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Appendix B

Health economics of ondansetron

Introduction

Children presenting with acute gastroenteritis often have high levels of vomiting. There is currently
no widely accepted method of treatment for the cessation of vomiting in such patients in the UK.
Vomiting is not only distressing to both patients and their families but can also interfere with the
oral rehydration process and can limit the success of oral rehydration therapy (ORT). Children
who are unable to tolerate rehydration fluids orally are then given intravenous fluid therapy (IVT),
which in turn has additional significant resource implications. It is thought that the use of anti-
emetics may be effective in the cessation of vomiting and may in turn help with the successful
delivery of ORT, thereby reducing the need to treat with IVT. Consequently, this would have cost
saving implication for the NHS through fewer admissions for IVT. Ondansetron is recognised as
an effective anti-emetic and is used frequently in post-operative patients and also in oncology.
The GDG felt that an economic analysis would help guide recommendations regarding its use.

Economic analysis

A literature review identified several articles investigating the effectiveness of ondansetron
in children with vomiting due to gastroenteritis. The evidence was for both oral and IV uses
of ondansetron but the evidence for the efficacy of IV ondansetron was limited and thus the
economic analysis only considers oral administration. None of the articles retrieved included any
data regarding costs or cost-effectiveness.
A simple economic model was constructed to assess the cost-effectiveness of ondansetron. The
model probabilities are taken from a meta-analysis that pooled the results of three RCTs 160,163,164
comparing the effects of administration of oral ondansetron against placebo in children with
vomiting. Model probabilities are presented in Table B.1. The three main outcomes considered are:

• cessation of vomiting
• need for IVT
• hospitalisation.
Model costs are taken from the decision analytical model for the cost-effectiveness of IVT versus
ORT for children with dehydration (Appendix A). All cost inputs are presented in Table B.2.
The cost for ondansetron was obtained from the British National Formulary for Children (BNFC
2007). 209 It is assumed that only one dose of ondansetron (at a strength of 4 mg) is given to the
vomiting patient.
The effectiveness of ondansetron is measured by an increase in the cessation of vomiting. The need
for further IVT and hospitalisation are both measures of resource use subsequent to treatment. To

Table B.1 Model probabilities
Outcome Control Distribution Ondansetron Distribution
Cessation of vomiting a 0.652 Beta (α = 116, β = 62) 0.862 Beta (α = 156, β = 25 )

Hospitalisation 0.099 Beta (α = 23, β = 210) 0.039 Beta (α = 9, β = 223)
Need for IV treatment 0.339 Beta (α = 79, β = 154) 0.137 Beta (α = 30, β = 189)
a The outcome of ‘cessation of vomiting’ was only reported in two of the trials. 163,164

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