In Reply: Evidence for Equivalent Cardiotoxicity of the 5‐HT 3 Receptor Antagonists

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.

An evaluation of potential signals for ventricular arrhythmia and cardiac arrest with dolasetron, ondansetron, and granisetron in the fda combined spontaneous reporting system/adverse event reporting system

BACKGROUND

Of the US Food and Drug Administration (FDA)-approved5-hydroxytryptamine type 3 (5-HT3)-receptor antagonists, dolasetron, ondan-setron, granisetron, and palonosetron, only dolasetron and palonosetron have a precaution in their FDA labeling concerning corrected QT interval (QTc) prolongation. At FDA approved doses, QTc prolongation has been observed in clinical trials with some 5-HT3 receptor antagonists (however, palonosetron has been only recently approved, with few published clinical data available). However, due to patient exclusion criteria, such trials with 5-HT3 receptor antagonists may have failed to examine the risk of these agents in "real world" patients with cancer.

OBJECTIVE

The aim of this analysis was to assess the potential risk for selected cardiac adverse events associated with dolasetron, ondansetron, and granisetron use.

METHODS

The FDA combined Spontaneous Reporting System/Adverse Event Reporting System database was analyzed. The process of analyzing such a database for early warnings of potential hazards is known as signal generation. The statistical technique proportional reporting ratio (PRR) was used to aid detection of a potential signal within the database. PRR is the observed proportion of a given adverse event for the drug of interest (the number of events of interest for the drug divided by the total number of reports for the drug) divided by the expected proportion. Through the third quarter of 2002, the database was searched using the preferred term electrocardiogram qt corrected interval prolonged.

RESULTS

One, 3, and 0 cases were reported for dolasetron, ondansetron, andgranisetron, respectively. The number of cases did not satisfy 1 of the 3 criteria we utilized to define a potential signal, the 3 criteria being: 3 or more reported cases of the adverse event, a PRR value of at least 2, and a χ(2) value of >4. As this term may be unlikely to be reported, the database was also searched using the term ventricular arrhythmias and cardiac arrest. The PRR, used as a parameter to detect a potential signal within the database, was 3.23, 1.31, and 1.13 for dolasetron, ondansetron, and granisetron, respectively. The number of observed ventricular arrhythmias and cardiac arrests was ∼3-fold higher with dolasetron compared with the expected value (calculated by dividing the individual agent's total number of events reported by the proportion of adverse events for all agents combined). The results for dolasetron fulfilled the criteria we used to define a potential signal.

CONCLUSIONS

This analysis detected a potential signal for ventricular arrhythmiasand cardiac arrest with dolasetron, but not with ondansetron or granisetron. However, there are limitations of a PRR analysis, which include only measuring cases that have been reported, providing relative frequencies instead of actual rates, and not providing information on the severity of adverse events or causal relationships. In addition, our analysis does not include consideration of concomitant medications, and only 2 search terms were used. Errors in identifying potential signals may also include confounding factors, such as the underlying disease, potential confusion with reporting under trade and generic names, and potential multiple reporting of the same case.

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.