Neurokinin-1-receptor antagonists: a new approach in antiemetic therapy

The role of area postrema neurons expressing H-channels in the induction mechanism of nausea and vomiting

The area postrema is one of the circumventricular organs, lacks a blood-brain barrier, and is well known as the chemoreceptor trigger zone for emesis. Area postrema neurons are sensitive to emetic chemical substances carried in the blood plasma. Our previous study demonstrated the presence of 3 types of neurons characterized by different ion channels expressed in each cell type, but the type or types of area postrema neurons involved in the induction of nausea and/or emesis have remained unclear. To clarify the role of the most populous cells, which express the hyperpolarization-activated cation channel (H-channel), in induction of nausea and/or emesis, we investigated the effects of ZD7288 (an H-channel inhibitor) on apomorphine-induced conditioned taste aversion (CTA) to saccharin and c-Fos expression in the area postrema. We found that ZD7288 inhibited the acquisition of CTA and reduced apomorphine-induced c-Fos expression in the area postrema, indicating the involvement of the cells expressing H-channels in the induction of nausea and/or emesis. Finally, we discuss the role of cells expressing H-channels in the mechanism of nausea and/or vomiting.

Treatment of nausea and vomiting in terminally ill cancer patients

Nausea and vomiting is a common and distressing symptom complex in patients with far-advanced cancer, affecting up to 60% of individuals at some stage of their illness. The current approach to the palliative care of patients with nausea and vomiting is based on identifying the cause, understanding its pathophysiology and knowing the pharmacology of the drugs available for its amelioration. The following six main syndromes are identified: gastric stasis, biochemical, raised intracranial pressure, vestibular, mechanical bowel obstruction and ileus. A careful history, focused physical examination and appropriate investigations are needed to elucidate the syndrome and its cause, so that therapy is rational. Drugs are the mainstay of treatment in terminal cancer, and the main classes of antiemetic agents are prokinetics, dopamine antagonists, antihistamines, anticholinergics and serotonin antagonists. Dexamethasone and octreotide are also used, especially in bowel obstruction. Non-drug measures are important in relieving the associated distress. Patients should be able to die comfortably, without tubes. Despite decades of practice affirming this approach, the evidence base is weak and well designed studies are urgently needed.

Similarities of the neuronal circuit for the induction of fictive vomiting between ferrets and dogs

Previous studies suggested that the following neuronal circuit participates in the induction of vomiting by afferent vagal stimulation in decerebrated paralyzed dogs: (1) afferent fibers of the vagus nerve, (2) neurons of the solitary nucleus (NTS), (3) neurons of the prodromal sign center near the semicompact part of the nucleus ambiguus (scAMB), (4) neurons of the central pattern generator in the reticular area adjacent to the compact part of nucleus ambiguus (cAMB), (5) respiratory premotor neurons in the caudal medulla, (6) motor neurons of the diaphragm and abdominal muscles. However, the commonality of this neuronal circuit in different species has not yet been clarified. Thus, this study was conducted to clarify this point. This study clarified for the first time that fictive vomiting in decerebrated paralyzed ferrets could be induced by vagal stimulation, and could be identified by centrifugal activity patterns of the phrenic and abdominal muscle nerves. The distributions of c-Fos immunoreactive neurons in the NTS, scAMB and cAMB areas in ferrets that exhibited fictive vomiting were denser than those in ferrets that did not. Application of the nonNMDA receptor antagonist into the 4th ventricle produced the reversible suppression of fictive vomiting. The NK1 receptor immunoreactive puncta were found in the reticular area adjacent to the scAMB. Microinjections of NK1 receptor antagonist into the reticular areas on both sides abolished fictive vomiting. All these results in the ferrets are identical with results previously obtained in dogs and cats. Therefore, this suggests that the above neuronal circuit commonly participates in the induction of emesis in these animal species.

Aprepitant as salvage therapy in patients with chemotherapy-induced nausea and emesis refractory to prophylaxis with 5-HT(3) antagonists and dexamethasone

BACKGROUND

Despite prophylaxis with 5-HT(3) antagonists and dexamethasone, nausea/emesis are common chemotherapy- induced toxicities. The aim of this trial was to evaluate the efficacy of adding the NK1 antagonist aprepitant in patients refractory to standard prophylaxis.

PATIENTS AND METHODS

Patients with significant nausea/vomiting despite prophylaxis with 5-HT(3) antagonists and dexamethasone were eligible. Aprepitant was added to the same antiemetic regimen used during previous cycles.

RESULTS

34 patients received 92 cycles of chemotherapy with aprepitant which was applied orally at 125 mg on day 1 and 80 mg on days 2 and 3. All patients were refractory to standard antiemetic prophylaxis during cisplatin-based (n = 12) or other chemotherapy (n = 22). With the addition of aprepitant, all patients reported subjective improvement. The number of patients with nausea for >4 days decreased from 24 (71%) to 4 (12%) (p < 0.001), and the number of those with emesis for >2 days decreased from 26 (77%) to 0 (0%) (p < 0.001). In 12 patients receiving aprepitant for >2 cycles (3-8) the efficacy was maintained. No toxicity possibly related to aprepitant was observed.

CONCLUSION

Aprepitant demonstrated significant activity in patients with nausea/vomiting refractory to prophylaxis with 5-HT(3) antagonists and dexamethasone.

Incidence of chemotherapy-induced nausea and vomiting in Mexico: healthcare provider predictions versus observed

OBJECTIVE

An understanding of the incidence of chemotherapy-induced nausea and vomiting (CINV) may assist healthcare providers (HCP) when making treatment decisions. We investigated the incidence of CINV after highly or moderately emetogenic chemotherapy (HEC or MEC), in comparison with predictions of CINV by HCP.

RESEARCH DESIGN AND METHODS

This prospective study was conducted at nine oncology centers in Mexico. Eligible patients were >/=18 years old and scheduled to receive a single, initial cycle of chemotherapy. Patients recorded nausea severity, episodes of emesis, and rescue medication use for the first 5 days after chemotherapy. HCP predicted the general incidence of acute (day 1) and delayed (days 2-5) CINV.

RESULTS

A total of 82 patients were enrolled, with complete data available for 73. Mean age was 50 years; 67 (92%) were women; and 57 (78%) received HEC, while 16 (22%) received MEC. HCP predictions were comparable to the incidence of acute CINV after HEC and MEC and of delayed CINV after MEC. However, HCP predictions underestimated delayed CINV after HEC. 75.4% of patients (95% CI: 62.2-85.9) reported delayed nausea and HCP predicted 41.7% (95% CI: 30.2-55.0); 63.2% of patients (95% CI: 49.3-75.6) reported delayed emesis and HCP predicted 31.8% (95% CI: 21.0-44.5). Limitations of the study include the small sample size, possible selection bias and lack of a standardized antiemetic regimen.

CONCLUSIONS

Healthcare providers underestimated the incidence of delayed CINV after HEC. There is a need for a better understanding of the incidence of delayed nausea and emesis, which remain common side-effects of chemotherapy.