• Attend your hospital appointment to undergo some assessments to find out more about your IBS and see if it is appropriate for you to take part in the study
• Attend your hospital up to 5 more times over 16 weeks.
• Complete a diary to record the details of your bowel movements, your abdominal pain and any side effects.
• Respond to 2 text messages every day (optional) to let us know about your bowel movements and abdominal pain.
• Take your study medication for 12 weeks and do not take any new medication or start a new diet
• You will also be asked, if you agree to provide blood, stool or biopsies and undergo more detailed assessment to help the researchers better understand IBS and how the drug works. These are optional.

It is important to realise that if you agree to enter the study neither you nor your doctor will be able to choose which treatment you get. This will be chosen at random by a computer. You will be told what treatment you have been given once all the data in the study has been collected. If you have been taking the placebo during the study you may still be able to try ondansetron after the study has finished and you should discuss this further with your doctor.

Yes. You will receive £175 inconvenience allowance. £75 will be paid once you have been randomised (Visit 3) and £100 at the completion of treatment and follow-up periods (Visit 6). Additional payments will be made for some of the optional studies.

Ondansetron has been widely used for over 25 years. We are using a low dose. At the doses we will be using the main side effects are constipation and headache. Almost all drugs can cause allergic reactions such as wheeze and skin rash, rarely the drug can cause dizziness.
As with many drugs, the effect of this treatment on an unborn child are unknown; therefore if you are pregnant, breast-feeding, or if you intend to become pregnant during the study you will not be able to take part. All participants will also be required to use a reliable form of contraception during the study and at least 90 days after treatment has finished.

Your GP and the other doctors involved in your clinical care will be aware that you are taking part in the study as part of standard clinical practice, but otherwise all information about you will remain confidential.
The information needed for study purposes will be collected on paper forms or via a text message. Data will be sent from your hospital to the Clinical Trials Research Unit (CTRU) at the University of Leeds. You will be allocated a study number, which will be used along with your date of birth and initials to identify you on each paper form. Your full name will be included on your consent form and a copy of this will be sent to the CTRU by fax, standard Royal Mail post or email. This information collected about you will be handled strictly in accordance with the consent that you have given and will not be accessed by any other personnel. Your data will be entered onto a secure database held at the CTRU in accordance with the 2018 Data Protection Act.