Current position of 5HT3 antagonists and the additional value of NK1 antagonists; a new class of antiemetics

Comparative evaluation of triplet antiemetic schedule versus doublet antiemetic schedule in chemotherapy-induced emesis in head and neck cancer patients

PURPOSE

To compare the antiemetic combination of palonosetron, dexamethasone, and aprepitant (PDA) with antiemetic combination of ondansetron and dexamethasone (OD) in head and neck cancer patients receiving docetaxel, carboplatin, and 5-FU based chemotherapy.

METHODS

Sixty previously untreated patients were randomly divided into two groups of thirty patients each. The PDA group received a combination of palonosetron 0.25 mg intravenously (IV), dexamethasone 12 mg IV, and capsule aprepitant per oral. OD group received ondansetron 16 mg IV, and dexamethasone 12 mg IV for emesis control. The primary objective was to compare the efficacy of two antiemetic schedules for preventing acute and delayed CINV (chemotherapy-induced nausea and vomiting). The primary efficacy end point was complete response (CR).

RESULTS

All the patients tolerated both schedules well. The antiemetic response for acute emesis (first 24 hours) in PDA versus OD group was: CR was 86.7 versus 60%. For delayed emesis (from day 2-5) in PDA versus OD group CR was 83.3 versus 53.3%. The intensity of acute nausea (first 24 hours) in PDA versus OD group was: no nausea-70 versus 46.6%. The intensity of delayed nausea (from day 2-5) in PDA versus OD was: no nausea-76.6 versus 43.3%. The CR to both acute and delayed emesis (no vomiting from day 1-5) in PDA versus OD group was 83.3 versus 53.3% (p < 0.05, significant). The CR to nausea (no nausea from day 1-5) in PDA versus OD group was 70 versus 43.3% (p < 0.05, significant).

CONCLUSION

Although both the schedules were tolerated well, the PDA schedule (palonosetron, aprepitant, and dexamethasone) was significantly better than the OD schedule (ondansetron and dexamethasone) in controlling cancer CINV in the acute as well as delayed phases.

Ramosetron hydrochloride for the prevention of cancer chemotherapy induced nausea and vomiting: The Indian experience

BACKGROUND

Despite the advent of 5-HT3 antagonists, control of delayed gastrointestinal adverse events with cancer chemotherapy is still not optimal. This open label, active controlled, multicentric clinical trial was undertaken to assess the comparative efficacy and safety of ramosetron with ondansetron for the prevention of acute and delayed nausea and vomiting associated with emetogenic cancer chemotherapy in adult patients in India.

MATERIALS AND METHODS

Enrolled patients received treatment with ramosetron hydrochloride 0.1 mg or ondansetron hydrochloride 4 mg tablets once daily in the morning for 5 days starting 1 h before the start of chemotherapy. Severity grades of nausea and vomiting were recorded on a daily basis for a period of 5 days and complete response rate (CRR) and effective rate (ER) were calculated. Clinical adverse events were recorded and hematological and biochemical investigations were performed for safety assessment.

RESULTS

A total of 114 patients in ramosetron group and 100 patients in ondansetron group completed the study and were eligible for efficacy and safety analysis. CRR and ERs show that while ramosetron is non-inferior to ondansetron in the control of early nausea and vomiting (occurring during the first 24 h) after the treatment with emetogenic chemotherapy, it is superior to ondansetron in the control of delayed nausea and vomiting (occurring after the first 24 h). The proportion of patients achieving a cumulative complete response (for the entire study period) is significantly greater in ramosetron group as compared to ondansetron group (27.2% vs. 7.0%; P < 0.001). Ramosetron was well tolerated by all the study participants.

CONCLUSIONS

Ramosetron is significantly more effective than ondansetron for the control of delayed nausea and vomiting induced by emetogenic cancer chemotherapy.

Treatment of chemotherapy-induced nausea and vomiting

BACKGROUND

Recent improvements in medical oncology include both development of anticancer and supportive therapy. Serotonin receptor antagonists were introduced in clinical practice 20 years ago. Since then, the prevention and treatment of chemotherapy-induced nausea and vomiting allows continuing efficacious chemotherapy that earlier had to be stopped sometimes for intolerance.

AIM

This anniversary review summarises the current antiemetic arsenal focussing on the most potent antiemetic drugs such as serotonin and substance P receptor antagonists.

RESULT

Antiemetic treatment improves quality of life under chemotherapy and contributes to the survival benefit as well. In spite of the use of these new drugs, a significant number of patients still experience nausea and vomiting. Special complications like delayed emesis can be alleviated by combination therapies.

CONCLUSION

Prevention and optimal management of chemotherapy-induced nausea and vomiting should be a goal for most patients receiving emetogenic chemotherapy.

Anti-emetic drugs in oncology: pharmacology and individualization by pharmacogenetics

OBJECTIVE

Nausea and vomiting are the most distressful side effects of cytotoxic drugs in cancer patients. Antiemetics are commonly used to reduce these side effects. However, the current antiemetic efficacy is about 70-80% in patients treated with highly-emetogenic cytotoxic drugs. One of the potential factors explaining this suboptimal response is variability in genes encoding enzymes and proteins which play a role in metabolism, transport and receptors related to antiemetic drugs. Aim of this review was to describe the pharmacology and pharmacogenetic concepts of of antiemetics in oncology.

METHOD

Pharmacogenetic and pharmacology studies of antiemetics in oncology published between January 1997 and February 2010 were searched in PubMed. Furthermore, related textbooks were also used for exploring the pharmacology of antiemetic drugs. The antiemetic drugs which were searched were the 5-hydroxytryptamine 3 receptor antagonists (5-HT3RAs), dopamine antagonists, corticosteroids, benzodiazepines, cannabinoids, antihistamines and neurokinin-1 antagonists.

RESULT

The 5-HT3RAs are widely used in highly emetogenic chemotherapy in combination with dexamethasone and a neurokinin-1 antagonist, especially in acute phase. However, the dopamine antagonists and benzodiazepines were found more appropriate for use in breakthrough and anticipatory symptoms or in preventing the delayed phase of chemotherapy induced nausea and vomiting. The use of cannabinoids and antihistamines need further investigation. Only six articles on pharmacogenetics of the 5-HT3RAs in highly emetogenic chemotherapy are published. Specifically, these studies investigated the association of the efficacy of 5-HT3RAs and variants in the multi drug resistance 1 (MDR1) gene, 5-HT3A,B and C receptor genes and CYP2D6 gene. The pharmacogenetic studies of the other antiemetics were not found in this review.

CONCLUSION

It is concluded that pharmacogenetic studies with antiemetics are sparse. It is too early to implement results of pharmacogenetic association studies of antiemetic drugs in clinical practice: confirmation of early findings is required.

Effectiveness of a single-day three-drug regimen of dexamethasone, palonosetron, and aprepitant for the prevention of acute and delayed nausea and vomiting caused by moderately emetogenic chemotherapy

PURPOSE

Chemotherapy-induced nausea and vomiting includes both Acute (0-24 h) and Delayed (24-120 h) components with different physiologic mechanisms. A combination of a serotonin antagonist, a corticosteroid, and an NK-1 antagonist has proven effective against this problem. However, standard antiemetic regimens require administration over 3-4 days after chemotherapy. The present study evaluated a more convenient single-day three-drug antiemetic regimen for patients receiving moderately emetogenic chemotherapy.

MATERIALS AND METHODS

Chemotherapy-naïve patients with solid tumors receiving cyclophosphamide and/or doxorubicin were eligible. Patients could not have pre-existing etiologies for vomiting. Prior to chemotherapy, patients received a single dose of aprepitant 285 mg p.o., dexamethasone 20 mg p.o., and palonosetron 0.25 mg i.v. A daily patient diary recording episodes of emesis and severity of nausea was then kept for 5 days. Any further antiemetics were considered rescue medication.

RESULTS

Forty-one eligible and evaluable patients (40 women, one man) with breast cancer were entered on study. Most were receiving adjuvant chemotherapy. Complete Response (no vomiting, no rescue medication) was seen in 51% of patients, including 76% with Complete Response for the Acute period and 66% for the Delayed period. No emesis was reported for 100% of patients in the Acute period and 95% in the Delayed period. No Nausea was seen in 32% of patients. No untoward toxicities were seen.

CONCLUSION

A single-day three-drug antiemetic regimen is feasible and effective for protection against both Acute and Delayed vomiting after moderately emetogenic chemotherapy. Formal comparison to a standard multi-day antiemetic regimen is warranted.

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.

Interethnic differences in genetic polymorphisms of CYP2D6 in the U.S. population: clinical implications

DNA polymorphisms have been identified in the genes encoding a number of the cytochrome P450 (CYP) enzymes, leading to wide interindividual variation in drug clearance. CYP2D6 metabolizes a significant number of clinically used medications, and genetic variants of the CYP2D6 isozyme that result in varying levels of metabolic activity are of clinical importance in some settings. The exact nature of the clinical effect caused by polymorphisms of the gene depends on the drug in question and the specific variant alleles expressed, as individual variants result in differing phenotypes with a range of levels of enzymatic activity. Compromised drug efficacy due to CYP2D6 variation has been documented with a variety of agents, and this review considers a number of examples, including the 5-HT(3)-receptor antagonists, which are used in oncology supportive care for the prophylaxis of nausea and vomiting. CYP2D6 is involved in the metabolism of all of the most commonly available agents, except granisetron, and their efficacy and side effects may therefore be affected by the CYP2D6 polymorphism. Significant interethnic differences in CYP2D6 allele frequencies have been demonstrated from studies across many countries. However, incidences of polymorphisms in the U.S. population have been challenging to characterize because of the country's wide ethnic diversity. The CYP2D6 polymorphism may become more important as robust clinical tests become widely available and as the use of multiple medications and the attendant risk for drug-drug interactions increases.

Medical management of radiation injuries: current approaches

The current approach to medical management of irradiated patients begins with early diagnosis of radiation injury. Medical assessment of radiation dose is based on event history, symptomatology and laboratory results, with emphasis on time to emesis and lymphocyte depletion kinetics. Dose assessment provides a basis for early use of haematopoietic growth factors that can shorten the period of neutropaenia for patients with acute radiation syndrome. Assessments of haematopoietic, gastrointestinal and cutaneous syndromes have improved in recent years, but treatment options remain limited. Selected examples of current developments are presented.

The Pathophysiology of Chemotherapy-Induced Nausea and Vomiting

Chemotherapy-induced nausea and vomiting is a major debilitating side effect of oncology treatment despite recent advances in pharmaceutical management. Nurses who provide care to patients experiencing nausea and vomiting are often only marginally aware of the pathophysiological processes involved in the treatment. A better understanding of the science behind current interventions to reduce nausea and vomiting may help nurses use those interventions more effectively. This article reviews current knowledge about the pathophysiology of chemotherapy-induced nausea and vomiting. By understanding the pathophysiology behind this patient experience, gastroenterology nurses can develop a better understanding of the common symptoms of nausea and vomiting in general. When a nurse understands the complexity of factors causing nausea and vomiting, he or she will be better able to provide appropriate interventions to reduce these symptoms.

5-hydroxytryptamine type-3 receptor antagonists for chemotherapy-induced and radiotherapy-induced nausea and emesis: can we safely reduce the dose of administered agents?

BACKGROUND

Nausea and emesis as a consequence of chemotherapy or radiotherapy can have an adverse effect on patients' quality of life during cancer treatment and may last for > 5 days after administration. Guidelines suggest that, used at appropriate doses, the 5-hydroxytryptamine type-3 (5-HT3) receptor antagonists--which are considered the antiemetic "gold standard" when they are administered in combination with corticosteroids--demonstrate equivalent efficacy and safety. However, due to financial considerations, these agents often are used at lower doses than recommended.

METHODS

A literature review of relevant publications pertaining to the control of chemotherapy-induced nausea and emesis and dosing issues of the 5-HT3 receptor antagonists was undertaken to provide a comprehensive review of dosing issues relevant to the 5-HT3 receptor antagonists.

RESULTS

The issue of "down dosing" was particularly pertinent because of the nature of the 5-HT3 receptor antagonist dose-response curve: A steep dose-response profile within a narrow dose range suggests that antiemetic control will be lost suddenly after dose deescalation. However, the array of predisposing and confounding patient factors indicates that it is unlikely that a loss of antiemetic control will be apparent across a population; rather, individuals will experience loss of control as the dose is reduced below threshold. Of the 4 5-HT3 receptor antagonists currently licensed in the United States (granisetron, ondansetron, dolasetron, and palonosetron), ondansetron is used sometimes at lower than optimal doses, and there is evidence to suggest that even the approved oral dose of dolasetron may be suboptimal.

CONCLUSIONS

Suboptimal dosing not only will be detrimental to patients' quality of life but, ultimately, will prove counterproductive in terms of hospital resources, and it will add to the already significant socioeconomic burden associated with cancer therapy. Therefore, the dose of antiemetic agent administered should be sufficiently high to ensure good emesis control across the whole patient population.

Optimising antiemetic therapy: what are the problems and how can they be overcome?

BACKGROUND

Management of chemotherapy- or radiotherapy-induced emesis has improved significantly following the introduction of the 5-HT3-receptor antagonists. Prophylactic use of these agents is recommended for the prevention of both chemotherapy- and radiotherapy-induced nausea and vomiting, given with a corticosteroid. Despite these advances, nausea and vomiting remain among the most feared and debilitating adverse effects of cytotoxic therapy. The shift towards a more elderly population of patients with cancer presents additional considerations for supportive care, with an emphasis on achieving control of nausea and vomiting, whilst minimising toxicity and avoiding drug-drug interactions. This review presents some of the key issues for consideration in optimising antiemetic therapy. The PubMed search engine was used to search for relevant literature (up to December 2004) and relevant international congress materials collected during 2003 and 2004.

SCOPE

While the early stages of nausea and vomiting are 5-HT-mediated, identification of a role for substance P in late emesis has led to the development of the NK1-receptor antagonist, aprepitant. As a new agent, the clinical profile of aprepitant is still being explored, including its interaction with concomitant medications. Patients who achieve good control of acute and late-acute nausea and vomiting have a reduced risk of experiencing delayed onset symptoms, emphasising the importance of prophylactic management with effective agents. Although the 5-HT3-receptor antagonists are widely considered to have equivalent efficacy, they vary in half-life and the nature of antagonism at receptors. Their metabolic profiles also differ, with cytochrome P450 (CYP) metabolism affecting their propensity for drug-drug interactions. Several sets of guidelines are available that outline recommendations for selection and use of antiemetic therapy. However, under-use of 5-HT3 receptor antagonists has been reported in both the radiotherapy and chemotherapy settings, and some commonly used doses may be suboptimal.

CONCLUSION

In optimising antiemetic therapy, wider implementation of guidelines is desirable, as is consideration of each patient's individual needs. Safety and tolerability of supportive care medications should be a key consideration, and cardiovascular warnings and the possibility of drug-drug interactions should be given sufficient consideration, particularly in view of the older age of the population with cancer.

Is there a pharmacological basis for differences in 5-HT3-receptor antagonist efficacy in refractory patients?

5-HT3-receptor antagonists are the current antiemetic 'gold standard' for chemotherapy- and radiotherapy-induced nausea and vomiting. Interestingly, studies have shown that patients experiencing poor control of acute chemotherapy-induced nausea and vomiting with one antiemetic therapy may respond well to another agent, including a drug of the same class. This review examines pharmacological differences between the 5-HT3-receptor antagonists in order to determine potential reasons for their differing efficacy, particularly in relation to refractory emesis. Differences in drug metabolism by the cytochrome P450 system, inadequate dosing of the respective agents, differences in onset and duration of action, and effects on serotonin release and reuptake are discussed.

5-HT3A receptor subunits in the rat medial nucleus of the solitary tract: subcellular distribution and relation to the serotonin transporter

The 5-hydroxytryptamine 3 (5HT3) receptor is a serotonin-gated ion channel implicated in reflex regulation of autonomic functions within the nucleus of the solitary tract (NTS). To determine the relevant sites for 5-HT3 receptor mediated transmission in this region, we used electron microscopic immunocytochemistry to examine the subcellular distribution of the 5HT3 receptor subunit A (5HT3A) in relation to the serotonin transporter (SERT) in the intermediate medial NTS (mNTS) of rat brain. The 5HT3A immunolabeling was detected in many axonal as well as somatodendritic and glial profiles. The axonal profiles included small axons and axon terminals in which the 5HT3A immunoreactivity was localized to membranes of synaptic vesicles and extrasynaptic plasma membranes. In dendrites and glia, the 5HT3A immunoreactivity was located on the plasma membranes or in association with membranous cytoplasmic organelles. The dendritic plasmalemmal 5HT3A labeling was prominent within and near excitatory-type synapses from terminals including those that resemble vagal afferents. The 5HT3A-labeled glial processes apposed 5HT3A-immunoreactive axonal and dendritic profiles, some of which also contained SERT. Terminals containing 5-HT3A and/or SERT were among those providing synaptic input to 5HT3A-labeled dendrites. Thus, 5HT3A has a subcellular distribution consistent with the involvement of 5-HT3 receptors in modulation of both presynaptic release and postsynaptic responses of mNTS neurons, some of which are serotonergic. The results further suggest that the neuronal as well as glial 5HT3 receptors can be activated by release of serotonin from presynaptic terminals or by diffusion facilitated by SERT distribution at a distant from the synapse.

Chemotherapy-induced nausea and vomiting: current and new standards in the antiemetic prophylaxis and treatment

Nausea and vomiting are considered as two of the most distressing side-effects of chemotherapy. Chemotherapy-induced nausea and vomiting have been classified into acute, delayed and anticipatory based on the time of onset. The frequency of nausea and vomiting depends primarily on the emetogenic potential of the chemotherapeutic agents used. With the introduction of the 5-HT3 receptor-antagonists in combination with dexamethasone in the early 1990s approximately 70% of patients receiving highly emetogenic chemotherapy were protected from acute emesis. However, 40% of patients have symptoms in the delayed phase. Another group of antiemetics, the neurokinin-1-receptor-antagonists, have recently been introduced. The addition of neurokinin receptor (NK1 receptor)-antagonists to standard therapy significantly improves emesis protection in the acute and in particular in the delayed phase by approximately 20%. Due to these new developments, revised antiemetic guidelines have been set. Here, the most recent developments in antiemetic therapy, including these guidelines, are reviewed.

Granisetron: An Update on its Clinical Use in the Management of Nausea and Vomiting

Nausea and vomiting are typical side effects of cytotoxic therapy and some surgical procedures. These symptoms can represent a major therapeutic challenge and, if inadequately controlled by antiemetic treatment, will result in increased mortality, morbidity, and health care costs. However, the management of nausea and vomiting has improved greatly in recent years following the introduction of the 5-HT3-receptor antagonists, known as 'setrons.' In light of recent developments in antiemetic care, including the approval of the first neurokinin-1-receptor antagonist aprepitant (Emend; Merck and Company, Inc.; West Point, PA) and a new 5-HT3 receptor antagonist palonosetron (Aloxi; MGI Pharma; Minneapolis, MN), this article provides an update on the clinical experience gained with the 5-HT3-receptor antagonist granisetron (Kytril; Roche Laboratories, Inc.; Nutley, NJ) for the management of chemotherapy-induced, radiation-induced, and postoperative nausea and vomiting, and also reviews its use in special patient populations. Granisetron is a potent and highly selective 5-HT3-receptor antagonist that has little or no affinity for other receptors, a characteristic that is thought to underlie the favorable side-effect and safety profiles of this agent. Extensive clinical trial data have shown granisetron to be an effective and well-tolerated agent for the treatment of nausea and vomiting in the oncology and surgical settings. Granisetron has also been shown to be effective and well tolerated in special populations, such as patients refractory to antiemetic treatment, patients with hepatic or renal impairment, and children. Data also suggest that its safety profile and minimal potential for drug-drug interactions would make it an antiemetic agent of choice for elderly cancer patients.

Aprepitant for chemotherapy-induced nausea and vomiting

Although the development of serotonin receptor antagonists has greatly improved treatment for chemotherapy-induced nausea and vomiting, patients receiving chemotherapy continue to experience this troublesome side effect. On March 26, 2003, the U.S. Food and Drug Administration approved aprepitant (Emend, Merck & Co., Inc., Whitehouse Station, NJ) for use in combination with standard antiemetic agents for acute and delayed nausea and vomiting with initial and repeat courses of highly emetogenic therapy. Aprepitant appears to provide superior control of acute and delayed emesis compared to standard antiemetic therapy. Aprepitant was well tolerated in phase III studies, with side effects similar to standard therapy. Healthcare providers need to be aware of potential drug interactions with aprepitant. Oncology nurses continue to play a key role in helping patients adhere to their antiemetic schedules, stressing the importance of prevention of nausea and vomiting.