Granisetron vs ondansetron: is it a question of duration of 5-HT3 receptor blockade?

Efficacy of palonosetron in postoperative nausea and vomiting (PONV)-a meta-analysis

INTRODUCTION

Palonosetron is a second-generation 5-HT3 receptor antagonist with proposed higher efficacy and sustained action for prophylaxis of postoperative nausea and vomiting (PONV).

METHODS

Randomized controlled trials involving adult population undergoing elective surgery under general anesthesia comparing palonosetron to placebo, ramosetron, granisetron, and ondansetron were included. Data were extracted for vomiting incidence (VI), complete response (no nausea/vomiting; Complete Response [CR]), and rescue antiemetic need. This was categorized as early phase (24 hours postoperative for ramosetron and 6 hours for rest) and delayed phase (48 hours for ramosetron and 24 hours for rest). VI and CR were used as markers of drug efficacy. Any adverse effects were evaluated.

RESULTS

Twenty-two trials (4 with 3 groups) were included (comparing palonosetron to placebo in 5, ramosetron in 5, granisetron in 4, and ondansetron in 12 subgroups). Palonosetron demonstrated statistical superiority over placebo for VI and CR, both early/delayed PONV prevention. For delayed phase, palonosetron surpassed ramosetron in all 3 variables; however, none of the variables attained statistical significance during early phase. In early phase, palonosetron had better VI and CR than did granisetron; however, variables other than CR (better for palonosetron) failed to achieve statistical significance for delayed phase. All 3 outcomes were significantly better for palonosetron compared with ondansetron in delayed phase, but statistical superiority could only be demonstrated for VI in early phase. Being inconsistently documented across trials, nausea scores could not be evaluated.

CONCLUSION

Palonosetron is as safe as and more effective than placebo, ramosetron, granisetron, and ondansetron in preventing delayed PONV. For early PONV, it has higher efficacy over placebo, granisetron, and ondansetron.

Chemotherapy-induced emesis in elderly cancer patients: the role of 5-HT3-receptor antagonists in the first 24 hours

OBJECTIVE

This review highlights the need to optimize 5-HT3-receptor-antagonist-based antiemetic therapy for elderly cancer patients, particularly during the first 24 h after receiving chemotherapy, based on knowledge of the chemotherapeutic regimen, comorbidity, polypharmacy, dosing convenience and age-related health.

BACKGROUND

The proportion of elderly people (over 65 years of age) in the general population is increasing. Compared with the general population, elderly people have a greater risk of serious diseases, such as cancer and cardiovascular disease. Their chemotherapy can be compromised by factors including comorbidity, declining organ function, polypharmacy, drug-drug interactions and cognitive impairments. The use of aprepitant in this elderly population with many concomitant medications is not discussed. Many chemotherapeutic regimens are highly emetogenic, and nausea and vomiting are rated among the most distressing side effects of chemotherapy. The emetogenic potential of various chemotherapy regimens is reviewed, demonstrating clear differences in severity and time of symptom onset. Such differences are particularly important during the first 24 h after administration, when control of emetic symptoms can help to prevent the occurrence of subsequent episodes. The matter is further complicated by inter-patient differences in susceptibility to nausea and vomiting resulting from multiple factors including gender, age and alcohol intake. Individual patient evaluation is essential to identify those patients most at risk. Elderly patients may also be particularly sensitive to the serious physiological and physical effects of nausea and vomiting. Education about symptom management needs to recognize specific learning barriers in the elderly, such as declining sensory perception or cognitive impairment. 5-HT3-receptor antagonists have long been the gold standard for treating chemotherapy-induced nausea and vomiting. Pharmacological differences between 5-HT3-receptor antagonists suggest the need for careful consideration of individual patient characteristics. Selection of the most appropriate agent will optimize antiemetic therapy for elderly cancer patients.

CONCLUSION

Chemotherapy-induced emesis in elderly cancer patients needs optimal control by a 5-HT3-receptor antagonist with uncomplicated 24-hour efficacy and good tolerability. Choosing a 5-HT3-receptor antagonist with a long duration of action, low risk of drug-drug interactions and once-daily dosing is important to ensure effective prophylaxis against nausea and vomiting in the elderly and simplify management for patients with cognitive impairment, declining organ function and comorbidity.

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.

Selective serotonin 5-HT3 receptor antagonists for postoperative nausea and vomiting: are they all the same?

Selective serotonin 5-HT(3) receptor antagonists have proven safe and effective for the management of postoperative nausea and vomiting. Dolasetron, granisetron, ondansetron and tropisetron selectively and competitively bind to 5-HT(3) receptors, blocking serotonin binding at vagal afferents in the gut and in the regions of the CNS involved in emesis, including the chemoreceptor trigger zone and the nucleus tractus solitarii. Despite their shared mechanism of action, 5-HT(3) receptor antagonists have different chemical structures and exhibit differences in receptor binding affinity, dose response and duration of effect. Furthermore, although dolasetron, granisetron, ondansetron and tropisetron are all extensively metabolised by the cytochrome P450 (CYP) system, different components of this system predominate in the metabolism of each of these agents. Hence, although these agents are considered equally effective in the overall population, their pharmacokinetic and pharmacodynamic differences may explain the variability in individual responses to these drugs. This review discusses the pharmacological profiles of dolasetron, granisetron, ondansetron and tropisetron, and the clinical implications of differences in their profiles.

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.

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.

Treatment implications for radiation-induced nausea and vomiting in specific patient groups

Radiation-induced nausea and vomiting (RINV) affect the management and quality of life of cancer patients. Current guidelines for RINV prevention recommend prophylaxis with a 5-hydroxytryptamine (5-HT(3))-receptor antagonist for patients receiving moderately or highly emetogenic radiotherapy regimens. Randomised trials have compared such antagonists with conventional antiemetics, and have demonstrated their efficacy and safety. Special consideration is needed for antiemetic treatment in certain patient groups, particularly the elderly and those with renal or hepatic impairment. Radiation oncologists should be aware of the effect on antiemetic treatment of factors such as comorbid conditions (particularly cardiovascular disease), polypharmacy and drug-drug interactions, and choose the agent with the lowest potential for additional complications. The most appropriate antiemetic treatment to improve patient compliance and quality of life should ideally combine proven efficacy with uncomplicated administration and convenient dosing regimens.

Chemotherapy-induced nausea and vomiting: the importance of acute antiemetic control

Nausea and vomiting are two of the most feared side effects of cancer chemotherapy and radiotherapy. Chemotherapy-induced nausea and vomiting can be broadly categorized as acute (occurring within 24 hours of therapy), delayed (persisting for 6-7 days after therapy), or anticipatory (occurring prior to chemotherapy administration). Breakthrough and refractory nausea and vomiting describe the symptoms of uncontrolled emesis. Evidence suggests that good control of nausea and vomiting during the acute period correlates with the control of delayed emesis. Conversely, protection failure during the first 24 hours has a high predictive value for delayed emesis in the same cycle. The 5-HT(3)-receptor antagonists, regarded as the 'gold standard' in antiemetic therapy, are the first-line treatment for moderately and highly emetogenic chemotherapy and radiotherapy regimens in adults and children. Evidence suggests that the 5-HT(3)-receptor antagonists administered in combination with corticosteroids afford the best protection from symptoms of acute emesis and, by extrapolation, the most effective prevention of delayed emesis. Antiemetic therapeutic guidelines stress that the goal of therapy is to prevent cytostatic-induced nausea and vomiting. Therefore, the prophylactic use of the most effective antiemetic regimen-taking into consideration the emetogenicity of the chemotherapy and individual patient characteristics-must be adhered to in order to prevent acute, delayed, and anticipatory nausea and vomiting.