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The delayed-emesis syndrome from cisplatin: phase III evaluation of ondansetron versus placebo.

Cisplatin may evoke both an acute emetic response during the first 24 hours following treatment and a less well-recognized syndrome of delayed emesis. While delayed emesis is usually less severe in terms of frequency of vomiting episodes, the problem continues to result in significant morbidity. In comparison with acute emesis, the exact pathogenesis of the delayed emesis syndrome remains unclear. Although a combination of oral metoclopramide and dexamethasone is effective in many patients in preventing delayed emesis, almost 50% continue to experience at least one emetic episode when treated with this regimen. A phase III multicenter study has evaluated oral ondansetron versus placebo in the prevention of the delayed-emesis syndrome in 50 patients during days 2 through 5 following high-dose cisplatin administration. Although the daily rates of complete emetic control, failure, and control of nausea favor ondansetron, this trial is statistically inconclusive in establishing efficacy of ondansetron as a single agent in the prevention of delayed emesis. Ondansetron was well tolerated in the dose and schedule used.

Adult↗

DAT-582, a novel serotonin3 receptor antagonist, is a potent and long-lasting antiemetic agent in the ferret and dog.

The antiemetic effects of a novel serotonin3 receptor antagonist, DAT-582 [(6R)-(-)-N-[1-methyl-4-(3-methylbenzyl)hexahydro-1H-1,4- diazepin-6-yl]-1H-indazole-3-carboxamide dihydrochloride] were compared with those of the existing serotonin3 receptor antagonists, ondansetron and granisetron, in experimental animals. In ferrets, DAT-582 (0.003-0.1 mg/kg i.v. twice) dose-relatedly prolonged the latency to the first emetic episode and decreased the number of emetic episodes induced by cisplatin (10 mg/kg i.v.). DAT-582 was more potent than ondansetron or granisetron in inhibiting the emesis. The emesis induced by cyclophosphamide (150 mg/kg i.v.), doxorubicin (15 mg/kg i.v.) or combination of cisplatin (3.3 mg/kg i.v.), cyclophosphamide (50 mg/kg i.v.) and doxorubicin (5 mg/kg i.v.) was also inhibited by DAT-582 (0.1 mg/kg i.v., twice). When administered 2 hr before cisplatin in ferrets, DAT-582 decreased markedly the number of emetic episodes induced by cisplatin at 0.1 mg/kg i.v., whereas ondansetron and granisetron were without effect even at 0.3 mg/kg i.v. DAT-582 (0.1 mg/kg i.v.), when administered in the ferrets which were vomiting after cisplatin, immediately and almost completely blocked the subsequent emesis. Furthermore, DAT-582 (0.1 mg/kg i.v.) completely inhibited the cisplatin (3 mg/kg i.v.)-induced emesis for 24 hr after cisplatin in three of five dogs. In addition, DAT-582, at 0.3 and 1 mg/kg, p.o., inhibited the cisplatin-induced emesis in dogs. However, DAT-582, even at 3 mg/kg s.c., did not inhibit the apomorphine (0.3 mg/kg,, s.c.)-induced emesis in dogs, or the nicotine-, copper sulfate- or motion stimulus-induced emesis in the house musk shrew, Suncus Murinus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[Personality and emesis in the patient treated with antineoplastic chemotherapy].

A sample of twenty cancer patients following chemotherapy realize MMPI questionnaire, and another one for valuation of emetic and anticipatory phenomena in relation to said therapy. The authors came to the conclusion that 36.8% of the sample had anticipatory nausea and vomiting, 63.6% anticipatory dysphoria, and 66% emetic incidents after chemotherapy. The conclusion, through comparison of personality variables, is that all patients showed neuroticism and depression scales increased, in relation to healthy population. Depression variable increased especially in patients that didn't present anticipatory nausea and vomiting. Likewise, patients with anticipatory symptoms or emetic incidents after chemotherapy present an increased social introversion variable.

Adolescent↗

Ondansetron (GR 38032F): a novel antiemetic effective in patients receiving a multiple-day regimen of cisplatin chemotherapy.

In a multicenter trial, we evaluated the antiemetic efficacy of ondansetron, a selective serotonin type 3 (5-HT3) receptor antagonist, in 42 adult chemotherapy-naïve patients receiving a multiple-day cisplatin regimen (20-40 mg/m2 per day for 4-5 days). Thirty-one patients received 3 daily doses of ondansetron (0.15 mg/kg) given intravenously every 6 hours (first dose 30 minutes prior to cisplatin administration); 11 additional patients received an identical dosage and schedule except that a fourth daily dose was added 17.5 hours after cisplatin administration. No other antiemetics were administered. Forty patients were evaluable for efficacy response. Thirteen patients (33%) had no vomiting at any time during the 5-day study. When emetic episodes were evaluated on a daily basis, complete protection (zero emetic episodes) ranged from 50-75%, and major protection (less than or equal to 2 emetic episodes) ranged from 65-93%. The majority of therapy failures occurred on days 3 and 4. Side effects were minor and transient; no extrapyramidal side effects were observed. Ondansetron appears to be a safe and effective antiemetic when administered during a multiple-day cisplatin-containing chemotherapy regimen.

Adolescent↗

Symposium on microbiology update: old friends and new enemies. Bacillus cereus.

Bacillus cereus is an environmentally ubiquitous, Gram-positive, spore-forming bacillus responsible for 2 distinct foodborne disease syndromes as well as other manifestations of pathogenicity. The rapid-onset, "emetic," foodborne-disease syndrome is associated with an emetic toxin; the delayed-onset, "diarrheal" syndrome is associated with elaboration of enterotoxin. The majority of methods for detection of these toxins have relied on in vivo testing. More recent work on purification of enterotoxin facilitated the development of a rapid, specific, fluorescent immunodot assay and a tissue culture screening assay for enterotoxin. Work on characterization and detection of emetic toxin is ongoing.

Animals↗

Comparison of two different high doses of metoclopramide in the prevention of chemotherapy-induced emesis.

A randomized double-blind study was conducted to compare the anti-emetic efficacy of 1 mg/kg vs 2 mg/kg metoclopramide, administered 5 times over a period of 8.5 h in 50 cancer patients treated with platinum-containing regimens (cisplatin, ethylenediamine platinum II malonate or spiroplatin). Twenty-six patients were treated with combination chemotherapy, mainly consisting of cisplatin and 5-fluorouracil. No statistically significant differences were observed with respect to the protection against nausea and vomiting between the two dose levels of metoclopramide. However, in the group of patients who received a high dosage of cisplatin (70-100 mg/m2), or ethylenediamine platinum II malonate (800-900 mg/m2), there was a significant difference in nausea and vomiting between patients who had and those who had not received prior chemotherapy, most probably due to anticipation. No difference in the severity of the side effects was observed with the 2 metoclopramide dose levels. Considerable interpatient variation was present in serum metoclopramide levels. No clear correlation was observed between serum metoclopramide levels and prevention of platinum-induced emesis. We conclude that 1 mg/kg of metoclopramide is just as effective as 2 mg/kg as an anti-emetic agent in patients receiving platinum-based chemotherapy, and that metoclopramide serum levels are not related to the anti-emetic effect.

Adult↗

Acute radiation-induced vomiting in area postrema-ablated cats.

A dose-response relationship was established in normal unanesthetized cats for emetic incidence, latency to onset of vomiting, and duration of emetic activity over a period of 24 h after whole-body exposure to 60Co radiation at selected doses between 7.5 and 90 Gy. Each episode of vomiting, i.e., retching and expulsion, was recorded oscillographically as its characteristic intrathoracic pressure waveform by means of a catheter inserted some days before into the superior vena cava. The gamma-radiation dose of 45 Gy evoked vomiting optimally with an incidence of 92% and an average onset time of 98 min. When administered to animals prepared chronically with surgical ablation of the area postrema, the same dose of radiation evoked vomiting in four of five test cases and with an average time to onset that was not by either measure significantly different from normal. Vomiting was also elicited in all of six normal cats exposed to an intestinal dose of 45 Gy X radiation with the head shielded. The same form of irradiation evoked vomiting in two of three chronically postremectomized cats. Successful ablation of the area postrema was determined functionally by emetic refractoriness to an injection of digitalis and confirmed for completeness by histological examination. It is concluded that the area postrema is not an essential element in the reflex mechanism of radiation-induced vomiting and, therefore, no physiological basis exists for dependence on a centrally acting chemogenic factor in radioemesis.

Animals↗

Dose-response relationships of the objective and subjective antiemetic effects and of different side effects of metoclopramide against cisplatin induced emesis.

The graded and quantal responses of metoclopramide (MCL, Paspertin) were studied in patients (17-71 years) treated with cisplatin in combination with other cytostatics. The lowest dose of MCL was 0.125 mg/kg b.w./h i.v. over 2 h as loading infusion, then 0.0625 mg/kg/h over 24 h as the maintenance infusion, the total dose being 1.75 mg/kg per treatment cycle (n = 25). At the same schedule three different higher doses of MCL were run with total doses of 3.5 (n = 44), 7.0 (n = 120), and 14.0 (n = 161) mg/kg per cycle of cisplatin. The mean number of emetic episodes in historical control patients without MCL (n = 41) at the four different doses of cisplatin was 4.2 episodes at 25 mg/m2 of cisplatin, 6.9 episodes at 60 mg/m2, 14.9 at 90, and 21.6 episodes at 120 mg/m2 of cisplatin. The quantitative dose-response curves of the four doses of the emetic agonist cisplatin were shifted to the right by increasing doses of MCL. The following doses of cisplatin for greater than or equal to 95% antiemetic protection (i.e. only 0-2 emetic episodes as clinically sufficient protection) were obtained (at the respective mg/kg of MCL given in brackets): 13 (at 1.75 MCL), 25 (at 3.5 MCL), 42 (at 7 MCL), and 80 (at 14 MCL) mg/m2 of cisplatin, respectively. The MCL dose in order to provide greater than or equal to 95% of the patients against every mg/m2 of cisplatin was about 0.15 (range 0.13-0.18) mg/kg MCL per cycle (i.e. 6.5 mg/m2 of cisplatin are antagonized by 1 mg/kg of MCL).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

High-dose metoclopramide in the treatment of cis-platinum induced emesis. A dose-finding study.

In 92 patients receiving 270 cytostatic courses which all included cis-platinum, the antiemetic efficacy of medium- or high-dose metoclopramide was investigated. Metoclopramide was given intravenously 4 times during a 6-hour period (1/2 h before and 1 1/2, 3 1/2 and 5 1/2 h after cytostatic treatment) in a total dose of 1, 2, 4, 6, or 8 mg/kg. Nausea, emetic episodes, and side effects were registered during 24 h. The 1 mg/kg dose was given in 20 courses for which the average of emetic episodes was 16. In the four higher dosed groups the averages were 8, 8, 5, and 6, respectively. The average number of emetic episodes was significantly higher (p less than 0.001) in the 1 mg/kg metoclopramide group than in the 250 higher dosed courses. The frequency of side effects seemed independent of the dose in the interval 2-8 mg/kg while diarrhoea and other side effects tended to be less frequent in the 1 mg/kg metoclopramide group. Since antiemetic effect of metoclopramide in the dose interval 2-8 mg/kg did not increase with the dose, it is recommended to treat cis-platinum-induced emesis with 2 mg/kg metoclopramide given intravenously as 4 doses during a 6-hour period.

Adult↗

The piglet as a suitable animal model for studying the delayed phase of cisplatin-induced emesis.

In 46 weaned piglets we surgically implanted a cannula in the jugular vein and electrodes for ECG and EMG recordings. After a 4- to 5-day recovery, piglets were hydrated, then dosed with cisplatin (5.5 mg/kg i.v.) and recorded continuously for the next 60 h. Thirteen piglets (i.e., controls) received only cisplatin. Twenty-three other piglets received, 15 min before cisplatin, an i.v. injection of granisetron (0.25, 0.5, 2 or 7 mg/kg) or ondansetron (0.5, 2 or 7 mg/kg). Ten other piglets received, in addition to cisplatin, multiple injections of granisetron (1 mg/kg) and ondansetron (3.5 mg/kg). All control piglets exhibited both acute and delayed emesis. The first vomiting occurred with a latency of 2.13 +/- 0.82 hr after cisplatin administration; emetic intensity reached a peak (5 vomits/hr) within 2 hr and then decreased rapidly. No vomiting was observed between the 16th and 18th hr. The mean number of vomits during the first 16th was 18.4 +/- 2. Delayed emesis started at the 18th hr and lasted until the 58th hr. The mean number of vomits during the whole of the delayed phase was 9.6 +/- 2.4; the highest emetic intensity (1.2 vomit/hr) occurred between the 21th and the 22th hr. Pretreatment with a 5-HT3 receptor antagonist increased significantly the latency of the first emetic event in a dose-dependent manner. However, the severity of the acute phase was reduced significantly only with granisetron at the dose of 7 mg/kg, although the severity of the delayed phase remained unchanged, irrespective of the dose of granisetron. Three about five piglets treated repeatedly with granisetron did not vomit throughout the chemotherapy course. In contrast, no complete control was observed with repetitive injections of ondansetron. Cisplatin inducing both acute and delayed vomiting in the piglet without any lethality; this animal is a suitable model in which to study the pathogenesis of delayed emesis.

Animals↗

Use of oral and intravenous ondansetron in patients treated with cisplatin.

Ondansetron, a selective 5-HT3 antagonist, has been shown to be effective in preventing chemotherapy-induced nausea and vomiting. From July and August 1991, 25 patients were accrued in a phase II study to assess the efficacy of ondansetron in patients receiving cisplatin-containing chemotherapy. Patients received intravenous cisplatin 100 mg/m2, given either as a 24-hour infusion on day 1 or in divided doses as eight-hour infusions daily on days 1 to 3. Each patient received 24 mg of ondansetron per day for six days. Intravenous dexamethasone 24 mg was given daily on the days of cisplatin infusion. The emetic episodes and degree of nausea were evaluated daily. "Good" control of emesis (0-2 episodes of vomiting) and nausea (mild or no nausea) ranged from 64-100% and 88-100% respectively. Failure in emesis control occurred most frequently on days 3 and 4. Ondansetron was generally well tolerated with only minimal side-effects. One patient developed unexplained encephalopathy which resolved completely. Our results suggest that ondansetron is an effective anti-emetic agent with minimal toxicities. Randomised studies comparing ondansetron against "standard" anti-emetics should be conducted.

Administration, Oral↗

Ondansetron for efficient emesis control during total body irradiation.

Ondansetron is a 5-hydroxytryptamine receptor antagonist which has shown activity in the prevention of emesis following cytotoxic and radiation therapy for cancer. We describe our experience using ondansetron in 25 patients undergoing fractionated total body irradiation (TBI) 12 Gy/3 days as conditioning for bone marrow transplantation. Antiemetic efficiency was investigated during the 3 days of TBI prior to high-dose cytotoxic chemotherapy. Twenty-two of the 25 patients (88%) achieved sufficient emesis control with less than three emetic episodes whereas the remaining 12% experienced three to five emetic events during their worst 24-h period. Eleven patients (44%) had complete control with no vomiting at all. Of 75 'patient days', 52 (69%) were without any emesis, 20 (27%) were associated with one to two and only three (4%) with three to five emetic episodes. Headache occurred in four patients (16%). No other significant adverse effects were seen, in particular no extrapyramidal reactions due to ondansetron. Our data confirm that ondansetron plays a major role in the antiemetic management of patients undergoing TBI.

Adolescent↗

Granisetron in the prevention of vomiting induced by conditioning for stem cell transplantation: a prospective randomized study.

We conducted a prospective randomized study to compare granisetron, a 5-hydroxytryptamine-3 receptor antagonist with standard anti-emetics (control group) consisting mainly of metoclopramide, in the prophylaxis of emesis induced by conditioning prior to stem cell transplantation. Fifty-eight patients were evaluable for analysis. The number of emetic episodes expressed in terms of patient-days was significantly lower in the granisetron group than in the control group (P < 0.001). During the first 24 h of conditioning, 27 of the 31 patients (87.1%) in the granisetron group achieved control of emesis with less than three emetic episodes (major < or = ) a day compared with 37.0% in the control group (P < 0.001). The same degree of emesis control was maintained throughout the conditioning period in 51.% of patients in the granisetron group compared with 0% in the control group (P < 0.001). Adverse reactions were observed in 11.4% of patients in the granisetron group and in 25.9% in the control group. None of the events were serious. Based on these data, we conclude that granisetron is superior to standard antiemetics in protecting against the vomiting induced by conditioning for stem cell transplantation.

Adolescent↗

A canine model for determination of the therapeutic index of cytokine inhibitors.

Using tumor necrosis factor (TNF) inhibition in dog blood as a measure of efficacy, and canine emesis as a measure of toxicity, we were able to assign a therapeutic index to rolipram, a prototypic anti-inflammatory compound. Because both assays were performed in the same species, the ambiguities associated with comparing the physiologic effects of drugs on various species was avoided. Rolipram, a standard phosphodiesterase type IV inhibitor, was a prototypic test compound characterized by a number of cardiovascular and central nervous system side effects, as well as its in vitro and in vivo inhibition of TNF. Initial experiments with canine whole blood incubated with lipopolysaccharide resulted in nanogram-per-milliliter concentrations of TNF that could be significantly reduced by in vitro addition of a 0.03 microM concentration of rolipram. Because rolipram inhibited canine TNF production in vitro, a protocol was devised in which TNF inhibitory activity was measured in a series of blood samples from dogs infused with increasingly high doses of rolipram. This yielded the efficacy half of the therapeutic index, whereas the emetogenic dose represented the side effect portion of the index. Rolipram was infused stepwise into conscious dogs at gradually increasing doses. The infusion was stopped when vomiting occurred, and the cumulative dose was reported as the emetic dose. Rolipram caused emesis in dogs at a cumulative dose of 0.1 mg/kg. At each dose of rolipram, blood was collected. The whole blood was incubated in vitro with lipopolysaccharide to induce TNF production, which in turn was quantified by the L929 bio-assay. Theoretically, if the rolipram infusion raised blood values high enough, the rolipram in whole blood would inhibit TNF production and be reflected by a lack of TNF activity in the L929 assay. In this assay system, rolipram's 50% effective dose in the TNF assay was always at least 33-fold lower than its emetic dose of 0.1 mg/kg. This gave rolipram a therapeutic index of at least 33:1 (0.003 versus 0.1 mg/kg) on the basis of its activity in a canine efficacy model (TNF inhibition) and a toxicity model (emesis induction). Experimental compounds were tested for their emetic dose as well as TNF 50% effective dose, with the goal of obtaining a therapeutic index better than that of rolipram. Thus the coupling of cytokine activity with overt toxicity was used to arrive at the therapeutic index of a compound. The therapeutic index was used to rank compounds as to their efficacy/toxicity profile. This ranking was used to eliminate several anti-inflammatory compounds that had a therapeutic index less than that of rolipram.

Animals↗

Effects of talipexole on emesis-related changes in abdominal afferent vagal activity and ileal serotonin metabolism in rats.

The involvement of abdominal afferent vagal activity and serotonergic mechanisms were examined following intravenous administration of talipexole, a dopamine D2 receptor agonist used for treatment of Parkinson's disease, in anesthetized rats. Intravenous administration of dopamine receptor agonists including D1/D2 components increased the spontaneous firing of afferent vagal neurons as did 2-methyl-5-hydroxytryptamine. Both talipexole (0.25-1.0 mg/kg) and bromocriptine (1.0-10.0 mg/kg) increased vagal nerve activity in a dose-dependent manner, and the effect of 10 mg/kg of bromocriptine was significantly greater than that noted with 1.0 mg/kg of talipexole. Increasing vagal firing induced by talipexole was prevented by pretreatment with granisetron, but not with metoclopramide or by spinal section, indicating that afferent vagal firing was mediated via stimulation of the 5-HT3 receptors on the neurons and secondarily caused by stimulation of dopamine receptors. On the other hand, bromocriptine at 5 mg/kg increased 5-HIAA concentration in the ileum, and serotonin turnover (5-HIAA/5-HT) was increased approximately 4-fold when compared to the vehicle group. Bromocriptine also increased the activities of tryptophan hydroxylase and monoamine oxidase. Talipexole at 0.5 mg/kg did not affect ileal 5-HT metabolism and the enzymatic activities. These findings suggest that dopamine receptor agonists may induce changes in abdominal afferent vagal activity and ileal 5-HT metabolism similar to those observed with emetic compounds, and that talipexole has a much smaller influence on serotonin-mediated responses than does bromocriptine with equipotent antiparkinsonian doses. One of the possible reason why talipexole showed fewer emetic side effects in patients with Parkinson's disease may be that the emetic responses triggered by D2 receptor stimulation may secondarily cause an increase of abdominal afferent vagal activity, which may be weakened by the 5-HT3 receptor antagonistic property of talipexole.

Abdomen↗

Randomized, double blind, dose-response trial across four oral doses of dolasetron for the prevention of acute emesis after moderately emetogenic chemotherapy. Oral Dolasetron Dose-Response Study Group.

BACKGROUND: This double blind parallel group study assessed the acute antiemetic efficacy of four oral doses of dolasetron mesylate in cancer patients receiving their first course of intravenous chemotherapy with doxorubicin and/or cyclophosphamide. METHODS: Patients were randomized to receive 25, 50, 100, or 200 mg of dolasetron mesylate 30 minutes prior to chemotherapy and were monitored for nausea and emetic episodes for the next 24 hours. RESULTS: Three hundred and nineteen cancer patients at 32 sites completed the study. Most patients were female (81%); of this group, 69% had breast carcinoma. A highly statistically significant linear trend demonstrating improved response with higher doses was detected for complete response (no emetic episodes and no rescue medication) (P < 0.001), for complete plus major response (0-2 emetic episodes and no rescue medication) (P < 0.001), and for patient visual analog scale assessments of nausea (P = 0.001) and general satisfaction with antiemetic therapy (P = 0.001). No serious adverse events were noted. The most frequent adverse event was mild, self-limiting headache, which has been reported with other drugs in this class. CONCLUSIONS: Single oral doses of dolasetron mesylate were found to be effective in preventing acute emesis in cancer patients receiving moderately emetogenic chemotherapy.

Administration, Oral↗

Efficacy and safety of oral granisetron versus oral prochlorperazine in preventing nausea and emesis in patients receiving moderately emetogenic chemotherapy.

PURPOSE: To compare the efficacy and safety of oral granisetron hydrochloride tablets with that of oral prochlorperazine sustained-release capsules in preventing nausea and emesis induced by moderately emetogenic chemotherapeutic agents. PATIENTS AND METHODS: In this multicenter, double-blind, randomized, parallel group study, oral granisetron and oral prochlorperazine were compared in 230 chemotherapy-naive, adult cancer patients who received moderately emetogenic chemotherapy. Patients were stratified by gender and randomized to receive either 1.0 mg oral granisetron HCI twice a day for 7 days, or 10 mg oral prochlorperazine sustained-release capsules twice a day for 7 days. The first dose was given 1 hour before initiation of chemotherapy and the second dose 12 hours after the first dose. Patients were evaluated for emetic episodes, extent of nausea, and adverse events for 7 days after the start of chemotherapy. Primary efficacy parameters were complete response (no emetic episodes, no greater than mild nausea, no antiemetic rescue) and total control (no emetic episodes, no nausea, no antiemetic rescue) in the 24 hours after the start of chemotherapy. RESULTS: Granisetron was significantly more effective than prochlorperazine in achieving a complete response (74% vs. 41%, respectively) and total control of nausea and vomiting (58% vs. 33%, respectively) at the 24-hour assessment. Complete response at 24 hours was significantly higher in the granisetron-treated patients than in prochlorperazine-treated patients. In women, granisetron showed a complete response rate of 69% versus 38% with prochlorperazine; in men, granisetron showed a complete response rate of 92% versus 61% with prochlorperazine. Both regimens were well tolerated, with headache (36% for granisetron, 29% for prochlorperazine) and constipation (31% for granisetron, 6% for prochlorperazine) the most common adverse events. CONCLUSIONS: : Oral granisetron 1 mg twice a day was significantly more effective than oral prochlorperazine sustained release capsules 10 mg twice a day in complete response and total control of nausea and vomiting at 24 hours after chemotherapy. Both agents were well tolerated.

Administration, Oral↗

Cyclophosphamide increases 5-hydroxytryptamine release from the isolated ileum of the rat.

We recently reported that chronic administration of cyclophosphamide significantly increased urinary 5-hydroxyindole acetic acid (5-HIAA) excretion in rats indicative of a release of 5-hydroxytryptamine (5-HT) from intestinal enterochromaffin (EC) cells. Cyclophosphamide is considered to be an inactive prodrug and require conversion to active emetic metabolities (e.g. phosphoramide mustard) by hepatic metabolism. However the presence of cytochrome P450 in the intestine raises the possibility of cyclophosphamide metabolism in the wall of the intestine, a site which would have considerable significance for 5-HT release and the emetic effects of cyclophosphamide. The aim of this study was to investigate whether cyclophosphamide could induce the release of 5-HT from the isolated ileum and to examine its mechanism of action. Cyclophosphamide (10(-6)M and 10(-7)M) induced a concentration dependent increase of 5-HT from rat isolated ileum. This cyclophosphamide-induced 5-HT release was significantly reduced by granisetron (10(-6)M and 10(-7)M) or atropine (10(-7)M and 10(-6)M). Tetrodotoxin (10(-6)M completely inhibited the increased 5-HT release induced by cyclophosphamide. These results suggest that cyclophosphamide has the capacity to induce 5-HT release via activation of enteric cholinergic neurons. In addition the in vitro study demonstrate for the first time that cyclophosphamide may be activated to emetic metabolites at extra-hepatic sites (e.g. intestine) and that conversion at these sites could contribute to the mechanism of cyclophosphamide induced emesis.

Animals↗