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Lack of complete correlation between emetic and T-cell-stimulatory activities of staphylococcal enterotoxins.

This study examined the emetic activity of several staphylococcal enterotoxin type A and B (SEA and SEB, respectively) mutants that had either one or two amino acid residue substitutions. New sea gene mutations were constructed by site-directed mutagenesis; gene products were obtained with glycine residues at position 25, 47, 48, 81, 85, or 86 of mature SEA. Culture supernatants from Staphylococcus aureus RN4220, or derivatives containing either sea or a sea mutation, were analyzed for the ability to stimulate proliferation of murine splenocytes, as determined by incorporation of [3H]thymidine. Culture supernatants containing SEA-N25G (a SEA mutant with a substitution of glycine for the asparagine residue at position 25), SEA-F47G, or SEA-L48G did not stimulate T-cell proliferation, unlike supernatants containing the other substitution mutants. Purified preparations of SEA-N25G had weak activity and those of SEA-F47G and SEA-L48G had essentially no activity in the T-cell proliferation assay. All mutants except SEA-V85G, which was degraded by monkey stomach lavage fluid in vitro, were tested for emetic activity. SEA-C106A and two SEB mutants, SEB-D9N/N23D and SEB-F44S (previously referred to as BR-257 and BR-358, respectively), whose construction and altered immunological properties have been reported previously, were also tested in the emetic assay. Each mutant was initially administered intragastrically at doses of 75 to 100 micrograms per animal; if none of the animals responded, the dose was increased four-to fivefold. SEA-F47G, SEA-C106A, and SEB-D9N/N23D were the only mutants that did not induce vomiting at either dose tested; these three mutants had reduced immunological activity. However, there was not a perfect correlation between immunological and emetic activities; SEA-L48G and SEB-F44S retained emetic activity, although they had essentially no T-cell-stimulatory activity. These studies suggest that these two activities can be dissociated.

Amino Acid Sequence↗

Methodology in anti-emetic trials.

The most promising anti-emetic drugs are identified during preclinical testing. Phase I and II clinical studies are used to optimize doses and schedules for the various routes of administration. Most methodological issues arise in relation to phase III studies. A prospective, randomised, double-blind, parallel-subjects design is recommended. Stratification helps balance the factors influencing emesis between the 2 arms of a randomised study. The most important of these are the strength of the emetic stimulus, prior exposure to chemotherapy, age, sex and a history of chronic alcohol consumption. The evaluation of efficacy of an anti-emetic should include its efficacy in controlling acute post-chemotherapy nausea and vomiting as well as anticipatory and delayed emesis. The side effects of an anti-emetic must also be considered since they may negate any anti-emetic advantage. Patients and observers have reported successfully evaluating these parameters using both categorical and linear-analogue scales.

Antiemetics↗

Anti-emetic efficacy of tropisetron and metoclopramide.

Post-operative vomiting, especially in ambulatory surgical patients, remains a troublesome problem. This placebo-controlled, randomized, prospective double-blind trial was designed to evaluate the efficacy of two prophylactic anti-emetic regimens on post-operative vomiting in 1-day thyroid surgery. Altogether 60 elective surgical patients were followed for 4 h post-operatively. All patients were American Society of Anesthesiologists physical status of I or II and aged between 22 and 60 years: group 1 was saline control; in groups 2 and 3, metoclopramide (0.2 mg/kg) or tropisetron (5 mg) was administered, respectively, as an intravenous single dose during induction. Patients were pre-medicated. A standardized anaesthetic technique consisting of thiopentone-succinylcholine for induction and fentanyl-nitrous oxide-halothane-pancuronium for maintenance of anaesthesia was used. A 'rescue' anti-emetic was provided in case of continued vomiting or at the patient's request. Anti-emetic inefficacy was defined as request for rescue anti-emetic and/or vomiting episode during the first 4 h post-operation. The number of patients vomiting was 12/20 (60%), 10/20 (50%) and 1/20 (5%) within the first 2 h post-operation in groups 1, 2 and 3, respectively (P > 0.05 for groups 1 and 2; P < 0.01 for groups 2 and 3; P < 0.001 for groups 1 and 3). In group 2, three patients required rescue medication during the first 2 h post-operation, but no significant difference was observed between groups 2 and 3 (P > 0.05). None of the cases in any of the groups needed any rescue medication during post-operative 2-4 h. It is concluded that tropisetron is a highly effective anti-emetic drug in the prophylaxis of post-operative vomiting.

Adult↗

[Anti-emetic effect of ondansetron in cisplatin induced nausea and vomiting--a randomized clinical trial].

The anti-emetic effect of ondansetron in cisplatin induced nausea and vomiting was studied in a randomized cross-over trial in 52 patients. The dose of cisplatin was 80-120 mg/M2 iv drip given in 1-3 days. The patients randomly received ondansetron or our routine anti-emetic regimen in the first cycle of chemotherapy. All the patients were crossed-over to the other anti-emetic regimen on the second cycle of the same cisplatin containing regimen. The results showed that ondansetron was superior to our routine anti-emetic regimen in controlling acute nausea and vomiting. 86% of patients treated with ondansetron and 20.4% treated with the routine regimen had a complete or marked response (O-2 emetic episodes). The mean frequency of vomiting were 1.3 times in ondansetron and 8.0 times in the routine regimen (P less than 0.01). Control of delayed emesis was comparable in the two arms. No patient had neurological symptoms in the ondansetron group whereas 4 patients in the routine group had extrapyramidal symptoms.

Adult↗

Effective emetic control during conditioning of children for bone marrow transplantation using ondansetron, a 5-HT3 antagonist.

Preparation for bone marrow transplantation (BMT) uses the extremely emetogenic combination of chemotherapy and total body irradiation (TBI). Ondansetron is a selective 5-HT3 antagonist and has clear anti-emetic capabilities. The efficacy of the drug was assessed in 15 children (aged 2-17 years) who received high dose cyclophosphamide (on days -6 and -5) and TBI (days -3 to 0 inclusive). During days -6 to -4 when the emetic effect of cyclophosphamide would be most pronounced, 12 of the 15 patients (80%) had fewer than five emetic episodes during their worst 24-h period, 11 (73%) had fewer than three vomits whilst nine (60%) experienced no vomiting or retching. Eleven patients progressed to TBI and 10 (91%) had fewer than five emetic events in the worst 24-h period (days -3 to +2), six (55%) had no vomiting at all. Of 100 evaluable 'patient-days' 83 (83%) were without any vomiting or retching and a further 10 'patient-days' had only one or two emetic episodes. There were no significant side-effects noted and in particular no extrapyramidal reactions. Headaches and constipation, which have been seen in adult studies, were not reported by patient or parent on any of the study days and transient elevation of liver enzymes were noted in only two patients. Ondansetron has a major role in preparing patients for BMT.

Adolescent↗

The influence of cyclizine and perphenazine on the emetic effect of meptazinol.

The effectiveness of 50 mg cyclizine and 2.5 mg perphenazine against the emetic sequelae of 100 mg meptazinol were studied in a randomized double-blind placebo-controlled trial. Three groups of 40 women received the opioid, together with an anti-emetic by i.m. injection, as premedication prior to minor gynaecological surgery. Beneficial or noxious effects were noted at standard time intervals and anaesthesia standardized as incremental methohexitone with nitrous oxide/oxygen. In the placebo group, 33 out of 40 subjects experienced either nausea or vomiting at some time after the opioid. Cyclizine, 50 mg, provided significant reduction of emetic tendency in both pre-operative and post-operative phases of the study with 22 out of 40 subjects experiencing nausea or vomiting overall. Perphenazine, 2.5 mg, showed no useful anti-emetic effect. Both anti-emetics increased the soporific effect of premedication at the 90-min interval. Subjects receiving perphenazine experienced significantly more dizziness than those of other groups.

Azepines↗

[Correlation of dopamine and serotoninergic components in the neurochemical organization of the emetic mechanism].

It was found out in experiments on the pigeons that the destruction of serotoninergic neurons of the brain after preliminary introduction (intraventricular) of 5,6-dihydroxytriptamin blocked the development mechanism of emesis evoked by cisplatin and radiation action, but increased readiness to the development of emetic reaction evoked by apomorphine. On the other hand the destruction of dopaminergic neurons of the brain by 6-hydroxydopamine did not cause emetic condition by introduction emetic-causing substances (apomorphine, cisplatin, copper sulphate) and by X-ray even with a dose, which ensures 100% emetic effect (ED100) on the control group of pigeons. The mechanism of dopamine and serotonin participation in the neurochemical organization of the emetic mechanism is discussed.

5,6-Dihydroxytryptamine↗

THE MECHANISM OF THE EMETIC ACTION OF SODIUM SALICYLATE.

In the dog, the emetic ED50 for sodium salicylate was 256+/-113 mg/kg for the intravenous route with a mean latency of 10.4+/-3.96 min, and for the oral route 228+/-68 mg/kg with a mean latency of 18.2+/-2.63 min. Values are means with standard errors. Ablation of the emetic chemoreceptor trigger-zone gave complete protection against the emetic action of 300 mg of sodium salicylate intravenously but only partial protection against the emetic action of the same dose of sodium salicylate orally. Either the intravenous salicylate acted on the trigger-zone or ablation of the trigger-zone interfered with afferent nerves from peripheral receptors responding to intravenous salicylate and which were different from the receptors responding to oral salicylate. After supradiaphragmatic vagotomy, there was equal protection against intravenous and oral salicylate. Two explanations can be advanced. First, the receptors responding to intravenous and those responding to oral salicylate have a common path in the vagus nerves; or second, afferent fibres in the vagus nerve normally maintain the vomiting centre in a reactive state. When these fibres are cut any other afferent fibres become less effective in evoking vomiting. Spinal transection gave partial and spinal transection with vagotomy gave complete protection. It is concluded that further work is necessary to decide which of the two explanations obtained.

Animals↗

Studies on the emetic and antiemetic properties of zacopride and its enantiomers.

In ferrets, the oral emetic activity of zacopride was compared with its R- and S-enantiomers. Increasing doses of 0.01, 0.1, 1.0, 10.0 and 31.6 mg/kg of zacopride or its 2 enantiomers were each administered at hourly intervals to separate groups of animals until emesis occurred. The emetic (100%) dose for zacopride and its S-enantiomer was 0.11 mg/kg p.o. (cumulative dose). The R-enantiomer at a cumulative dose of 42.71 mg/kg p.o. produced emesis in 25% of the animals. By the i.p. route zacopride and its S-enantiomer were more potent than the R-enantiomer in blocking the emetic activity of 0.1 mg/kg p.o. of zacopride. The involvement of 5-HT3 mechanisms is indicated by a correlation between zacopride and its enantiomers to cause and prevent emesis and their affinity at 5-HT3 binding sites. Further, the putative 5-HT3 agonists, 2-methyserotonin and phenylbiguanide, at 10 mg/kg p.o., produced emesis that was blocked by zacopride (0.1 mg/kg i.p.) or ICS 205-930 (1 mg/kg i.p.). The results suggest that in the ferret the S-enantiomer is predominantly responsible for both the emetic and antiemetic properties of zacopride and that 5-HT3 agonism and antagonism are involved in these actions.

Administration, Oral↗

The emetic effect of B-HT 920 and apomorphine in the dog: antagonism by haloperidol.

Recent investigations have suggested that the alpha 2-adrenoreceptor agonist B-HT 920 is also a dopamine (DA) agonist with a selectivity for presynaptic receptors. In the present study, the emetic effect of B-HT 920 was investigated. Intravenous injections of B-HT 920 (0.32-10.0 micrograms/kg) and a DA2-agonist apomorphine (3.2-100.0 micrograms/kg) caused dose-dependent emesis. The ED50 of B-HT 920 and apomorphine were 3.2 and 12.3 micrograms/kg, respectively. When haloperidol (10.0-24.5 micrograms/kg i.v.), a DA2-antagonist, was given 5 minutes before B-HT 920 (10 micrograms/kg) or apomorphine (32 micrograms/kg), it caused a dose-dependent prevention of B-HT 920- and apomorphine-induced emesis. The ED50 of haloperidol in preventing the emetic effect of both drugs was identical (13.5 micrograms/kg). In contrast, haloperidol (32 micrograms/kg i.v.) did not prevent the emetic effect of ouabain (40 micrograms/kg i.v.). Neither did yohimbine (0.1 mg/kg i.v.), an alpha 2-adrenoreceptor antagonist, prevent the emetic effect of B-HT 920 (10 micrograms/kg). These results suggest that B-HT 920, acting like apomorphine, induces emesis by activating DA2-receptors probably in the chemoreceptor trigger zone of the area postrema.

Adrenergic alpha-Agonists↗

Behavioral studies of emetic sensitivity in the ferret.

The ferrets' responsiveness to several known and putative emetic agents was evaluated using a variety of agents that were injected subcutaneously and/or intravenously. Apomorphine was consistently emetic at relatively high doses (100 micrograms/kg) when injected subcutaneously in large male ferrets (> or = 1.4 kg). The responsiveness to apomorphine was anomalous in that subcutaneous injections produced a more consistent response than intravenous ones. In addition, ferrets rapidly become tolerant or tachyphylactic to subcutaneously administered apomorphine. Area postrema ablation, but not abdominal vagotomy, rendered ferrets refractory to the emetic effects of apomorphine. This species, relative to dog and humans, proved to be insensitive to a variety of pharmacologic agents including angiotensin II, gastrin, histamine, Leu-enkephalin, neurotensin, serotonin, and vasopressin. Cisplatin elicited forceful retching and emesis. Emetic responses were obtained with substance P and Met-enkephalin in individual animals but were inconsistent. Sensitivity to DAGO [D-Ala2,MePhe4,Gly-ol5 enkephalin] was variable. Results of this study indicate that the ferret is not an optimal model for all forms of emesis.

Animals↗

Emetic action of the prostanoid TP receptor agonist, U46619, in Suncus murinus (house musk shrew).

The emetic action of the prostanoid TP receptor agonist, 11alpha,9alpha-epoxymethano-15S-hydroxyprosta-5Z,13E-dienoic acid (U46619; 300 microg/kg, i.p.), was investigated in Suncus murinus. The emetic response was reduced by 76% following bilateral abdominal vagotomy (P<0.001) and by reserpine (5 mg/kg, i.p., 24 h pretreatment; P<0.05) but U46619 administered i.c.v. (30-300 ng) was not emetic, suggesting a peripheral mechanism involving monoamines. However, fenfluramine (5 mg/kg, repeated treatment) and para-chlorophenylalanine (100-400 mg/kg) and ondansetron (0.3-3 mg/kg) were inactive (P>0.05) to reduce U46619-induced emesis precluding a role of 5-HT and 5-HT(3) receptors in the mechanism. Similarly, phentolamine (0.3-3 mg/kg), propranolol (3 mg/kg), and their combination, and metoclopramide (0.3-3 mg/kg), domperidone (0.3-3 mg/kg), droperidol (0.3-3 mg/kg), scopolamine (0.3-3 mg/kg) and promethazine (0.3-3 mg/kg) were inactive (P>0.05) to reduce the retching and vomiting response. However, the tachykinin NK(1) receptor antagonist, (+)-2S,3S(-3-(2-methoxy-5-trifluoromethoxybenzyl)amino-2-phenylpiperidine) (CP-122,721; 1-10 mg/kg) antagonized emesis (P<0.01). In conclusion, U46619-induced emesis appears to be mediated via a predominant peripheral mechanism sensitive to reserpine and is not likely to involve adrenoceptors, dopamine, 5-HT(3), muscarinic or histamine (H(1)) receptors. The action of CP-122,721 to reduce U46619-induced emesis extends the spectrum of anti-emetic action tachykinin NK(1) receptor antagonists to mechanisms involving TP receptors.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Induction of emetic response to staphylococcal enterotoxins in the house musk shrew (Suncus murinus).

The emetic responses induced by staphylococcal enterotoxin A (SEA), SEB, SEC2, SED, SEE, SEG, SEH, and SEI in the house musk shrew (Suncus murinus) were investigated. SEA, SEE, and SEI showed higher emetic activity in the house musk shrew than the other SEs. SEB, SEC2, SED, SEG, and SEH also induced emetic responses in this animal model but relatively high doses were required. The house musk shrew appears to be a valuable model for studying the mechanisms of emetic reactions caused by SEs.

Animals↗

The abdominal visceral innervation and the emetic reflex: pathways, pharmacology, and plasticity.

In recent years the role of the area postrema in the emetic reflex has been predominant and the involvement of the abdominal visceral innervation has tended to be overlooked. This paper attempts to redress the balance reflex by reviewing aspects of the existing literature and complementing this with original studies from the ferret. In view of the widespread use of the ferret in studies of emesis and particularly in the characterization of the antiemetic actions of 5-HT3 receptor antagonist, the opportunity is taken to assess the suitability of this species for studies of emesis. It is concluded that the ferret is sensitive to a wide range of emetic stimuli including intragastric irritants, opiate and dopamine receptor agonists, many cytotoxic drugs, and radiation. For several stimuli it is more sensitive than other species and for radiation on the basis of its ED100 it appears to be the most sensitive of the laboratory animals studied. Using electrical stimulation of the central end of the dorsal vagal trunk in the abdomen in conscious and anaesthetized animals, the vagal afferents were shown to be capable of eliciting emesis. Using lesioning studies an involvement of the vagus in the emetic response to a number of cytotoxic drugs (e.g., cisplatinum, cyclophosphamide, mustine) and radiation was demonstrated, although the magnitude of the effect varied with the different stimuli. An attempt is made to reconcile these observations with previous studies of area postrema ablation. The problems of interpreting the effects of nerve lesions are critically discussed in light of preliminary evidence presented here that there may be a degree of plasticity in the emetic pathway following such lesions. The range of antiemetic effects of 5-HT3 receptor antagonists is reviewed and an attempt is made to identify the site(s) at which these agents act. Results are presented that suggest a link between the vagus and 5-HT3 receptor antagonism. These studies are discussed together with others and lead us to propose that (in the ferret) 5-HT3 receptor antagonists have their main antiemetic effect by acting on vagal afferent terminals in the wall of the upper gut with an additional minor site either in the nucleus tractus solitarius or presynaptically on the vagal afferent terminals in the medulla where binding sites for 5-HT3 receptor ligands have recently been demonstrated in this species.

Abdomen↗

Efficacy of emetic and United State pharmacopoeia ipecac syrup in prevention of drug absorption.

The efficacy of both the emetic syrup prepared in the previous report and the United States Pharmacopoeia (USP) ipecac syrup concerning the prevention of drug absorption was investigated in 4 beagle dogs using a randomized and cross-over design. In order to control the intragastric pH of the beagle dogs, the administration of pentagastrin or hydrochloric acid (HCl)-glycine buffer (pH 1.5) was tested. The intragastric pH changed from 7.2 to 1.8 with the intramuscular administration of pentagastrin, but the primary emesis occurred more slowly. On the other hand, the HCl-glycine buffer (pH 1.5) gave the appropriate emesis. Therefore, the HCl-glycine buffer (pH 1.5) was used to control the intragastric pH of the beagle dogs. Acetaminophen (AcA), salicylic acid (SA) and kanamycin (KM) as markers were administered orally after conditioning the intragastric pH at 1.5. The emetic syrup or the USP ipecac syrup was then administered. The recovery rate of AcA and KM from vomit was 42-65%. The emetic syrup and the USP ipecac syrup significantly reduced the absorption of AcA from the calculation of pharmacokinetic parameters compared to the control syrup. It was observed that the absorption of cephaeline (CP) in the emetic syrup was less than that of CP in the USP ipecac syrup.

Absorption↗

Site of emetic action of oral copper sulfate in dogs. (I) Thresholds of various portions of gastrointestinal tract to locally applied copper sulfate.

Emetic thresholds to copper sulfate administered into the Pavlov pouch, Forrest pouch, Thiry fistulas of the jejunum and ileum, and duodenal, jejunal and ileal catheters were measured in dogs to conjecture the site of emetic action of copper sulfate. The oral emetic threshold had been measured preoperatively. In the stomach, the pyloric antrum had a high sensitivity, while the corpus had a low sensitivity to the topically applied copper sulfate. In the intestine, the sensitivity was high in the duodenum, whereas a low sensitivity was noted in the jejunum. Almost no sensitivity was observed in the ileum. Thus it would appear that the site of the emetic action of copper sulfate was the pyloric antrum and/or duodenum.

Administration, Oral↗

Cardio-respiratory effects of paraquat with and without emetics on Wistar rats.

We investigated the effects of paraquat products both containing and devoid of emetics on the cardio-respiratory functions of Wister rats. Anesthetized rats were administered intravenously 0.46 ml/kg Gramoxone, a commercial product containing 24% paraquat and an emetic. Paraquat equivalence equalled 110 mg/kg body weight. ECG and respiratory curves were recorded with a polygraph. Fifteen seconds after injection, A-V block and bradycardia occurred and the heart stopped beating soon after. Though the heart was severely affected, the respiratory curve differed very little from pre-injection values. Administration of pure, 24% paraquat solution (110 mg/kg body weight) inhibited respiration and almost no change was recorded by the ECG. Administration of Paragreen A, a commercial product containing 24% paraquat with no emetic, produced slight change in the ECG but respiration soon became strained and stopped. In accordance with this data, we propose that the emetic contained in Gramoxone is primarily responsible for the cardiovascular failure.

Animals↗

Use of taste repellants and emetics to prevent accidental poisoning of dogs.

Twelve taste repellents and 3 oral emetics were tested. The taste repellents were capsaicin, capsicum, oleoresin, sucrose octaacetate, quinine tonic, quassia wood extract, vanillamide, horseradish extract, caffeine, pepperoni enhancer, acorn extract, and commercially available bitter and hot flavors. The emetics tested were: antimony potassium tartrate, apomorphine, and copper sulfate. Intake of a 20% sucrose solution by Beagles was significantly depressed by addition of vanillamide at concentrations greater than 0.001%, by capsicum and capsaicin at concentrations greater than 0.01%, and by horseradish extract, pepperoni enhancer, and a commercially available hot flavor at concentrations greater than 0.1%. Antimony potassium tartrate, when added to the 20% sucrose solution at a concentration of 0.1%, produced emesis as did apomorphine at a concentration of 0.005% and copper sulfate at 1%. When the emetic antimony potassium tartrate was combined with vanillamide in a 20% sucrose solution, intake was reduced to less than 20 ml, and vomiting occurred within 15 minutes. Capsaicin (0.02%) inhibited intake of ethylene glycol to less than the lethal dose in 5 dogs tested. Incorporation of such taste repellents and/or emetics into potentially poisonous substances would reduce accidental poisoning of animals and children.

Accident Prevention↗