Weerts ZZRM, Essers BAB, Jonkers DMAE, et al. A trial-based economic evaluation of peppermint oil for the treatment of irritable bowel syndrome. United European Gastroenterol J. November 2021;9(9):997-1006. doi:10.1002/ueg2.12134.
Irritable bowel syndrome (IBS) has a negative impact on quality of life due to causing chronic abdominal pain and altered bowel habits. It is a disorder of the brain-gut-interaction and can be associated with high costs for patients, the healthcare system, and society. These costs include consultations, ER visits, hospitalizations, and prescribed medications, on top of indirect costs, including missed work and being in pain at work. Peppermint (Mentha × piperita, Lamiaceae) oil has been frequently used to treat IBS; however, there has been no trial assessing the cost-effectiveness of peppermint oil. The authors conducted a multicenter, placebo-controlled, double-blind trial-based economic evaluation to assess the cost-effectiveness of peppermint oil on patients with IBS.
This study was conducted between August 2016 and March 2018 at the following four Dutch hospitals: Maastricht University Medical Center+, Maastricht; Hospital Gelderse Vallei, Ede; Alrijne Hospital, Leiden; and Medical Center Leeuwarden, Leeuwarden. Inclusion criteria included men and women between the age of 18 and 75 with IBS. Patients also had to fulfill the Rome IV criteria and score ≥ 3 for mean daily worst abdominal pain during a two-week run-in period. No exclusion criteria were given.
Patients in the peppermint group were given either 182 mg of small-intestinal release peppermint oil in enteric-coated soft gel capsules (Tempocol®; WillPharma SA; Wavre, Belgium). The placebo ingredients were not stated, nor was it stated if they appeared similar. It was also not specified how often the capsule was taken.* Patients were instructed to take the treatment for eight weeks after a two-week run-in period and were followed by a six-month follow-up period with no study medication.
The economic evaluation was conducted with 2017 euros and used Dutch guidelines for cost-calculations, the Consolidated Health Economic Evaluation Reporting Standards checklist, and the Professional Society for Health Economics and Outcomes Research guidelines. Costs included direct costs, indirect costs, and treatment costs. Several sensitivity analyses were also performed.
Of the 189 patients screened, 126 were selected. Sixty-four were in the placebo group, and 62 were in the peppermint group. Of the 126 selected, 120 completed the study. The mean age was 35.5 ± 15.2 for the placebo group and 32.0 ± 11.2 for the peppermint oil group.
There was an improvement in the quality of life for the peppermint group compared to placebo; however, it was not significant. Peppermint oil showed a significant decrease in direct costs compared to placebo; however, there were no significant differences between groups for indirect costs. P-values were not given.*
It was calculated that the peppermint oil group saved €40.00. Using the cost-effectiveness plane, 46% of simulations found that peppermint oil was a dominant treatment compared to placebo. In 36% of simulations, it was found to be more effective, but at a higher cost, and 18% showed peppermint oil to be inferior. The net probability showed that peppermint was cost effective 50% of the time for a willingness-to-pay (WTP)-threshold of €1,000 and 56% at a WTP-threshold of €10,000.
After using sensitivity analyses, peppermint oil was shown to dominant 51% of the time in the simulations when using the main clinical outcome instead of quality-adjusted life-year (QALY) and when using uncorrected QALYs. Uncorrected QALYs also showed more effectiveness at a higher cost in 40% of the simulations. The WTP-threshold of €10,000 also increased to 58%. When looking at the healthcare perspective, the peppermint oil was dominant 65% compared to placebo in Institute for Clinical and Economic Review simulations and 85% in WTP-threshold of €10,000.
The authors conclude that treatment for IBS with slow-release peppermint oil was cost effective from a societal and healthcare perspective. Potential limitations included using estimations of cost, not including potential long-term mental healthcare costs, missing data for presenteeism, not verifying absent days were for IBS or for other comorbidities, only using a placebo compared to the peppermint oil, and most patients being similar in demographics. More research will be needed to compare to other treatments and using a broader demographic.
The authors state potential conflict of interest.
*More detailed information on medication and outcomes are given in Weerts ZZRM, Masclee AAM, Witteman BJM, et al. Efficacy and safety of peppermint oil in a randomized, double-blind trial of patients with irritable bowel syndrome. Gastroenterology. January 2020;158(1):123-136. doi: 10.1053/j.gastro.2019.08.026.