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5-HT3 receptor antagonists for radiotherapy-induced vomiting


Clinical bottom line

5-HT3 receptor antagonists are effective for complete control of emesis in acute radiotherapy-induced vomiting. NNTs are 2 or 3 when compared with placebo or metoclopramide regimens, though in small numbers of trials.


MR Tramèr et al. Efficacy of 5-HT3 receptor antagonists in radiotherapy-induced nausea and vomiting: a quantitative systematic review. European Journal of Cancer 1998 34: 1836-1844.

Radiotherapy induces a distinct pattern of nausea and vomiting: an asymptomatic latent period of one or two hours, followed by an acute six to eight hour period of nausea and vomiting, followed by recovery. The most sensitive part of the body is the upper abdomen.


The review used number of databases to discover trials exploring the efficacy of 5-HT3 receptor antagonists for radiotherapy-induced nausea and vomiting. The date of the last search was January 1997. Valid studies were deemed to be randomised controlled studies, in which other potentially emetogenic treatments (like chemotherapy) were avoided. The main outcome sought was complete control of emesis (patients with no vomiting or nausea).


Forty trials were found with 1404 patients, but many were excluded. Information on all the excluded trials is given, making this a rich data set for anyone interested in other facets. The review is helpful in picking out eight duplicated reports.

Five trials met the inclusion criteria. Two had placebo controls and three had metoclopramide controls(one with dexamethasone as well). The results are shown in Table 1.

Table 1: Complete control of emesis over 24 hours


Complete control/Total




Number of trials

with treatment

with comparator

Relative benefit (95%CI)

NNT (95%CI)

5HT3 alone Placebo




4.5 (1.1 to 18)

2.9 (1.7 to 11)

5HT3 alone Metoclopramide with or without dexamethasone




2.0 (1.5 to 2.5)

2.7 (2.1 to 4.0)

In other analyses over longer periods, there was no evidence that 5-HT3 receptor antagonists were of benefit. Constipation and headache were associated with 5-HT3 receptor antagonist use compared with other antiemetics or placebo.


This is a fine systematic review. The weight of evidence is not great, but the completeness of the review makes it the obvious place to start if planning new and better trials on existing or new treatments or treatment regimens. It informs about design, conduct and endpoints.