

The 5-HT3 receptor is a neurotransmitter-gated ion channel. It is a member of the Cys-loop family of receptors, which also includes nicotinic acetylcholine, glycine and GABAA receptors. Each member of the family consists of an arrangement of five subunits surrounding a central ion-conducting pore. The 5-HT3 receptor binding site is composed of six loops from two adjacent subunits, and the critical ligand binding residues within these loops are well documented. There are a range of 5-HT3 receptor agonists and competitive antagonists, but it is the antagonists that dominate their clinical use. Studies have proposed a range of disease symptoms that might be amenable to 5-HT3 receptor selective compounds; however, so far only the treatment of emesis and irritable bowel syndrome have been fully realised. In this review, the authors look at the structure, function and distribution of 5-HT3 receptors and how this may influence their role in disease. The authors also describe the existing clinical applications of 5-HT3 antagonists and the future potential of these drugs.

Antiemetic therapy in cancer: an update

Although nausea and vomiting are widely recognised as two of the most distressing symptoms of cytotoxic therapy, there is still concern over the adequate control of these symptoms in the cancer population. Recently updated Antiemetic Consensus Guidelines recommend the prophylactic treatment of all patients at moderate-to-high risk of experiencing nausea and vomiting following chemotherapy and radiotherapy. It is important that these guidelines are fully adhered to; however, when considering which antiemetic regimen is most appropriate in an individual patient, it is also important to consider individual patient-related factors. In addition, certain patient groups, such as the young or the elderly, may be in need of specific consideration due to age-related factors that may influence treatment decisions.

5-HT(3)-receptor antagonists in the management of nausea and vomiting in cancer and cancer treatment

The 5-HT(3)-receptor antagonists, considered as 'gold standard' therapy for cancer patients, are generally perceived to have similar efficacy and safety profiles, andmost antiemetic guidelines do not distinguish between agents. However, important pharmacological differences exist between agents, which may translate into potential benefits for some patients. In particular, 5-HT(3)-receptor antagonists vary in the nature of their receptor antagonism and plasma half-lives, possibly leading to differences in duration of action. Agents with a longer duration of action provide antiemetic protection throughout the acute emetic period (24 h) with a single daily dose, whereas shorter-acting agents, e.g. ondansetron, may require multiple dosing for full efficacy. Differences also exist between agents in their hepatic metabolism and cardiovascular safety, which may present particular problems for elderly patients who often receive additional medications for comorbid conditions, increasing the risk of drug-drug interaction. Recent antiemetic guidelines from the National Comprehensive Cancer Network recommend preferential use of palonosetron for moderately emetogenic chemotherapy; however, this agent is newly approved and key clinical questions remain unanswered by clinical trial data. Selection of an appropriate 5-HT(3)-receptor antagonist should be based on proven efficacy and safety, as well as on the individual characteristics of the patient.

Carbonyl reduction of naltrexone and dolasetron by oxidoreductases isolated from human liver cytosol

The opioid receptor antagonist naltrexone and the antiemetic 5-HT(3) receptor antagonist dolasetron are ketonic drugs that are efficiently reduced to their corresponding alcohols in-vivo. These experiments aimed at characterizing the role in these reactions of individual oxidoreductases present in human liver cytosol. Aldo-keto reductases (AKRs) and carbonyl reductase (CR, EC 1.1.1.184) purified from human liver cytosol were incubated with varying substrate concentrations and 6beta-naltrexol or reduced dolasetron were analysed by HPLC. AKR1C1, AKR1C2, and AKR1C4 were able to reduce both substrates. On the basis of k(cat)/K(m) values, AKR1C4 was nearly 1000-fold more efficient in reducing naltrexone than was AKR1C1, while AKR1C2 was of intermediate efficiency. Substrate inhibition was observed on incubating AKR1C2 or AKR1C4 with naltrexone. In contrast, dolasetron was also a substrate of CR. AKR1C1 and AKR1C4 were the most efficient enzymes in producing reduced dolasetron. We concluded that the efficient reduction of naltrexone by AKR1C4 probably causes the high 6beta-naltrexol/naltrexone ratio in man. The rapid disappearance from human plasma of dolasetron given intravenously and its virtual absence after oral dosage are explained by its liability to reduction by several enzymes, including CR which shows widespread expression in human tissues.

Open-label, randomized comparison of the efficacy of intravenous dolasetron mesylate and ondansetron in the prevention of acute and delayed cisplatin-induced emesis in cancer patients

PURPOSE

The aim of this study is to compare the antiemetic efficacy and tolerability of intravenous dolasetron mesylate and ondansetron in the prevention of acute and delayed emesis.

MATERIAL AND METHODS

From April 2002 through October 2002, a total of 112 patients receiving cisplatin- based combination chemotherapy were randomized to receive a single i.v. dose of dolasetron 100 mg or ondansetron 8 mg, 30 minutes before the initiation of chemotherapy. In the ondansetron group, two additional doses of ondansetron 8 mg were given at intervals of 2 to 4 hours. To prevent delayed emesis, dolasetron 200 mg p.o. daily or ondansetron 8 mg p.o. bid was administered from the 2(nd) days to a maximum of 5 days. The primary end point was the proportion of patients that experienced no emetic episodes and required no rescue medication (complete response, CR) during the 24 hours (acute period) and during Day 2 to Day 5+/-2 days (delayed period), after chemotherapy. The secondary end points included the incidence and severity of emesis.

RESULTS

105 patients were evaluable for efficacy. CR rates during the acute period were 36.0% for a single dose of dolasetron 100 mg, and 43.6% for three doses of ondansetron 8 mg. CR rates during the delayed period were 8.0% and 10.9%, respectively. There was no significant difference in the efficacy between the two groups. Adverse effects were mostly mild to moderate and not related to study medication.

CONCLUSIONS

A single i.v. dose of dolasetron 100 mg is as effective as three i.v. doses of ondansetron 8 mg in preventing acute and delayed emesis after cisplatin-based chemotherapy, with a comparable safety profile.

Palonosetron: a unique 5-HT3-receptor antagonist for the prevention of chemotherapy-induced emesis

Palonosetron (Aloxi) is a 5-HT(3)-receptor antagonist antiemetic indicated for the prevention of acute and delayed nausea and vomiting following moderately emetogenic chemotherapy and for acute nausea and vomiting following highly emetogenic chemotherapy. Although it is the fourth member of this class to enter the US market, palonosetron is distinguished by distinct pharmacological characteristics. It has a higher binding affinity for the 5-HT(3 )receptor and a terminal serum half-life at least four times greater than any other available agent of this class (approximately 40 h). The high affinity and long half-life may explain the persistence of antiemetic effect throughout the delayed emesis risk period. The indications for palonosetron are supported by one dose-ranging study and three large, randomised, Phase III studies that all demonstrated at least equivalent activity (and in some cases, superior activity) compared to other 5-HT(3)-receptor antagonists. In spite of the pharmacological differences, the side effect profile of palonosetron is comparable to that of other 5-HT(3)-receptor antagonists. Palonosetron may prove valuable in combination therapy for delayed emesis and may be an appropriate agent for clinical settings, such as multiple-day chemotherapy, where acute emesis is repeatedly induced. Palonosetron provides a convenience advantage if multiple-day 5-HT(3)-receptor antagonist therapy is anticipated and is a unique addition to the antiemetic armamentarium.

Comparative review of 5-HT3 receptor antagonists in the treatment of acute chemotherapy-induced nausea and vomiting

Since their introduction, 5-HT3 receptor antagonists have become the agents of choice in the prevention of acute chemotherapy-induced nausea and vomiting and are generally superior to high-dose metoclopramide regimens. The availability of four different agents (ondansetron, granisetron, dolasetron, and tropisetron) within this class has prompted investigations into potential differences between the drugs, which appear to be few. More importantly, the results of recently conducted randomized comparative trials in patients receiving moderately or highly emetogenic chemotherapy have demonstrated similar efficacy. Although study designs and patient populations differed, seven large comparative trials in patients receiving highly emetogenic chemotherapy reported no significant differences in complete or complete plus major response rates among the agents. Similar results were generally reported in trials evaluating patients receiving moderately emetogenic chemotherapy. The safety and tolerability of these agents also appear to be similar. The most common adverse events include headache, gastrointestinal effects, lightheadedness, and sedation. All agents are available in both intravenous and oral dosage forms and may be administered as a single dose.

Pooled analysis of three large clinical trials to determine the optimal dose of dolasetron mesylate needed to prevent postoperative nausea and vomiting. The Dolasetron Prophylaxis Study Group

STUDY OBJECTIVE

To identify the maximally effective dolasetron dose (i.e., maximum efficacy with minimum adverse events) for prevention of postoperative nausea and vomiting (PONV) using the statistical power generated in a pooled patient sample from three large, nearly identical clinical trials.

DESIGN

Three randomized, multicenter, placebo-controlled, double-blinded trials.

SETTING

Trials 1, 2, and 3 enrolled patients at 10, 25, and 17 hospitals and/or surgical centers, respectively.

PATIENTS

A total of 1,946 ASA physical status, I, II, and III patients. Trials 1 and 2 enrolled only female patients (n = 916) undergoing gynecologic surgery. Trial three enrolled 722 females (approximately 70% gynecologic surgeries) and 308 males (approximately 46% orthopedic surgeries) undergoing a variety of surgical procedures.

INTERVENTIONS

All surgical procedures used balanced general anesthesia. Patients received 12.5, 25, 50, or 100 mg of the antiemetic, dolasetron, near the end of anesthesia.

MEASUREMENTS AND MAIN RESULTS

Efficacy endpoints were identical and measured for 24 hours: complete response (no vomiting or rescue medication) and maximum nausea, reported using a 100-mm visual analog scale (VAS). Safety was assessed using adverse event reports, laboratory and electrocardiographic data, and vital signs. All four dolasetron doses produced significant increases in complete response and decreases in maximum VAS nausea compared with placebo (p < 0.01). No increased efficacy was observed with dolasetron doses higher than 12.5 mg. Safety was similar between each dolasetron dose and placebo.

CONCLUSION

Dolasetron 12.5 mg, given near the end of anesthesia, is the maximally effective dose studied for preventing postoperative nausea and vomiting.

Open-label comparison of the antiemetic efficacy of single intravenous doses of dolasetron mesylate in pediatric cancer patients receiving moderately to highly emetogenic chemotherapy

BACKGROUND

Nausea and vomiting are among the most unpleasant adverse side effects of cancer therapy.

PROCEDURE

An open-label dose-escalation study was conducted to assess the appropriate intravenous dose of dolasetron for pediatric patients undergoing chemotherapy. Patients received dolasetron in single intravenous doses of 0.6 (n = 10), 1.2 (n = 12), 1.8 (n = 12), or 2.4 (n = 12) mg/kg 30 min before receiving emetogenic chemotherapy. Pharmacokinetic parameters were evaluated at each dose level and efficacy was evaluated over the first 24 hr following the administration of dolasetron.

RESULTS

A complete response was achieved in 10% of patients given 0.6 mg/kg, 25% of patients given 1. 2 mg/kg, 67% of patients given 1.8 mg/kg, and 33% of patients given 2.4 mg/kg. Peak plasma concentrations (Cmax) were observed between 0. 33 and 0.75 hr following dolasetron infusion. Cmax and area under plasma concentration-time (AUC) increased with larger doses of dolasetron, while terminal disposition half-life (t1/2) and apparent clearance (Clapp) were not significantly changed with respect to dose. For 1.8-mg/kg dolasetron, the t1/2 was 4.98 hr and the maximum plasma concentration (tmax) 0.47 hr. Adverse events were mild to moderate. No serious events occurred. Conclusions. This study suggests that a single intravenous dose of 1.8 mg/kg is the optimum single intravenous dose for controlling chemotherapy-induced emesis in pediatric patients.

Safety, tolerability, antiemetic efficacy, and pharmacokinetics of oral dolasetron mesylate in pediatric cancer patients receiving moderately to highly emetogenic chemotherapy

PURPOSE

The safety, antiemetic efficacy, and pharmacokinetics of single oral doses of dolasetron, a new highly selective 5-HT3 receptor antagonist, were evaluated in children with cancer undergoing treatment with moderately to highly emetogenic chemotherapy.

PATIENTS AND METHODS

A total of 32 children, ages 3 to 18 years, were enrolled in a nonrandomized, multicenter, open-label, dose-escalation study. Three oral dose levels (0.6, 1.2, or 1.8 mg/kg) were studied. Safety, efficacy, and pharmacokinetic parameters were assessed over 24 hours at each dosage level.

RESULTS

The most effective dose was 1.8 mg/kg; 60% of the patients achieved a complete or major response (< or =2 emetic episodes in 24 hours). A complete response was achieved in 3 of 9 patients (33%) who received 0.6 mg/kg, 4 of 13 (31%) patients who received 1.2 mg/kg, and 5 of 10 (50%) patients who received 1.8 mg/kg of dolasetron. Overall, dolasetron was well tolerated. Adverse events were mild and similar to those reported in adults. Peak plasma concentrations (Cmax) of dolasetron's active reduced metabolite, MDL 74,156, were dose proportional and occurred, on the average, within 1 hour of oral administration. The half-life (t1/2) in plasma was approximately 6 hours for all dose levels, and the mean clearance (CLapp) was unrelated to dose.

CONCLUSIONS

Oral dolasetron is safe and effective in reducing chemotherapy-induced nausea and vomiting, particularly at the 1.8-mg/kg dose level. These results support further evaluation of oral dolasetron in larger randomized clinical trials in the pediatric cancer population.

Reduced resource utilization in patients treated for postoperative nausea and vomiting with dolasetron mesylate. MCPR44 Study Group

STUDY OBJECTIVE

To compare the effect of four different increasing increasing intravenous (i.v.) doses of dolasetron mesylate (12.5 mg, 25 mg, 50 mg, and 100 mg) versus placebo on resource utilization in patients who experienced and were treated for postoperative nausea and vomiting (PONV).

DESIGN

Prospective, double-blind, randomized, multicenter study.

PATIENTS

620 ASA physical status I, II, and III male and female outpatients scheduled for surgery with general anesthesia.

INTERVENTIONS

Patients who experienced postoperative nausea (duration > or = 5 min, self-reported as moderate to severe) or vomiting (> or = 1 emetic episode) within 2 hours of arrival in the postanesthesia care unit (PACU) were given a single i.v. dose of dolasetron mesylate (12.5 mg, 25 mg, 50 mg, or 100 mg) or placebo infused for at least 30 seconds.

MEASUREMENTS AND MAIN RESULTS

Resource utilization in the PACU was assessed by time spent by nurses and/or doctors with patients for PONV and the use of hospital resources such as patient/bed linens and staff/emesis supplies. A significantly (p < 0.05) lower proportion of dolasetron-treated patients compared to placebo-treated patients required new patient/bed linens and staff/emesis supplies. Patients in the placebo group required the greatest amount of care from nurses and/or doctors compared to patients receiving dolasetron.

CONCLUSIONS

Treatment with dolasetron can significantly decrease the utilization of emesis supplies and other hospital resources, including staff/emesis supplies and patient/bed linens. In addition, patients receiving dolasetron used fewer health care resources in time spent by hospital personnel than patients who were not treated with dolasetron.

Single- and multiple-dose pharmacokinetics of oral dolasetron and its active metabolites in healthy volunteers: part 2

The single- and multiple-dose pharmacokinetics and dose-proportionality of oral dolasetron and its active metabolites over the therapeutic dose range was investigated in 18 healthy men. In an open-label, randomized, complete three-way crossover design, each subject received three separate doses: 50, 100, and 200 mg doses of dolasetron mesylate solution given orally. Each dose was administered on the morning of Days 1 and 3-7 during each of the three treatment periods. Serial blood and urine samples were collected for 48 h after the first and last doses. Blood was analysed for dolasetron and hydrodolasetron concentrations; urine was analysed for dolasetron, the R(+) and S(-)-enantiomers of hydrodolasetron, and the 5'-hydroxy and 6'-hydroxy metabolites of hydrodolasetron. Dolasetron was rarely detected in plasma. Hydrodolasetron was formed rapidly, with a time to maximum concentration (t(max)) of less than 1 h. Steady-state conditions for hydrodolasetron were reached 2-3 days after starting once-daily dosing. Although statistical significance was found for hydrodolasetron AUC(0->infinity) and C(max) between dose groups after both single and multiple doses of dolasetron, the differences were small and unlikely to be of clinical significance. About 17-22% of the dose was excreted in urine as hydrodolasetron, with the majority (> 83%) as the R(+) enantiomer.

Effect of infusion rate on the pharmacokinetics and tolerance of intravenous dolasetron mesylate

OBJECTIVE

To evaluate the safety, tolerance, and pharmacokinetics of dolasetron mesylate and its active metabolite hydrodolasetron when dolasetron mesylate was administered intravenously at increasing infusion rates.

DESIGN

A double-blind, placebo-controlled, parallel-group study.

METHODS

Forty-nine healthy nonsmoking male volunteers were randomly assigned to receive intravenous doses of dolasetron mesylate 100 mg or placebo. Three groups of 16 subjects each (12 dolasetron mesylate, 4 placebo) received escalating infusion rates (50, 100, then 200 mg/min). Physical examinations, vital signs, laboratory tests, and adverse events were recorded before and after administration of the study drug. Serial blood samples and 12-lead electrocardiogram measurements were obtained for 24 hours after the infusion. Plasma samples were analyzed for dolasetron and hydrodolasetron.

RESULTS

Dolasetron mesylate was well tolerated, with no apparent differences in vital signs or adverse event profiles among the different rates of infusion. In general, the pharmacokinetics of dolasetron and hydrodolasetron were superimposable among the three infusion rate groups. Plasma dolasetron concentrations declined rapidly in all three infusion rate groups, with mean elimination half-life (t1/2) of less than 10 minutes. The reduced metabolite hydrodolasetron, which accounts for most pharmacologic activity, formed rapidly, with maximum concentrations occurring between 0.4 and 0.5 hours and disappeared with a mean t1/2 of 8-9 hours. The correlation coefficients of least-squares regression analysis between the pharmacokinetic parameters and the infusion rate of dolasetron were less than 0.083 and the slopes were not significantly different from 0, suggesting that none of the hydrodolasetron pharmacokinetic parameters were affected by rate of infusion.

CONCLUSIONS

The intravenous administration of dolasetron 100 mg over 0.5-2 minutes did not significantly alter the pharmacokinetic profiles of either dolasetron or hydrodolasetron. In addition, the safety profile of dolasetron did not change with increasing rate of infusion. Therefore, the rate of infusion of dolasetron mesylate appears to have no pharmacokinetic or clinical implications when assessed over a 0.5-2-minute time period.

Pharmacokinetics of dolasetron after oral and intravenous administration of dolasetron mesylate in healthy volunteers and patients with hepatic dysfunction

In previous studies, dolasetron was shown to have both renal and hepatic elimination mechanisms. This study was conducted to determine the impact of varying degrees of hepatic dysfunction on the pharmacokinetics and safety of dolasetron and its reduced metabolites. Seventeen adults were studied: six healthy volunteers (group I), seven patients with mild hepatic impairment (Child-Pugh class A; group II), and four patients with moderate to severe hepatic impairment (Child-Pugh class B or C1; group III). Single 150-mg doses of dolasetron mesylate were administered intravenously and orally, with a 7-day washout period separating treatments. After intravenous administration, no differences were observed between healthy volunteers and patients with hepatic impairment in maximum plasma concentration (Cmax), areas under the plasma concentration-time curve (AUC), or elimination half-life (t1/2) of intact dolasetron. No significant differences were found in Cmax, AUC, or apparent clearance (C(lapp)) of hydrodolasetron, the primary metabolite of dolasetron. The mean t1/2 increased from 6.87 hours in group I to 11.69 hours in group III. After oral administration, C(lapp) of hydrodolasetron decreased by 42%, and Cmax increased by 18% in patients with moderate to severe hepatic impairment. There were less changes in patients with mildly hepatic impairment. Total percentage of dose excreted as metabolites was similar for healthy volunteers and patients with hepatic impairment, although urinary metabolite profiles differed slightly. Dolasetron was well tolerated and there were no apparent differences in adverse effects between groups or treatments. Because hepatic impairment did not influence Cl(app) of hydrodolasetron after intravenous administration, and the range of plasma concentrations of hydrodolasetron after oral administration was not different from those observed in healthy volunteers, dosage adjustments are not recommended for patients with hepatic disease and normal renal function.

Intravenous dolasetron and ondansetron in prevention of postoperative nausea and vomiting: a multicenter, double-blind, placebo-controlled study

BACKGROUND

Intravenous dolasetron mesilate has shown efficacy in the prevention of postoperative nausea and vomiting (PONV) when administered as a single dose prior to emergence from anesthesia. This trial compared intravenous dolasetron and ondansetron for the prevention of PONV when administered at induction of anesthesia.

METHODS

This double-blind, placebo-controlled, multicenter trial randomized patients to one of four single IV treatments placebo, 25 or 50 mg dolasetron, or 4 mg ondansetron. Efficacy was measured by complete response (0 emetic episodes and no rescue medication), nausea severity and patient satisfaction as measured on a visual analog scale (VAS), investigator's rating, of nausea severity, and total response (complete response with no nausea [< or = 5 mm VAS]).

RESULTS

514 patients at 24 sites were evaluated for efficacy. The 50 mg dolasetron and 4 mg ondansetron doses were statistically equivalent, and superior to placebo, for all efficacy measures. Complete response rates were 49%, 51%, 71% and 64% for placebo, 25 and 50 mg dolasetron, and ondansetron, respectively. Dolasetron 50 mg was statistically superior to 25 mg dolasetron for complete response, total response, VAS maximum nausea, time to first emetic episode, and patient satisfaction. The majority of adverse events were of mild-to-moderate intensity. Headache was the most frequently reported treatment-related adverse event with a 3%-5% incidence across treatments.

CONCLUSION

When given at induction of anesthesia, 50 mg intravenous dolasetron is equivalent to 4 mg ondansetron and superior to 25 mg dolasetron and placebo for the prevention of PONV. All treatments were safely administered and well tolerated.

Intravenous dolasetron mesilate in the prevention of postoperative nausea and vomiting in females undergoing gynecological surgery

STUDY OBJECTIVE

To evaluate a range of doses of intravenous (i.v.) dolasetron mesilate, in preventing postoperative nausea and vomiting (PONV).

DESIGN

Double-blind, placebo-controlled, randomized, multicenter trial.

SETTING

Ten hospitals and/or surgical centers.

PATIENTS

281 women undergoing gynecologic surgery with general anesthesia.

INTERVENTIONS

Patients received one of four single, i.v. doses of dolasetron mesilate (12.5 mg, 25 mg, 50 mg, and 100 mg) or placebo administered following cessation of anesthesia.

MEASUREMENTS AND MAIN RESULTS

Patients were monitored for 24 hours following study drug administration. The antiemetic efficacy of each dolasetron mesilate dose was evaluated by recording the number and timing of emetic episodes, and the effects on nausea were assessed by use of visual analog scales (VAS). Safety was assessed by adverse event reports, clinical laboratory tests, electrocardiographic (ECG) measurements, and monitoring vital signs. Complete responses (patients with no emetic episodes and no escape antiemetic medication requirements in 24 hours) were achieved by 54% in the 12.5-mg, 67% in the 25-mg, and 59% in both the 50-mg and 100-mg dolasetron mesilate dose groups, and by 43% in the placebo group. Nausea VAS assessments demonstrated that dolasetron-treated patients were significantly (p = 0.048) more likely to report no nausea (VAS score < 5 mm) than those in the placebo group. Adverse events reported generally were mild in intensity, and there were no clinically significant changes in laboratory tests, vital signs, or ECG parameters.

CONCLUSIONS

Dolasetron was effective and well tolerated for the prevention of PONV in female patients undergoing gynecologic surgery with general anesthesia.

Intravenous dolasetron mesilate ameliorates postoperative nausea and vomiting

PURPOSE

To compare the efficacy, safety, and tolerability of dolasetron mesilate with placebo for the treatment of postoperative nausea and vomiting (PONV).

METHODS

In a randomized, multicentre, double-blind, placebo-controlled study 337 adult patients undergoing surgery with general anaesthesia received one of four single, doses of dolasetron mesilate iv (12.5, 25, 50, or 100 mg) or placebo. Study medication was administered postoperatively when the patient reported nausea lasting 10 min or when one emetic episode occurred within two hours of the patient's arrival in the recovery room. Efficacy was assessed by the investigators over the 24-hr study period by recording the number and timing of emetic episodes, the severity of nausea, the timing of administration of escape antiemetic medications, and patients' and investigators' satisfaction with antiemetic therapy.

RESULTS

The study sample was predominately women, and the surgical procedures were primarily gynaecological. All dolasetron mesilate doses produced higher complete response rates than placebo (P < 0.05). Only approximately one-third of dolasetron patients required escape antiemetic medication compared with more than 50% of patients in the placebo group. Both patient and physician satisfaction with dolasetron treatment was high. The most common adverse event was mild or moderate headache for both placebo-treated patients and dolasetron-treated patients. Clinical laboratory results were unremarkable.

CONCLUSION

Single doses of dolasetron mesilate iv, given after the first episode of PONV, were both effective and safe in this adult patient population.

A double-blind, multicentre comparison of intravenous dolasetron mesilate and metoclopramide in the prevention of nausea and vomiting in cancer patients receiving high-dose cisplatin chemotherapy

The potent serotonin receptor (5-HT3) antagonists are new highly selective agents for the prevention and control of chemotherapy-induced nausea and vomiting that have been shown to be comparable to or more effective than traditional metoclopramide regimens. This study was designed to compare the antiemetic efficacy of dolasetron and metoclopramide in chemotherapy-naive and non-naive cancer patients receiving high-dose cisplatin-containing chemotherapy. This multicentre, double-blind, randomized trial compared the efficacy and safety of single i.v. doses of dolasetron mesilate salt (1.2 or 1.8 mg/kg) and metoclopramide (7 mg/kg) in 226 patients for the prevention of acute emesis and nausea associated with the administration of high-dose (> or = 80 mg/m2) cisplatin. Efficacy and safety were evaluated for 24 h. Complete responses were achieved by 57%, 48%, and 35% of patients given dolasetron mesilate 1.8 mg/kg (P = 0.0009 vs metoclopramide), dolasetron mesilate 1.2 mg/kg (P = 0.0058 vs metoclopramide), and metoclopramide, respectively. Overall, dolasetron was significantly more effective than metoclopramide for time to first emetic episode, nausea, patient satisfaction, and investigator global assessment of efficacy. Males, chemotherapy-naive patients, and alcoholics had higher response rates. Dolasetron was well tolerated, with mild-to-moderate headache most commonly reported. Twelve percent of patients receiving metoclopramide reported extrapyramidal symptoms compared with 0% of patients receiving dolasetron. In conclusion, dolasetron mesilate was effective for the prevention of CINV with high-dose cisplatin. Single i.v. doses of dolasetron mesilate were more effective than 7 mg/kg metoclopramide in preventing nausea and vomiting induced by highly emetogenic cisplatin-containing chemotherapy. In addition, 1.8 mg/kg dolasetron mesilate consistently produced the highest response rates and appears to be the most effective dose for further clinical development.

Validation of a reversed-phase HPLC method for directly quantifying the enantiomers of MDL 74,156, the primary metabolite of dolasetron mesylate, in human plasma

A direct chiral HPLC method has been developed and validated to quantitate the enantiomers of MDL 74156, the primary metabolite of dolasetron mesylate, in human plasma over the concentration range 1.70-340 ng ml-1. Dolasetron mesylate is a 5-HT3 receptor antagonist that is currently being developed as an antiemetic. Both enantiomers of MDL 74154 and the internal standard (granisetron) were first extracted from alkanized plasma using methyl t-butyl ether. The analytes were then back-extracted into formic acid, separated on a ovomucoid-bonded HPLC column, and detected by native fluorescence (excitation wavelength of 274 nm and emission wavelength of 345 nm). The complete validation demonstrated the method to be accurate, precise, and specific for the direct quantitation of MDL 74156 enantiomers in human plasma. This procedure has been used on a routine basis to quantify the relative concentrations of each enantiomer of MDL 74 156 in both oral and intravenous pharmacokinetic studies of dolasetron mesylate in normal human volunteers.

Antiemetic efficacy of two different single intravenous doses of dolasetron in patients receiving high-dose cisplatin-containing chemotherapy

This randomized, double-blind, parallel-group, multicenter study compared the antiemetic effectiveness, safety, and tolerability of two different intravenous (i.v.) doses of dolasetron mesylate (0.6 and 1.8 mg/kg) in cancer patients receiving their first course of high-dose cisplatin-containing chemotherapy (> or = 75 mg/m2). Efficacy was assessed by recording the timing, number, and severity of emetic episodes in the 24 h following high-dose cisplatin. Safety was evaluated by monitoring adverse events, vital signs, clinical laboratory parameters, and electrocardiograms. Of the 62 patients enrolled in the study, 29 received 0.6 mg/kg of dolasetron mesylate and 33 received 1.8 mg/kg. Patients who received dolasetron mesylate 1.8 mg/kg consistently experienced a greater degree of antiemetic control than those who received 0.6 mg/kg. Complete responses were achieved by 55% of patients who received 1.8 mg/kg compared with 31% for the 0.6-mg/kg group. The 1.8-mg/kg group achieved a significantly (p = 0.039) higher complete/ major response rate than the 0.6-mg/kg group (77% vs 55%, respectively) and a significantly (p = 0.004) longer time to the first emetic episode (> 24 h vs 13.5 h, respectively). More than 80% of patients were either satisfied or very satisfied with dolasetron treatment. The most common adverse events were mild to moderate in intensity, consistent with other studies, and included headache (24.1% of patients) and diarrhea (4.8%). These results demonstrated that a single 1.8-mg/kg i.v. dose of dolasetron mesylate provided effective antiemetic activity in a majority of patients given high-dose cisplatin for the first time and should be evaluated further in clinical trials.

Pharmacokinetics of the active metabolite (MDL 74,156) of dolasetron mesylate after oral or intravenous administration to anesthetized children

BACKGROUND

Dolasetron mesylate is a selective 5-HT3 receptor antagonist under investigation as an antiemetic in children. Published studies indicate that its antiemetic activity results from the active metabolite (MDL 74,156), which is produced within 10 minutes of administration of dolasetron mesylate.

METHODS

The pharmacokinetics of MDL 74,156 and the safety and tolerability of dolasetron mesylate were studied after a single oral or intravenous dose of 1.2 mg.kg-1 dolasetron mesylate to healthy children from 2 to 12 years of age. Oral dolasetron was administered to 12 children 1 to 2 hours before anesthesia. Intravenous dolasteron was administered to 18 children at induction of anesthesia. Serial blood samples were collected for 24 hours after dosing to measure the plasma concentration of MDL 74,156. Indexes of liver and kidney function were determined, and electrocardiograms and adverse events were recorded.

Simultaneous measurement of dolasetron and its major metabolite, MDL 74,156, in human plasma and urine

A selective and sensitive analytical method for the simultaneous measurement of dolasetron (I) and its major metabolite, MDL 74,156 (II), in human plasma and urine samples has been developed using a structural analogue. MDL 101,858, as internal standard (I.S.). The compounds were extracted from plasma and urine using solvent extraction after the addition of the I.S. Chromatographic separation was carried out on a reversed-phase HPLC column and detection and quantification was by fluorescence with excitation and emission wavelengths of 285 and 345 nm, respectively. Linear responses were obtained over concentration ranges of 5 to 1000 pmol/ml for plasma samples and 20 to 1000 pmol/ml for urine samples with correlation coefficients for the calibration curves exceeding 0.999 in all cases. Intra-day and inter-day reproducibility yielded limits of quantification of 10 pmol/ml for I and 5 pmol/ml for II plasma and 50 pmol/ml for I and II in urine. The method has been applied to the simultaneous analysis of both compounds in plasma and urine samples coming from clinical pharmacokinetic studies.

Pharmacokinetics of single intravenous and oral doses of dolasetron mesylate in healthy elderly volunteers

Dolasetron mesylate (MDL 73,147EF, Anzemet; Hoechst Marion Roussel, Laval, Canada) is a 5-HT3 receptor antagonist undergoing clinical evaluation for use as an antiemetic agent. The pharmacokinetics of dolasetron and its reduced metabolite (MDL 74,156) were studied after administration of single intravenous and oral doses of dolasetron mesylate 2.4 mg/kg in 18 healthy elderly subjects. Expressed as the dolasetron base, this dose was 1.8 mg/kg. Dolasetron was rapidly metabolized to the reduced metabolite, which appeared in plasma within 10 minutes after intravenous or oral administration. The mean half-life (t1/2) of dolasetron was 0.24 hours after intravenous administration and 0.50 hours after oral administration. The pharmacokinetic parameters of the reduced metabolite were similar after intravenous and oral administration. The apparent absolute bioavailability of the reduced metabolite was 89%, and it had an elimination t1/2 of approximately 7 hours and an apparent volume of distribution (Vd beta) of 4.69 L/kg. Dolasetron was not detected in urine. Metabolites were excreted in urine almost completely within 24 hours of administration. The primary metabolite detected in urine was the (+)-enantiomer of the reduced metabolite, which accounted for 25.35% (+/- 7.79%) and 18.88% (+/- 7.65%) of the intravenous and oral doses, respectively. Hydroxylated metabolites accounted for 5% or less of the total dose via either route. The pharmacokinetics of the reduced metabolite after single intravenous or oral doses in elderly volunteers were consistent with pharmacokinetics observed in both young healthy men and cancer patients receiving high-dose cisplatin chemotherapy. Dosage adjustments of dolasetron mesylate on the basis of age do not appear to be necessary.

Therapeutic equivalence of single oral doses of dolasetron mesilate and multiple doses of ondansetron for the prevention of emesis after moderately emetogenic chemotherapy. European Dolasetron Comparative Study Group

This multicentre, randomised, double-blind study was designed to compare the anti-emetic efficacy and safety of single oral doses of dolasetron mesilate with that of the approved oral, multiple-dose regimen of ondansetron in 399 cancer patients receiving moderately emetogenic chemotherapy. Single oral doses of 25, 50, 100 or 200 mg of dolasetron mesilate were administered 1 h prior to the initiation of moderately emetogenic chemotherapy. Multiple doses of ondansetron (8 mg x 3 or 8 mg x 4) capsules, or matching placebo for patients randomised to dolasetron, were given 1.5 h before and 6.5, 14.5 and 22.5 h after the start of chemotherapy (total dose = 32 mg). Efficacy was evaluated for 24 h after the initiation of chemotherapy. The most frequently used moderately emetogenic chemotherapeutic agents included cyclophosphamide, doxorubicin and carboplatin (28.4, 23.1 and 20.6% of patients, respectively). A statistically significant (P < 0.001) linear dose-response relationship was observed over the entire dolasetron dosage range for all efficacy parameters. Complete response rates were 45.0, 49.4, 60.5 and 76.3% for 25, 50, 100 and 200 mg dolasetron mesilate, respectively, and 72.3% of ondansetron patients. A single oral 200 mg dolasetron mesilate dose was therapeutically equivalent to ondansetron for all efficacy parameters and patient satisfaction was high. Overall, there were no significant differences in the incidence of adverse events between any of the dolasetron mesilate doses, or between dolasetron and ondansetron. Headache was most frequently reported (approximately 15% for each drug). No clinically important changes in vital signs or clinical laboratory parameters were observed with either drug. In conclusion, a single oral 200 mg dolasetron mesilate dose was therapeutically equivalent to multiple-dose ondansetron in the prevention of emesis and nausea following moderately emetogenic chemotherapy.

Pharmacology of serotonin as related to anesthesia

Serotonin (5-hydroxytryptamine) is an important biogenic amine that fulfills the role of neurotransmitter and neuromodulator. It has been a focus of interest during the last decade. Its diversity of pharmacologic actions is related to a wide variety of receptors and effector mechanisms. Seven serotonin receptor families have been identified thus far. They are genetically different transmembrane proteins composed of several hundred amino acids. The majority of these are G-protein-coupled, except the 5-HT3 receptors, which are directly ligand gated to fast ion channels. Serotonin is widely distributed in the body within the central and peripheral nervous systems, smooth muscles, and platelets, in particular. Consequently, its effects manifest mainly in these organs and influence a wide variety of neural, vascular, smooth muscle, and platelet functions. (Melatonin, a physiologically active metabolite of serotonin, is also instrumental in affecting many neural and hormonal functions.) Several selective agonists and particularly many selective antagonists have been developed for serotonin, which helped the serotonin receptor subtype classification. Some of these drugs are also used therapeutically in the treatment of migraine (eg, sumatriptan, which is a 5-HT1 receptor agonist), vascular disorders (5-HT2 antagonists), and nausea and vomiting (5-HT3 antagonists, eg, dolasetron, granisetron, ondansetron, and tropisetron), and have been investigated in gastrointestinal motility disorders (5-HT4 antagonists) and behavioral psychopathologies (5-HT1 agonists and 5-HT2-4 antagonists). Serotonin reuptake inhibitors are of particular clinical importance in the treatment of psychological illness. Future use of these drugs is also envisioned in the treatment of certain types of pain syndromes. Awareness of the serotonergic drugs and the recognition of possible drug interactions among drugs that influence serotonergic mechanisms in humans are becoming increasingly important in the practice of anesthesiology.

Comparison of the pharmacokinetics of dolasetron and its major active metabolite, reduced dolasetron, in dog

Dolasetron mesilate (Anzemet) ((2 alpha, 6 alpha, 8 alpha, 9a beta)-octahydro-3-oxo-2,6-methano-2H-quinolizin-8-yl-1 H-indole-3-carboxylate monomethane-sulfonate) is a 5-HT3 receptor antagonist, which is in development for the treatment of chemotherapy-induced emesis. The ketone moiety of dolasetron is rapidly reduced by carbonyl reductase to form an alcohol, reduced dolasetron (red-dolasetron), which is the major pharmacologically active metabolite in humans. The pharmacokinetics of dolasetron and red-dolasetron were compared in dog, after single intravenous (i.v.) (2 mg/kg) and oral (p.o.) (5 mg/kg) administration of [14C]dolasetron or [14C]red-dolasetron. Pharmacokinetic parameters of dolasetron showed a terminal elimination half-life (t1/2) of 0.1 h, total body plasma clearance (Cltot) of around 109 mL/min/kg, apparent volume of distribution (aVd beta) of 0.83 L/kg, and bioavailability (F) of 7%. Pharmacokinetic parameters of red-dolasetron, calculated after dolasetron or red-dolasetron administration, were very similar. The t1/2 was around 4.0 h, Cltot 25 mL/min/kg, aVd beta 8.5 L/kg, and F around 100%. The apparent first-order formation rate constant (ki) of red-dolasetron was 7 h-1, which was similar to the first-order elimination rate constant (kel) of dolasetron. Cmax of red-dolasetron was similar, after po administration of either compound, but the median Tmax was 0.33 h after dolasetron, compared with 1.5 h after red-dolasetron. The first-order absorption rate constants (ka) of dolasetron and red-dolasetron were 14 h-1 and 2 h-1, respectively. Dolasetron transport across Caco-2 cell monolayers was also higher than that of red-dolasetron. Thus dolasetron was more quickly absorbed than red-dolasetron, and its administration led to the more rapid appearance of red-dolasetron in plasma. There appears to be no advantage in the direct administration of the metabolite, especially as in humans oral administration of dolasetron, 30 min before chemotherapy, has been shown to be effective in preventing emesis.

Dose-ranging evaluation of the antiemetic efficacy of intravenous dolasetron in patients receiving chemotherapy with doxorubicin or cyclophosphamide

Selective 5-HT3 antagonists have proven to be safe and effective for the prevention of chemotherapy-induced nausea and vomiting. Dolasetron is a new highly selective addition to this class of antiemetics that has been shown to have significant antiemetic activity in patients receiving cisplatin-containing regimens. This pilot study was designed to evaluate the antiemetic efficacy of dolasetron in cancer patients receiving doxorubicin and/or cyclophosphamide. This study used an open-label, non-randomized design to evaluate the efficacy and safety of intravenous dolasetron in the prevention of emesis in patients receiving doxorubicin (25-75 mg/m2) and/or cyclophosphamide (400-1200 mg/m2). Sixty-nine patients received a single, intravenous dose of dolasetron over 15-20 min beginning 30 min prior to the start of chemotherapy. Dose levels of dolasetron studied were: 0.3, 0.6, 1.2, 1.8 and 2.4 mg/kg. Patients were monitored for emesis, nausea and adverse events for 24h after the start of chemotherapy. Overall, 61% of patients experienced complete control of emesis. No significant trend towards increased antiemetic efficacy (P = 0.076) or nausea control with increasing dolasetron dose was noted, although the power to detect significant differences was limited by the small number of patients on the 0.3-mg/kg and 2.4-mg/kg dose levels. Age, gender, and type of chemotherapy were significant predictors of complete antiemetic control. Adverse events were generally mild and included headache, chills, lightheadedness, fever, diarrhea, dizziness, and asymptomatic prolongation of ECG intervals. Intravenous dolasetron is safe and effective in the prevention of emesis induced by doxorubicin and/or cyclophosphamide.

5-HT3 receptors: pharmacologic and therapeutic aspects

The serotonin 5-HT3 receptor is unique among the seven serotonin receptor "families" that have been recognized so far. It functions not as a G-protein coupled but as a direct ion channel gated receptor. Because of the varied neural functions linked to this receptor, intensive research interest has developed in recent years about its basic and clinical pharmacology, which are summarized in this review. Some new agonists and many new antagonists have been developed. These agents have a useful role as selective pharmacologic research probes, and some of them can be used therapeutically as potent and selective anti-nausea and antiemetic drugs, particularly in patients undergoing cancer chemotherapy treatment or general anesthesia procedures. Potential applications of these agents include the treatment of some behavioral disorders in mental disease, drug addiction, and certain types of pain syndromes.

A double-blind, placebo-controlled, dose-ranging safety evaluation of single-dose intravenous dolasetron in healthy male volunteers

The safety and tolerability of dolasetron mesylate, a potent and selective 5-HT3 receptor antagonist, were evaluated after single intravenous doses in healthy male volunteers. In this double-blind, placebo-controlled, randomized, phase I study, 80 subjects received either placebo or dolasetron in escalating doses (0.6 to 5.0 mg/k). Subjects were monitored for adverse events, vital sign and laboratory alterations, and changes in electrocardiographic (ECG) intervals and electroencephalographic (EEG) patterns. Overall, the percentage of subjects reporting adverse events was similar in those receiving dolasetron (44/64; 68.8%) or placebo (10/16; 62.5%); most adverse events were mild in severity. Subjects receiving dolasetron reported a higher incidence of central nervous system (headache and dizziness/lightheadedness), gastrointestinal (increased appetite and nausea), and visual adverse events and taste alterations. No clinically significant changes in laboratory variables were observed. Transient and asymptomatic ECG changes (small mean increases in PR interval and QRS complex duration versus baseline) were noted in several subjects at 1 to 2 hours after infusion at doses > or = 3.0 mg/kg. Transient, mild blood pressure decreases were observed in five subjects, including one on placebo. Dolastron mesylate was well tolerated in single intravenous doses up to 5.0 mg/kg in healthy male volunteers. Clinical studies of the drug are ongoing for antiemetic indications.

Pharmacokinetics of dolasetron following single- and multiple-dose intravenous administration to normal male subjects

Dolasetron, Anzemet, a 5-hydroxytryptamine receptor antagonist, is under investigation as an antiemetic agent. The keto-reduced metabolite of dolasetron has been identified in human plasma and is probably responsible for the majority of the antiemetic activity. This study evaluated the pharmacokinetics of dolasetron and the reduced metabolite following single and multiple intravenous (IV) infusions of dolasetron mesylate in healthy male subjects. Four groups of subjects (six active/two placebo) received either dolasetron mesylate or placebo in single IV doses ranging from 0.30 to 0.60 mg kg-1 on day 1 and multiple IV doses ranging from 0.60 to 1.20 mg kg-1 d-1 on days 2-9. Dolasetron could be detected for less than 1 h, while the reduced metabolite appeared rapidly in the plasma, reaching a maximal plasma concentration in less than 1 h. Reduced metabolic maximal plasma concentration was proportional to the dose and the area under plasma concentration curve was linear based on regression analysis. The half-life of reduced metabolite ranged from 3.82 to 7.46 h. The mean renal clearance of reduced metabolite was 2.20-4.43 mL min-1 kg-1 and was dose independent. All of the evidence supports dose independent pharmacokinetics for the reduced metabolite. Upon multiple dosing, the reduced metabolite AUC can be predicted from the single-dose pharmacokinetics of this metabolite.

Simultaneous measurement of the major metabolites of dolasetron mesilate in human urine using solid-phase extraction and high-performance liquid chromatography

A method based on solid-phase extraction and high-performance liquid chromatography (HPLC) has been developed for the simultaneous quantitation of the principal active metabolites of dolasetron mesilate [i.e. MDL 74,156 (II), MDL 102,382 (III) and MDL 73,492 (IV)] in human urine. The method has been validated over the concentration range of 200-5000 pmol/ml for all three metabolites. Within-day and day-to-day coefficients of variation were less than 9 and 14%, respectively, for the three metabolites. The method allowed the simultaneous quantitation of III, IV and II and the evaluation of the urinary excretion of these metabolites in human urine following the administration of dolasetron mesilate.