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In this study, a new strategy for the simultaneous quantization of five serotonin 5-hydroxytryptamine receptor antagonists—ondansetron, azasetron, ramosetron, granisetron, and tropisetron—either in infusion samples or in injection dosage form was first established based on high-performance liquid chromatography combined with a quantitative analysis of multiple components by a single marker. The quantitative analysis of multicomponents by a single marker method was conducted with ondansetron as an internal reference substance and performed using relative retention time and ultraviolet spectral similarity as the double indicator. The quantitative analysis of the 5-HT3 receptor antagonists was calculated and investigated based on the relative correction factors. Chromatographic separation was achieved using a C18 column (150 mm × 4.6 mm, 5.0 μm), and the mobile phase was composed of acetonitrile-0.05 mol·L−1 potassium dihydrogen phosphate (pH 4.0) (25 : 75) at a flow rate of 1.0 mL·min−1 and detection wavelengths of 307 nm (ondansetron, azasetron, ramosetron), 302 nm (granisetron), and 285 nm (tropisetron). In addition, the accuracy of the quantitative analysis of multicomponents by a single marker method was compared with an external standard method, and no significant difference was observed between the two methods. The established method is rapid, is easy, and does not require many reference substances, and it can been successfully applied as part of the quality control of the five 5-HT3 receptor antagonists in their injection dosage form and infusion sample drugs in hospitals.

// Bao-Xia Fang 1, * , Fu-Chao Chen 1, * , Dan Zhu 2 , Jun Guo 3 and Lin-Hai Wang 2 1 Department of Pharmacy, Dongfeng Hospital, Hubei University of Medicine, Shiyan, Hubei 442008, P.R. China 2 Department of Pharmacy, Renmin Hospital, Hubei University of Medicine, Shiyan, Hubei 442000, P.R. China 3 Department of Oncology, Dongfeng Hospital, Hubei University of Medicine, Shiyan, Hubei 442008, P.R. China * These authors contributed equally to this work Correspondence to: Lin-Hai Wang, email: wanglhpharmacy@sina.com Keywords: chemotherapy-induced nausea and vomiting; antiemetic; dexamethasone; azasetron; drug stability Received: May 30, 2017 Accepted: October 13, 2017 Published: October 31, 2017 ABSTRACT Combination antiemetic therapy has become common practice for the prevention of nausea and vomiting caused by anticancer drugs. In this study, we investigated the stability of azasetron hydrochloride 0.1 mg/mL plus dexamethasone sodium phosphate 0.05, 0.1, or 0.2 mg/mL in 0.9% sodium chloride injection and stored in polyolefin bags and glass bottles over a period of 14 days at 4°C and 48 hours at 25°C. The stability studies were evaluated by visual inspection, pH measurement, and a high-pressure liquid chromatography assay of drug concentrations. During the study period, the concentration of each drug in the various solutions remained above 97% of the initial concentration at both 4°C and 25°C when protected from room light. Under the condition of 25°C with exposure to room light, the concentrations of both drugs were significantly lowered over 48 hours. The pH value decreased, and the color changed from colorless to pink. Our study demonstrates that the azasetron-dexamethasone mixture at a clinically relevant concentration seems to be stable for 48 hours at 25°C and for 14 days at 4°C when packaged in polyolefin bags or glass bottles and protected from room light. The room light is the main influential factor on stability. Clinicians should be aware that combinations of azasetron hydrochloride and dexamethasone sodium phosphate in solution with light exposure should be avoided.

Background Carboplatin (CBDCA) is known to exhibit a high emetic risk among moderate-emetic risk anticancer drugs, and the dose of CBDCA varies in different therapies. In concurrent chemoradiotherapy (CCRT) for non-small cell lung cancer (NSCLC), the weekly administration of CBDCA (area under the curve (AUC) 2 mg/ml/min) and paclitaxel (PTX: 40 mg/m2) is frequently applied as standard therapy. However, the optimal antiemetic measures in the use of such low-dose CBDCA remain unclear. In this study, we retrospectively assessed the antiemetic effect of a single-dose of a first-generation 5-hydroxytryptamine-3 receptor antagonist (5-HT3RA) and dexamethasone in the weekly CBDCA+PTX therapy in CCRT. Patients and methods The subjects were patients with NSCLC who were administered weekly CBDCA+PTX therapy in CCRT between January 2011 and December 2016 at our Department. As an antiemetic measure, a first-generation 5-HT3RA, azasetron (10 mg, orally) or granisetron (3 mg, intravenously), and dexamethasone (9.9 mg, intravenously) were administered on day 1. The patients were evaluated for the following efficacy end-points for the first cycle: Complete response (CR; defined as no vomiting or retching episodes with no rescue medication) in the acute phase (0-24 hours), delayed phase (>24-120 hours), and overall phase (0-120 hours). Other efficacy endpoints evaluated were no vomiting or retching, and no nausea in all phases. Results The subjects we assessed in this study were 46 patients who were administered weekly CBDCA+PTX therapy in CCRT. For the overall, acute, and delayed phases, the complete response rates were 89.1%, 100%, and 89.1%, respectively. The rate of no nausea in the overall, acute, and delayed phases was 78.3%, 100%, and 78.3%, respectively. The rate of no vomiting in the overall, acute, and delayed phases was 95.7%, 100%, and 95.7%, respectively. Conclusion A single dose of a first-generation 5-HT3RA and dexamethasone had a favorable suppressive effect on nausea and vomiting in weekly CBDCA+PTX therapy for NSCLC.

A 14-year-old girl without any relevant medical history was transferred to our institution due to worsening headache along with nausea, vomiting, and generalized tonic-clonic (GTC) seizures for 7 days. She was also noted to have multiple psychological and behavioral abnormalities for 1 day. Her headache was described as severe holocephalic pain aggravated when lying down and alleviated after vomiting. No throbbing or phonophobia/photophobia was observed. Her seizures occurred once or twice a day, lasting about 1 minute each and resolving spontaneously. Symptoms were refractory to rotundine (dopamine D1 receptor antagonist), azasetron (antiemetic), mannitol, oxcarbazepine, and phenobarbital.

BACKGROUND: The aim of this study was to evaluate the antiemetic effect of aprepitant and to determine how to provide triple combination therapy (aprepitant/azasetron/dexamethasone) to women receiving paclitaxel/carboplatin moderately emetogenic chemotherapy (MEC). MATERIAL AND METHODS: The current study was a prospective study of 163 women with gynecologic cancers. We compared the digestive symptoms scores (nausea, vomiting, appetite loss, and dietary intake) of 37 women with ovarian cancers before and after aprepitant administration. We also compared these symptoms in women who underwent 193 cycles of triple combination therapy with symptoms of women who underwent 226 cycles of double combination therapy. For triple combination therapy, azasetron, dexamethasone (reduced dose: 40% of 20 mg), and aprepitant (125 mg) were administered on Day 1, followed by only aprepitant (80 mg) administration on Days 2 and Day 3. RESULTS: In 37 women with ovarian cancer, three symptoms, nausea, appetite loss, and dietary intake, were significantly improved by primarily adding aprepitant to double combination therapy in the delayed phase of MEC. Upon comparing their digestive symptoms in all cycles, however, these three symptoms were not significantly different in the delayed phase. Furthermore, all four symptoms in all cycles were worse following triple combination therapy than following double combination therapy in the acute phase (p

A simple and rapid high-performance liquid chromatography with diode array detector (HPLC-DAD) method has been developed and validated for simultaneous quantification of five antiemetic agents in infusion samples: dexamethasone, ondansetron, granisetron, tropisetron, and azasetron. The chromatographic separation was achieved on a Phenomenex C18column (4.6 mm × 150 mm, 5 μm) using acetonitrile-50 mM KH2PO4buffer-triethylamine (25 : 74 : 1; v/v; pH 4.0). Flow rate was 1.0 mL/min with a column temperature of 30°C. Validation of the method was made in terms of specificity, linearity, accuracy, and intra- and interday precision, as well as quantification and detection limits. The developed method can be used in the laboratory to routinely quantify dexamethasone, ondansetron, granisetron, tropisetron, and azasetron simultaneously and to evaluate the physicochemical stability of referred drugs in mixtures for endovenous use.

Antiemetic prophylaxis with aprepitant, a 5-hydroxytryptamine3 (5-HT3) receptor antagonist and dexamethasone is recommended for patients receiving intravenous cisplatin chemotherapy. Whether the same antiemetic regime is superior for hepatic transcatheter arterial infusion chemotherapy with cisplatin (CDDP-TAI) is unknown. We conducted a retrospective study of antiemetic prophylaxis protection against chemotherapy-induced nausea and vomiting (CINV) in CDDP-TAI at Nagasaki University Hospital. The rate of complete response (CR) to antiemetics in the acute (

For the quantification of azasetron in rat plasma samples, a column-switching HPLC method was developed and validated. Following dilution of plasma samples with mobile phase A (17 mM potassium phosphate buffer (pH 3.0)) and simple protein precipitation by addition of perchloric acid (60%), the mixture was directly injected onto the pre-column. After endogenous plasma substances were eluted to waste, the analyte was transferred to the trap column by switching the system. Then, the analyte was back-flushed to the analytical column for separation with mobile phase B (a 22:78 v/v mixture of acetonitrile and 17 mM potassium phosphate buffer (pH 3.0)) and detected at 250 nm using a photodiode array detector. A linear standard curve was obtained in the concentration range of 10-800 ng/mL with the correlation coefficient (r) of 0.9998. The intra- and inter-day precision and accuracy values for azasetron were in the ranges of 0.3-12.9% and 89.7-101.4%, respectively. The method was valid in terms of specificity, precision, and accuracy. In addition, this efficient analytical method was successfully applied to determine plasma concentrations of azasetron following oral administration of azasetron at a dose of 4.0 mg/kg to rats.

To evaluate the antiemetic effects of 5-HT(3) receptor antagonists, we investigated the relationship between condition of food intake and occurrence of nausea and vomiting. We collected data such as sex, age, disease, combination of steroids and central antiemetic agents, eating condition, and vomiting condition from medical records in 33 hematologic cancer patients receiving chemotherapy; combination with 5-HT(3) receptor antagonists. The conditions of food intake and nausea/vomiting were checked at 4 mealtime points (lunch, supper, breakfast, and next lunch) after chemotherapy, and were recorded as 1, 3, or 5 as each condition score. To calculate eating scores and nausea/vomiting scores, the sum of scores from 4 mealtime points was used. We found a significant negative correlation between eating scores and nausea/ vomiting scores (n=62, p

We investigated the laxative activity of an extract of agarwood leaves from Aquilaria sinensis. The laxative activity was measured in mice by counting the stool frequency and stool weight, and the drugs were orally administered. An acetone extract of agarwood leaves and senna (a representative laxative drug) both increased the stool frequency and weight, but a methanol extract did not. The laxative effect of the acetone extract was milder than that of the anthraquinoid laxative, senna, and the former did not induce diarrhea as a severe side effect. We identified the main constituent contributing to the laxative effect of the acetone extract as genkwanin 5-O-beta-primeveroside (compound 4). Compound 4 strengthened the spontaneous motility and induced contraction in the ileum. This ileal contraction induced by compound 4 was inhibited by atropine, but not by azasetron, suggesting that the effect of compound 4 was mediated by acetylcholine receptors, and not by serotonin. The laxative mechanism for compound 4 may in part involve stimulation of intestinal motility via acetylcholine receptors.

The effects of three serotonin-3 (5-HT(3)) receptor antagonists, azasetron, ondansetron, and ramosetron, on cytochrome P450 (CYP) 1A2-mediated 7-ethoxyresorufin O-deethylation, CYP2C9-mediated tolbutamide hydroxylation, CYP2C19-mediated S-mephenytoin 4'-hydroxylation, CYP2D6-mediated debrisoquine 4-hydroxylation, CYP2E1-mediated chlorzoxazone 6-hydroxylation, CYP3A4-mediated nifedipine oxidation, and CYP3A4-mediated testosterone 6beta-hydroxylation activities in human liver microsomes were compared. Azasetron and ramosetron at a concentration of 1 or 10 muM neither inhibited nor stimulated any of the metabolic activities. On the other hand, ondansetron competitively inhibited CYP1A2 and CYP2D6 activities, and the inhibition constants (K(i)) were 3.2 and 21.0 muM, respectively, which are much higher than the reported plasma concentrations after clinical intravenous or oral dosing. The free fractions of the three 5-HT(3) receptor antagonists in the incubation mixture estimated by ultracentrifugation were more than 68.6%. These results suggest that azasetron, ondansetron, and ramosetron do not cause clinically significant interactions with other drugs that are metabolized by CYPs via the inhibition of metabolism.

EUFEPS conference on drug transporters at Copenhagen : integrative approaches in ADME research.

Neutrophil functions play an important role in the antibacterial or antitumor host defense system. Ondansetron, granisetron, ramosetron, and azasetron are often used in gynecological patients as a prophylaxis against postoperative emesis or chemotherapy-induced emesis. In this study, using an ex vivo system, we have shown that these antiemetics at clinically relevant concentrations had no effect on superoxide (O–2) and hydrogen peroxide (H2O2) production of neutrophils, although high doses of these drugs significantly inhibited it to a similar degree. The drugs failed to impair chemotaxis or phagocytosis and to scavenge O–2 or H2O2 generated by an acellular system. Inhibition of the reactive oxygen species production may be due to attenuation of calcium elevation in neutrophils with these antiemetics. Our findings suggest that we are able to use these antiemetics in gynecological patients with cancer or those undergoing surgery without great caution.

The occurrence of delayed emesis induced 24 h after the administration of a non-platina chemotherapeutic agent, doxorubicin hydrochloride (doxorubicin), as well as behaviors such as feeding, drinking and defecation were examined in dogs. A single intravenous administration of 2 mg/kg doxorubicin induced emesis within 24 h of administration in some dogs, while delayed emesis was observed 24 h after administration in all dogs. This delayed emesis emerged strongly at day 3 or 4 and decreased at day 5. Hypophagia, the decreased frequency of drinking and the increased frequency of defecation were induced shortly after delayed emesis. Twenty-four hours after the administration of doxorubicin, a daily dose of 0.3 and 1 mg/kg/day, p.o. azasetron, a 5-HT3 antagonist, was administered for 4 days. Doxorubicin-induced delayed emesis was observed to decrease by about 30 and 50%, respectively. This result suggests that 5-HT3 receptors play a role in the mechanism of delayed emesis. Azasetron was found to improve the increased frequency of defecation, but exerted no obvious effect on hypophagia or on the decreased frequency of drinking. Taken together, we suggest that doxorubicin-induced emesis in dogs is a useful method to study further the mechanisms of delayed emesis and to investigate novel therapeutic agents against delayed emesis.

Aseries of 4-amino-5-chloro-2-methoxy-N-(1-substituted piperidin-4-ylmethyl)benzamides was synthesized as novel gastroprokinetic agents. The affinity of these compounds for the 5-hydroxytryptamine 4 (5-HT4) receptor was evaluated. Among these compounds, 4-amino-5-chloro-2-methoxy-N-[1-[5-(1-methylindol-3-ylcarbonylamino)pentyl]piperidin-4-ylmethyl]benzamide (3f, Y-34959) showed a higher affinity for the 5-HT4 receptor (Ki = 0.30 nmol/L) than for other receptors, and was confirmed to be a potent 5-HT4 receptor agonist having contractile effects in the isolated guinea-pig ascending colon (EC50 = 1.2 nmol/L). In dogs, compound 3f increased gastroprokinetic motility of both the gastric antrum and the ascending colon. In addition, this effect on the colon was inhibited by azasetron, a selective 5-HT3 receptor antagonist, demonstrating that the effect of gastroprokinetic agents having 5-HT3 receptor antagonism on the colon were reduced compared with that of selective 5-HT4 receptor agonists.

The in vitro metabolism of azasetron was investigated in the presence of liver microsomes each from male and female rats, and male dogs, in order to elucidate the cause of sex or species difference in the excretion of metabolites of azasetron hydrochloride observed in vivo. The NADPH generating system was required for each reaction process in azasetron metabolism. The N-oxidation of the azabicyclooctane ring was increased markedly with increasing pH from 7.4 to 8.5 in dog liver microsomal incubation mixture, while decreased markedly by exposure of microsomes to mild heat (50°C for 60 sec). Moreover, this N-oxidation was inhibited by methimazole (MTZ), but was hardly inhibited by metyrapone (MP). These results indicate that the N-oxidation of the azabicyclooctane ring is mainly catalyzed by the flavin-containing monooxygenases (FMO) in dog liver microsomes. The N-oxidation of the azabicyclooctane ring in rat liver microsomes were also increased markedly with increasing pH from 7.4 to 8.5 in the specimen, while still remained more than 40% of control activity when mildly heated microsomes were used. Moreover, this oxidation was partially inhibited by MTZ, MP and SKF-525A. These results indicate that both FMO and the cytochrome P-450 (P-450) take part equally in N-oxidation of the azabicyclooctane ring in rats. The activities of N-demethylation and hydroxylation of M1 were hardly decreased, when mildly heated microsomes were used, while strongly inhibited by SKF-525A and MP. Accordingly, it seems that N-demethylation and hydroxylation of Ml are catalyzed by P-450. As no difference was observed in the intrinsic clearance by liver (CLint) for azasetron N-demethylation between male rats and dogs, this reaction is apparently not related to species difference. The CLint of N-oxidation of the azabicyclooctane ring and hydroxylation of the benzene ring in male dogs were large in comparison with the values in male and female rats. Hence, the results strongly suggest that species difference in the excretion is caused by the difference of these enzyme activities. The CLint of N-demethylation of azasetron in male rats was large in comparison with the values in female rats. Therefore, sex difference in the excretion would attribute to the difference of this enzymatic activity between male and female rats.

5-HT(3) receptor antagonists are widely used as antiemetic agents in clinical setting, of which palonosetron, with a long elimination half life (t(1/2)), has recently become available. It is important to evaluate the concentration of serotonin when investigating the antiemetic effects of 5-HT(3) receptor antagonists, as those effects are not based solely on the t(1/2) value. We theoretically evaluated the antiemetic effects of three 5-HT(3) receptor antagonists (granisetron, azasetron, palonosetron) on cisplatin-induced nausea and vomiting by estimating the time course of the 5-HT(3) receptor occupancy of serotonin. We estimated the 5-HT(3) receptor occupancy of serotonin in the small intestine, based on the time course of plasma concentration of each 5-HT(3) receptor antagonist and the time course of concentration of serotonin near the 5-HT(3) receptor in the small intestine after administration of cisplatin. The antiemetic effect of each 5-HT(3) receptor antagonist was evaluated based on the normal level of 5-HT(3) receptor occupancy of serotonin. Our results suggest that an adequate antiemetic effect will be provided when a dose of 75 mg/m(2) of cisplatin is given to patients along with any single administration of granisetron, azasetron, or palonosetron at a usual dose. On the other hand, the 5-HT(3) receptor occupancy of serotonin was found to be significantly lower than normal for several days after administration of palonosetron, as compared to granisetron and azasetron, indicating that constipation may be induced. Our results show that granisetron, azasetron, and palonosetron each have an adequate antiemetic effect after administration of 75 mg/m(2) of cisplatin.

症例は57歳, 男性。肺腺癌 (cTIN2M1: Stage IV). CBDCA+MMC+VDSによる17回目の化学療法時, azasetron静注約5分後に激しい左前胸部痛を訴え, 緊急入院となった. 心電図上II, III, aVFのST上昇が認められたが, 冠拡張剤投与にて速やかに改善した. azasetron投与時のみ胸痛が誘発され, azasetronにより誘発された下壁の冠動脈攣縮による狭心症と考えた. Treadmill運動負荷試験では, 虚血性変化を認めなかった. 多発性肺転移による呼吸不全で4ヵ月後に死亡, 剖検にて器質的な冠動脈狭窄は認めなかった. 5-HT3受容体拮抗型制吐剤の循環器系への副作用の報告は稀であるが, 冠動脈への影響も念頭に置く必要があると考えられた.

The aim of the present study was to develop a transdermal drug delivery system for azasetron and evaluate the correlation between in vitro and in vivo release. The effects of different adhesives, permeation enhancers, and loadings of azasetron used in patches on the penetration of azasetron through rabbit skin were investigated using two‐chamber diffusion cells in vitro . For in vivo studies, azasetron pharmacokinetic parameters in Bama miniature pigs were determined according to a noncompartment model method after topical application of transdermal patches and intravenous administration of azasetron injections. The best permeation profile was obtained with the formulation containing DURO‐TAK 87‐9301 as adhesive, 5% of isopropyl myristate as penetration enhancer, and 5% of azasetron. The optimal patch formulation exhibited sustained release profiles in vivo for 216 h. The in vivo absorption curve in Bama miniature pigs obtained by deconvolution approach using WinNonlin® program was correlated well with the in vitro permeation curve of the azasetron patch. These findings indicated that the developed patch for azasetron is promising for the treatment of delayed chemotherapy‐induced nausea and vomiting, and the in vitro skin permeation experiments could be useful to predict the in vivo performance of transdermal azasetron patches. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:4540–4548, 2012

Several 3-substituted 5-chloro-2-methoxybenzamides were synthesized and evaluated for serotonin-3 (5-HT 3 ) receptor binding affinity. The 5-HT 3 receptor antagonistic activity of zacopride, a representative 5-HT 3 receptor antagonist, was unchanged by the replacement of the 4-amino substituent on the aromatic moiety by a 3-dimethylamino substituent. This finding prompted a structural modification of azasetron, another 5-HT 3 receptor antagonist. Consequently, a new series of 3,4-dihydro-2H-1,4-benzoxazine-8-carboxamides was obtained and these compounds were found to be more potent than 3,4-dihydro-3-oxo-2H-1,4-benzoxazine-8-carboxamides. In particular, (S)-N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro-3,4-dihydro-4-methyl-2H-1,4-benzoxazine-8-carboxamide showed a high affinity for 5-HT 3 receptors (K i = 0.051 nM) and especially potent antagonistic activity against the von Bezold-Jarisch reflex (ED 50 = 0.089 μg/kg i.v.) in rats.

Aseries of 4-amino-5-chloro-2-methoxy-N-(1-substituted piperidin-4-ylmethyl)benzamides was synthesized as novel gastroprokinetic agents. The affinity of these compounds for the 5-hydroxytryptamine 4 (5-HT4) receptor was evaluated. Among these compounds, 4-amino-5-chloro-2-methoxy-N-[1-[5-(1-methylindol-3-ylcarbonylamino)pentyl]piperidin-4-ylmethyl]benzamide (3f, Y-34959) showed a higher affinity for the 5-HT4 receptor (Ki = 0.30 nmol/L) than for other receptors, and was confirmed to be a potent 5-HT4 receptor agonist having contractile effects in the isolated guinea-pig ascending colon (EC50 = 1.2 nmol/L). In dogs, compound 3f increased gastroprokinetic motility of both the gastric antrum and the ascending colon. In addition, this effect on the colon was inhibited by azasetron, a selective 5-HT3 receptor antagonist, demonstrating that the effect of gastroprokinetic agents having 5-HT3 receptor antagonism on the colon were reduced compared with that of selective 5-HT4 receptor agonists.

Repeated intermittent administration of psychostimulants causes behavioral sensitization in rodents. Previous studies using serotonin (5-HT) receptor ligands show that the 5-HT system is involved in cocaine-induced behavioral sensitization in rats, but the role of the 5-HT system has not been studied in mice. The present study examined the effects of the 5-HT 1A receptor agonist osemozotan, the 5-HT 2 receptor antagonist ritanserin and the 5-HT 3 receptor antagonist azasetron on cocaine-induced behavioral sensitization in male ddY mice. Repeated administration of cocaine for 7 days enhanced cocaine-induced locomotor activity, and this sensitization was observed even after withdrawal for 7–14 days. Cocaine-induced behavioral sensitization after a 7-day withdrawal was significantly reduced with the coadministration of osemozotan, ritanserin or azasetron with cocaine repeatedly for 7 days. A single injection of osemozotan or ritanserin before cocaine challenge also reduced repeated cocaine-induced behavioral sensitization. However, none of these ligands inhibited cocaine-induced behavioral sensitization, when each drug was administered for 7 days after repeated cocaine administration. These results suggest that the central 5-HT system plays a role in the development and expression, but not maintenance, of behavioral sensitization in cocaine-treated mice.

The absorption characteristics of azasetron, a serotonin type 3 (5-HT3) receptor antagonist which is used for the treatment of chemotherapy-induced emesis and nausea, were investigated in rabbits. The serum concentrations of azasetron following rectal administration as a suppository increased rapidly and showed the mean tmax value of 0.18 h. The concentrations were greater after rectal administration than those after oral administration. The absolute bioavailability was significantly different between the rectal, 52.9% and oral doses, 21.6%. The mean Cmax and tmax values after the rectal dose were 904.8 ng/ml and 0.18 h, respectively, whereas those after the oral dose averaged 124.7 ng/ml and 0.85 h, respectively. These results indicate that azasetron is absorbed to a greater extent and more rapidly into the systemic circulation via the rectum than via the intestine in rabbits. Consequently, the suppository form of azasetron hydrochloride may be feasible for the treatment of chemotherapy-induced acute emesis and nausea.

The involvement of serotonin (5-HT) receptor subtypes in motor activity of the ex vivo vascularly perfused rat duodenum was investigated. Clusters of phasic contractions (CPCs), migrating in an oral to anal direction, were obtained without any stimulation. Drug effects were evaluated by changes in different components of the pressure waves, such as motor index (MI), frequency, amplitude and duration of the CPC. The effect of 5-HT depletion on motor activity was examined in animals treated with p-chlorophenylalanine (PCPA). The MI, frequency and duration of CPC were decreased by PCPA, but the amplitude was not affected, suggesting that endogenous 5-HT may play an important role in regulation of the motor activity of the rat intestine. The importance of the 5-HT receptor subtypes in the regulation of motor activity was examined. Neither the nonselective 5-HT1 and 5-HT2 receptor antagonist, methysergide, nor the 5-HT2 receptor antagonist, ketanserin, affected motor activity. However, the 5-HT3 receptor antagonists, granisetron and azasetron, decreased percentage MI, frequency, percentage amplitude and percentage duration of CPC. The 5-HT4 receptor antagonist, SB204070, exerted both excitatory and inhibitory actions, with a higher dose (10 n M) stimulating percentage MI, frequency, percentage amplitude and percentage duration, and a lower dose (0.1 n M or 1 n M) decreasing percentage MI and percentage duration of CPC. These results suggest that endogenous 5-HT regulates the motor activity of the rat duodenum through 5-HT3 and 5-HT4 receptors, with the former mediating the stimulatory influence and the latter mediating both stimulatory and inhibitory influences.

5-Hydroxytryptamine3 (5-HT3)-receptor blocking activities of KB-R6933 (6-amino-5-chloro-1-isopropyl-2-(4-methyl-1-piperazinyl)-benzimidazole dimaleate) were assessed in vivo and in vitro. Intravenous administration of KB-R6933, granisetron, ondansetron and azasetron inhibited 5-HT-induced bradycardia (von Bezold-Jarisch reflex) in anesthetized rats, with ED50 values of 0.071, 0.71, 4.0 and 0.82 microg/kg, respectively. The inhibitory effect of KB-R6933 at a dose of 0.3 microg/kg lasted for at least 8 hr, whereas those of granisetron at 30 microg/kg, ondansetron at 100 microg/kg and azasetron at 30 microg/kg nearly disappeared within 2-4 hr. Oral administration of KB-R6933 and granisetron also inhibited the bradycardia, with ED50 values of 0.41 and 76.3 microg/kg, respectively. In guinea pig ileum, KB-R6933 concentration-dependently antagonized 5-HT-evoked contraction and reduced the maximal contraction (pK(B)=8.75). Granisetron, ondansetron and azasetron shifted the dose-response curve for 5-HT to higher concentrations with no reduction of maximal contraction, and their pK(B)s were 7.65, 7.00 and 6.29, respectively. In a radioligand receptor binding study, KB-R6933, granisetron, ondansetron and azasetron displaced [3H]GR65630 binding to rat entorhinal cortex membrane, with Ki values of 0.066, 0.99, 2.70 and 2.5 nM, respectively. On the other hand, KB-R6933 exhibited negligible affinities for other receptors or binding sites tested, except for a weak affinity for the cholinergic M1-receptor, even at concentrations up to 10 microM. These results suggest that KB-R6933 is a potent and selective 5-HT3-receptor antagonist with a longer duration of action than those of existing 5-HT3-receptor antagonists.

1. 1. We investigated 5-hydroxytryptamine3 (5-HT3) receptor-mediating contractions and relaxations in the guinea-pig isolated distal colon using various 5-HT3 receptor agonists and antagonists, including GK-128 (2-[(2-methylimidazol-l-yl) methyl]benzo[f]thiochromen-l-one monohy-drochloride hemihydrate). 2. 2. Selective 5-HT3 receptor agonists, 2-methyl-5-HT and m-chlorophenylbiguanide, produced spantide-insensitive contraction and atropine-insensitive contraction and the relaxation. These agonists showed a small, but significant, difference of potency between contraction and relaxation. 3. 3. GK-128 competitively blocked both 2-methyl-5-HT- and m-chlorophenylbiguanide-induced responses with similar potency. The affinities of GK-128 for spantide-insensitive contraction and atropine-insensitive contraction were tenfold higher than for relaxation. 4. 4. Other selective 5-HT3 receptor antagonists, azasetron and tropisetron, also exhibited higher affinity in contraction than in relaxation, but the extent of their affinity differences was smaller than that observed in GK-128. In contrast, granisetron, ramosetron and ondansetron exhibited no significant differences in their affinity values among the three responses. 5. 5. These results suggest that the 5-HT3 receptors which mediate contraction and relaxation in the guinea-pig distal colon may not be the same, and that GK-128 is a 5-HT3 receptor antagonist with a stronger potency for contraction.

Several 3-substituted 5-chloro-2-methoxybenzamides were synthesized and evaluated for serotonin-3 (5-HT 3 ) receptor binding affinity. The 5-HT 3 receptor antagonistic activity of zacopride, a representative 5-HT 3 receptor antagonist, was unchanged by the replacement of the 4-amino substituent on the aromatic moiety by a 3-dimethylamino substituent. This finding prompted a structural modification of azasetron, another 5-HT 3 receptor antagonist. Consequently, a new series of 3,4-dihydro-2H-1,4-benzoxazine-8-carboxamides was obtained and these compounds were found to be more potent than 3,4-dihydro-3-oxo-2H-1,4-benzoxazine-8-carboxamides. In particular, (S)-N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro-3,4-dihydro-4-methyl-2H-1,4-benzoxazine-8-carboxamide showed a high affinity for 5-HT 3 receptors (K i = 0.051 nM) and especially potent antagonistic activity against the von Bezold-Jarisch reflex (ED 50 = 0.089 μg/kg i.v.) in rats.

The function of serotonin (5-HT)3 receptors on colonic transit was investigated in unanesthetized rats. The colonic transit was accelerated by 5-HT (10 mg/kg, s.c.), 2-methyl-5-HT (30 mg/kg, s.c.), neostigmine (0.03-0.1 mg/kg, s.c.), corticotropin releasing factor (CRF; 1 μg intracerebroventricular administration) and restraint stress (for 45 minutes). A potent and selective 5-HT3 receptor antagonist, aza-setron {(±)-N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxamide monohydrochloride; 0.01–10 mg/kg, p.o.} inhibited the 5-HT-, CRF- and stress-accelerated colonic transit in a dose-dependent manner. Ondansetron (10 mg/kg, p.o.) and granisetron (1 mg/kg, p.o.) also inhibited the stress-accelerated colonic transit, but azasetron was more effective than these two drugs. Atropine methylbromide (0.1 mg/kg, s.c.) and tetrodotoxin (0.01 mg/kg, s.c.) inhibited the accelerated colonic transit under stress conditions, but methysergide (10 mg/kg, s.c.), SDZ205-557 (10 mg/kg, s.c.), domperidone (30 mg/kg, p.o.), trimebutine (300 mg/kg, p.o.), and metoclopramide (30 mg/kg, p.o.) did not. Azasetron (10 μg) administered intracerebroventricularly did not inhibit the stress-induced acceleration. These results suggest that endogenous 5-HT which is released through stress accelerates the colonic transit via the 5-HT3 receptors and finally a cholinergic mechanism. It is considered that azasetron inhibits colonic transit particularly under stress conditions through the blockade of the peripheral 5-HT3 receptors. Azasetron may improve bowel function in stress-related colonic dysfunction like irritable bowel syndrome.

Purpose: We compared the prophylactic effects of intravenously administered azasetron (10 mg) and ondansetron (8 mg) on postoperative nausea and vomiting (PONV) in patients undergoing gynecological laparoscopic surgery under general anesthesia. Materials and Methods: We studied 98 ASA physical status I or II 20-65 years old, female patients, in this prospective, randomized, double blind study. Patients were randomly divided into two groups and received ondansetron 8 mg (group O) or azasetron 10 mg (group A) 5 min before the end of surgery. The incidence of PONV, Visual Analogue Scale (VAS) for pain, need for rescue antiemetic and analgesics, and adverse effects were checked at 1, 6, 12, 24, and 48 h postoperatively. Results: The overall incidence of PONV was 65% in group O and 49% in group A. The incidence of PONV was significantly higher in group O than in group A at 12-24 h postoperatively (nausea; 24% vs. 45%, p = 0.035, vomiting; 2% vs. 18%, p = 0.008), but there were no significant differences at 0-1, 1-6, 6-12 or 24-48 h. Conclusion: In conclusion, azasetron (10 mg) produced same incidence of PONV as ondansetron (8 mg) in patients undergoing general anesthesia for gynecological laparoscopic surgery. Azasetron was more effective, in the intermediate post-operative period, between 12 and 24 h.

Background This study was designed to mainly evaluate the activity and safety of olanzapine compared with 5-hydroxytryptamine3(5-HT3) receptor antagonists for prevention of chemotherapy-induced nausea and vomiting(CINV) in patients receiving highly or moderately emetogenic chemotherapy (HEC or MEC). The second goal was to evaluate the impact of olanzapine on quality of life (QoL) of cancer patients during the period of chemotherapy. Methods 229 patients receiving highly or moderately emetogenic chemotherapy were randomly assigned to the test group [olanzapine(O) 10 mg p.o. plus azasetron (A) 10 mg i.v. and dexamethasone (D) 10 mg i.v. on day 1; O 10 mg once a day on days 2-5] or the control group (A 10 mg i.v. and D 10 mg i.v. on day 1; D 10 mg i.v. once a day on days 2-5). All the patients filled the observation table of CINV once a day on days 1-5, patients were instructed to fill the EORTC QLQ-C30 QoL observation table on day 0 and day 6. The primary endpoint was the complete response (CR) (without nausea and vomiting, no rescue therapy) for the acute period (24 h postchemotherapy), delayed period (days 2-5 poschemotherapy), the whole period (days 1-5 postchemotherapy). The second endpoint was QoL during chemotherapy administration, drug safety and toxicity. Results 229 patients were evaluable for efficacy. Compared with control group, complete response for acute nausea and vomiting in test group had no difference (p > 0.05), complete response for delayed nausea and vomiting in patients with highly emetogenic chemotherapy respectively improved 39.21% (69.64% versus 30.43%, p < 0.05), 22.05% (78.57% versus 56.52%, p < 0.05), complete response for delayed nausea and vomiting in patients with moderately emetogenic chemotherapy respectively improved 25.01% (83.07% versus 58.06%, p < 0.05), 13.43% (89.23% versus 75.80%, p < 0.05), complete response for the whole period of nausea and vomiting in patients with highly emetogenic chemotherapy respectively improved 41.38% (69.64% versus 28.26%, p < 0.05), 22.05% (78.57% versus 56.52%, p < 0.05), complete response for the whole period of nausea and vomiting in patients with moderately emetogenic chemotherapy respectively improved 26.62% (83.07% versus 56.45%, p < 0.05), 13.43% (89.23% versus 75.80%, p < 0.05). 214 of 299 patients were evaluable for QoL. Comparing test group with control group in QoL evolution, significant differences were seen in global health status, emotional functioning, social functioning, fatigue, nausea and vomiting, insomnia and appetite loss evolution in favour of the test group (p < 0.01). Both treatments were well tolerated. Conclusion Olanzapine can improve the complete response of delayed nausea and vomiting in patients receiving the highly or moderately emetogenic chemotherapy comparing with the standard therapy of antiemesis, as well as improve the QoL of the cancer patients during chemotherapy administration. Olanzapine is a safe and efficient drug for prevention of CINV.

Y-25130( (+/-)N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro-4-methyl-3-oxo-3,4-dihydro - 2H-1,4-benzoxazine-8-carboxamide hydrochloride) is a potent and selective 5-HT3 receptor antagonist free of dopamine receptor blocking activity. This compound was effective against emesis induced in animals by cytotoxic drugs or by total body X-radiation. When given prophylactically, the doses required to completely inhibit cisplatin-induced emesis in dogs and doxorubicin and cyclophosphamide-induced emesis in ferrets were 0.1 and 0.3 mg/kg i.v., respectively. Y-25130, at the dose of 0.3 mg/kg i.v., almost completely inhibited X-radiation-induced emesis in ferrets. When given during emesis, the doses required to completely inhibit cisplatin-induced emesis in dogs and doxorubicin- and cyclophosphamide-induced emesis in ferrets were 0.1 and 0.3 mg/kg i.v., respectively. The i.v. dose of 0.3 mg/kg of Y-25130 was enough to almost completely inhibit cisplatin-induced emesis in dogs for 24 h. From these results, it is suggested that Y-25130 may become an effective antiemetic drug against emesis induced by anticancer therapy.

A serotonin antagonist azasetron, which is relatively hydrophilic and cationic compound, has been shown to exhibit a relatively high and a dose-dependent increase of intestinal absorbability. In the present study, the significant contribution of a specific secretory mechanism to the nonlinear intestinal absorption of azasetron and other drugs was studied. The initial uptake rate of azasetron by Caco-2 cells was saturable and temperature-dependent, demonstrating a participation of a carrier-mediated uptake process. Net transport of [14C]azasetron from basolateral-to-apical-side across Caco-2 cells was greater than that from apical to basolateral side. When 0.5 mM unlabeled azasetron was included in the apical side medium, apical-to-basolateral transport of [14C]azasetron was enhanced, whereas basolateral-to-apical transport was decreased. However, when higher concentrations of unlabeled azasetron were added, a decreased apical-to-basolateral and an increased basolateral-to-apical transport of [14C]azasetron were observed.Furthermore, first-order intestinal absorption rate constants of azasetron, which were evaluated by Doluisio's technique in rats, exhibited a complicated nonlinear feature. Namely, the rate constant was increased with increasing concentration of azasetron from 0.01 to 10 mM, whereas the value was decreased at higher concentrations up to 60 mM. These results may demonstrate that an intestinal absorption of azasetron includes two nonlinear processes, including carrier-mediated uptake and specific secretory mechanisms. Interestingly, since cyclosporin A inhibited secretory process of azasetron in Caco-2 cells, P-glycoprotein may be involved as the secretory mechanism. Similar nonlinear increase of intestinal absorption was observed in cyclosporin A after intra-ileal administration in rats. In addition, intestinal absorption of cyclosporin A was increased with a coadministration of P-glycoprotein inhibitor.These results demonstrate that the specific intestinal secretory mechanism is a significant factor, resulting in nonlinear increase of oral bioavailability.