Long-term maintenance treatment with 300 mg thiamine for fatigue in patients with inflammatory bowel disease: results from an open-label extension of the TARIF study.

Objective And Aims: Fatigue is common in inflammatory bowel disease (IBD). In a RCT we demonstrated reductions in fatigue after 4 weeks' treatment with high-dose oral thiamine. We aimed to investigate whether 300 mg thiamine daily for 12 weeks could maintain the achieved levels of fatigue in patients with IBD after a 4-week intervention with high-dose thiamine; and evaluate the effect of a 6-month period where patients were free to take oral thiamine.

Methods: A randomised, open-label, controlled trial, performed as a long-term extension (LTE) study of an initial randomised, high-dose thiamine trial. Patients were allocated 1:1 to 300 mg oral thiamine or no thiamine for 12 weeks. Subsequently, the patients were allowed to self-treat with over-the-counter (OTC) oral thiamine 6-month.

Results: Regardless of allocation in the LTE study fatigue severity increased in the study period. No significant effect of 300 mg oral thiamine were found, when stratifying for initial allocation in the high-dose study or fatigue level at entry in the LTE study. Patients who took OTC thiamine had lower level of fatigue 6 month later (7.8; 95% CI: 5.5-10.1) when compared to the remains (11.0; 95% CI: 9.2-12.8) ( = .02). After the 6-months follow-up without restrictions, 66% of patients had reached normal fatigue levels.

Conclusions: We found no beneficial effect on fatigue from thiamine taken in doses of 300 mg per day for 12 weeks following high-dose treatment. After a 6-months follow-up without restrictions 66% had reached a normal level of fatigue.

Clinical Trial Registration: The trial was registered at ClinicalTrials.gov under study identifier NCT03634735.