Peppermint Oil for the Treatment of Irritable Bowel Syndrome: Optimizing Therapeutic Strategies Using Targeted Delivery

Inclusion criteria

• Age between 18 and 75 years;
• Diagnosed with Irritable Bowel Syndrome according to the Rome IV criteria:

(Recurrent abdominal pain, at least 1 day/week for the last 3 months; Symptom onset at least 6 months prior to diagnosis; Associated with two or more of the following:

• Pain related to defecation;
• Pain associated with a change in frequency of stool;
• Pain associated with a change in form (appearance/consistency) of stool
• Based on the medical history and previous examination, no other causes for the abdominal complaints can be defined. Especially no history of:

• Inflammatory Bowel Disease;
• Celiac Disease;
• Thyroid dysfunction (if not well-regulated). If alarm symptoms (including unexplained rectal blood loss or weight loss) are present, a colonoscopy has been performed and was negative for other causes.
• Women in fertile age (<55 years old) must use contraception or be postmenopausal for at least two years.
• Average worst abdominal pain score (on 11-point NRS) of > 3, during the two-week run-in period.

Exclusion criteria

• Insufficient fluency of the Dutch language;
• Any previous use (also incidental use) of peppermint oil capsules in the last 3 months prior to inclusion (the use of peppermint tea, menthol candy etc. is allowed);
• The inability to stop regular use of medication affecting the gastro-intestinal system (such as Non Steroidal Anti Inflammatory Drugs (NSAID), laxatives, prokinetics, opioids, smasmolytics and anti-diarrhoeal drugs). This use should be halted at least 1 week before enrollment into the run-in period;

• The use of 1 antidepressant drug is allowed, providing dosing has been stable for > 6 weeks before enrollment;
• The use of 1 proton pump inhibitor (PPI) is allowed, providing dosing has been stable > 6 weeks before enrollment;
• Previous major abdominal surgery or radiotherapy interfering with gastrointestinal function:

• Uncomplicated appendectomy, cholecystectomy and hysterectomy allowed unless within the past 6 months;
• Other surgery upon judgment of the principle investigator;
• History of liver disease, cholangitis, achlorhydria, gallstones or other diseases of the gallbladder/biliary system;
• Pregnancy, lactation;
• Using drugs of abuse;
• Known allergic reaction to peppermint.